Can We Really Touch Anything?

[Applause]

Can we, can we really touch something? So, I can touch the camera. The question of, can we really touch something, is a great one. Well, let's say we have two electrons. I imagine what we mean by touching is that they come in and they actually physically touch. Now, one of the problems is an electron actually has zero size, as far as we can tell, no volume. So, these would be infinitely scaled up.

How do the electrons actually interact with each other? Well, they interact by exchanging a particle. In the case of the electrons, it's a photon that they exchange. So, as they come in, a photon is passed from one to the other, which changes the momentum of both of them and pushes them off. So, they never really have to touch in order to interact with each other, to exchange that particle and therefore change their momentum and change directions, experiencing a force.

So, I guess what do we mean by touching something? Every time we touch something, we are exchanging force-carrying particles with it, and that is touching. If photons are both quanta of light and the force carriers of the electromagnetic force, does that mean that photons propagate magnetic fields? And if so, why can't these photons be seen? That's because the photons are not real photons, they're virtual.

Now, this is a bit of a problematic topic, and one which I hope to address in detail in a coming episode. The basic idea with virtual particles is you can't detect them. They're particles that are there, but you cannot directly detect them, and they may not follow all of the laws that we force real particles to adhere to. For example, there's the Einstein energy-momentum relation, E = mc^2 + p^2c^2, and a virtual particle doesn't necessarily need to obey this equation.

So, you can't really detect it because if you did, it would have to be a real particle and then it can't disobey those equations like that. So, this is something that I will delve into in a future episode.

"Who are your top three most inspirational scientists?"

I'm going to take Einstein, Feynman, and Tesla.

"Who are your most inspirational scientists?"

Hey, Derek. I guess a question that's been on the minds of a lot of us for a while now is, who would win a chin-up competition between you and Henry from Minute Physics?

Now, I wish this was a hypothetical, but we actually did this on the tube in London, so roll the [Music] tape.

Well, [Music] keep going! Loser! That was nice. You're the champ! How are you feeling?

I thought it would be Henry. That guy is ripped!

So, at school, they say atoms want to have their outermost electron shells full and will willingly become ions in order to achieve that. Well, why? And why do the shells have the electron holding capacity of 2, 8, 18, and 32, and so on?

Specifically, let me deal with the electron shells first. See, if you accept that electrons are not only particles but also waves, then if they are waves bounded to a nucleus, that means that they must be standing waves. So, you may be used to standing waves on a string. They don't seem to move anywhere; they just wiggle back and forth. Or you can have standing waves in two dimensions on a plate.

What you notice is that these standing waves take on particular stable patterns. So, bound electrons are just standing waves in three dimensions, and the mathematical solutions are called the spherical harmonics because of the number of stable configurations you can have with growing amounts of angular momentum. There are different amounts of electrons that can fit into every state, and that goes with Pauli's Exclusion Principle, which says no two electrons can have the same state because they're fermions.

So, the whole point is what we're looking at is standing electron waves, and there are only certain of them which are stable, which are possible, which you can see in analogy to, say, vibrations in a plate.

So, why do atoms want the outer electron shell to be full? Well, this kind of minimizes the energy state of the whole system. So, let's say you had two atoms. If you actually remove the electron off one atom and stuck it in the other so that they both now had full shells, you would find that the total energy is now lower than it was before when the electrons were in their previous configurations.

So, the point is, it's just like a ball rolling down a hill; everything in nature wants to go to the lowest energy state.

"Why are the available frequencies of light continuous?"

I keep hearing that atoms absorb and emit photons of particular frequencies which correspond to the energy levels of their electrons. So, where do all the other colors come from?

Okay, it's true that atoms emit particular colors due to electrons jumping between certain allowed orbits around them. But we get different frequencies of light when these atoms bind up into molecules or even solids or when they form plasmas because then the charges are flying around all over the place. And in those cases, there are no longer these clearly defined energy levels for the electrons where they can jump and only produce certain distinct colors.

Then, they have whole bands of electron energy levels. So, we can get a real range of colors, so that's what we see from the Sun or from hot solids. So, that's why we get a continuous range of frequencies because the electron bands of energy allow virtually any transition.

"Derek, can I get a Veritasium shirt so I can look nearly as cool as you?"

It's funny you should mention that, Gray, because Veritasium actually now has a t-shirt. So, if you want to get one, you can click on this shirt. Go ahead, click on it or click on the link in the description.

For your viewers interested in pursuing a science career, what field do you think is going to be the most exciting in the coming centuries, and why?

Look, I can't say I know what fields of science are going to be important in the coming centuries, but at least in the coming decades, I would put my money on genetics. You know, if you think about the Human Genome Project, that took about ten years and a billion dollars to sequence one human genome. And within the next couple of years, you should be able to do it in a week for a hundred bucks.

So, the pace of growth is simply extraordinary in that field of science, and that's why if I were going into science now, I might select that kind of field.

"Have you ever downloaded a book from Audible.com?"

I have actually downloaded a book from Audible.com, and I was listening to it on my most recent trip, which was handy because I was on this plane that didn't have an entertainment system, and I was also listening to it in the airport. And I found it really a good way to pass the time.

So, if you're interested in downloading audiobooks, then you should probably try Audible.com. And I have a book to recommend to you; it is Richard Dawkins' book, The Selfish Gene. I read this a few years ago, and I found it really enlightening.

But I have a bit of a spoiler alert—uh, well, not really a spoiler, more of a clarification on the title. I mean, it sounds like a book about a gene for being selfish, but that's not what it's actually about. What it's about is the fact that genes themselves act in selfish ways.

And this I found a kind of enlightening revelation because if the genes are acting selfishly, then the organism can act altruistically, if you get what I mean. So, if you haven't read that book or listened to it, you should definitely check it out.

And if you want to download it for free, you can just go to Audible.com/Veritasium. You know, I really want to thank Audible.com for supporting me in this, my 500,000 subscriber video. It really means a lot to have their support so I can keep going and hopefully get another 500,000.

"One last question, Derek: I'd like to know, how, obeying the laws of physics, have you ever managed to put these jeans on?"