Cosmology Speculation

[BenBurch]

You know, Cosmology isn't my field. (Though sometimes I wonder if I should change that...)

I have been thinking about what the observational differences between the universe expanding because of actual momentum difference between ourselves and distant cosmological objects, and the universe expanding because inflation never actually stopped, just slowed to a subluminal rate?

I see there are some papers on extended inflation, some posit a model that would be predicted to make distortions in the CMB that we do not observe, but some also would produce no such artifacts. And I am trying to figure out what experiment would show us if space were still inflating? I am wondering if there would be something akin to frame dragging we would observe.

Thoughts by the physics types here?

 

[sol invictus]

The universe is undergoing inflation right now (due to dark energy), and as far as we can tell that will continue indefinitely.

 

[edd]

There's nothing that different about inflation - it's just accelerated expansion, like sol says. The mechanism causing it might have some interesting physics but the expansion itself isn't any different from expansion at later time - it's just that it's doing it faster and faster, basically exponentially.
You seem to be asking if there's a way to tell if space is expanding or if things are just moving through it. I'd say the answer is no to that, and that it's not useful to draw a distinction between the two.
Something like http://www.roe.ac.uk/~jap/book/expandspace.pdf applies as much to inflation as later cosmological expansion.
Otherwise I'm not completely sure what you're getting at.

 

[Perpetual Student]

You seem to be asking if there's a way to tell if space is expanding or if things are just moving through it. I'd say the answer is no to that, and that it's not useful to draw a distinction between the two.

Isn't true that the speed of light is not a limiting factor if space is expanding? Would that also not imply that there is no energy involved if space were expanding but energy would be required for objects to be moving through space?

 

[Bishadi]

You know, Cosmology isn't my field. (Though sometimes I wonder if I should change that...)

I have been thinking about what the observational differences between the universe expanding because of actual momentum difference between ourselves and distant cosmological objects, and the universe expanding because inflation never actually stopped, just slowed to a subluminal rate?

it is the hubble telescope that provides the per se evidence of redshift. Then likewise the mathematical scheme of the entropic path to equilibrate that renders an 'expanding' universe.

There is no evidence other than some stars/galaxies share this 'redshift' of the light (wavelengths change). (but then mass in between the line of sight can also cause a redshift.) I would seek to find the material evidence that uses coordinates between others stars, then i believe the 'expansion' can be reduced to belief) (my prediction)

There is no dark matter/energy. As them bodies are associating between each other (exchanging energy) and that potential is not observed in any cosmology that i know of. ie....think in casimir in which 2 bodies can increase a potential by exchanging energy (an entanglement caused by em)

I see there are some papers on extended inflation, some posit a model that would be predicted to make distortions in the CMB that we do not observe, but some also would produce no such artifacts.

the CMB itself could be many other fields that can be detected and have nothing to do with the big bang.

A method of proving the big bang from a central point is wrong within an entropic frame of mathematics, is if you tap a pond at a central point, then the waves do not return, unless they hit something. With newtons law of motion that would mean, nothing is affecting the mass if existence was in a vacuum; the mass would maintain its trjectory, indefinitely. (no mass would return to combine into stars).

These points of logic can assist any in observing from their own perspective.

And I am trying to figure out what experiment would show us if space were still inflating?

The answer to that is found by noting that the foolishness held to the idea of 'entropy' as conditioned in the 2nd law of thermodynamics created the foundations to a REQUIREMENT of an expanding universe. Otherwise, i rather enjoy your inquiry.

Try another idea; if the universe is expanding and the per se particles can release in a vector, then the stars on the outer edge would be releasing a solar wind, away from the center of the universe, hence a per se 'expansion' either exists, or i have the concept that energy could not go out to a nothing, and that SHOULD be provable.


ie... since there is no perfect vacuum anywhere between 2 points of mass, then that idea would be tough to prove.

But it is one that I am working on and so far, the one item that renders the concept to a logical frame is the blackness of space. (ie.... there is nothing there to detect, without a detector (mass) then the exchange is relevant to the recieving mass (double slit experiment, shares the mass of the detector, IS relevant)

There, you now have my speculations too!

 

[edd]

Isn't true that the speed of light is not a limiting factor if space is expanding? Would that also not imply that there is no energy involved if space were expanding but energy would be required for objects to be moving through space?

You could argue that energy is involved - you could say it's gravitational potential energy converting to and from kinetic energy.

Plus, the speed of light is a limit, one just has to be careful how it is applied. http://www.astro.ucla.edu/~wright/cosmo_02.htm#MD

 

[LarianLeQuella]

There, you now have my speculations too!

And here we were hoping for an intelligent conversation (or at least intelligible)... Could you please put your specualtions back, so we can get on with the thread?

What I am more interested in than just the inflation, but the mechanism that this dark energy uses on the basic structure of space(time). As I have been lead to believe, there is a fine structure to spacetime at the plank scale, but we haven't been able to observe this. I suppose once we can, we'll know a lot more, and may even find this dark energy.

Sorry for not making sense, I think I have a contact high from post #5.

 

[sol invictus]

Isn't true that the speed of light is not a limiting factor if space is expanding? Would that also not imply that there is no energy involved if space were expanding but energy would be required for objects to be moving through space?

One really can't reason that way. Speed is defined to be the derivative with respect to time of the position of a well-localized object, like a particle. In an inertial frame of reference, the speed of a massive object cannot reach or exceed the speed of light, and the speed of light (or any other massless particle) is always constant.

One cannot define the speed of the expansion of space like that, because there is no position to differentiate. Moreover there are no inertial frames in an expanding spacetime, and therefore there is no reason to believe the speed of light is a limit on the coordinate speed of even a massive object (and in fact it is not).

Apart from the mathematics, what the physics says is that a massive object will never overtake a pulse of light. That's essentially all there is to it. But expansion of space that's "faster than light" doesn't alter that fact, because it sweeps both light and massive particles along with it.

 

[Perpetual Student]

Originally Posted by Bishadi
There, you now have my speculations too!

And here we were hoping for an intelligent conversation (or at least intelligible)... Could you please put your specualtions back, so we can get on with the thread?

I solved this problem quite easily by putting Bishadi on "ignore" some time ago. It makes these threads more interesting and much more enjoyable.

 

[Perpetual Student]

One really can't reason that way. Speed is defined to be the derivative with respect to time of the position of a well-localized object, like a particle. In an inertial frame of reference, the speed of a massive object cannot reach or exceed the speed of light, and the speed of light (or any other massless particle) is always constant.

One cannot define the speed of the expansion of space like that, because there is no position to differentiate. Moreover there are no inertial frames in an expanding spacetime, and therefore there is no reason to believe the speed of light is a limit on the coordinate speed of even a massive object (and in fact it is not).

Apart from the mathematics, what the physics says is that a massive object will never overtake a pulse of light. That's essentially all there is to it. But expansion of space that's "faster than light" doesn't alter that fact, because it sweeps both light and massive particles along with it.

I think I understand that, thanks.
What about energy? If the separation of two objects is increasing because they are moving through space, we can measure the energy of one object relative to the other, or the energy of both relative to some other frame of reference. But if space were expanding causing two objects to increase their separation, is it not true that there would be no way to measure any energy?

 

[Dancing David]

it is the hubble telescope that provides the per se evidence of redshift. Then likewise the mathematical scheme of the entropic path to equilibrate that renders an 'expanding' universe.

Now that is funny, so Hubble used the Hubble to make the discovery that got the telescope named after him!

 

[Bishadi]

And here we were hoping for an intelligent conversation (or at least intelligible)... Could you please put your specualtions back, so we can get on with the thread?

NO as your very next line rendered a huge scope of ill regard to logic.

What I am more interested in than just the inflation, but the mechanism that this dark energy uses on the basic structure of space(time).

There is no dark matter and show us all where einstein was bending space with dark matter/energy?!

ie.. the inflationary 'big bang' approach is far older, then any dark matter that was added to the cosmology picture after the hubble telescope provided evidence that the evidence observed (mass curve of the galaxy arm) does not match, the mathematical predictions of the planck models.

You are using a cross analogy of disciplines that is inconsistant with both the physical evidence (mass curve) and the mathematics. (big bang theory; expansion)

As I have been lead to believe, there is a fine structure to spacetime at the plank scale,

belief is all it is

but we haven't been able to observe this.

a fine fact

I suppose once we can, we'll know a lot more, and may even find this dark energy.

it dont exist as a substance but the observed potential as entangled energy between the bodies.

Sorry for not making sense, I think I have a contact high from post #5.

I agree............. as to combine the dark matter/energy (addition of 78% more crap into the universe to make the computer simulations work), with the inflationary scope to the universe is not physics................

What your thread is doing is using newspaper and speculations compounded to previous speculations as if a bunch of columnist are creating a belief that has little relevance to reality.

There is not such thing as dark crap.............. as it is like suggesting you can walk to hawaii because most of that out there is land, but you cant see it and have to trust, because the idiots with computer simulations told you 'its there'.

put your feet back on the ground!~!!!!!!

 

[Bishadi]

Now that is funny, so Hubble used the Hubble to make the discovery that got the telescope named after him!

you got me......

hubble shared the red shift (via mathematics)and hubble shared the mass curve (via obervational evidence and now dark BS mathematics)

what a hubble bubble

telll the redshifters the dark crap did it (that'll be funky math)

 

[Ziggurat]

A method of proving the big bang from a central point is wrong within an entropic frame of mathematics, is if you tap a pond at a central point, then the waves do not return, unless they hit something.

The universe is a giant pond!

Which means the earth is screwed once the cosmic carp show up.

 

[BenBurch]

Wow, sorry I asked. I hadn't meant for this to be troll bait.

I know that "dark energy" is an expansive effect, but is it a proper force, or an expansion of space, and could you tell the difference? It's the latter question that interests me.

 

[kalen]

As I understand it, our reasons for believing in an (outwardly) accelerating universe comes from the fact that, at high z, our standard candles are fainter than they would appear if the universe was non-accelerating.

Right?

However, this same evidence suggests to me that the universe is decelerating (slowing down it's expansion - a negative outward expansion). Since light has a finite speed, as we look farther and farther out into the universe, we are also looking farther and farther back in time. If, at high z, the standard candles we look at appear fainter than expected it is because the universe was expanding at a greater rate in the past. Since the rate of expansion of the universe "presently" (at small z) is slower, it must be said that the expansion of the universe is slowing down, not speeding up.

 

[edd]

Wow, sorry I asked. I hadn't meant for this to be troll bait.

I know that "dark energy" is an expansive effect, but is it a proper force, or an expansion of space, and could you tell the difference? It's the latter question that interests me.

Don't worry - I have B on ignore too. Takes too much brain energy to attempt to parse him, and I've never succeeded anyway.

Dark energy is not a force. It's a source of a force. It's a source of bog standard gravity, just as matter is a source of bog standard gravity. It's just that its properties mean it sources it in quite a different way.

You can't disentangle expanding space from peculiar velocities as a general rule, except in the case you otherwise know the distance and what the redshift should be at that distance. Basically only when you already know the answer, and the observation disagrees.

 

[edd]

kalen: does http://www.astro.ucla.edu/~wright/cosmology_faq.html#CC help?
(Ned is a marvellous resource, I must say!)

 

[MattusMaximus]

I have been thinking about what the observational differences between the universe expanding because of actual momentum difference between ourselves and distant cosmological objects, and the universe expanding because inflation never actually stopped, just slowed to a subluminal rate?

What do you mean by "actual momentum difference"? Are you meaning that, from a commonly defined frame of reference, there is a relative motion between two objects through spacetime? Because that is what's happening between the Milky Way and Andromeda galaxies - they actually have a relative motion towards one another, even though the spacetime between them is expanding via Hubble's Law, dark energy, etc.

In addition, I'm not sure what you're getting at when you say "inflation never actually stopped". That's because, in the context of modern cosmology, inflation has a very precise meaning...

In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 10⁷⁸ in volume, driven by a negative-pressure vacuum energy density.[1] The inflationary epoch comprises the first part of the electroweak epoch following the grand unification epoch. It lasted from 10⁻³⁶ seconds after the Big Bang to sometime between 10⁻³³ and 10⁻³² seconds. Following the inflationary period, the universe continues to expand. ...

 

[sol invictus]

I think I understand that, thanks.
What about energy? If the separation of two objects is increasing because they are moving through space, we can measure the energy of one object relative to the other, or the energy of both relative to some other frame of reference. But if space were expanding causing two objects to increase their separation, is it not true that there would be no way to measure any energy?

It's pretty tricky to define energy in a useful way in curved spacetime. There do exist definitions, but they don't have all the nice features of energy in flat space.