Is Dark Energy Necessary for the Acceleration of the Universe's Expansion?

  • Thread starter Thread starter gregtomko
  • Start date Start date
  • Tags Tags
    Dark energy Energy
AI Thread Summary
The discussion centers on the relationship between energy, mass, and the universe's accelerating expansion, questioning whether the energy released by stars through nuclear fusion could account for this acceleration without invoking dark energy. Participants debate the mechanics of how energy from stars might influence the universe's expansion, with some arguing that the energy radiated does not effectively push stars apart due to equal forces acting in all directions. The idea that dark energy is necessary for explaining the observed acceleration is challenged, with some suggesting that existing energy dynamics could suffice. However, others emphasize that current astrophysical understanding attributes the acceleration to dark energy, which remains a mystery in cosmology. The conversation highlights the complexity of cosmic expansion and the ongoing search for a comprehensive explanation.
gregtomko
Messages
71
Reaction score
0
If the mass of the universe is constantly being converted to energy through nuclear fusion, and nothing can travel outside of space-time, then isn't the ratio of energy to mass increasing? If so, then wouldn't the only possible option be for an acceleration of the universe's expansion?
 
Astronomy news on Phys.org
Sorry if this was a stupid question. It just occurred to me that maybe the extra energy would be converted to mass in the form of the extra velocity of the matter in the universe. Maybe this cancels out the lost mass that used to be stored in the binding energy, which was released by the nuclear fusion. Is that it?
 
Stars shine in all directions, so the energy can't be translated into a single direction.
 
mathman said:
Stars shine in all directions, so the energy can't be translated into a single direction.

Stars shine their energy through space-time...
Please explain your reference to "energy can't be translated into a single direction" , I don't understand, what direction are you referring to?
 
gregtomko said:
If the mass of the universe is constantly being converted to energy through nuclear fusion, and nothing can travel outside of space-time, then isn't the ratio of energy to mass increasing? If so, then wouldn't the only possible option be for an acceleration of the universe's expansion?

I don't follow your logic at all. How would you propose that the reactions taking place inside stars creates an effect that spreads out evenly throughout the universe and causes the creation of space. I REALLY don't see how you get from one to the other.
 
gregtomko said:
Sorry if this was a stupid question. It just occurred to me that maybe the extra energy would be converted to mass in the form of the extra velocity of the matter in the universe. Maybe this cancels out the lost mass that used to be stored in the binding energy, which was released by the nuclear fusion. Is that it?
I think not. By what process would that happen?
 
phinds said:
How would you propose that the reactions taking place inside stars creates an effect that spreads out evenly throughout the universe and causes the creation of space.

Chronos said:
By what process would that happen?

The energy released through fusion has to go somewhere. Stars radiate their energy reasonably uniformly as far as I know. As the energy is released from the stars they lose mass. All stars are doing this, and they have been for quite some time. Since there is no space-time outside of the matter in the universe, that energy is contained inside the confines of that matter. I know I am not an astrophysicist, that's why I am asking the question.When particles are hit by photons, the particles get pushed slightly, if I am not mistaken. That energy keeps bouncing around, or being absorbed and then radiated, until it eventually is converted through those slight pushes on particles into mass again, in the form of velocity.

The question is, with less mass over time, and more energy over time, why wouldn't acceleration be expected?

Thanks for your replys phinds and Chronos, I can use all the help I can get :-)
 
Last edited:
gregtomko said:
...
When particles are hit by photons, the particles get pushed slightly, if I am not mistaken. That energy keeps bouncing around, or being absorbed and then radiated, until it eventually is converted through those slight pushes on particles into mass again, in the form of velocity. ...

But the expansion of space is NOT "pushing" on anything, it's just creating space, which creates more distance between objects that are not gravitationally bound.

The whole MECHANISM of "dark energy" just isn't what you seem to think it is.
 
phinds said:
the expansion of space is NOT "pushing" on anything, it's just creating space, which creates more distance between objects that are not gravitationally bound.

That is what I am saying. The photons released from the stars have a net effect of pushing against the other particles in the universe. The stars are all pushing against each other, and also against whatever other matter is around them. When a photon from one star hits a particle in another star, that is energy which helps to create more distance between them. The expansion of space is the particles pushing against each other, using the bonding energy released by nuclear fusion.
 
Last edited:
  • #10
gregtomko said:
That was what I am saying. The photons released from the stars have a net affect of pushing against the other particles in the universe. The stars are all pushing against each other, and also against whatever other matter is around them. When the photon from one star hits another particle in another star, that is energy which helps to create more distance between them. The expansion of space is the particles pushing against each other, with the bonding energy released by nuclear fusion.

As far as I'm aware there is no evidence to support this conjecture. LOTS of smart physicists have spent a lot of time trying to figure out what dark energy is and I don't find it believable that they have overlooked such a straightforward explanation.
 
  • #11
phinds said:
As far as I'm aware there is no evidence to support this conjecture. LOTS of smart physicists have spent a lot of time trying to figure out what dark energy is and I don't find it believable that they have overlooked such a straightforward explanation.

The OP isn't asking about dark energy though right? Just regular ol' run of the mill energy. He's proposing that dark energy doesn't exist.
 
  • #12
dacruick said:
The OP isn't asking about dark energy though right? Just regular ol' run of the mill energy. He's proposing that dark energy doesn't exist.

There is SOMETHING that causes the creation of space in between galaxies and thus causes an accelerating expansion of the universe. We call that something "dark energy" which is shorthand for "we have not a CLUE what is causing this". We see the effects, and as I said, lots of physicists spend lots of time thinking about what the hell it IS. There's a Nobel Prize in there for whoever figures it out first.

The OP is suggesting that the accelerating expansion is not due to dark energy but is a result of a mechanism using existing mechanics that causes the stars to push against each other and that THIS causes the accelerating expansion. This completely overlooks the fact that in a universe with all the stars pushing against each other, none of them move as a result at all, much less expand, much less have an accelerating expansion. It just doesn't work.
 
  • #13
Right, I am just asking if there is all this energy being released by the stars, which would have to have an effect of expanding the universe, why is another form of energy needed? Unless all the energy of all the stars through all of time just isn't enough?
 
  • #14
gregtomko said:
Right, I am just asking if there is all this energy being released by the stars, which would have to have an effect of expanding the universe, why is another form of energy needed? Unless all the energy of all the stars through all of time just isn't enough?

But it WOULDN'T have that effect. What makes you think it would? What is the evidence?
 
  • #15
phinds said:
There is SOMETHING that causes the creation of space in between galaxies and thus causes an accelerating expansion of the universe. We call that something "dark energy" which is shorthand for "we have not a CLUE what is causing this". ... This completely overlooks the fact that in a universe with all the stars pushing against each other, none of them move as a result at all, much less expand, much less have an accelerating expansion. It just doesn't work.

I thought they were moving away from each other, and that's why we need dark energy in the first place.
 
  • #16
our posts 12 and 13 crossed. What do you say to what I pointed out in post 12 ?
 
  • #17
That when a photon is released from one particle, and hits another particle, it causes the two to be pushed slightly apart.
 
  • #18
gregtomko said:
I thought they were moving away from each other, and that's why we need dark energy in the first place.

They are moving away from each other apparently as a result of the big bang. The velocity is ACCELERATING and that is what is attributed to dark energy. That is, dark energy is NOT why is causing the expansion of the universe, it is what's causing the expansion to accelerate.
 
  • #19
Further, the belief is that dark energy, whatever it is, has been around since the big bang, but it was only about 8 billion years ago that everything had spread out enough that it was able to start counteracting gravity and causing the expansion to accelerate instead of slowing down.
 
  • #20
guys...
The OP knows everything is moving away from each other. We all agree on this.

The OP is positing that the output of stars pushes very other star away, having the net effect of everything moving away from each other. If this were the case, we would not need any form of exotic energy to explain the expansion we see.

The question is: where is the flaw in his idea that EM radiation contains momentum, yet does not seem to push stars away from each other.
 
  • #21
I am saying that when a photon is released from a particle in one star, and hits a particle in another star, that it slightly pushes those two particles apart. Any energy left over in that photon will eventually collide with another particle and have the same effect. This keeps going until all the energy has been absorbed
 
  • #22
DaveC426913 said:
guys...
The OP knows everything is moving away from each other. We all agree on this.

The OP is positing that the output of stars pushes very other star away, having the net effect of everything moving away from each other. If this were the case, we would not need any form of exotic energy to explain the expansion we see.

The question is: where is the flaw in his idea that EM radiation contains momentum, yet does not seem to push stars away from each other.

I though I had that on nailed in one of the posts up there somewhere, where I pointed out that each star would feel the same push from all directions so nobody would move. Am I looking at that the wrong way?
 
  • #23
DaveC426913 said:
guys...
The OP knows everything is moving away from each other. We all agree on this.

The OP is positing that the output of stars pushes very other star away, having the net effect of everything moving away from each other. If this were the case, we would not need any form of exotic energy to explain the expansion we see.

The question is: where is the flaw in his idea that EM radiation contains momentum, yet does not seem to push stars away from each other.

Thanks, that was exactly what I was asking :-)
 
  • #24
phinds said:
I though I had that on nailed in one of the posts up there somewhere, where I pointed out that each star would feel the same push from all directions so nobody would move. Am I looking at that the wrong way?

Thats true for the inner stars of the universe, but the ones nearer to the outer edges have more pushing them away from the center than towards the center.
 
  • #25
gregtomko said:
Thats true for the inner stars of the universe, but the ones nearer to the outer edges have more pushing them away from the center then towards the center.

There you go with that EDGE stuff again. There is no edge, there is no center.

EDIT: OOPS ... sorry about that "there you go again" ... I had this thread confused with another. My second sentence holds though.
 
  • #26
Right, I know, I was more specifically referring to the distance away from the point of singularity where the big bang started.
 
  • #27
gregtomko said:
Right, I know, I was more specifically referring to the distance away from the point of singularity when the big bang started.

THERE IS NO POINT. there is no center, there is no edge, there is no point of where the big bang happened. It happened everywhere and everywhere is the center (which is just another way of saying there is no center).
 
  • #28
gregtomko said:
Right, I know, I was more specifically referring to the distance away from the point of singularity where the big bang started.
There isn't one. No point in the universe is any closer to the origin of the Big Bang than any other point. Or put another way: the centre of the universe is everywhere.

[D'oh! beat me. You would explain why you look blue-shifted... :-p]
 
  • #29
So the stars which have traveled less distance from the singularity, are between the ones that have traveled farther. The ones nearer to the singularity would feel equal pressure from the farther ones. The ones which have traveled farther however have more pressure from the inner stars.
 
  • #30
Another thought. Up until about a dozen years ago, physicists were convinced that the expansion was slowing down due to gravity. That is, the expansion was a result of the initial pressure from the big bang. A sort of ballistic trajectory, if you will, and gravity was thought to be acting to slow it down.

Why would physicists have believed that if the mechanism you suggest would have kept the expansion going and even caused acceleration?

The guys who FOUND the acceleration were absolutely stunned and thought they had the wrong answer and had screwed up somehow. It took a while for them to be convinced that they actually HAD discovered acceleration.
 
  • #31
Oh, ok, let me think about that for a while, THANKS!
 
  • #32
gregtomko said:
So the stars which have traveled less distance from the singularity, are between the ones that have traveled farther. The ones nearer to the singularity would feel equal pressure from the farther ones. The ones which have traveled farther however have more pressure from the inner stars.

There is no "nearer to the singularity". There is no center. The singularity happened EVERYWHERE.
 
  • #33
gregtomko said:
So the stars which have traveled less distance from the singularity, are between the ones that have traveled farther. The ones nearer to the singularity would feel equal pressure from the farther ones. The ones which have traveled farther however have more pressure from the inner stars.

Yeah greg, you must disabuse yourself of this notion that any place in the universe is any closer for farther from the origin of the BB.

Take a deflated balloon, glue pennies all over its surface. Now inflate the balloon to the size of a beachball. Which balloon can lay claim to being closest to the origin, when the balloon was tiny? None of them. All of them.

Our 3D universe is equivalent to the 2D surface of this balloon. The surface of the balloon has no centre. All points are equally (that is to say, not) privileged.
 
  • #34
DaveC426913 said:
Yeah greg, you must disabuse yourself of this notion that anyplace is the universe is any closer for farther from the origin of the BB.

Take a deflated balloon, glue pennies all over it. Now inflate the balloon to the size of a beachball. Which balloon can lay claim to being closest to the origin, when the balloon was tiny? None of them. All of them.

So there is no centre of the universe?
 
  • #35
dacruick said:
So there is no centre of the universe?

Correct. Or more accurately, everywhere is the centre.
 
  • #36
DaveC426913 said:
Correct. Or more accurately, everywhere is the centre.

In your balloon analogy, is the distance between the centre of the balloon and any point on the surface represented in our universe as time?
 
  • #37
phinds said:
There is no "nearer to the singularity". There is no center. The singularity happened EVERYWHERE.

Ok, but if there only ended up being 3 stars, just for simplicities sake, and they happened to be oriented in a line, with one in the middle and the others on either side. Then wouldn't the one in the middle have equal energy pushing on it, and the ones on either end have energy only pushing from one side?
 
  • #38
gregtomko said:
Ok, but if there only ended up being 3 stars, just for simplicities sake, and they happened to be oriented in a line, with one in the middle and the others on either side. Then wouldn't the one in the middle have equal energy pushing on it, and the ones on either end have energy only pushing from one side?

pending my last post being correct, that would mean that they are both being "pushed by energy" in the same direction of time. So I would have to say that the idea of being "pushed by energy" here is misleading.
 
  • #39
dacruick said:
In your balloon analogy, is the distance between the centre of the balloon and any point on the surface represented in our universe as time?

Remember, it is an analogy, and does break down if you "stretch" it too far. You could look at the expansion of the balloon as the dimension of time.

It was very small. Now it's big. Eventually it will get so large as to burst and scare the baby, making your mom yell at you and send you outside.
 
  • #40
Either way, wouldn't all those photons pushing all the particles apart help to expand the "balloon?"
 
  • #41
gregtomko said:
Either way, wouldn't all those photons pushing all the particles apart help to expand the "balloon"?

Yes, that is the flaw in your argument. The question no one has answered yet is 'why is this otherwise plausible mechanism not so'? 'Why does photon pressure not push stars apart'?
 
  • #42
gregtomko said:
Either way, wouldn't all those photons pushing all the particles apart help to expand the "balloon"?

gregtomko, we have tried 6 ways from Sunday to help you understand that your idea just doesn't work. I think at this point it would make sense for you to find some reliable sources and read up on the whole thing. This will not only make you forget about your current line of thought, it will also teach you a bunch. This spotty explanation by semi-random questions that were're giving you here is not the best way to go about this.
 
  • #43
Ok, sounds good to me. Thanks for your time though, I really appreciate it!
 
  • #44
phinds said:
gregtomko, we have tried 6 ways from Sunday to help you understand that your idea just doesn't work.
At the risk of being pedantic, all we've really done is explain why we have better ideas. We have not actually shown how his hypothesis is wrong.

I have too many beers in me to create an answer right now, but I think you deserve one.
 
  • #45
DaveC426913 said:
At the risk of being pedantic, all we've really done is explain why we have better ideas. We have not actually shown how his hypothesis is wrong..

OK, I'll bite ... where did I go wrong with the "same pressure from all directions ==> no movement" explanation?
 
  • #46
I hope it has to do with the balloon example, because I don't understand how pressure between all the particles on the "balloon" wouldn't have the result of pushing them all farther apart from each other. Even when you add the third dimension, that too being contiguous with itself and the other dimensions, I don't see what difference it makes.

If I figure that one out, and how Bell's theorem works, I will happy. :-)
 
Last edited:
  • #47
phinds said:
OK, I'll bite ... where did I go wrong with the "same pressure from all directions ==> no movement" explanation?
Not sure...
 
  • #48
DaveC426913 said:
Not sure...

Guess I asked that one badly. What I mean is, why is that not a good explanation? What is incorrect about it?
 
  • #49
What I am missing is why equal pressure from all directions does not translate to equal expansion in all directions.
 
  • #50
Got it:

One of the ways we know that this pressure does not explain expansion is this:

If this pressure from stars were the right idea, then pressure (and thus expansion) would be greatest between objects in close proximity and lesser between objects of greater separation. Two stars one hundred light years apart would push each other with greater force than two stars one hundred thousand light years apart. Two stars a mere one light year apart would push dramatically stronger yet.

But that is not what we observe. What we observe is exactly the opposite. Objects that are farther apart are accelerating away from each other the fastest, whereas objects in close proximity are accelerating away slower. Furthermore, objects even closer than this (scales less than galaxies) are not accelerating away from each other at all.

The proposed mechanism does not explain what we actually observe.
 

Similar threads

B I Need Help on Understanding Some Basic Astrophysics / Sand Clock Universe
Replies
5
Views
2K
B Dark Energy: Are We All Missing The Obvious?
Replies
4
Views
2K
B The accelerating expansion of the universe
Replies
3
Views
2K
I Big bang balloon?
Replies
5
Views
177
B Can the "Dark Energy" concept be wrong?
Replies
13
Views
2K
I Energy conservation in Doppler (NOT cosmological) redshifts?
Replies
13
Views
3K
I On Hubble's constant, the expansion of the Universe and vacuum energy
Replies
6
Views
2K
B Questions regarding energy in the universe
Replies
3
Views
2K
Expansion of the universe, acceleration limit
Replies
23
Views
4K
I Question about the cosmological constant
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top