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  • We take it for granted that our universe contains planets, stars and galaxies

  • because those are the things we see but the only reason these big structures

  • exist is because of the nature of nothingness - empty space. But to

  • understand why we have to go back to the beginning. The very beginning. The big bang.

  • You know, I always thought that in the Big Bang the observable universe

  • started as a point and then just expanded steadily more or less to the

  • point that we're at today but that's not actually how it happened.

  • There were four different phases in the universe's expansion. To start it was expanding

  • steadily but then after just a tiny fraction of a second the expansion just

  • blew up and the whole universe increased in size by like ten to the twenty six

  • times in a very short period of time and that period is known as inflation and

  • then just as abruptly as it began inflation stopped and after that the

  • universe continued expanding but at a decreasing rate so the expansion of the

  • universe was actually slowing down which is exactly what you expect if the

  • universe is full of massive objects that gravitationally attract each other

  • but then about five or six billion years ago the expansion of the universe

  • started speeding up again and this is thought to be caused by dark energy,

  • an energy tied to space. So before that time there was enough matter, the matter

  • density was high enough, that it was pulling everything back together slowing

  • down the expansion but once the universe reached a critical size

  • well then there was enough dark energy to start pushing things apart and that

  • is the phase that we're still in the expansion of the universe is accelerating.

  • Now, this story doesn't really explain the formation of galaxies

  • until you tie in the nature of nothingness

  • now ordinarily we think of everything around us as made of particles of atoms

  • and electrons but our best theories of physics are actually field theories that

  • say all these particles should be seen as just excitations in fields.

  • The word "field" always gets me because it makes me think of... well, fields.

  • but a field is just something that has a value everywhere in space.

  • So every subatomic particle has its own field: an electron field, an up quark field,

  • a down quark field, a neutrino field, and so on...

  • And anywhere there's an excitation in this field

  • that is some energy in the field

  • well that is where we will observe particles. So out in completely empty

  • space where the values for all of these fields are basically zero.

  • but here's the thing

  • it's impossible to make a field perfectly flat and 0.

  • You cannot take a quantum field and make it completely quiet.

  • It's the Heisenberg uncertainty principle.

  • It says you can't take a particle and pinpoint it to exactly zero energy

  • likewise you can't take a quantum field and make it exactly flat everywhere.

  • Now, this is important because ordinarily these fluctuations are really really

  • tiny and they only affect subatomic processes but during that period of

  • inflation the universe expanded in size so rapidly and so incredibly that those

  • tiny fluctuations got blown up to the scale of the observable universe

  • Now, without them we think the matter distribution in the universe would have

  • been completely homogeneous completely uniform and that means the gravitational

  • force on any object in the universe would have been the same in all

  • directions which means nothing would ever have collapsed into the big

  • structures that we see today but thanks to these fluctuations there were

  • slightly denser and less dense regions and of course the denser regions had

  • stronger gravitational fields so they pulled in the matter from around them

  • and that clumped together the matter into huge gas clouds that would go on to be

  • the galaxies that contain the stars and the planets and the things we know today

  • you can actually see the imprint of these quantum fluctuations in the

  • leftover radiation from the Big Bang the cosmic microwave background radiation

  • the quantum fluctuations in the fields were amplified to big classical fluctuations

  • in the density of

  • matter from place to place and those fluctuations in the density of matter show up

  • in the universe today as temperature differences in the cosmic background

  • radiation and ultimately in things like stars and planets and galaxies

  • I think it is incredible that without these fluctuations in the vacuum these tiny

  • insignificant things that we take for granted our universe might really

  • contain nothing. Nothing of interest anyway...

  • Speaking of vacuum

  • this episode was supported in part by Dyson who sent me their 360 eye vacuuming robot

  • it's got this little camera on the top that can see 360 degrees around it now

  • it uses that vision plus some complex math and trigonometry to work out its

  • location precisely and to figure out where it's cleaned already and where it

  • still needs to clean it actually makes a map that you can see on your phone using

  • the dyson app and you can use that app also to control the vacuum or to

  • schedule it even when you're not at home so I for one welcome robots taking over

  • the housework you want to find out more you can click the link in the

  • description so i want to thank Dyson for supporting me and I want to thank my

  • patreon supporters and of course you for watching

We take it for granted that our universe contains planets, stars and galaxies

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B2 universe field expansion quantum big bang matter

Galaxies From Nothing

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    BH posted on 2016/10/06
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