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.

So how do the electrons actually interact with each other? Well they interact by exchanging

a particle. In the case of the electron 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,

experience a force. So I guess well 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? Well 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 are particles that are there but you cannot directly detect them.

And they may not obey all of the laws that we force real particles to adhere to. For

example there is the Einstein energy momentum relation E squared equals m naught c squared,

squared, plus p squared c squared. 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 you can't disobey those equations like that. So this is something

that I'll delve into in a future episode. Who are your top three most inspirational

scientists? I'm gonna 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 MinutePhysics?

Now I wish this was a hypothetical but we actually did this on the tube in London so

roll the tape. I thought it would be Henry - that guy is

ripped! So in school they say atoms want to have their

outer-most electron shells full, and will willingly become ions in order to achieve

that. Well, why? And why do the shells have the electron-holding capacities of 2,8,18,

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. And 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 which can

fit in every shell 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-most shell to be full? Well this kind of minimises the energy state of

the whole system, so let's say you had two atoms. if you actually removed 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. It's

that 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?

OK it's true that atoms emit particular colours 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's no longer these

clearly defined energy levels for the electrons where they can jump and only produce certain

distinct colours. Then there are 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, Grey,

because Veritasium actually now has a T-shirt. So if you want to get 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 every 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 audio books 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. Ah, 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 five hundred thousand subscriber video. It really means

a lot to have their support so I can keep going and hopefully get another five hundred

thousand.

One last question, Derek, I'd like to know how, obeying the laws of physics, you ever

managed to put these jeans on.