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  • One of the most amazing things about atoms

  • is that they're mainly empty space.

  • If an atom were as wide as your arm span,

  • then the electrons would all be whizzing about inside the volume enclosed by your fingertips,

  • meanwhile the nucleus would be sitting in the center,

  • and its diameter would be smaller than the width of a single human hair...

  • So all of the atoms that make up you and me

  • and all the seemingly solid things in the universe

  • are mostly empty space.

  • Now, this is incredible.

  • But what is even more mind-boggling is that empty space is not truly empty...

  • I know because I've seen it.

  • This is a simulation by Prof. Derek Leinweber at the University of Adelaide.

  • It was made using a supercomputer to crunch the calculations of Quantum Chromo-Dynamics.

  • Now that is the theory of fundamental particles called 'quarks',

  • the building blocks of protons and neutrons,

  • and how they interact with each other through 'gluons'.

  • What you're looking at here is the energy density of the gluon field fluctuations.

  • Where('s) the little red spots come out, the energy density is very high...

  • and it fades down through the colors.

  • So, in the lowest energy, the field fluctuations are not rendering in this animation

  • so we can actually see into it.

  • And what we see is a bubbling soup of quantum field fluctuations,

  • that come and go incredibly quickly.

  • The frame rate of this simulation is one million billion billion frames per second.

  • Now that is truly high speed...

  • The dimensions of this box are absolutely tiny.

  • They are millionth of a billionth of a meter.

  • roughly enough space to stick two protons.

  • But there are no protons here...

  • This is a simulation of the vacuum on its own,

  • what we normally think of as 'empty space'.

  • Empty space is actually full of this quark-and-gluon field fluctuations.

  • And, on average, it is possible to annihilate a quark from empty space, 'cause it's not empty...!

  • That just sounds like the most ridiculous idea that ...

  • you're meant to have empty space, and yet you can go and get rid of stuff from it...

  • That's right. So it isn't empty !

  • Now it seems counterintuitive that the vacuum at its lowest energy state should contain all of this stuff.

  • But, in fact, to clear out the fluctuations

  • and create a truly empty vacuum would require a lot of energy.

  • The empty vacuum actually costs an enormous amount of energy to create,

  • and if you were able to create it,

  • you'd discover that that ... is actually unstable... that

  • any sort of perturbation would push that empty vacuum

  • into something where the vacuum is actually full of quantum field fluctuations.

  • Well, this may not be as strange as it first appears...

  • I mean, consider a permanent magnet.

  • It has a magnetic field around it at low energy, at room temperature.

  • Not because the individual little magnetic moments

  • of all the atoms inside are lined up.

  • But if you were to heat it up,

  • you would give thermal energy to all those particles.

  • And at a certain point, called the Curie Temperature,

  • they would be so randomly aligned

  • that there would no longer be an overall magnetic field.

  • So it actually takes energy to get rid of the permanent magnetic field.

  • Hmm, this is just like the quantum vacuum.

  • And undertanding how the quantum vacuum fluctuations work

  • gives us a sense of what the fundamental particles do,

  • like 'where are you most likely to find a quark?'

  • And it turns out that the quark likes to sit on top of those lumps.

  • Now those lumps come into and out of existence fairly quickly and so ...

  • we like to think of the quarks as hopping from one lump over to the next lump, as it appears,

  • and then on to another one.

  • I like to think of it as a hiker trying to cross a stream that's running around...

  • Every now and then a stone pops up because the water swirled around it.

  • So you put your foot there... You're looking for the next spot...

  • If you go quickly enough, you might not get your feet wet...

  • Uh, so I think quarks are very much do... well we know quarks are very much doing the same thing.

  • So while it is true that you and I and all of the other atoms in the universe are mostly empty space,

  • it is also true that empty space isn't truly empty...

  • And in fact it is these vacuum fluctuations which are essential for our existence.

One of the most amazing things about atoms

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B2 empty empty space vacuum quark energy space

Empty Space is NOT Empty

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    林宜悉 posted on 2020/03/28
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