can we?
Can we really touch something?
So like, can I 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.
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.