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

[phinds]

I am not sure where I am going with it either, it just seems like there might be some significance if there was a similarity. It would at least be a way to disprove an intuitive, yet overly simplistic connection.

I see what you are saying, but even if the quantities were exactly the same, it would have no significance because of the lack of a mechanism relating the two. They just really don't have anything to do with each other.

 

[Drakkith]

What I am questioning is if the total quantity of energy released through nuclear fusion throughout the history of the universe is enough to equal the acceleration we observe. Not if we see certain effects on certain systems. As a whole, the proportion between how much energy is necessary to accelerate the universe as we see, and the amount of energy released in stars throughout time... is that a known ratio?

It is not. It isn't even close.

 

[gregtomko]

It is not. It isn't even close.

Which way is it not close, and where can I find information on that?

 

[gregtomko]

phinds, I don't want to sound sarcastic, but if the two quantities just happened to be the same, you don't think there would be some significance?

 

[phinds]

phinds, I don't want to sound sarcastic, but if the two quantities just happened to be the same, you don't think there would be some significance?

No more than I would find it significant that the total amount of fuel costs for all ocean going vessels this year was the exact same amount as the total fuel costs for all the cars this year. They just don't have anything to do with each other.

 

[gregtomko]

If the whole business of dark energy is so unknown, how can you be sure of that? I would think that conservation of energy in the universe, is far more unified than the international market price for fuel.

 

[Drakkith]

Which way is it not close, and where can I find information on that?

It's not nearly enough. The Earth experiences around 5.823 x 10^8 Newtons of radiation pressure. The force of gravity from the Sun is about 3.5222 x 10^22 Newtons. That means that the radiation pressure reduces the net force on Earth to 35,221,999,999,999,417,700,000 Newtons. (Round it off and its 3.5222x10^22)

 

[phinds]

If the whole business of dark energy is so unknown, how can you be sure of that? I would think that conservation of energy in the universe, is far more unified than the international market price for fuel.

Well, you have to imagine a mechanism whereby the use of energy in stars has an effect that is STRONGER the farther away you are from the star. I just don't buy it. I stand by my statement but I'll grant you that I don't KNOW that it isn't happening. I'd be willing to be lots of money against it though, and I'm not a betting man.

 

[gregtomko]

It's not nearly enough. The Earth experiences around 5.823 x 10^8 Newtons of radiation pressure. The force of gravity from the Sun is about 3.5222 x 10^22 Newtons. That means that the radiation pressure reduces the net force on Earth to 35,221,999,999,999,417,700,000 Newtons. (Round it off and its 3.5222x10^22)

I am not talking about the instantaneous acceleration on our solar system. The question is about the total energy released throughout time by starts in the universe, related to the total acceleration we see in the universe as a whole.

 

[gregtomko]

you have to imagine a mechanism whereby the use of energy in stars has an effect that is STRONGER the farther away you are from the star

That seems to be the similarity between dark energy and dark matter, they are stronger than they should be, the farther away you get. That was the inspiration for the question.

 

[Drakkith]

I am not talking about the instantaneous acceleration on our solar system. The question is about the total energy released throughout time by starts in the universe, related to the total acceleration we see in the universe as a whole.

Extrapolating that out, since radiation pressure is mainly produced by stars, and stars only make up about 1.5% of all matter and dark matter (the stuff that generates gravity), then we can see that the contribution of radiation pressure is absolutely miniscule compared with the combined gravity of the universe. (As my post above showed we can think of radiation pressure as a reduction in gravitation force)

That seems to be the similarity between dark energy and dark matter, they are stronger than they should be, the farther away you get. That was the inspiration for the question.

We have no idea what to expect from either dark matter or dark energy.
Also, what about them is stronger?

 

[gregtomko]

Extrapolating that out, since radiation pressure is mainly produced by stars, and stars only make up about 1.5% of all matter and dark matter (the stuff that generates gravity), then we can see that the contribution of radiation pressure is absolutely miniscule compared with the combined gravity of the universe.

That would be quite informative if the whole concept of dark matter was at all understood.

We have no idea what to expect from either dark matter or dark energy.
Also, what about them is stronger?

I thought that's what I was saying. That dark energy is needed to explain the extra acceleration of the universe the farther away we look. That dark matter is needed to explain the gravitational pull to hold stars farther away from the center of galaxies. The farther away, the stronger the "dark" forces appear to be.

 

[phinds]

That seems to be the similarity between dark energy and dark matter, they are stronger than they should be, the farther away you get. That was the inspiration for the question.

True for dark energy, not dark matter. Yeah, I get the connection, but I still don't believe there's the correlation that you are looking for.

EDIT: I should add --- I learned some time ago that the universe really doesn't give a rat's *** WHAT I believe.

 

[Drakkith]

That would be quite informative if the whole concept of dark matter was at all understood.

OR you could admit that radiation pressure is not a likely possibility to explain universal expansion. That seems much more reasonable than one liners aimed at someone's post you simply don't like. In the future try to understand the subject more before shooting down someone who has actually done the math.

I thought that's what I was saying. That dark energy is needed to explain the extra acceleration of the universe the farther away we look. That dark matter is needed to explain the gravitational pull to hold stars farther away from the center of galaxies. The farther away, the stronger the "dark" forces appear to be.

Dark matter is spread throughout the galaxy, not concentrated in the center. It's effects don't get stronger with increasing distance. Dark energy does not either. The [STRIKE]acceleration[/STRIKE] rate of expansion increases with distance because the space in between galaxies is expanding all at the same rate. IE if you break space down into chunks you will find that each piece is expanding at the same rate. Hence the reason the expansion is faster at increasing distances is because you have more pieces of space expanding between us.

Edit: The expansion is accelerating because of dark energy.

 

[gregtomko]

OR you could admit that radiation pressure is not a likely possibility to explain universal expansion. That seems much more reasonable than one liners aimed at someone's post you simply don't like. In the future try to understand the subject more before shooting down someone who has actually done the math.Dark matter is spread throughout the galaxy, not concentrated in the center. It's effects don't get stronger with increasing distance. Dark energy does not either. The acceleration increases with distance because the space in between galaxies is expanding all at the same rate. IE if you break space down into chunks you will find that each piece is expanding at the same rate. Hence the reason the expansion is faster at increasing distances is because you have more pieces of space expanding between us.

I specifically said I didn't know if radiation pressure is the mechanism. In reference to dark matter, I was saying that it appears to be more influential the farther from the centers of galaxies. Isn't that the whole concept, that galaxies rotations look odd because the outer stars rotate faster than they should? This is true or they wouldn't need to call it "dark matter" right? Just as "dark energy" is more influential on objects farther away from us. If it was a simple relationship there would be no question. Earlier in this line of posts it was stated that the reason the energy of fusion couldn't explain the acceleration of the universe, was somehow it did not fit the characteristics of the observed expansion. I am asking what is the observed relationship. I don't Know what the connection is, that's why I am asking.

 

[Drakkith]

I specifically said I didn't know if radiation pressure is the mechanism. In reference to dark matter, I was saying that it appears to be more influential the farther from the centers of galaxies. Isn't that the whole concept, that galaxies rotations look odd because the outer stars rotate faster than they should?

That is only one observed effect of dark matter. Gravitational lensing is another one. Saying the "dark forces" appear stronger further out implies that the actual force of gravity or expansion increases as distance increases.

This is true or they wouldn't need to call it "dark matter" right? Just as "dark energy" is more influential on objects farther away from us. If it was a simple relationship there would be no question. Earlier in this line of posts it was stated that the reason the energy of fusion couldn't explain the acceleration of the universe, was somehow it did not fit the characteristics of the observed expansion. I am asking what is the observed relationship. I don't Know what the connection is, that's why I am asking.

For every million parsecs of distance from the observer, the rate of expansion increases by about 74 kilometers per second. One parsec = 3.26 light years. Is that what you wanted?

 

[gregtomko]

Saying the "dark forces" appear stronger further out implies that the actual force of gravity or expansion increases as distance increases.

That is your own conclusion, I am not sure that is the relationship.

For every million parsecs of distance from the observer, the rate of expansion increases by about 74 kilometers per second. One parsec = 3.26 light years. Is that what you wanted?

I am looking more specifically for the ratio of the amount of energy needed to accelerate the mass of the universe as we see it, compared to the amount of energy released through nuclear fusion in the stars of the universe throughout its expansion.

 

[Drakkith]

That is your own conclusion, I am not sure that is the relationship.

What? What relationship?

I am looking more specifically for the ratio of the amount of energy needed to accelerate the mass of the universe as we see it, compared to the amount of energy released through nuclear fusion in the stars of the universe throughout its expansion.

The energy needed to accelerate entire galaxies to a significant fraction of the speed of light? To throw out a guess I'd say more energy than has ever been output by every star in every galaxy combined.

 

[gregtomko]

That is exactly what I am interested in. I am sure there is a better understanding than a guess. I don't doubt you are correct about the ratio.

 

[gregtomko]

What? What relationship?

"Saying the "dark forces" appear stronger further out implies that the actual force of gravity or expansion increases as distance increases."

That relationship. That is an odd conclusion.

 

[gregtomko]

In the future try to understand the subject more before shooting down someone who has actually done the math.

So you have done the math? I thought that nobody has ever done the math to explain dark matter, isn't that the whole point?

 

[Drakkith]

"Saying the "dark forces" appear stronger further out implies that the actual force of gravity or expansion increases as distance increases."

That relationship. That is an odd conclusion.

I don't see how. That is exactly the conclusion your statement brings me to.

So you have done the math? I thought that nobody has ever done the math to explain dark matter, isn't that the whole point?

I've done the math for a little bit of radiation pressure. I don't even know what you want to know about dark matter and energy that hasn't already be said. I think you should read up on dark matter and energy on wikipedia. You seem to have some misconceptions that could be cleared up by those articles.

 

[Chronos]

Dark matter does not clump. The dark matter haloes believed to surround galaxies are diffuse, but, there is so much of it [compared to baryonic matter], it need not be very dense to have a profound gravitational influence.

 

[gregtomko]

That is exactly the conclusion your statement brings me to.

I am not trying to draw a conclusion, just ask a simple question.

I don't even know what you want to know about dark matter and energy that hasn't already be said.

All I would like to know is the ratio of energy released from stars through fusion, to that needed for the acceleration of the expansion of the universe. If you could point me to that particular wikipedia page I would appreciate it.

 

[Drakkith]

All I would like to know is the ratio of energy released from stars through fusion, to that needed for the acceleration of the expansion of the universe. If you could point me to that particular wikipedia page I would appreciate it.

There isn't one because it isn't possible for radiation pressure to cause the expansion of the universe. You can't even calculate the "needed energy" because the two effects aren't even related. Radiation pressure would never result in galaxies receding from us greater than the speed of light, only expansion of space will do that.

 

[phinds]

There isn't one because it isn't possible for radiation pressure to cause the expansion of the universe. You can't even calculate the "needed energy" because the two effects aren't even related. Radiation pressure would never result in galaxies receding from us greater than the speed of light, only expansion of space will do that.

I've been trying to tell him that for several posts now, but for some reason he doesn't want to believe it.

 

[gregtomko]

Not the radiation pressure, just the straight a = F/m

 

[gregtomko]

Or is that what I am missing? Is the radiation pressure equal to the total energy released from stars?

 

[Drakkith]

Not the radiation pressure, just the straight a = F/m

Or is that what I am missing? Is the radiation pressure equal to the total energy released from stars?

Energy is released from stars as both EM radiation and as Neutrinos. Neutrinos interact so weakly with matter that they effectively do nothing in regards to our discussion. EM radiation is where radiation pressure comes from. The solar wind is another way that a Star loses energy/mass, however the effect is even less than the radiation pressure, especially over large distances.

 

[gregtomko]

Thanks for your reply Drakkith, it didn't seem right that radiation pressure could account for all energy released from stars. The basic reason for this post in the first place, is that I am curious about the amount of energy released from stars, and how that relates to the purely F=ma of the universe. Somehow a mechanism got introduced into the conversation, and complicated the issue. I just would like to know if there is enough energy released through fusion to accelerate the universe as we see it. Irrespective of the specific mechanism. Or is there just not enough energy to begin with?

 

[Drakkith]

Thanks for your reply Drakkith, it didn't seem right that radiation pressure could account for all energy released from stars. The basic reason for this post in the first place, is that I am curious about the amount of energy released from stars, and how that relates to the purely F=ma of the universe. Somehow a mechanism got introduced into the conversation, and complicated the issue. I just would like to know if there is enough energy released through fusion to accelerate the universe as we see it. Irrespective of the specific mechanism. Or is there just not enough energy to begin with?

Let me first say that I don't think the idea even fits with being possible, however assuming that it might be there simply isn't enough energy to do that. As I demonstrated in my previous posts the radiation pressure is simply much too weak. To even cause an actual acceleration the radiation pressure would need to overcome gravity, and it is not doing that.

 

[gregtomko]

radiation pressure is simply much too weak. To even cause an actual acceleration the radiation pressure would need to overcome gravity, and it is not doing that.

I understand that. It is fascinating to me that in this thread I have been bombarded by assumptions of mechanisms, and reasons why there is no correlation. I am not trying to draw a correlation, or propose a mechanism. I would just like to know about the quantities of energy involved. I really had no idea this was such a contentious question.

 

[gregtomko]

The reason I originally posted this question is, I would like to know if there is too little energy released from stars fusion, to through whatever mechanism, cause the acceleration of the expansion of the universe as we observe it. If there is a difference in the quantity of energy available, to energy needed, is there a known ratio? Or even any understanding of what the ratio might be?

 

[Drakkith]

I understand that. It is fascinating to me that in this thread I have been bombarded by assumptions of mechanisms, and reasons why there is no correlation. I am not trying to draw a correlation, or propose a mechanism. I would just like to know about the quantities of energy involved. I really had no idea this was such a contentious question.

Why would we not ask for mechanisms? The question is entirely unanswerable without taking a mechanism into account.

The reason I originally posted this question is I would like to know if there is too little energy released from stars fusion, to through whatever mechanism, cause the acceleration of the expansion of the universe as we observe it. If there is a difference, is there a known ratio?

To my knowledge no, there is not enough energy to do this through any mechanism. I don't believe there is a ratio because I don't believe there is even a mechanism that could cause the acceleration of the expansion from the release of energy by stars. Someone correct me if I'm wrong.

 

[PAllen]

The reason I originally posted this question is, I would like to know if there is too little energy released from stars fusion, to through whatever mechanism, cause the acceleration of the expansion of the universe as we observe it. If there is a difference in quantities of energy, is there a known ratio?

If you assume (a la Newton, in violation of GR) that you could have a static background space in which stars fuse, emit energy, acting altogether as a mixed gas of light, particles, and stars: then you would have decreasing rate of expansion not acceleration. All contributors to pressure of the gas would decrease as the universe expanded. Thus, this hypothesis is trivially counter-factual.