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One of the most amazing things about atoms
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is that they're mainly empty space.
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If an atom were as wide as your arm span,
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then the electrons would all be whizzing about inside the volume enclosed by your fingertips,
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meanwhile the nucleus would be sitting in the center,
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and its diameter would be smaller than the width of a single human hair...
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So all of the atoms that make up you and me
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and all the seemingly solid things in the universe
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are mostly empty space.
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Now, this is incredible.
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But what is even more mind-boggling is that empty space is not truly empty...
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I know because I've seen it.
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This is a simulation by Prof. Derek Leinweber at the University of Adelaide.
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It was made using a supercomputer to crunch the calculations of Quantum Chromo-Dynamics.
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Now that is the theory of fundamental particles called 'quarks',
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the building blocks of protons and neutrons,
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and how they interact with each other through 'gluons'.
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What you're looking at here is the energy density of the gluon field fluctuations.
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Where('s) the little red spots come out, the energy density is very high...
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and it fades down through the colors.
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So, in the lowest energy, the field fluctuations are not rendering in this animation
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so we can actually see into it.
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And what we see is a bubbling soup of quantum field fluctuations,
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that come and go incredibly quickly.
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The frame rate of this simulation is one million billion billion frames per second.
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Now that is truly high speed...
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The dimensions of this box are absolutely tiny.
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They are millionth of a billionth of a meter.
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roughly enough space to stick two protons.
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But there are no protons here...
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This is a simulation of the vacuum on its own,
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what we normally think of as 'empty space'.
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Empty space is actually full of this quark-and-gluon field fluctuations.
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And, on average, it is possible to annihilate a quark from empty space, 'cause it's not empty...!
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That just sounds like the most ridiculous idea that ...
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you're meant to have empty space, and yet you can go and get rid of stuff from it...
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That's right. So it isn't empty !
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Now it seems counterintuitive that the vacuum at its lowest energy state should contain all of this stuff.
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But, in fact, to clear out the fluctuations
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and create a truly empty vacuum would require a lot of energy.
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The empty vacuum actually costs an enormous amount of energy to create,
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and if you were able to create it,
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you'd discover that that ... is actually unstable... that
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any sort of perturbation would push that empty vacuum
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into something where the vacuum is actually full of quantum field fluctuations.
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Well, this may not be as strange as it first appears...
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I mean, consider a permanent magnet.
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It has a magnetic field around it at low energy, at room temperature.
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Not because the individual little magnetic moments
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of all the atoms inside are lined up.
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But if you were to heat it up,
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you would give thermal energy to all those particles.
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And at a certain point, called the Curie Temperature,
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they would be so randomly aligned
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that there would no longer be an overall magnetic field.
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So it actually takes energy to get rid of the permanent magnetic field.
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Hmm, this is just like the quantum vacuum.
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And undertanding how the quantum vacuum fluctuations work
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gives us a sense of what the fundamental particles do,
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like 'where are you most likely to find a quark?'
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And it turns out that the quark likes to sit on top of those lumps.
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Now those lumps come into and out of existence fairly quickly and so ...
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we like to think of the quarks as hopping from one lump over to the next lump, as it appears,
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and then on to another one.
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I like to think of it as a hiker trying to cross a stream that's running around...
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Every now and then a stone pops up because the water swirled around it.
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So you put your foot there... You're looking for the next spot...
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If you go quickly enough, you might not get your feet wet...
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Uh, so I think quarks are very much do... well we know quarks are very much doing the same thing.
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So while it is true that you and I and all of the other atoms in the universe are mostly empty space,
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it is also true that empty space isn't truly empty...
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And in fact it is these vacuum fluctuations which are essential for our existence.