Why is dark energy necessary?

In summary, the conversation revolves around the idea that as the mass of the universe is converted to energy through nuclear fusion and nothing can travel outside of space-time, the ratio of energy to mass would increase, possibly resulting in an acceleration of the universe's expansion. However, there is no evidence to support this conjecture and it is not a widely accepted explanation for dark energy. The concept of dark energy remains a mystery and is still being studied by physicists.
  • #1
gregtomko
71
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?
 
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  • #2
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?
 
  • #3
Stars shine in all directions, so the energy can't be translated into a single direction.
 
  • #4
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?
 
  • #5
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.
 
  • #6
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?
 
  • #7
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 :-)
 
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  • #8
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.
 
  • #9
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.
 
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  • #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... :tongue:]
 
  • #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.
 
<h2>1. What is dark energy and why is it necessary?</h2><p>Dark energy is a hypothetical form of energy that is believed to make up about 68% of the total energy in the universe. It is necessary because it helps explain the observed accelerated expansion of the universe.</p><h2>2. How does dark energy affect the universe?</h2><p>Dark energy is responsible for the accelerated expansion of the universe, meaning that the space between galaxies is expanding at an increasing rate. This expansion also affects the growth of structures in the universe, such as galaxy clusters.</p><h2>3. Can we detect or observe dark energy?</h2><p>Currently, we do not have any direct methods for detecting or observing dark energy. However, its effects can be observed through the accelerated expansion of the universe and the growth of large-scale structures.</p><h2>4. Is dark energy necessary for our existence?</h2><p>Dark energy is not necessary for our existence as it primarily affects the large-scale structure of the universe. However, it is necessary for our understanding of the universe and its evolution.</p><h2>5. What are some theories about the origin of dark energy?</h2><p>There are several theories about the origin of dark energy, including the cosmological constant theory, which suggests that dark energy is a constant property of space, and the quintessence theory, which proposes that dark energy is a dynamic field that changes over time.</p>

1. What is dark energy and why is it necessary?

Dark energy is a hypothetical form of energy that is believed to make up about 68% of the total energy in the universe. It is necessary because it helps explain the observed accelerated expansion of the universe.

2. How does dark energy affect the universe?

Dark energy is responsible for the accelerated expansion of the universe, meaning that the space between galaxies is expanding at an increasing rate. This expansion also affects the growth of structures in the universe, such as galaxy clusters.

3. Can we detect or observe dark energy?

Currently, we do not have any direct methods for detecting or observing dark energy. However, its effects can be observed through the accelerated expansion of the universe and the growth of large-scale structures.

4. Is dark energy necessary for our existence?

Dark energy is not necessary for our existence as it primarily affects the large-scale structure of the universe. However, it is necessary for our understanding of the universe and its evolution.

5. What are some theories about the origin of dark energy?

There are several theories about the origin of dark energy, including the cosmological constant theory, which suggests that dark energy is a constant property of space, and the quintessence theory, which proposes that dark energy is a dynamic field that changes over time.

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