Bjarne on: Dark Energy, only an illusion.

[Brian-M]

If sub-atomic particles were expanding, we'd lack reliable reference points to check for it.
Yet, to me, it 'feels' like they are expanding.

Devil's Advocate: "Actually, sub-atomic particles are contracting and space is remaining the same, which just makes it look like space is expanding to those ignorant of The Truth."

 

[sol invictus]

I'm not talking about comoving velocity, but recession velocity as absolute distance* between two particles comoving with their local Hubble flow, with respect to the time of a comoving particle. Then v = (a'/a)d = Hd, where a is the scale factor. This holds exactly in de Sitter spacetime with a constant H, hence my initial puzzlement at your objection.

There's no such thing as "absolute distance" in GR. But yes - if by "distance" and "velocity" you mean what are usually called "physical distance" (comoving distance times a) and its derivative with respect to FRW time, then indeed the ratio of velocity to distance is a'/a, which is the definition of H, the Hubble "constant". So that relation holds exactly in any FRW space (since it's a definition). You're correct that H is only actually constant in de Sitter space.

Aah. I see where you're coming from. You're making doing something completely different than I was (which was just an isolated mass in an otherwise empty universe, and is exactly Hubble-like in the long-distance limit). But yours is a much more interesting case. Thank you.

What's cute is that one can obtain the precise Friedman equation - including the correct numerical coefficients - from that little Newtonian analog. But it's just a trick, the physics really doesn't make sense in a Newtonian framework.

 

[Vorpal]

There's no such thing as "absolute distance" in GR.

Yes, I know--the definition I've given above is foliation-dependent and hence 'absolute' is really a misnomer. But that's what d'Inverno calls it, and I've seen it called that by some astronomers as well.

What's cute is that one can obtain the precise Friedman equation - including the correct numerical coefficients - from that little Newtonian analog. But it's just a trick, the physics really doesn't make sense in a Newtonian framework.

Heh, yeah. I remember that in d'Inverno as well. It just didn't occur to me to do it here because I was getting mentally stuck on the isolated gravitating mass, even though it would be more appropriate.

 

[Bjarne]

You're using Neal Adams as a reference for earth history and geology?
The crank who believes the Earth started out as a small sphere and has been expanding in size (like a balloon) for thousands of years?

The Universe started like a small dot.
99,9999999 % of what we normally think is matter, is space
Why should “that” space not expand, -(be a exception)?

The simple answer is that certain types of metric expansion allow bound systems to remain bound. For that reason, systems that are bound (star systems, galaxies, solid bodies like planets etc.) do not expand.

This is only words

Here's a simple example to begin with: imagine a big pile of pebbles that is big enough to hold together by gravity alone…….(etc)

This was a long explanation, but not evidence, - only speculation.

There are 3 main points

1.) Space is space.
It doesn’t matter where space is (inside or outside a galaxy, or inside or outside matter).
If spaceis affected one place it must be affected everywhere.
There exsist nothing in the unievrse to prevent that to happen.
Anything else doesn’t make sense.

2.) WHAT should determinate;
that space one place but not another expands.
There is in fact no known force or anything that can stop space for expanding some on place and not another, also not gravity.
The distances between astronomic bodies are not the cause to that "should" happen either.

3.)Where exactly are the border:
for where space expand and not expand ?
There are no such “borders”
It’s beyond common sense if it “should be”

Why do you say so? If you consider a toy problem, like the acceleration of a (momentarily) stationary particle in a Schwarzschild spacetime with dark energy driven by a cosmological constant Λ, then d²r/dt² = -GM/r² + Λc²r/3. This can be interpreted as the usual gravitational attraction with an additional outward force proportional to distance, which is just what one would expect from cosmic expansion.

You must make up you mind.
Either space expands here on Earth (doesn’t matter how much) or it is not.
1.) Does space here at the surface of the Earth expand or does it not? -Please answer the question, yes or no.
2.) If not simply tell me why?
What is the evidence (except that we haven’t discovered it )
3.) Where is the "border" where space expands and not expands ? (!)
Please answer the question ( I know you can't, - is that not a problem) ? (!)

What expansion?

http://www.youtube.com/watch?v=oJfBSc6e7QQ

It makes plenty of sense. The expansion of the universe is so small that it's not measurable over distance the size of a solar system, and is relatively minor over the size of a galaxy. It's only over the truly vast distances of intergalactic distances that the cumulative effect of the expansion adds up to something huge. No problem.

Fine that you agree to the fact that space also here must expand.
But you have a problem, for example: we can measure the Moon only is moving away from us with the speed: 4 cm per year.

The Hubble constant is :

22 km/s per Mly

Or 22.000 m/s per = 9.46E15 Meter

That distance is 24894736 times the distance to the moon.

Hence the moons “should” move away with 22000 / 24894736 = 0.00088 m/s
Or 22000 * 365*24*60*60 / 24894736 per year = 27869 meter per year.

This is not the case.
So you too should once again consider why on Earth space here is not expanding.
Or a more correct question: Why doesn’t is seems to be the case.

That doesn't make much sense to me.
Density is mass/volume ... but space has no mass and volume is defined by how much space is being occupied. So how can space have density?

Right we are talking about a strange “object” = space.
Since it can expand it must have “some kind of density”
Word can in this case not comprehend what space really is, but this is the best expression we can use.

Even if this was true, gravitational, nuclear & electromagnetic forces would pull the atoms/molecules/earth together... so the earth would remain the same size even if space was expanding at a different rate around the earth because of the mass of the earth.

We have not reason to believe so.
Instead we can see e have a big problem

1. Space around you (as you elf admit) should “expand”
2. You can not see or measure it (!)
3. Is that because everything around you expands ? (!)
4. If point 3 not is correct we have a BIG problem., because why should space here not expand ? (!)

That's one kooky video
First claim, that the tectonic plates fit together perfectly…………….(etc)

I am not saying Neal Adams is completely correct, he also many some times admit he in some cases is guessing for example what the cause of the expanding Earth is.
What dinosaurs did or did not is not important.

But he could very well be right that the Earth is expanding, - simply because this form a logical synthesis .


But off course we must be willing to give up the subduction speculation...

-----------

 

[sol invictus]

There is in fact no known force or anything that can stop space for expanding some on place and not another, also not gravity.

Nonsense. That's exactly what gravity predicts.

3.)Where exactly are the border:
for where space expand and not expand ?
There are no such “borders”

Yes, there are. They are very roughly 5 Mpc away from us (the edge of the local group of galaxies).

1.) Does space here at the surface of the Earth expand or does it not? -Please answer the question, yes or no.

No.

2.) If not simply tell me why?

Because of its gravity, the gravity of the sun, the gravity of the solar system, the Milky Way... and because it's held together fairly rigidly by internal stresses and tensions. To make the earth expand would require tearing rocks apart, and that requires force. Even if there were no local gravity, the force due to the Hubble expansion is far, far, far too weak to break a lump of rock apart.

The Hubble constant is :

22 km/s per Mly

Or 22.000 m/s per = 9.46E15 Meter

That distance is 24894736 times the distance to the moon.

Hence the moons “should” move away with 22000 / 24894736 = 0.00088 m/s
Or 22000 * 365*24*60*60 / 24894736 per year = 27869 meter per year.

This is not the case.

Your calculation is wrong. The moon is about 10^-14 Mpc away from the earth on average. Therefore, if it were moving with the Hubble flow (it isn't and shouldn't be), its velocity with respect to earth would be - using the correct value of H - (10^-14 Mpc)(74 km/(s*Mpc)) = 7 10^-10 m/s = 2 cm per year.

Actually that would be very easily detectable (the precision to which the earth-moon distance is known is astonishing), but it isn't happening - just as is correctly predicted by general relativity.

 

[Bjarne]

Nonsense. That's exactly what gravity predicts.

Nonsense
Einstein did not believe that space could expand or contract, even though his own calculation shows it was so.
Are you saying that the curvature of space has something to do with the expanding space, and that it can stop space expanding?
You even don’t know what the curvature of space really is.

Yes, there are. They are very roughly 5 Mpc away from us (the edge of the local group of galaxies).

So on the one side of the line gravity stops space expanding - on the other side gravity does not. HA HA HA how funny. Do you self belive in this crap ?

Your calculation is wrong. The moon is about 10^-14 Mpc away from the earth on average.

It’s not wrong
The moon is about 380.000 Km or 380.000.000 Meter from us.

 

[PixyMisa]

One light year is 10¹⁶ metres, near enough.

A million light years (Mly) is 10²² metres.

We'll call the distance from the Earth to the Moon 4 x 10⁸ metres.

So that's a ratio of 2.5 x 10¹³.

22 km/s divided by 2.5 x 10¹³ is .000000000088 metres per second, or 2.7 centimetres per year. Which is very close to the number sol invictus came up with, and exactly a million times less than your figure.

It's also not happening, but that's a whole 'nother story.

 

[Bjarne]

One light year is 10¹⁶ metres, near enough.

A million light years (Mly) is 10²² metres.

We'll call the distance from the Earth to the Moon 4 x 10⁸ metres.

So that's a ratio of 2.5 x 10¹³.

22 km/s divided by 2.5 x 10¹³ is .000000000088 metres per second, or 2.7 centimetres per year. Which is very close to the number sol invictus came up with, and exactly a million times less than your figure.

It's also not happening, but that's a whole 'nother story.

LY = 300.000 * 365 * 24* 60 * 60 = 9.46E15
MLY = 9,46 E21
Not 10²² metres

Try again, its not few centimetre the moon "should" move away but * 10.

Anyway it doesn’t happen
It doesn’t seem like space here expands.
It should, - because there is no reason to that space here not should expand as well.

 

[Pixie of key]

No way

It is not space who expanding.

Atoms expanding in space who dont expanding

Scientific experiments

The argument about the expanding space is an empty argument! There is no way
to make scientific experiments with a space. The argument about expanding
space is not science. It is a religion!

The thing that particules radiate their energy is not an empty claim.
Particules can be examined and make scientifical experiment with them and
this way proof this claim to be true.

Let´s take long chutes from different materials into the space and place
telescopes to them to observe some known place of a star. If the energy that
comes to the chutes makes the photons moving in the chute to bend towards
the chute, we can this way observe that this star concerned seems to be in a
different place than it is known to be!

The sun does not curve the space. The energy coming towards the sun makes
photons passing by the sun to bend towards the sun, because the hot / thick,
small and little exterior surface possessing particules do not interact with
the photons passing by the sun!

Even Einstein once told us that the massive the object is, the slower the
time is.

In relation to the size of a star there is much more energy / substance in
the stars than in the photons. The substance / energy is denser in the stars
than what it is in the photons. The time of the stars is so slower than the
time of the photons!

This way the time of the old photons is faster than the time of the new
photons and the photons radiating from the stars do not tranfer their
kinetic energy to the photons passing by the star as much as the photons
coming towards the star do. This way the light bends at the same time it
passes the star without supposedly the star would bend the space!

http://www.youtube.com/user/Etimespace

.

 

[Dancing David]

What is totally wrong here is you. It is actually well known why there is expansion between galaxies and not within galaxies. That you don't know that means that you do not understand the basics of this field.

Considering that the rate of expansion of the Hubble Constant works out to ~493km/sec/Mpc and a MPC is 3.085677581x10²² meters we then get that the Hubble Constant per meter is
~4930m/sec/(3.085677581x10²²)
or a rate of~1.6x10^-22 m/sec.

Gosh I wonder why we can't detect something that small.
ETA:
Looks like Sol I beat me to it and stressed that is doesn't apply on the local scale anyhow.

 

[Molinaro]

MLY = 9,46 E21
Not 10²² metres

Try again, its not few centimetre the moon "should" move away but * 10.

Are you are calling the difference between those 2 numbers *10 ?

 

[quarky]

Devil's Advocate: "Actually, sub-atomic particles are contracting and space is remaining the same, which just makes it look like space is expanding to those ignorant of The Truth."

sweet

 

[Thabiguy]

This is only words

This was a long explanation, but not evidence, - only speculation.

As per your request, it was merely an attempt to enlighten you on layman level, not an attempt at a proper mathematical treatment of the issue, which I assumed would be too complicated for you to follow.

Your problem was how to reconcile the universal expansion of the universe with the lack of expansion of bound systems (such as star systems or galaxies); in your words, this made "no sense" to you. But the fact is, as I wrote, that for certain types of expansion, such result is a necessary consequence of the model that can be proven mathematically (here is one example), which shows that your feeling that it "makes no sense" is merely due to your unfamiliarity with the relevant science and your decision to rely on uneducated intuition instead of taking effort to properly understand the issue.

What I wrote was an attempt at a rough (and inevitably inaccurate) explanation that might be accessible to your intuition. If that doesn't satisfy you, feel free to acquaint yourselves with the science involved (I would recommend getting familiar with general relativity first, then for example these two papers list a summary of works key to the scientific debate about the issue). Unless you do that, your complaints that it makes no sense to you are going to be unremarkable.

 

[PixyMisa]

LY = 300.000 * 365 * 24* 60 * 60 = 9.46E15
MLY = 9,46 E21
Not 10²² metres

Shrug. The difference is 5%. Which is irrelevant you are wrong by a factor of a million.

I rounded the light year up by just over 5% to make the calculations simpler. I also rounded up the distance between the Earth and the Moon by just over 5% to make the calculations simpler. That way you can easily spot the error you made.

Try again, its not few centimetre the moon "should" move away but * 10.

What is that supposed to mean?

Oh, and by the way, the Earth is not expanding.

 

[Bjarne]

Shrug. The difference is 5%. Which is irrelevant you are wrong by a factor of a million.

I forgot M in MLY
But it doesn’t matter
We can easy calculate that the Moon (or the Sun) “should” move away from us mush faster.
It doesn’t seems to happen, and that's the point.

 

[Bjarne]

As per your request, it was merely an attempt to enlighten you on layman level, not an attempt at a proper mathematical treatment of the issue, which I assumed would be too complicated for you to follow.

Your problem was how to reconcile the universal expansion of the universe with the lack of expansion of bound systems (such as star systems or galaxies); in your words, this made "no sense" to you. But the fact is, as I wrote, that for certain types of expansion, such result is a necessary consequence of the model that can be proven mathematically (here is one example), which shows that your feeling that it "makes no sense" is merely due to your unfamiliarity with the relevant science and your decision to rely on uneducated intuition instead of taking effort to properly understand the issue.

What I wrote was an attempt at a rough (and inevitably inaccurate) explanation that might be accessible to your intuition. If that doesn't satisfy you, feel free to acquaint yourselves with the science involved (I would recommend getting familiar with general relativity first, then for example these two papers list a summary of works key to the scientific debate about the issue). Unless you do that, your complaints that it makes no sense to you are going to be unremarkable.

I have read the two papers.
But these mainly demonstrate how confused and divided we are.
For example quote from the one paper introduction:
“Many authors have studied the effects of cosmological expansion on local dynamics with various and often conflicting conclusions.”

This is still so.
I simply can’t imaging that gravity or anything else can distinguish between where space must expand and where not.

The point with this thread is mainly to ask the question:
Is the gravity effect on space that space stretch, - and hence the exact same property as stretching / expanding space. Yes or no ?

If the answer is yes, space around us is stretching too.

Before being able to answer that question correct, we must know what gravity is.
Which mean we must know what the curvature of space is?
Does curvature of space simply mean stretching of space?

Now let us assume that the answer to the questions is YES.
This would mean that the “density of space” not is homogeneous, but “thinner” closer to matter / gravity.
And that would properly also mean that “thin space” do not (at least primarily) contribute so much to the expansion of the Universe.
But secondary it will off course also be an effect, because when space between galaxies gets “thinner” there will be a domino effecting space inside for example galaxies as well (sorry for the confusion).

One more consequence is that in the same way that we can not “trust” time, we also can not trust distances.

-------------------------------------------------------------------------------------------------
Now to the question; - what about space inside matter.

The conclusion of the other paper is;

We have presented a simple definitive question about the influence of the expansion of the universe on a very
particular system: a classical “atom.” And we have found a simple definitive answer: In the long-term our atom either
ignores the expansion (after some initial disturbance), and has an asymptotically constant size, or it is disrupted by the influence of the cosmological expansion and it stretches in size at the same rate as the universe

Which mean you can ride the horse you want.

Hence it is not sure that one meter between two distances galaxies, also is 1 meter here by us, (75.000 LY inside a galaxy).
Here one meter will (maybe) be stretching and relative much longer compared to 1 meter between 2 distance galaxies.
Simple because space here (also inside matter) is stretching too.

And “finally” this also means that space (and therefore also 1 meter) in the previously (younger) universe were relative much "shorter" compared to how (relative) “longer” 1 meter is today.
Which mean that when we observe something (light-motion) that happens billion of years ago, we can not be sure that we can use the meter-stick we are used to today.
BUT we do so, and this could certainly be too stupid.

I am not saying that all this is solved; there is a lot to consider, especially what really 1 meter is today and what tomorrow.
We have no way to check if it has change over night.
Even the Hubble constant 22 km/s per MLY this is something that happens billion of LY away from us.
How “long” or rather how “short” is 1 meter a place that is much weaker affected by background gravity. ?

 

[sol invictus]

Nonsense
Einstein did not believe that space could expand or contract, even though his own calculation shows it was so.

He didn't believe it even though he said he did, discovered a theory that predicted it, wrote papers describing precisely how it happens, and believed Hubble's evidence that it was. Sure.

And even if you were right, who cares? General relativity doesn't depend on what Einstein believed; it's a theory in its own right, and it appears to describe our world.

Are you saying that the curvature of space has something to do with the expanding space, and that it can stop space expanding?

The curvature of spacetime.

So on the one side of the line gravity stops space expanding - on the other side gravity does not. HA HA HA how funny. Do you self belive in this crap ?

It's not a line, it's a surface. And very roughly speaking, yes, that's exactly what happens. There's nothing particularly weird about it - you could very easily arrange a similar situation with electric forces, or with currents in a fluid or gas, or with a ball rolling on a curved surface, or with all sorts of other systems.

It’s not wrong

It's wrong.

 

[Skamandros]

One is the strong gavitatonal energy two is the week expanding spaces and the three is the strong dark energy is so sinple poeple Einstein saw these.

 

[Bjarne]

He didn't believe it even though he said he did, discovered a theory that predicted it, wrote papers describing precisely how it happens, and believed Hubble's evidence that it was. Sure.

The cosmological constant was his biggest mistake he said, but first when he discovered he was wrong.

And even if you were right, who cares? General relativity doesn't depend on what Einstein believed; it's a theory in its own right, and it appears to describe our world.

Of cause it is important whether a theory is built on what we believe or what we know.

We don’t know what the curvature of space really is, (or how matter and space is connected).
We don’t know if the nature of the curvature in facts means; “stretching space” and whether this property is exactly the same property as expanding (stretching space).

Hence off course we also don’t know how gravity and expanding space affect each other.

It’s not a secret that both the (apparently) acceleration of the Universe and gravities missing ability to slow down, not fits with the models we believes to be true.

Something is terrible wrong, so don’t say that we understand the “connection”.
We believe we do, but we also know it doesn’t reflect reality.

If it did (fit) we should not invent new speculations all the time, such as for example the idea that gravity disappears into unknown dimension, and much more science fiction, - just to attempt to reach a overall model that can comprehend all the contradictions we are facing regarding that question...

Simply spoken, it’s too much we don’t know, and that’s exactly the challenge. – I mean not to make the majority believe, but to prove what is fact.

 

[Reality Check]

The cosmological constant was his biggest mistake he said, but first when he discovered he was wrong.

Einstein is reported to have said that the cosmological constant was his greatest blunder. He was wrong - the cosmological constant may turn out to be his one of his greatest success since it could explain the observation of dark energy.

If by "he discovered he was wrong" you mean that Einstein thought that his blunder meant that General Relativity was wrong then you are totally wrong. Setting the cosmological constant to zero just restricts the possible solutions to GR. It has no effect (AFAIK) on non-cosmological solutions to GR. For example, the cosmological constant is not used when calculating the GR corrections that enable the Global Positioning System to work.

The rest of your post displays an ignorance of GR and science in general.
The ignorance of GR:

• We do know what the curvature of space-time really is. It has a strict mathematical definition.
• We do know the connection between matter (i.e. energy/stress) and the curvature of space-time.
• We do know what the effects of expanding space-time are.
• We do know how gravity and expanding space-time affect each other.

The ignorance of the nature of science comes in your naive expectation that science has absolute truths. A scientific theory is never set in stone and true for ever and ever. Science is not religion with a set of dogma that never changes. Science is the process of constructing ever more accurate models of what the universe is like. So we find that theories of gravity have become better and better over the centuries (history of gravitational theory).

So the fact is that we do not know everything and do not expect to ever do so. Your problem is that we know a lot and you show no sign of learning any of this accumulated knowledge.