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oliviabutsmart · 1 month

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Where have I been?

So I assume that there's still people following my account, waiting for the next update on languages or physics Friday. And obviously I have taken much more than a "month's break".

Where I have been is that I have been both recovering from severe trauma, and have been dealing with my honours year.

This post is to keep a public record of what has been happening, and also to just not leave the small amount of people who are interested in what I say.

Part 1 - Bad shit happened

CW: Suicide, Emotional Abuse, Online Sexual Violence, Physical Stress Disorders

Between May 2023 - January 2024 I was coerced into an abusive relationship with my now ex. How was I coerced?

You see, over October 2022 - May 2023, I was in a friend group that was severely abusive and cowardly. I was bullied to the point that I ended up in hospital after I tried to end my life - and then left for dead because someone I trusted had manipulated all of my friends into leaving me.

But there was one person who didn't leave me for dead. And he took advantage of me. Of course, I was extremely vulnerable. I was in a state of severe depression, unable to stand up for myself, feeling desperately alone.

He stayed with me, and threatened to leave me if I decided to enter into any romantic or sexual relationship with someone else.

Of course, this relationship wasn't healthy. We were not compatible with eachother. And if I had more willpower I would've been able to leave after recognising it.

Being forced into a relationship, coerced into sexual interaction, forced to look after this man who had more insecurities than words in the bible.

It led me to being frustrated, and obviously lashing out in small, yet continuous ways.

Eventually I found out that he had been lying about his age. He told me he was 26. I was 20. He was actually 17. The moment I heard about it I dumped him. I had enough. He had crossed a red line that I could not accept.

Legally speaking, I am in the right. The age of consent in Australia is 16. If he were to try and prosecute me, he would be in prison, because he would have legally sexually assaulted me.

That's the important point. After a few months of contemplation, I had realised that what he had done is sexually assaulted me. I was not only coerced, but I "consented" under false pretences. He had violated both the "informed" and "consent" parts of informed consent.

Morally speaking, I'm fine. Really, I don't think anyone with half a brain could see the problem, especially if I was lied to. And really, 17/20 is so much better than other age disparities.

Regardless, the news hurt me greatly. I personally would've never consented to a relationship if he was under the age of 19. I felt disgusted. I spent a week shitting blood, vomiting, and watching my hair fall out.

I had asked him, quite explicitly, to not talk about anything sexual from now on. And to delete any inappropriate images to me unless I report him.

Do you know what he did next? He tried to coerce me back into a relationship. He threatened to stop being friends with me if I tried getting another partner. He talked about some of the most sexually inappropriate stuff to me.

In effect, he sexually harassed me. I was extremely uncomfortable talking to him in that manner. But he continued to threaten me and tried to convince me that what he did was not that bad and if I were to re-date him it would be "not that bad" - it was awful.

I decided to stop talking to him, for two weeks. Just so I could get a break from him. At this point in time, I hadn't gotten to the point that I wanted to leave him, just to be friends.

I came back after two weeks. Suddenly, he now had a new boyfriend. Which I believe was some pathetic attempt to get back at me for not wanting to be in a relationship with him.

He then tried to turn things around on me. He said that my constant frustrated outburst hurt him, and he used that as the excuse to bully me.

So I decided to stop talking to him again, for a few months this time. During this time, I tried working on getting better, so that eventually I could leave him.

I am posting this now, because I have just sent a last "go fuck yourself"-type message to him and blocked him.

The reason why I haven't posted anything here is simply because he followed me. He would've seen anything I wrote. And I wanted to block him all in one go when I felt confident enough.

Of course, you can obviously see why I would want to keep a public record of this. This person is extremely manipulative and duplicitous. And he could very easily misconstrue the facts to the point that I appear as if I'm in the wrong.

Unfortunately for him, I have a lot of evidence to back up my side, in the form of a full DM transcript. I hope I never have to use that evidence. But I will if I have to.

Think of this situation as a Pyrocynical/Kwite type situation (except I am much less famous than them and probably will never be as famous as them). From what I understand, they were accused of [child "liking"] by someone who was lying about the truth.

Honours year

This is more good news than bad news. I've just been incredibly busy as well. I started my honours year. And honestly, while it's very cognitively exhausting, it's also a great cure from all of the trauma and depression I have.

Unfortunately, it's extremely difficult doing that, and any other side projects, on top of rebuilding my life from a year and a half of abuse.

End

So for now, I'm going to just stop with the Physics Friday and Language updates. I may drop some random ones here or there, but they'll be on the frequency of once per like two months.

At the same time ... I just kinda don't like tumblr. It's extremely toxic. So much more than compared to reddit. And that's really saying something.

I've left a lot of queer spaces online because of how toxic and unwelcoming a lot of them have become to people who, say, don't like seeing homophobic slurs.

It's so simple and yet so mind-boggling. But I can't handle the emotional pain of that to be honest.

So that's it. I'd like you to not talk to my abuser(s). I want nothing to do with him. I don't want to interact with him at all. I don't want to be reminded of how I was mistreated.

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oliviabutsmart · 4 months

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No Physics Friday for at least the next month

I need to focus on getting my honours year/this year in general in-order. So I'm rather busy rn and will be for a bit.

Apologies for all the delays.

#physics friday

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oliviabutsmart · 4 months

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Physics Friday will not happen this week

I am very stressed rn

#physics friday

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oliviabutsmart · 4 months

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No Physics Friday this and next week

Merry Christmas and happy new year!

#physics friday

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oliviabutsmart · 5 months

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Physics Friday #18: Sounds of the CMB - Baryon Acoustic Oscillations

Introduction: What Are BAOs?

It's time for colours!

Let's break down the term Baryon Acoustic Oscillations (BAOs) ...

A Hadron is a particle made of several quarks, a Baryon is a Hadron that contains an odd number of quarks.

Baryonic matter makes up a majority of the stable, visible matter in the universe. Both protons and neutrons are types of Baryons, so most Baryonic matter is, shockingly, atoms.

Acoustic generally has two definitions, one musicological and one scientific. Scientifically, any 'acoustic' thing involves sound. Specifically here, we're using it to discuss the production and propagation of sound.

Oscillations is a term very related to sound, if you read my posts on the mechanics of sound, oscillations, waves, periodic motion, are all the same phenomena.

Here, an acoustic oscillation is just a looping/repeated physical motion in a medium, like plasma.

Thus, putting everything together, a BAO is the physical motion in a plasma of hydrogen/helium, caused by the propagation of sound waves.

How do they form?

After the era of nucleosynthesis, but before the era of recombination, the universe was full of an opaque plasma of hydrogen/helium.

Sound waves require something that can create both a compression and expansion of this plasma, causing a pressure wave. A force that can pull things together and push things apart.

Thankfully, gravity is a great mechanism to pull things together. All that is required is a few thousand years, and some already pre-existing variations in density to get going.

So this plasma, in more dense regions, begin to pull more matter into those regions, creating a self-reinforcing cycle.

But how do we create the effect of expansion?

This plasma, is, well, hot. Very hot. And because it's everywhere, there's a lot of radiation being constantly emitted and re-absorbed.

When you begin to concentrate a lot of plasma into one location (thanks to gravity), you also concentrate the release of radiation.

Moreover, the speed the plasma accrues when it starts falling into the dense regions will also give it more energy, causing even more radiation to be released.

The effect is that in these denser clouds of gas, more radiation is produced. This produces a radiation pressure, which attempts to force atoms out of the dense regions.

Because of the every-where-ness of this plasma, the radiation pressure is strong enough to completely counteract gravity in some cases.

This generates sound waves, created by the constant tug-of-war between radiation pressure and gravity. These sound waves propagate throughout the early universe.

In Comes Dark Matter

Dark matter is predicted to represent a majority of the matter in our universe, because it is dark, it does not experience radiation pressure.

But because it still has mass, it does experience gravity. This means that the dark matter will stay within the denser regions without rebounding at all.

The dark matter within these regions are what allow regular matter to constantly fall in and out. Without it, the radiation pressure would blow apart the region and it'd become devoid of matter.

Freezing Things in Place

Suddenly, the universe cools to a point where, near simultaneously, matter cools to the point that it can exist as a gas rather than plasma.

Unlike plasma, gas does not absorb all forms of electromagnetic radiation. This is because electrons are now bound to their respective atoms.

This means that radiation pressure no longer comes into effect, and any radiation emitted at the moment of this cooling is free to travel across the universe.

The newly freed radiation is what we see in the CMB - but there's something important about it. It records a single snapshot of the current state of the sound waves propagating in the universe.

Imagine you have a high-speed camera and take a photo of a guitar string being plucked. At that very instant you can see the wave frozen in place, and can use that to determine it's properties.

Image Credit: Reddit

The remaining oscillations in the matter freeze too, allowing for the formation of our modern galaxy clusters, galaxies, and even stars.

How we Look at the Sound

Using the image of the CMB, we can measure the ripples of the sound waves using a Fourier analysis of the temperature gradients.

The temperature is used because it correlates to regions of high or low density, of course, the hotter a location is in space, the more matter managed to get in there, thus releasing more stuff.

A Fourier analysis is a very common technique in sound measurements. It takes any arbitrary mathematical function, and converts it into a frequency spectrum.

A Fourier analysis. On the top, the original signal, on the bottom, the signal's frequency spectrum Image Credit: The Mathematics of Waves and Materials Blog

We can conduct a Fourier analysis in two dimensions as well, we just perform two applications of the Fourier transform, but in two directions.

A 2D Fourier analysis. On the left, the original image, on the right, the image's 2D frequency spectrum Image Credit: Python Coding Block

We can then take this 2D image and plot it on a graph of the distance from the centre.

Applying the analysis and the plotting function to an image of the CMB we get this graph here:

Note that 'Multipole moment' is, for the sake of simplicity, a frequency spectrum Image Credit: Report of the Dark Energy Task Force, 2006

The above image is referred to as the power spectrum of the BAOs.

Adding constraints to Dark Matter/Energy

Dark Matter and Matter Density

The BAOs at the moment of them freezing become an incredibly useful measurement for the propagation of Dark Matter and Dark Energy.

Of course, dark matter is built into the equation, as they form a necessary component of the gravity force pulling things in. We can use the relative strength and period of the oscillations to estimate the amount of dark matter and it's ratio to Baryonic Matter.

Curvature

We can also use our graph for a second purpose: measuring the curvature of our universe.

You see, given the fact that our galaxies and galaxy clusters eventually end up forming from those regions of dense gas, and given that we know how 'far away' the CMB is (thanks to redshift).

We should know the approximate size of these dense gas regions in the CMB, given a certain curvature.

This will appear on our power spectrum as the shift in our graph, the location of our peaks along the x-axis.

In a universe that is hyperbolic, we should expect the density blobs to be small, and in a spherical universe, blobs that are larger. What we end up seeing is approximately a flat curvature.

Dark Energy

Now, thirdly, we can estimate the density of dark energy in our universe.

We can get this easily by measuring both matter density and curvature, as the two are related to the dark matter density.

But, we can also estimate it directly from analysing the power spectrum directly.

Dark energy affects the expansion of spacetime via the Friedmann equation, controlling for matter density, we can use the equation to quantify the Hubble parameter.

The size of the Hubble parameter, relative to our current Hubble constant, can be measured from the fact that the BAOs provide a standard measure of distance.

By analysing the power spectrum, we can effectively work backwards to derive a measurement for the Hubble parameter, and thus the presence of dark energy in the early universe.

Conclusion

Surprisingly a shorter-ish post this time, good on me.

Anyways I'll probably take a break for next week, as it's Christmas. Outside of that, I don't really know what else to say.

Follow if you want more, gib feedback on my post, and comment/repost your thoughts!

See ya later!

#physics friday #stem #academics #stemblr #science #physics #astronomy #astrophysics #cosmic microwave background

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oliviabutsmart · 5 months

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Physics Friday #17 [Opinion]: The Great Tau vs Pi Debate

I'm really going for these hot takes now! Just look at me help tear the internet apart!

Education Level: Primary School (Y5/6)

Topic: Trigonometry (Mathematics)

Introduction: What is Tau? (And also pi)

Chances are, are that you already know what pi is ...

π = 3.14159265358979323 ....

I wrote that from memory, yes, I remember 18 digits of pi.

Anyways, we all know what pi is. It's the ratio between a circle's circumference and diameter, it's the ratio between a square and a circle inscribed in the square.

Image Credit: GeeksforGeeks

Pi is also an angle, well, every real number is technically an angle. But pi is a special angle.

It represents a 180˚ turn in radians.

For those who also don't know what a radian is, it's sort-of a special unit of angle measure. Much like how we measure length in meters or feet, we can measure angles in degrees, radians, or revolutions.

A 1 Radian sector of a circle of radius 1 will have an arc length of 1. This makes a 1 rad ≈ 57.2958˚.

Image Credit: Mometrix Test Preperation

You may be able to see why we would prefer radians to degrees. Radians often clean up our equations and even more, it allows us to express common angles in terms of pi.

Because a circle's circumference is equal to 2π times it's radius, a full revolution is equal to 2π units around the circle.

Thus we can express:

270˚ = 3π/2 rad 180˚ = π rad 90˚ = π/2 rad 60˚ = π/3 rad 45˚ = π/4 rad 30˚ = π/6 rad

Looks pretty nice? Well, there's actually another constant we can use to express angle measurements.

Tau, or τ, is equal to 2π. That means that τ = 2π, and a full revolution is equal to τ radians.

Thus we can express:

270˚ = 2τ/3 rad 180˚ = τ/2 rad 90˚ = τ/4 rad 60˚ = τ/6 rad 45˚ = π/8 rad 30˚ = π/12 rad

Tau is a relatively new symbol in the world of mathematics. And it's rather prolific online now. Pi is still used as the universal constant to represent radians and other circle-based coordinates.

While Pi is standard, there's been a growing movement to make Tau the new standard for angle measures. Let's look at the argument.

(Common) Arguments for and against switching

This section will only focus on the main arguments for and against using Tau as a common constant for angle measures. Below is a Numberphile video that goes into some detail over the main arguments for the pi vs tau debate.

youtube

Let's look at the pro's of switching to Tau:

Taking portions of a full revolution is significantly easier to grasp conceptually (Half a revolution is τ/2, a quarter revolution is τ/4)

It simplifies several equations in physics and mathematics by removing a factor of 2, e.g. Circumference = 2πr = τr

And here are the cons:

It's an unnecessary level of effort to change everyone over to a different constant when π is already doing a good enough job

It introduces an additional factor of 1/2 in several equations in physics and maths, e.g. Area = πr² = τr²/2

Alright, now it's time for the hot takes/opinions

Pi is better. That's it.

Okay okay, so there are obviously reasons.

Changing Standards

Firstly, I do subscribe to the idea of "if it ain't broke don't fix it", Pi is universally used. When I mean universal I do mean universal. Outside of the online maths-education-space world, tau is relatively unknown if at all.

If you want to switch over to tau, you will need to convince a supermajority of establishments, teachers, or professors globally - across multiple different disciplines like Economics, Engineering, Mathematics, Physics, and Computer Science.

Not just that, but you want to absolutely avoid the relevant xkcd:

Which will come inevitably when you make Tau popular enough that a non-negligible amount of people use it, but not popular enough that you have a majority of the population convinced.

You might as well try change the number base we use.

Changing Hardware/Software

Pi has become so entrenched in our information age modern society that you'll also need to now alter lots of computer software and hardware.

On MacOS (and Windows to), π is a default character on a standard English keyboard layout (using the option keys). Whereas other greek letters are relegated to your typing program of choice's maths function.

This makes writing τ a lot less convenient than π on a lot of computers. One can be written with Option+P, and the other needs to be copy-pasted into every text every time you want to use it.

Not just that, but we also need to consider that most applications that use calculation software (i.e. Microsoft Excel), uses π.

Do you know why windows is so backwards compatible? A lot of Excel's software is legacy, meaning that a lot of Excel software is old and at risk of breaking with new updates. Many, many, financial systems require π otherwise they too would break.

What about programming languages? Most modern languages include a mathematics module, and in order to fully switch to τ, every single last one of them needs to implement changes.

This becomes difficult, especially with older languages that don't get as much updates or developments, but are still used regularly in a lot of programs.

If you fully fully want to change to tau you'd have to go through every instance of pi and change it to tau/2 in order to not confuse future readers of the program.

It's in my opinion that doing all of this ... is not needed when you're getting very diminished returns.

Introducing More Fractions

The second point, that tau introduces extra fractions, is also something I agree with.

Fractions are innately more difficult for a layperson to grasp. Especially more difficult than multiples of a number.

Switching to τ means introducing an additional factor of 1/2 in every equation. This is okay for small fractions like 1/2 or 1/4. But angle measures like 30˚ end up having factors of 12.

Do you know what 1/12 is? Could you reasonably ask a layperson to write out 1/12 of the top of their head?

But this spreads much more widely. Every integral now has extra fractions. Fractions are the most common reason why you fuck up an integral. Because doing arithmetic with fractions is innately harder than arithmetic with integers.

The main argument here is that in order to trade the conceptual-ness of simplifying angle measurements slightly and conceptually, you end up making a mess of a lot of other aspects of trigonometry in terms of the arithmetic.

The Online World is not the Only World

The most annoying thing I find about the tau vs pi debate is in how people advocate for tau. It's a microcosm of a lot of online activism.

Just because your movement has a presence online, does not mean that it's popular elsewhere. All you do when you promote things online is confuse or offend people when reality slaps you in the face.

The tau vs pi debate is the most tame of these online vs real world disparities, but it's a good example in the light form.

I've often seen that people who use tau generally use it without clarifying what tau means. This means that someone who is not familiar with the existence of tau (of which there are many), will be confused when you start using e^iτ/2 to represent -1.

It also isn't helpful as it doesn't actually extend the movement's reach outside of a very minimal niche ...

There are two Numberphile videos on Tau, often credited as what really kick-started everything. Both videos have only 1 million views. About 1/400th the population of the US, and 1/8000th the population of the globe.

When you realise the scale of how small your movement is, it can really put in perspective what is required. And also why people may ask more things of you.

If you want to advocate for τ or anything else, there's a right way to do it, and a wrong way. And ignoring feedback or requests is more a sign of stubbornness or immaturity.

Conclusion

If I were to have it my way, I'd actually prefer making our angle measure constant smaller. Instead, let us have a symbol representing a right-angled turn.

This would be great, as people often deal with right angles a lot more often than 180˚ turns and 360˚ turns. It also handily removes an extra factor of 1/2 from all equations.

Of course, there are obvious disadvantages. But let's be honest. The first criticism I gave still absolutely applies.

Relevant xkcd, again.

Anyways, hope you enjoyed the post. Of course, this is an opinion post, meaning that I would very much like to hear your own thoughts on tau vs pi! While I sounded a bit agitated at the end there its more because of this:

Tumblr is being a bitch and is fucking up my computer's processing power for some reason. Like seriously the speed at which I type is making the website load poorly.

Outside of that, next week will be on Baryon Acoustic Oscillations. See you later!

#physics friday #stem #academics #stemblr #science #mathematics #tau #pi #tau vs pi #trigonometry #Youtube

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oliviabutsmart · 5 months

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[Bonus Physics Friday?] Plagiarism and Originality

So you (the reader) may have watched the recent HBomberGuy video. I have too! And it's honestly a great (yet long watch). I highly recommend you read it.

youtube

After reading the video, it inspired me to add my own comments onto what I think is important to keep in mind about plagiarism and it's relevancy to this blog.

Unintentional Plagiarism

You yourself may eventually have to write something in the future. Whether it be code, a school/university project, text/literature, or even an academic paper.

I'm certain you've had some anxiety in the past (usually in school) of "what if I wrote something that was plagiarised?" when submitting documents to your teachers.

This anxiety often arises because when you are doing an academic assignment, the subject matter has already been covered many times over, so many times you may end up stumbling your way into writing something that already exists.

It is, in fact, possible to unintentionally plagiarise. But it often comes in a different form.

As seen in his video, often times, creators end up sharing video techniques and ideas when creating new work. More broadly, a lot of our art or 'content' in-general is in some-form derivative.

Here's an example from my own posts, expressing a very common cycle in how we develop our opinions or knowledge on things:

You hear from someone, or in a video, or by reading in a book a particular opinion/fact/idea/expression

You keep the idea in your head but forget the source you found it from

Eventually, months to years later, you recall the idea you had and write it down in a public place

You don't credit the source of the idea because it's lost to your mind, you think you yourself came up with the idea

This gives the idea that your ideas are completely original, but are instead pulled from another source. This is what I mean by "unintentional plagiarism" - often you yourself don't even know it's happening.

After writing 16 Physics Friday posts, I can now at least recall a few times where this has happened to me. Usually by way of me re-watching a video or seeing a video on youtube after the fact, where I'm like:

"Hey, I remember watching this video ... Hey, this is where I got that idea from!"

There are two examples that I can list right now, in fact:

In post #8, the definition of "Energy is the capacity to do work" came from a video by 'Professor Dave Explains'' on youtube. I cannot recall which video I got it from, but I do know it was a debunk

The idea for post #9 came from a video by 'Answer in Progress' titled "how fahrenheit fails you"

In both examples, either small sentence-level statements or whole topic ideas effectively get "copied" by my mind. However there is a core distinction between what I have labelled as unintentional plagiarism, and real "you did a word crime" plagarism.

Our Textual Fingerprint

It is a fact that almost all of our ideas are copied from somewhere else. Teachers in high school, internet pundits, other posts on social media. These, combined with our cycle of forgetting the source, create an effect of "plagarism"

What's important is that all of these ideas amalgamate, and get filtered through our own brain. I might have gotten the "energy is the capacity to do work" definition from one guy, but it combines itself in my head with every other association and factoid about energy I know.

Not just that, but it filters through my own head and my own words into different explanations, different expressions, different language.

The way you yourself construct ideas in your head is why we can consider it okay to express an idea that is still somewhat derivative. Because our own words, our own expressions garble that idea into something that is distinctly our own.

And that's the core point about avoiding plagiarism, both unintentional and intentional.

The best way to avoid plagiarism is to write it in your own words Source: every teacher in high school

Every person possesses a sort-of fingerprint. It exists in the way we write, the way we talk, even the way we communicate in other mediums like auditory (music, speech) or visual (performance, artistic, video) formats.

This fingerprint is detectable to most people. It's how you can tell when someone uses AI to write an article. Because ChatGPT has it's own literary footprint.

If my next Physics Friday post was written by someone else, you would be able to tell. Because the way I write is distinct. The errors, the mannerisms, the explanations are all constructed in a way that make the way I write unique to others.

Why does plagiarism happen?

I've seen plenty of examples of plagiarism in the past. In fact, I remember in Year 9, someone copied my entire essay on Australia's role in WWI, and I got off with a slap on the wrist for being so naive to share it with another student.

And with this experience, I've found that there are two main reasons why someone plagiarises, at least in the academic realm:

They have a lack of respect for the subject matter or their victim

Laziness or apathy

This is something the above video makes a point of as well, adding on a drive for success. Something which I wouldn't say is as common in academic media.

Really, the best way to stop yourself from stooping to the level of intentionally plagiarising is one of two things:

Force yourself to write something original, to write in your own words

Don't write it. Take a break or reconsider why you feel the need to do it

This is often why I end up writing opinion posts. I'd rather do that than be a piece of shit and copy a Veritasium video. Seriously, it's so tempting to just do a topic that Veritasium has already covered - he's a great creator and always picks all the good topics.

How it's relevant to Physics Friday (And how Wikipedia is actually a decent source)

All of my Physics Friday posts are written in my own words, usually all at once or in two seperate sessions on Friday. There is occasionally the odd quote from Wikipedia or other online sources. But the text is usually my own.

I mostly use other internet sources, like Wikipedia, or others, to effectively re-jog my memory. It helps remind me of what a particular mechanism is.

I don't cite them because usually I only read small sentences and then go "ah, now I recall the textbook's worth of information stored in my head". My external research never ends up becoming a real source in a proper sense.

The only exception is Wikipedia and my own lecture notes.

While my posts are not copy-paste descriptions from Wikipedia, the website does help guide me on particularly difficult-to-understand subjects. It helps me decide what exactly to talk about. Or check which ideas are often more common.

One example is the dark matter post (#4). I used it as my primary source for deciding on what was the most notable dark matter candidates to talk about. And the section headers are derived in some way from their article.

You can generally assume that for all of my physics posts, I have used Wikipedia in some way as a knowledge-check, to ensure I'm not spitting nonsense.

In fact, I recommend Wikipedia as further reading after looking at my post if interested. And to donate to their organisation, which I have done on several seperate occasions.

Definitions and Single-Sentence Quotes

Outside of images, the most common place where I directly quote from other sources are in the definitions I've used. I cannot actually remember if I've ever done it before on tumblr, but I've done it in the past for several academic writings.

Definitions are tricky. Because, especially with precise scientific definitions, there are only so many ways to construct a definition that:

Removes all ambiguity from the phenomenon

Perfectly describes all or most instances of the thing, and excludes any non-instance of the thing

If I'm not coming up with the definition myself, I generally aim to find the source of the definition. Something that already fails in some ways, as explained above.

The Easy Part: Citing a Source

When writing academic papers, sources are probably the most annoying part of it. Bibliography management is a pain.

When writing these Physics Friday posts, citing is the easiest thing I can do. There's no requirement to follow a strict standard like the APA.

Often giving the author's name or a link to the original content is enough information to credit the author.

This is why you see an image credit or video credit under each of my Physics Friday posts. Sometimes also on meme posts too!

Should we cite our memes?

This is an interesting question. No seriously. Take a second to think about this question properly.

A lot of our memes (and porn) come from artists on youtube, twitter, tumblr, etc. And I have found countless times where I'm like "huh, I like this guys' work ... where can I find more of it?" and just turn up nothing.

We appear to think that memes are not just public domain, but un-creditable public domain. Someone on youtube can copy a guy's voice-over of a meme, turn on ads for that video, and rake in cash. The original artist ends up getting none of the credit, or money.

For a lot of memes, it makes sense to copy it without credit. But the above paragraph applies to a certain subsection of memes, particularly the higher-effort ones.

Personally for me, when I have the capacity to share a meme I try to credit the original artist. Because I believe that person deserves the credit for making the funny.

At least for us, credit means we ourselves gain from it, we can look up the original and find more of the same.

My posts aren't trademarked

It's obvious to say, but "Physics Friday" is not limited to me. My goal with these posts are to get other people into following on and making their own style of posts in physics. To generally bolster the community.

If you want to do the Physics Friday thing, you do not need to ask for permission. That's all I need to say.

Conclusion: Why did I write this?

I've just spent the last hour writing a tumblr post after watching a HBomberGuy video. And now I am just wondering why I did that.

I guess I had a lot of things to say about plagiarism and writing your own work.

Oh well.

Look out for next Friday where I'll probably do an opinion piece on tau vs pi!

#physics friday #plagarism #hbomberguy #Youtube

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oliviabutsmart · 5 months

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Physics Friday #16: The Cosmic Microwave Background (CMB)

This was originally going to be a post on Baryon Acoustic Oscillations, but I think that it's better to first discuss the CMB broadly before getting onto that, keeping the post lengths short(er).

Introduction: Our bath of Microwave Radiation

The CMB is everywhere, literally. Where you stand right now you are being bombarded by a bath of microwave radiation originating from the CMB. In fact, it's part of what causes the static on old TVs.

Now don't worry, the radiation is very weak, so it's unlikely you'll actually be hurt.

The CMB ceased to exist about 13 billion years ago, what you see in the microwave part of the spectrum is just what was left over.

Because the speed of light is not infinite, when we look really far out in the distance, we actually look back in time.

Measuring an object 1 light-year away means we only see what that object looks like a year ago. Measuring an object 1 billion light-years away means we are looking at that object 1 billion years in the past (ignoring the expansion of the universe).

If we account for an expanding universe, light actually travels a lot further. Because what was 13 billion ly has expanded into ~40 billion ly. However, we still see it as 13 billion ly.

This allows us to see the universe in it's early stages of life.

Eras of the Early Universe

The eras of our universe are crucial to understanding the CMB. In the first few seconds after the big bang, we have the hadron era, where the first protons and neutrons form.

A few minutes later, the temperature of the universe drops enought that these protons and neutrons then form into stable atomic nuclei during what's known as big bang nucleosynthesis.

Effectively we have nuclear fusion happening everywhere in space, like in the core of most stars, including our sun.

Eventually our universe expands to such a point that the temperature drops below a point where we cannot have nuclear fusion. But the temperature is still high enough that the universe is exclusively plasma.

Plasma is the state of matter in which electrons cannot bind themselves to their respective atomic nuclei, the universe is considered 'ionised' - as it's all just electricity.

During this time, the universe is opaque. Because any light moving around in the universe gets instantly absorbed by the loose electrons or nucleons.

We'll have to wait a couple thousand years before the universe cools even further, to the point where we get normal gaseous matter. The universe suddenly becomes translucent. This is known as the era of recombination.

At the moment of this occurring, any light emitted by the previously hot plasma escapes and can travel freely through the universe unobstructed. This thermal radiation comes in the form of infrared radiation.

Travelling Radiation

The radiation of the CMB is the earliest possible light we can see in the universe. Because any previously-existing light is obscured by the plasma earlier-on.

The radiation emitted from the CMB travels across space in order to reach us. And during that time it gets 'corrupted' in a sense.

Redshift - Turning Infrared into Microwaves

Redshift is a phenomena where light waves will stretch, their wavelength is increased as they are released and move through space.

Expanding space means that the CMB is effectively moving away from us at very fast speeds. This creates a doppler effect where the light waves will inherently be released out towards us at a longer wavelength. This is called doppler redshift.

The expansion of space also affects the wavelength as the photon travels. The space in-between each photon's wavelength stretches too, creating more cosmological redshift.

For most objects, cosmological redshift is negligible, because the light doesn't travel far enough for space to expand inside the wave. But the CMB is very far away, meaning that both forms of redshift are non-negligible.

Image credit: Forbes

The CMB exists at a redshift of ~1100, this doesn't mean much on it's own. What it means is that red-coloured light will become shifted to short radio frequencies that you can pick up on your radio.

The Lyman-Alpha Forest

Of course, our translucent gas is not perfectly translucent. Gas can absorb and emit specific wavelengths of light that perfectly correspond to energy levels an electron can take within an atom.

The Lyman series is an example of hydrogen emission/absorption lines, and as the light travels through hydrogen gas, the wavelengths corresponding to the Lyman series gets absorbed by our atoms.

This process keeps happening. As redshift alters the wavelengths of the surviving waves, any gas obstructing the CMB's light will have fresh light to absorb.

The effect is this continual series of absorption lines appearing in the otherwise clear spectra of radiation. Creating a 'forest' of several absorption lines.

Image Credit: Wikipedia

Re-Ionisation

Some gas in the early universe ends up converting back into plasma, this is caused by gravity pulling on small inconsistencies in the gas density.

These bright spots of plasma were what formed the first stars, galaxies, and black holes. But for us, it also effects the CMB.

Of course, ionised gas is opaque, so any light that happens to come across a star in-formation is absorbed instantly.

Observing the CMB

There have been multiple attempts to view the CMB. Despite all of our obstructions, space is mostly empty. Not just that, but the visible blemishes on our dark sky (like the milky way) can be removed in-post.

There are three notable missions: COBE (1989-93), WMAP (2001-10), and lastly the ESA Planck/BICEP mission (2015-19). Each increasing in resolution, each adding more information to our measurements.

When the CMB was first observed in the COBE mission, it saw something really strange, the CMB was really smooth, and looked like it had a dipole in it. This is the top image on the below diagram.

Image Credit: NASA

This dipole is actually caused by the orbital motion of the Earth! Not just around the sun, but also within our galaxy.

Alright, so let's try and re-configure our calculations, this time we will account for the movement of the Earth.

What we get is the middle image. There's still a big band in the centre of the frame, which actually is caused by our milky way, as the milky way itself also emits microwave radiation.

Thus this gives us the lower image. A background which looks approximately the same everywhere, but is distinctly not on local scales. This discovery broke one of our main assumptions in cosmology at the time - which is that the background is the same in all directions.

Something interesting also occurs as well. When all movement in space is removed, the CMB becomes static. This means that the CMB can act as a universal frame of reference, from which all other reference frames can be compared against.

This concept appears to violate the principle of relativity, but at the same time, our cosmological models require a reference frame to compare against. This is one example of an unsolved problem in GR.

While there isn't a visible dipole in our CMB observations, a dipole would have significant ramifications on our frame-of-refernce models.

Refining the Map and Using it

WMAP and the Planck mission refined our data to a point where we can use it for more interesting measurements.

Image Credit: ESA

The size of each small blob actually corresponds to the curvature inherent in the universe. As when we look far back into space, different curvatures will create different apparent sizes.

Not just that, but we can use the CMB to observe the reverberations of sound waves, this analysis allows us to measure the amount of matter that existed in the early universe.

With both measurements of curvature and matter density, we can estimate both the strength of dark energy and the expansion rate of the universe, allowing us another method to quantify dark matter.

These two data points turn out to be observed using the same phenomena, Baryon Acoustic Oscillations (BAOs) - a future topic (maybe in 2 weeks' time).

Conclusion

The CMB is still being investigated and still being observed. The main reason is because it is our only existing window into viewing the early universe.

Not just that, but the CMB provides important data that gave rise to both inflation theory and the eventual formation of our structure in the universe.

I will eventually cover inflation theory. But sooner, I will talk about BAOs. As they are also a rather interesting discussion in cosmology. The measurement of BAOs is what has led to our current cosmological crisis, where the CMB's measurements misalign with other data points in measuring the strength of dark energy.

As always, please feel free to comment your thoughts, including criticisms. Follow if you want to see more!

#physics friday #stem #academics #stemblr #science #physics #astronomy #astrophysics #cosmic microwave background

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oliviabutsmart · 5 months

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I am a total fan of ur posts. It's so informative.

Hope ur okay?

I ... don't really want to say. It's a lot and I don't know how ok it is to share it with my followers, who are still random people on the internet, interested in things that aren't this.

Thanks for asking though!

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oliviabutsmart · 5 months

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Physics Friday will (most likely) be cancelled for this week

Beecause my parents have escalated things ... a lot

#physics friday #this is a cry for help

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oliviabutsmart · 6 months

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Physics Friday #15 [DWQ]: Multiverse theories

Preamble: What is DWQ?

This is another mini-series that will be ongoing. Similar to opinion posts, there is another type of post that I want to explore.

DWQ - Dealing with Quacks (alternatively, Crackpots or Nuts)

Both crackpots and quacks are unified by what they do. They propose there is something "fundamentally wrong with physics" and that they have this new theory that will change everything.

Their theory is about some fundamental truth with the universe. That the "physics establishment" is constantly attempting to chase ridiculous theories because they don't want to accept reality.

A crackpot is someone who generally has expertise in physics, or a related field like chemistry or engineering. Often they are motivated by a desire for fame.

A quack is someone who has no experience in the field, often with a monetary interest in what they are selling.

"Nuts", which is short for "religious nuts" are those who promote their ideas out of faith and a desire to spread their beliefs. They are more likely to strawman existing ideas first.

I hope that you, the reader, can already understand why I don't like these people. They muddy the waters, mess around with science communication, and give the profession a bad rep. They also lie and pedal disinformation, which ends up acting as a gateway to more serious conspiracy theories within the medical or political realm.

It's also important to identify that this acts on a scale. Technically, some string theorists are a lite form of crackpot - particularly in the way they present their theories and ideas to the public.

But they are significantly more respectable than a flat-earther, or a self-help guru, or a evangelical apologist.

The Multitude of Multiverse theories, or the MultiMultiverse

Multiverse theor(ies) are usually strawmans made by religious fanatics. Think PragerU as a great example.

The argument goes like this:

Scientists have no empirical explanation for fine tuning or the reason for the existence of the universe

In order to explain it, they constructed multiverse theory to explain the source of it

By occam's razor, the simpler argument is the existence of a creator entity, that fine-tuned things for us

Of course you can see how bad the arguments are. The problem is of course that science hasn't accepted any multiverse theory.

Multiverse theories are neat explanations or consequences of other theories, but they are either limited in their explanatory power, or their efficacy to test.

But what are the multiple multiverse theories? Here's three that people claim are multiverse theories:

Many worlds interpretation (a QM thing, and only a multiverse theory in pop culture)

Inflation multiverse theory (one possible consequence of the cosmic inflation hypothesis)

Just an actual multiverse theory (arguable cosmic inflation can lie here)

Many Worlds Interpretation

I've already run through the main gambit of what the Everett interpretation is, so I'm going to tackle this from a pop sci perspective.

When you were younger, you might've heard that the many worlds interpretation literally means many worlds. That with every decision you make, you create a new seperate branching reality. And that multiple realities can simultaneously exist.

Of course, there is an issue with this. Mainly that there aren't multiple realities - there is just one reality, in a superposition of states.

This superposition dictates there is one reality, just that this reality is probabilistic. These realties aren't separated by physical space. It's just one big 'wavefunction'.

Decisions in the many worlds interpretations are also examples of when pop sci goes wrong. It's not necessarily the religious nuts who cause this misconception.

What causes more splits in the wave function is the interactions within it. When an electron collides with a positron, when a chemical in your brain goes from one end to the other. Interaction is what creates these splits.

Technically, decisions are caused by the interactions between electrical signals in our brain, and us making a decision often involves interacting with the world around us. This is how the misconception arises, but the reality is that the split occurs well before and well after a choice is made.

Of course, it's important to state that, the many worlds interpretation is still not the "correct" interpretation. What it posits hasn't been proven.

Inflation Multiverse theory

Inflation theory in itself is already a bit on the rocks in terms of an explanation of why our universe is the way it is. There isn't really any way we can use GR/the standard model to explain why inflation happened. At least, without having to add an extra field or constant in our equations.

Generally, inflation is explained using the addition of a new inflaton field, which in the higher temperatures of the early universe, caused a rapid expansion of spacetime.

This rapid expansion is generated by the field living in a heightened energy state.

At some point, the field reaches a sudden drop-off, at which point the expansion rate suddenly slows down to our expected GR level. The inflaton field then remains at a local minima.

Where does the Multiverse theory come into this?

The drop-off of the inflaton field is not universal. It only occurs at particular points in spacetime. This creates a 'bubble' of space that slowly expands in comparison to the surrounding ocean of space that is rapidly expanding.

We exist in one of these bubbles, which expands at a normal rate. But we aren't the only bubble.

There could be several bubbles surrounding us. All separated by physical space that expands at incredible rates. These bubbles create an effective multiverse.

It's not technically a multiverse because every bubble is still in one single physical universe.

Generally, this version of inflation multiverse theory is better accepted as it has inflation theory to back it up. But it's still not provable, so it's not regarded as truth.

The actual Multiverse theories

There are several multiverse theories. But the key thread linking the other multiverses, is that there is no physical way to traverse the space in-between worlds, and that each universe is seperate in beyond a physical capacity.

I can't go into many different multiverse theories, because the main point is that they're all either bullshit or thought experiments.

One example is the "temporal multiverse theory" which states that time is actually a 3-dimensional quantity, were our multiverses are caused by separations in time.

When you go back in time and alter the past, you end up in an alternate timeline future. This is a common way to interpret most time travel movies or scenarios.

Another is the "10-dimension" theory. There are 3 dimensions of space, 3 dimensions of time, and 3 dimensions of "universe". What is this universe dimension? Well it's effectively supposed to be an altering of the fundamental physical parameters.

The problem is that we don't think that the universe happens to perfectly have three degrees of freedom in it's construction.

The 10th dimension is usually unexplained in this theory.

So what was that fundamentalist strawman about?

There is an idea in physics called "quantum darwinism". This theory basically states that from the many worlds interpretation, there will be one probabilistic reality where human consciousness lives in. And thus that version of reality will be the one we see, as it was fit for human life.

This principle can be extended to various different versions of multiverse theory. That out of the many possible realities, we observe the reality that created the perfect conditions for human life.

This argument, that the universe was predisposed to observation, because it had to circularly, is called the anthropic principle. It can be said that it's an extension of the copernican principle.

And that's it. That's the strawman. Of course, this form of darwinism is not really an actual theory, more a thought experiment.

Conclusion

This post is slightly less long than the other ones but still a lot. Oops! Ruh roh!

Anyways, I hope y'all like this post with a different topic. They will be rarer because I want to take my time tackling these types of posts. Please lmk if you think this post was informative or if you'd like to see more!

Next week will probably be on Baryon Acoustic Oscillations. Follow if you wanna see more!

#physics friday #stem #stemblr #academics #science #physics #astronomy #astrophysics #many worlds #quantum mechanics #cosmic inflation #I was going to use hashtag “inflation” but I then I thought about it #multiverse theory

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oliviabutsmart · 6 months

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Physics Friday #14: Sound (Part 2/2)

Preamble: Let's get straight into it

Education Level: Primary School (Y5/6)

Topic: Sonic Physics (Mechanics)

The previous part 1 of my sound post is here.

Pitch and Frequency

Pitch and frequency are related to eachother, the only difference being that frequency is a physical interpretation of sound and pitch is our own mental interpretation of it.

But what exactly is frequency?

Go back to last time's example of a tick sound occurring at regular intervals ... because this sound is repeating, we can describe it's behaviour by measuring mathematical properites:

How much time passes in-between each tick (Period)

How many ticks occur every second (Frequency)

These two ideas are related to eachother, in fact Frequency is 1/Period. If you have a tick every half-second, then you can say the tick occurs twice every second.

We measure sound in Hertz, which is effectively a measure of ticks per second.

Most sounds, however, don't work this way, with repeated ticks. They act as proper waves. With zones of high pressure (peaks), and low pressure (troughs). This is where we have to introduce another variable into our equation:

The physical difference separating each peak (Wavelength)

Since these waves travel forward in the air, a detector (like our ears) will pick up the peaks and troughs as they reach our ear. We can measure frequency or period by recording the speed at which our peaks reach our ear.

But we also can relate frequency to wavelength. After all, the further apart the waves are separated, the more time it'll take for a peak to reach us after the previous one.

We quantify this relationship using c = fλ. Where c is the speed of the wave, f is the frequency, and λ is the wavelength.

Notice that we can also say cT = λ, where T is the period. This demonstrates that the physical wavelength is proportional to the amount of time between each peak.

So where does pitch come in?

As mentioned in part 1, if we continue to decrease the time between each tick, or increase the frequency, at some point we'll begin to hear a sound.

This is our brain playing a trick on us. It's like frames-per-second but for our ears. Below some fps threshold, we can see the individual pictures of a video, but above the threshold, it looks like a continuous film. Notice that fps is also another form of frequency.

When we reach this level, our brain can't distinguish between each tick and sees it as one sound. We begin to hear our first sound.

At this point, frequency becomes tied to pitch. The more rapid the ticking becomes, the higher of a pitch we hear. This is a choice that our brain makes - it's purely psychological.

Mixing different pitches

Combining different pitches allows us to create a foundation for music. In western music, our source of harmonics comes from Pythagoras, who kinda fucked it up by not using irrational numbers.

An octave is defined as a higher sound that has twice the frequency of the lower sound i.e. a ratio of 2:1. One octave above middle C (at about 262 Hz) gives us C5 (at about 524 Hz).

We can create further subdivisions like a perfect fifth, where frequencies form a 3:2 ratio. Or a perfect fourth, which has a ratio of 4:3.

Volume, Intensity, and the Inverse Square Law

Volume is directly related to the amplitude of a sound wave. Effectively, how strongly is the air being compressed at each peak?

Again, volume is just another psychological interpretation of a physical phenomena. Similar to how our eyes see brightness.

Amplitude isn't just interpreted as volume, it is also the power that the sound waves carry. Smaller amplitudes correspond to less energy contained within the moving particles.

We measure intensity logarithmically, because that's what our ears here. Effectively a wave sounds twice as loud only if the wave is 100 times as amplified. It's a similar effect to pitch, where we multiply frequencies instead of adding them.

That's where the decibel scale comes in. 1 dB = a 10x increase in the sound's power output. The decibel scale is used generally for a lot of measurements of wave/power intensity. However it just so happens that our ears behave in very similar ways.

Image credit: soundear.com

Notice that louder sounds are more likely to damage our ear. That's because when loud sounds reach our ear, it causes the inner components to vibrate. This vibration amplitude generally is proportional to the amplitude of the waves.

Too loud of a sound means that our eardrums are vibrating with too great of a physical movement. This can create tears in tissue that damage our ears' sensitivity to sound.

Sound looses power over distance

If you stand far away enough from a sound source, it sounds fainter, eventually becoming unhearable.

This is because of the inverse square law. As sound spreads out over distance, it has to emanate in the form of a sphere, going outward in every direction, in order to maintain consistency of direction.

The same amount of power gets spread thinner and thinner over the bubble that it creates. The surface area of a sphere increases to the square of it's radius.

Image Credit: Wikipedia

Thus we get a decrease in volume over time.

What the Actual Fuck is Timbre, and how do you pronounce it? (also Texture too)

Unfortunately I still don't know how to pronounce it.

Timbre is defined as the quality and the colour of the sound we hear. It also includes the texture of the sound. It's sort of the catch-all for every other phenomena of sound.

Timbre is a bit more complex of a phenomena. In that, it combines basically everything else we know about how we hear sound. So I'll go one by one and explain each component of what makes Timbre Timbre.

Interference

Wave interference is an important property that needs to be understood before we actually talk about timbre. Sound waves often can overlap eachother in physical space, normally caused by multiple sound sources being produced at different locations.

These sound sources often will create new shapes in their waveform, via interference.

Constructive interference is when the high-pressure zones of two sound waves combine to produce an even-higher-pressure zone of wave. Effectively pressure gradient add onto eachother.

Destructive interference is when a high-pressure zone overlaps with a low-pressure zone, causing the pressure to average out to baseline, or something close to the baseline.

Image Credit: Arbor Scientific (Youtube)

We can look at multiple waves acting continuously over a medium to see how their amplitudes will add up together using interference. This is the origin of more unique wave patterns.

The shape of a wave

Sound waves can come in different varieties. While the most basic shape is the sine wave. We can add different intensities, frequencies and phases of sine waves to produce more complex patterns.

I won't go into how this combination works because that's better left for a Fourier series topic. Just know that pretty much any sound can be broken down into a series of sine waves.

These patterns have a different texture, as they combine multiple different monotone sounds. Take a listen to a sawtooth wave vs a sine wave:

Warning: the sawtooth wave will sound a lot louder than the sine wave.

This gives us a different sound texture.

Resonance

When you play a musical instrument at a particular frequency, the instrument is often resonating.

Say you produce sound within an enclosed box. Producing it at one end. Eventually the sound will reach the end of the box and bounce back from reflection (as we'll see later).

The sound will bounce back and forth, combining itself with the previous waves to produce more and more complex waveforms.

But there is a particular frequency, at which, the waves will perfectly interfere with eachother to produce what's known as a standing wave.

A standing wave will oscillate, but it will appear as if it's not moving forward. Of course, power is still moving throughout the wave, as we'll still be able to hear something.

This standing wave can only occur at a particular frequency, one in which the wave perfectly interferes with it's reflection within the box.

A standing wave (black) that is produced by two sine waves (blue and red) moving in opposite directions Image source: Wikipedia

This frequency is called the resonant frequency of the box. This frequency depends on several factors like the speed of the wave, the material inside the box, the shape of the box, and the length of the box.

The resonant frequency can be activated by our voices, as our voices or just blowing air is already a combination of different sound frequencies. The non-resonant frequencies will eventually loose all of their power as they destructively interfere, leaving only the resonant frequency, which gets amplified by what we put in

For example, you can fill a glass bottle halfway with some water, blow in it, and it will produce a particular sound. Fill it with more water, and the pitch increases - i.e. by adding the water we increase the resonant frequency.

All instruments have one or more resonant frequencies based on their material and shape (I say multiple because some instruments can me modelled as multiple boxes. Like a violin will have the inside of the wood, the wood itself, the strings, etc.).

Instruments also allow us to alter the resonant frequency by playing it differently (like putting a finger over your recorder's hole (phrasing)).

These differences in how we obtain resonance can also affect the quality of the sound.

Overtones

Resonance is not just generated with a single resonant frequency, we can create resonance with higher multiples of the the same fundamental frequency.

This is because in our box model, multiplying the fundamental frequency will allow us to create a standing wave, just with a shorter wavelength:

The A's stand for antinodes, which vibrate in the standing wave with the maximum amplitude. The N's stand for nodes, which do not move at all.

Image Credit: Macquarie University

Direct multiples of the fundamental frequency are called harmonics. Instruments can also produce other frequencies not directly harmonic depending on the structure of the 'box' they utilise.

These additional frequencies, ones which come often in fractional multiples of the fundamental are called partials. Both partials and harmonics represent the overtones of an instrument.

Overtones are what give sound additional character, as they allow instruments to not just resonate at the note they play, but at other combined frequencies. In some instruments, the overtones dominate over the fundamental - creating instruments that can play at much higher pitches.

Envelopes and Beats

Say we add two sine waves together (red and blue), each with slightly different frequencies, what we get is this:

Image Credit: HyperPhysics Concepts

We can see that the brown wave has a singular oscillation frequency, but also it's amplitude continuously scales with reference to this hidden envelope frequency, called the beat frequency (dotted line).

This difference between the actual wave's real frequency and the wave's overall frequency envelope. Is another source of timbre.

Notes, and the way we play them will often generate unique and different envelopes depending on how they are played. For example a staccato quarter-note will have a different envelope to a softly played quarter-note.

Other properties of Sound

Reflection

Different mediums mean different speeds of sounds e.g. molecules in wood (solid) are harder to move than molecules in air (gas).

These different speeds create several effects. Including the reflection of waves. Often waves require a bit of power in order to physically overcome the resistances to vibration of a particular medium.

Often this leads to sound waves bouncing back off harder-to-traverse surfaces.

Say that a sound wave travels through the air and reaches a wooden wall. The atoms vibrating in the air will hit against the wooden wall, transferring only some of their energy to the resistant wood.

The wood atoms on the border of the wall will bounce back, as expected. But this time they will transfer energy back into the air at a much greater magnitude due to newton's third law.

Thus while some of the sound wave ends up going deeper into the wood, the wood will push back and cause the air to vibrate in the opposite direction, creating a reflected wave.

Image credit: Penn State

We characterise the amount of power being reflected versus transmitted versus absorbed using portions:

A + R + T = 1

A = Power absorbed into the material (e.g. warms up the material)

R = Power reflected back

T = Power transmitted into the new medium

This is both an explainer as to why rooms are both very good, and very bad at keeping sound inside them. It really depends on the rigidity and shape of the material they are bordered by.

Refraction

Just like light, sound waves can also refract. Refraction is actually a lot simpler to understand once you already realise that waves will both reflect and transmit across medium changes.

Refraction is just combining the results of incomplete reflection (i.e. transmission) with some angle.

I won't go into refraction in too much detail, as it's worth a different topic. But effectively we experience snell's law but modified for sound.

Diffraction

Sound waves, like all waves propagate spherically (or circularly in 2D).

When travelling around corners, sound can often appear louder than if you were further away, looking at the source more directly.

This is because spherical waves will often 'curve' around corners. This is better described by light diffraction. Which is something for another time.

Conclusion

In conclusion, that's how sound works, mostly. This is a topic that is a little less closer to my expertise. Mainly because it delves into more musically-inclined phenomena that I am less familiar with. But I'm sure I did a good job.

Unfortunately, it seems like the plague of the long post is not yet over. Perhaps I need to get into a lot more specific topics to make things better for me and you (the reader).

Anyways, my exams are done. I am done. I do not have to do school anymore. Until I remember to have to get ready for my honours year (a.k.a. a mini-masters degree tacked on after your bachelor's degree).

Until next time, feel free to gib feedback. It's always appreciated. Follow if you wanna see this stuff weekly.

Cya next week where I will probably try another astronomy topic, or something like that.

#physics friday #stem #academics #stemblr #science #physics #sound #acoustics

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oliviabutsmart · 6 months

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Physics Friday will be delayed by a day again

Due to exam-related reasons.

Fortunately after this, I will be done with my semester!

#physics friday

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oliviabutsmart · 6 months

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Physics Friday #13: Sound (Part 1/2)

Preamble: Sound's kind of a big thing in town

Education Level: Primary School (Y5/6)

Topic: Sonic Physics (Mechanics)

Well, as the title suggests, sound is in fact a very big thing. We use our ears every day, to hear and to listen. And we also make sounds ourselves with musical instruments and voices.

Because of this, there is a myriad of different fields of study that focus heavily on our relationship to sound:

Physics/Astronomy - What is sound?

Engineering/Biology/Sound En. - How do we produce, record, or listen to sound?

Music/Linguistics/Psychology - How do we interpret and use sound for artistic or functional purposes?

All of these fields often need to work with eachother and mix their different purposes of analysis for the betterment of the academic medium. For example, a sound engineer still needs to know what sound is in order to record it. A music theorist still needs to know the structure of their sound-producing devices. etc.

But what we'll mainly focus on is the physics. And briefly touch on it's interaction with the rest of the academic sphere.

So, what is sound?

Sound is a longitudinal mechanical wave.

...

Well that's not very helpful. What is a wave and what does it mean to be mechanical?

A wave is simply some sort of periodic oscillation. It can constitute oscillating particles, mathematical objects, fields, or jumps.

Any form of motion that involves periodic motion or oscillation can be described by, or be related to, a wave, including:

Oscillations in electromagnetic fields

Air particles shifting back and forth

You jumping up and down at a regular interval

A satellite orbiting our planet

Vibrations in solid atoms

A mathematical function that repeats itself regularly

That's very general. So we often classify different types of waves based on what produces them (the generator), what they constitute (the medium), and what makes them move (the propagator).

Were, we come to the classification of the mechanical part of our wave. A mechanical wave requires a few things:

It is produced and propagated by the physical movement or vibration of matter

It is constituted of physical matter

This is how we derive the term mechanical. In physics, mechanical motion simply means something is physically pushing/pulling on you. Gravity is not mechanical but friction is.

But that's not the full picture. Because mechanical waves are a broad category of waves. Often we just generalise and call them all sound, but we can also subdivide our category.

Here's a list of other mechanical waves:

Earthquakes

Explosion blasts

Sound (well it does have to be on this list)

Water waves/ripples

String waves (like jump ropes)

Jumping up and down at a regular interval (stop doing that I can hear it from downstairs)

So what makes sound different? Well, it's not really much. In fact all of these could be reasonably called sound. What makes sound sound, is a matter of perception.

Light is an electromagnetic wave. But for a more pedantic person, electromagnetic waves aren't light. Technically, EM waves outside of what colours we can see aren't light - they're infrared or ultraviolet.

The same distinction goes for sound in a sense. Sound to us is just the mechanical waves we can hear. Or that creatures on earth can hear.

Another distinction we make with waves is how they oscillate. Because the way the particles in these waves move matter greatly.

We distinguish between longnitudinal and transverse.

Image credit: BJYU's

A longitudinal wave involves the particles inside it are moving back and forth - in the same direction the wave is moving.

A transverse wave is where these oscillations are perpendicular.

Both these wave methods are able to travel by physically moving the particles, but often through different means.

Transverse mechanical waves often require that their medium have some sort of tension that allows us to pull particles up and down. Like water or string.

Whereas longitudinal waves require pressure or spring-like forces to resist and react to squeezing and stretching. Like springs or fluids.

Often, when drawing sound waves, we draw it as transverse. And that's because both forms of waves can be mathematically be represented by the other. The 'height' of our transverse sound wave corresponds to the compression of the wave at that point.

Image credit: TEL Gurus

Now. We have a good definition of sound.

How do we produce it?

This is actually a very simple question. We just create the oscillatory motion ourselves. All we do is push the air around us back and forth regularly.

Via our voice

Our vocal folds are made of tiny flaps. When air is forced through them, they vibrate at a rapid pace.

These vibrations from our vocal chords travel turn into sound that travels through the fast-rushing air, and exits our mouths/noses using said air to create sound.

Via resonant chambers

Fast-travelling air doesn't necessarily need to be voiced for it to produce sound. Often we can make this sound by blowing in a chamber or box. Sometimes even connected to artificial vocal folds.

These work by cutting out certain pitches and vibrational modes of sound by either artificially producing new ones or forcing some to be 'resonated out'.

This is how most wind and brass instruments work. By both controlling airflow and producing artificial vibrations, we can effectively create our own version of our voice - producing sound!

Plucking, strumming, and striking

String and percussion instruments on a basic level involve artificially creating a sound wave by plucking/pounding their strings/skin.

These plucks travel up and down the instrument. As they travel, their shape alters and spreads out creating a myriad of vibrations. Which in a split-second devolve into only the resonant modes. Thus producing sound.

In pianos, this plucking occurs every time you press a key. With guitars it occurs manually. And with instruments like drums, striking has the same effect as plucking. You're just pushing instead of pulling.

When strumming a guitar, you're effectively doing this many times over by stroking the instrument to stoke a sound.

Violins operate by utilising friction. The force of moving the stick against the strings create small vibrations that allow us to produce a continuous sound.

Digitally

Sound produced by speakers are often made by all of the sound-producing methods above.

But what's more interesting is how you can produce sound artificially.

You can start doing this by waving your arms. Your movement causes vibrations in the air. And the faster the arms wave, the stronger these pressure differentials become. Eventually increasing the amplitude.

But in order to produce real sound, you need to do it at a really fast pace. So you should probably stop waving you're arms. You're embarrassing yourself in the McDonalds you're reading this in.

We can do this using the power of computation.

Say we have a small 'tick' sound, or a digital 'pluck', produced at a regular interval. Say, once every second. Let's increase this rate. More and more. Until we're producing it 262 times a second. This won't sound like a series of fast ticks. In fact, it will sound like an actual sound, the middle C note.

Unfortunately, that's the end of Part 1

I think it's better to try and end things here before continuing on. Why? Well I just think these posts are a bit too long. And at the same time I have exams coming up next week. So I'd rather focus on that first.

The topics I'll be covering next time will be:

Pitch and Frequency

Volume, intensity, and the inverse square law

What the actual fuck is Timbre/Tambre/Tombré (and how do you pronounce it)

How we hear sound

Resonance

Other wave like properties: Reflection, Refraction, and Propagation

After I complete this little sound topic, I want to utilise it in an actual astronomical example with Baryon Acoustic Oscillations (BAOs). So you can look forward to that too in the future as well.

Again with everything, please give feedback, comments, or anything else. But like, don't just say something that is clearly not useful like "you suck!" - like great, thanks for the heads up I already know dummy.

Don't forget to like and subscribe gamers. Just to be sure I want you to smash that like button again, and then smash it one third time for good luck.

Another important message:

Please please help me with this colour inversion issue it's making like all colours on tumblr text posts difficult to read. Is this like a global change on tumblr? Can someone help meee

The reference post is here:

#physics friday #stem #academics #stemblr #science #physics #sound

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oliviabutsmart · 6 months

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Hello,

I wantwd to thank you for teaxhing me an inspiring a at least 4 hour dicussion and research session between me and my friend regarding quantum mechanics. I had a very fun night. He just had his first class on this topic and i did my best translating and trying to understand this stuff and your post helped sooo much. Also this looks like you put in a lot of work, energy and time. Thank you for helping me and my friend with this. Also translating a topic i barely know from a second language has proven to be a useful exercise in contextual understanding. I appreciate the effort it has to take to make these posts. I wish i could help with the color issue, but the colors help at least me.

Well I'm really glad you had a fun discussion! You can really get in-depth with that aspect of quantum mechanics and the benefit is - is that it actually will end up in your university exams.

It must've been a little hard to translate, given I make plenty of grammatical errors and can have a bit of difficultly tackling the subject at a lower level.

I actually could talk about colour charge and quantum chromodynamics ... probably in a future post, maybe you'll find that helpful at some point in the future.

#physics friday #physics

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oliviabutsmart · 6 months

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Physics Friday #12: Interpreting Quantum Mechanics

Preamble: "God does not play dice"

Education Level: High School (Y9/10)

Topic: Quantum Mechanics (Physics)

Developing the Schrödinger Equation

Quantum mechanics had it's origin in the nature of light, and then over the course of 50 years from 1900 - 1950, the entire field of physics was overturned as we realised that waves weren't just limited to light, but everything.

This came to it's head in 1926 with the creation of the Schrödinger wave equation, which dictated how particle 'waves' evolve in time and space.

Now you've probably heard of the wavefunction. Effectively, it's a probability wave, where the amplitude of the wave corresponds to the most likely location you'd find the particle.

The wavefunction doesn't just involve a probability distribution in space, but also in other quantities.

For example, if you put an electron in a small box, you can imbue it with an energy.

But because of quantum mechanics, energy is quantised - there is an energy of X joules, 2X joules, 3X joules, etc. If you put an electron of 2.5X into the system it can't just work like that.

Which is why the electron forms a weighted combination of different states corresponding to specific multiples of our X value. And this superposition just so happens to be the average energy, which is considered the classical energy of the electron.

For example an electron with a superposition of 2X, 50% of the time, and being in state 3X 50% of the time. This averages out to 2.5X.

Collapsing the Wavefunction

But how do you find a particle? Or measure it's energy? Well, via what's known as the wavefunction collapse. When we take a look at the particle as a wave, it suddenly snaps to a specific value and then evolves from there.

This wavefunction collapse can occur for any observable property of the particle. If you measure the energy of our 2.5X particle in our above state, it's a 50/50 chance that you'll catch it in either state.

And once the coin flip occurs, the particle's energy will suddenly jump to 3X or 2X and remain at that value.

You may think this violates the conservation of energy, but remember that the act of 'measurement' intrinsically involves interacting with the electron - a very important point.

But wait, what does this collapse mean?

The Schrödinger equation does not explicitly mention this collapse. It simply describes the evolution of an undisturbed wavefunction. Thus, we need to include collapse as a part of the three postulates of QM:

Particle states are described by a wavefunction, a vector belonging to a Hilbert space

The Schrödinger equation dictates the time evolution of these states

Measurement of an observable (i.e. a hermitian operator) collapses the wavefunction to an observable's eigenstate (each eigenstate being associated with a probability of collapse)

But this still doesn't really answer the question. What is measurement? What counts as measuring an observable property of the particle?

Well here's the thing ... we don't have an answer ... it's an open question and the topic of this post.

The interpretations

An interpretation of quantum mechanics is effectively a theory that aims to answer this question: where and how does this measurement occur?

After almost a century since the formulation of standard QM, we have a litany of many interpretations, most of which fall on a spectrum of when exactly it occurs.

On one end, we have ideas where the wavefunction never existed in the first place, or that the wavefunction naturally collapses.

On the other, we have ideas that the wavefunction collapses at a point very far in the process, or even that it never collapses at all.

I'll talk about 6 of these interpretations, although some of these theories of collapse are more categories of theories.

Think of the Ocean (Pilot Wave)

In the 1920s, de Broglie developed an interpretation of quantum mechanics that posited that subatomic particles do, in fact, physically exist.

The source of the wavefunction and the probabilistic nature of quantum mechanics is caused by the particles being guided by a series of "pilot waves" - which push and move the particles around and imbue them with the motion and energy we observe.

The randomness comes from the fact that the waves themselves depend on the positions of all particles. These guiding waves are dictated by a special guiding equation.

dear lord that's complicated Image Credit: Wikipedia

This guiding equation, when applied to particles just so happen to result in our neat and clean Schrödinger equaiton.

So what happened to this theory?

The biggest problem with this theory is that it's non-local, meaning that the evolution of the guiding wave requires knowledge of all of the particles in the universe.

This of course, violates special relativity.

Another problem is that it lost the authors' support, or that the authors lost support. de Broglie rejected the theory in 1927 and David Bohm, the other author, was distanced from the other scientists for being outwardly socialist during the early red scares.

Pilot wave theory, in a sense, is so strict on the physicality of particles that it ends up sort-of wrapping around and becoming a many-worlds theory instead, to quote David Deustch:

Pilot-wave theories are parallel-universe theories in a state of chronic denial.

This arises from the problem of branching, a tacked-on attempt to reconcile the nature of the theory. That since the wavefunction was a physical thing, and the pilot wave and particles kept self-interacting, it sort of creates branching realities caused by distant communication with other particles.

Those silly numbers are hiding from us! (Hidden Variables)

The EPR (Einstein-Podolski-Rosen) paradox is another famous problem in QM, caused by entanglement.

Take two electrons and force them to collide with eachother, bounce off, and travel far into the distance. We know that after the interaction, these electrons propagate with free-particle wavefunctions. And we can fire them at eachother such that we don't know their momentums initially - i.e. they entangled.

Now wait for the electrons to travel very far away from eachother, and then measure one of the electrons momenta. In order to maintain conservation of energy, we instantly know what the momenta of the other electron is.

What we also know is that because of this measurement, and that the electron is entangled with the other, that we have just collapsed the other wavefunction instantaneously from a distance.

This is a problem, due to special relativity, we cannot transfer information faster than the speed of light. So clearly our QM is broken.

Hidden variable theories aim to solve the EPR paradox as well as just generally trying to interpret quantum mechanics. Effectively, there are a series of unobservable entities that dictate how wavefunctions collapse.

The wavefunction in the EPR paradox has a hidden variable stating the electrons' momenta so that we aren't violating causality, for example.

Fortunately, but unfortunately, this theory makes a testable prediction via Bell's theorem, which utilises entanglement to determine if these hidden variables work locally.

The experiments conducted show that only a non-local hidden variable theory is possible. One example of this just so happens to be our previous pilot-wave theory!

Observing isn't needed (Spontaneous Collapse)

We could be thinking of this wrong. Perhaps the wavefunction is real, and it is non-deterministic. But that at some point, it collapses on it's own.

There are several ways to do this, but at it's core, these are how the theories go:

There is an extra non-linear term in the Schrödinger equation, that is insignificant at the small scales

This non-linearity causes the wavefunction to be unstable, and prefers it to collapse to observable eigenvalues

With increasing complexity, this term becomes much more important, as more entanglement = more instability

The rate of decay increases as you entangle the system. And if a system is large enough, it's likely to collapse into a classical environment

Effectively, they say that the wavefunction will collapse on their own. And the reason we don't see it on larger scales, or see a collapse when measuring the system, is that the act of interaction (entanglement) causes the wavefunction to be more likely to collapse.

Of course, the theory has trouble reconciling with relativity. As entanglement works over large distances. Models can be made to try and say that entanglement over these distances increases instability for example, but we're still waiting on developments.

Lastly, we have the problem of tails. The wavefunction of a particle exists for all of physical space. At these far out distances, it is very possible for particles to get entangled with distant objects. Meaning that a wavefunction may end up collapsing further than we think.

The easy way out (Copenhagen)

The Copenhagen interpretation was developed in the 20s to attempt to come up with some placeholder answer to what collapse is. It is our middle-of-the-road theory which states that observation of an observable causes collapse.

Observation is defined as the act of applying an observable operator (like the energy operator) to the wavefunction by an external source to gain information on that operator's outcome.

The problem is that this is a meaningless statement. Because anytime a system entangles itself with something greater, it technically does this 'observation'.

Take the double split experiment.

Image Credit: Discovery Channel

What defines the moment of observation? Is it when:

The particles interact with the measuring laser

The measuring laser interacts with the larger observation device

An electronic signal is sent from the device to a computer

The light from the computer interacts with the conscious observer

We can't pinpoint the specific cut-off between the quantum world and the classical.

After all, we know that lasers can entangle themselves with atoms. And that electronic signals are nothing but moving electrons.

The point of the theory is that it's a placeholder. The definitions are ill-defined because we're kinda waiting for another theory to help us.

It's all in your head! (Consciousness)

The immediate answer to the Copenhagen interpretation could be that the collapse occurs at the end of the specified chain. When a conscious observer interacts with the entangled system.

It's a nice idea given that it kills two birds with one stone - it helps point to a physical theory on the nature of sentience, but also allows us to solve the measurement problem.

This does come into conflict with our current understanding of sentience. Our placeholder theorem is effectively that conscious experience is an emergent property of a series of interacting electrical signals in our brain.

This placeholder helps explain why humans are more 'sentient' than animals, or very young children, as we have a very active and complex central nervous system.

Of course, it's just a placeholder. We don't have an actual meaningful answer to sentience, and probably won't for a while. So for now it's left to the dark realm of god of the gaps.

Where it comes into conflict with QM is that a series of interacting electrical signals sounds exactly like an entangled system. So there clearly can't be just emergent properties involved otherwise we're just dealing with a spontaneous collapse theory.

There has to be something physically unique about a sentient brain to cause the collapse - effectively you require the existence of a soul. Something which is even further in the dark realms of philosophy.

Another issue is that it doesn't work with special relativity, as it violates the EPR paradox still.

We also need to determine what counts as sentient. Sentience isn't an on and off switch. There are many ways it can be expressed.

We know that some mammals have some form of conscious experience - so then are cats capable of collapsing the wavefunction?

Finally, what about the universe prior to consciousness? Did it just end up in an entangled nightmare until somehow we got an observer to collapse it all? How can something built of entangled particles end up collapsing itself at some given size?

This interpretation is very interesting, however if it turns out to be true, we'll be stuck with our measurement problem for quite a while.

For now, the biggest problem with the interpretation is that it opens the door to many, many quacks like Deepak Chopra. Who think that we can control this collapse with our minds and alter our reality by just thinking it away WoOOoOoWwowoWoOo!

Forever entangled (Many Worlds)

So, assuming that our consciousness theory is not the right answer, then what causes the collapse?

We can keep getting bigger and bigger:

The electrons in the double slit entangles with the laser photons entangles with the measurement device entangles with the electrical signals entangles with the computer entangles with the observer entangles with the room their in entangles with the Earth entangles with the solar system entangles with the galaxy ...

This out-spiralling entanglement continues without bound until the entire universe is in a superposition of states. And every time an interaction occurs we ourselves are being pulled into a new wavefunction.

This entanglement would've happened early, at about the time of cosmic inflation. But every new quantum event comes with a new set of entanglements.

This leads to the name Many Worlds, as we're creating new realities with every event.

Now it's important to note something important: this is not a multiverse theory. Multiverse theory is proposed source for cosmic inflation. Here, there is still one single universe. Much like how an electron in superposition isn't multiple actual electrons. The universe is just being treated as an electron.

This theory sounds far-fetched. Arguably the fact that it's unfalsifiable makes it not a good interpretation of QM. However, it is a lot simpler than the previous consciousness interpretation - it simply removes the need for a measurement process.

This satisfies Occam's razor as well. It doesn't require a mathematical formalism because the point of the theory is that the formalism doesn't exist.

However, not having a formalism makes it quite difficult to prove. It only seems to be correct in the sense that it doesn't necessarily say that measurement cannot happen, just that it's not measurement. It's entanglement.

Conclusion

Interestingly, the theories on the "wavefunction collapses early" side of the spectrum are more likely to be disproven. Primarily a consequence of the fact that they have the opportunity of making testable predictions.

Despite all of these interpretations, it's clear who stands as the best theories: spontaneous collapse and many worlds. They have their strengths, but they have fair grounding. You could argue that consciousness is also a fair contender, but it's a bit too much in the realm of fantasy - attempting to tie one big unanswered question with another.

Spontaneous collapse has proper mathematical formalism while many worlds seems to work well in an Occam's razor sense.

Regardless, that is a surface-level exploration into the many different ways we have attempted to answer the measurement problem. I hope y'all enjoyed this post and god I need to make them less long.

Please can someone fix this inverted colours issue it's like causing all of my colours on these posts to invert too thx

Reference post: https://www.tumblr.com/oliviabutsmart/732200630726377472/for-some-reason-some-reasons-only-some-images-i

Anyways, feedback appreciated, follow if want, send memes and send help.

#physics friday #stem #academics #stemblr #science #physics #quantum physics #quantum mechanics

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