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Author Topic: Is Space Fractal  (Read 4098 times)

Offline Gimmehendrix

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Is Space Fractal
« on: 16/01/2015 08:59:21 »

NB All these question relate to the properties of space and not the stuff floating about in it eg. galaxies, old bikes etc.
Is space made of 'stuff' and is this a fractal given that space is expanding.
In order to expand ,does space need energy and if so where does this come from.
Could  space be a 'field' and if so would it have a related particle?  eg. the 'spaceon'
If space needs energy to expand what are the implications of this at the big bang. Was ,for example, energy first transfered to creating matter then to space to cause inflation.


 

Offline evan_au

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Re: Is Space Fractal
« Reply #1 on: 17/01/2015 09:47:56 »
Quote from: Gimmehendrix
Is space made of 'stuff'?

I would prefer to say that space contains 'stuff' (matter), rather than it is made of matter.

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is this 'stuff' a fractal?
I'm not sure what fractal would mean in this context. But one aspect of fractals is that the closer you look, the more you find.

In one sense, the same is true of space. Due to the Heisenberg uncertainty principle, if you look at very short timeframes or higher energies, you can find virtual particles present. If you look on even shorter timeframes, you can find more particles.

Unlike mathematical fractals,  real fractals have a limit on resolution. For example, a fractal coastline is no longer fractal when you get down to the scale of atoms. It has been suggested that there can't be events that occur faster than the Planck units of time (about 10-44s)and length (about 10-35 m).

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In order to expand, does space need energy and if so where does this come from?
Yes, it needs energy; the source is somewhat mysterious, so it is called "Dark Energy". There are various theories about where it comes from.

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Could  space be a 'field'?
I would prefer to say that 'space contains fields' (eg the electromagnetic field, the gravitational field, etc), rather than 'space is a field'.

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and if so would it have a related particle?  eg. the 'spaceon'
As space contains fields, it supports the particles relevant to each of these fields, eg the photon and (so-far hypothetical) graviton.

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If space needs energy to expand what are the implications of this at the big bang. Was ,for example, energy first transferred to creating matter then to space to cause inflation.
This is also somewhat mysterious. One of the early theories about this was called "Inflation".
 

Offline JohnDuffield

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Re: Is Space Fractal
« Reply #2 on: 17/01/2015 13:56:08 »
No, space is not fractal.

No, space is not made of stuff. Instead stuff is made of waves in space.

No, space does not need energy in order to expand, conservation of energy applies. A balloon in vacuum doesn't need energy to expand either, provided it's a bubble-gum balloon. 

No, space isn't a field, because a field is a state of space.

 

Offline Bill S

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Re: Is Space Fractal
« Reply #3 on: 17/01/2015 16:30:11 »
Quote from: John
A balloon in vacuum doesn't need energy to expand either, provided it's a bubble-gum balloon.

Surely a balloon in a vacuum expands because it contains some sort of gas, which is matter, and therefore has energy.  A completely evacuated balloon would not expand in a vacuum; unless there is something very odd about bubble-gum.  Wouldn’t an evacuated bubble-gum balloon just be a lump of gum?
 

Offline JohnDuffield

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Re: Is Space Fractal
« Reply #4 on: 17/01/2015 16:42:59 »
Just imagine you have a balloon full of air in a vacuum. The pressure of the air inside the balloon is balanced by the tension in the skin. So the balloon stays the same size. To make it bigger, there's two options:

1) Increase the pressure. You do this by blowing some more air in. The pressure inside increases momentarily and the balloon expands until the pressure drops and is again balanced by the tension in the skin. Note that energy is pressure x volume, and you've added more energy to this system. 

2) Reduce the tension. You do this by snapping your magic fingers and making it a bubble-gum balloon. The tension reduces as the bubble-gum balloon expands. Yes the skin gets thinner so the tensile strength reduces so the balloon expands further and so on, but let's not go there. The important thing is that you haven't added any energy in this scenario. You are not in breach of conservation of energy.


 

Offline PmbPhy

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Re: Is Space Fractal
« Reply #5 on: 17/01/2015 20:05:45 »
Quote from: Gimmehendrix
NB
Welcome to the forum!! :)

What does NB stand for?

Quote from: Gimmehendrix
Is space made of 'stuff'...
No. Not in the least bit.

Quote from: Gimmehendrix
.. and is this a fractal given that space is expanding.
This question is moot since it depends on something which is false, i.e. there is no fractal to speak of.

Quote from: Gimmehendrix
In order to expand ,does space need energy and if so where does this come from.
Not sure. Let me look into it for you.

Quote from: Gimmehendrix
Could  space be a 'field' and if so would it have a related particle?
Not that I'm aware of. However it's believed that space-time is a field. See: Is spacetime a Field? by Dennis Lehmkuhl.
http://www.spacetimesociety.org/conferences/2006/docs/Lehmkuhl.pdf

Quote from: Gimmehendrix
If space needs energy to expand what are the implications of this at the big bang. Was ,for example, energy first transfered to creating matter then to space to cause inflation.
There is an hypothesis that the total energy of the universe is zero. See http://en.wikipedia.org/wiki/Zero-energy_universe to see why and where energy comes from and goes to.
 

Offline evan_au

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Re: Is Space Fractal
« Reply #6 on: 17/01/2015 20:46:42 »
Quote from: Gimmehendrix
[Does] space need energy to expand?
Quote from: evan_au
Yes, it needs energy
Quote from: JohnDuffield
No, space does not need energy in order to expand, conservation of energy applies. A balloon in vacuum doesn't need energy to expand either, provided it's a bubble-gum balloon.
Quote from: PmbPhy
There is an hypothesis that the total energy of the universe is zero.

These answers are consistent.
In the balloon analogy, the pressurized gas is the energy source which drives the stretching of the bubble-gum balloon. So it takes energy to stretch the balloon, but it comes from a different form of energy, leaving the total energy of the system unchanged.

So this adds three questions to the original question:
  • [Does] space need energy to expand?
  • Where does the energy come from?
  • Where does the energy go to?
  • And do they balance each other? (current thinking says we will define the answer to be "yes")
« Last Edit: 17/01/2015 22:21:09 by evan_au »
 

Offline jeffreyH

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Re: Is Space Fractal
« Reply #7 on: 18/01/2015 00:12:17 »
Space is not a balloon so there is no surface to push against. We have vacuum with energy and virtual particles. THIS energy is likely to be uniform, however mass has energy and this makes the distribution uneven. Add the electromagnetic field and the gravitational field and this adds to the imbalance in the system. The imbalance is ALWAYS localized and over the whole universe, whatever extent this has, the energy should be considered to be uniform. The increase in entropy will tend towards a universal uniform energy. For our universe this means heat death. However, until that point in time the energy and pressure are NOT uniform. It is not possible for them to be uniform otherwise we would not be talking on this forum because we would not exist.
 

Offline JohnDuffield

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Re: Is Space Fractal
« Reply #8 on: 18/01/2015 13:40:36 »
In the balloon analogy, the pressurized gas is the energy source which drives the stretching of the bubble-gum balloon. So it takes energy to stretch the balloon, but it comes from a different form of energy, leaving the total energy of the system unchanged.
So conservation of energy applies. Space doesn't need added energy to expand. In the standard balloon analogy you blow in more air, which is adding energy, so conservation of energy doesn't apply.  In most discussions about dark energy, it is said to remain at a constant energy density as space enlarges, and again we're in breach of conservation of energy. Conservation of energy is one of the most important tenets in physics, and I will not surrender it lightly.

Also note that gravitational field energy is positive. See this quote:

"the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy".

If you drop a brick from some great height on to planet Earth, some of the potential energy is converted into kinetic energy, and when this is radiated away into space you're left with a mass deficit. But there is no energy deficit. Conservation of energy applies. The same is true if all the matter in the universe fell into one big heap. The net energy of the universe is not zero. 

So this adds three questions to the original question:
Let's give 'em a go!

Does space need energy to expand?

Yes, but only its innate energy.

Where does the energy come from?

Space. It's already there.

Where does the energy go to?

Space!

And do they balance each other?

Yes, because they are each other. At the fundamental level, you cannot distinguish space and energy. If you started with some volume of space, then if you somehow took all the energy out of it, its volume would reduce to zero. But if you surrounded it with higher energy-density-space, its volume would reduce as the energy-density increased. Energy = volume x pressure, and the stress-energy tensor doesn't have an energy-pressure diagonal for nothing. 
« Last Edit: 18/01/2015 13:42:25 by JohnDuffield »
 

Offline Bill S

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Re: Is Space Fractal
« Reply #9 on: 18/01/2015 18:16:19 »
Quote from: Pete
What does NB stand for?

Nota bene: Take note. (Literally: Note well)
 

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Re: Is Space Fractal
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