Dark Energy

Discussion in 'Alternative Theories' started by Farsight, May 14, 2014.

  1. Farsight

    Messages:
    3,492
    Dark energy is usually portrayed as something mysterious, because mystery sells. But if you’ve read what Einstein said and got the gist of gravity, it isn’t mysterious at all. What is, is why Einstein didn't predict the expanding universe. But anyway, on page 185 of The Foundation of the General Theory of Relativity, Einstein said this: "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". That’s "dark" energy. And it’s right there in the room you’re in, right in front of your face.

    Let’s tuck you out of harm’s way, then take the air out of that room. Then we can line it with lead to keep out the cosmic rays, and make it cold and dark so there’s no particles in there. But there’s still a gravitational field in there. There’s still energy there. Some will say there’s virtual particles there, but there aren’t, not in any real sense. Check out Matt Strassler’s website and note this: "A virtual particle is not a particle at all". Virtual particles are like accounting units, like you divide the field into squares and say each is a virtual particle. They aren't real particles. They don’t actually pop in and out of existence. Hydrogen atoms don’t twinkle. Magnets don’t shine. There are no particles in your cold dark empty room. But there is energy there. And it is dark.

    Please Register or Log in to view the hidden image!


    Image credit: NASA

    Some will say it’s just field energy, but they aren’t giving you the whole story. For that, you have to read Einstein talking about field theory in 1929. He was referring to electromagnetic fields and gravitational fields, and he said this: "It can, however, scarcely be imagined that empty space has conditions or states of two essentially different kinds". Did you catch that? According to Einstein, a field is a state of space. It isn’t something separate to space, it’s a state of space. So field energy is really spatial energy. The energy of the gravitational field is the energy of space itself. You can’t see this energy. It isn’t made up of particles. The only thing that’s there is space. And like Einstein said in his Leyden Address, space isn’t nothing.

    It’s really important to appreciate this. And the way to do that, is to appreciate that waves run through it. If you’ve ever looked at displacement current you’ll know that Maxwell talked about transverse undulations. A ripple in a rubber mat is a transverse undulation. It’s a transverse wave. So are light waves. So are gravitational waves, which you can read about at LIGO. See where they talk about the two arms of the interferometer forming an L shape? See where they say "if the two arms have identical lengths”? The thing about waves is this: if a seismic wave moves through the ground, the ground waves. If an ocean wave moves through the sea, the sea waves. And if a gravitational wave moves through space? Space waves. Yes, space waves. And when it does, the two arms of the LIGO interferometer are no longer the same length.

    If you’ve got a rubber mat, give it a shake and watch the wave run through it. A wave in space is like that, but in a three-dimensional bulk. Like I was saying, space can be likened to a gin-clear ghostly elastic jelly. To emulate a gravitational field you insert a hypodermic needle and inject more jelly to represent the E=mc² energy of the Earth. The surrounding jelly is then pressed outwards, and now there’s an energy-pressure gradient in it. Because of this “the speed of light varies with position”. And because of that, light curves. That’s what Einstein said. Light curves like a car veers when it encounters mud at the side of the road:

    Please Register or Log in to view the hidden image!



    Note that the squares are flattened where the gravitational field is. And notice that I said space is like some gin-clear ghostly elastic jelly, and that you inject more jelly to represent energy. It’s like energy and space are the same thing. Take a look at the clear night sky. Don’t look at the moon or the stars. Just look at the space between those stars. Dark, isn’t it? What are you looking at? Dark energy. And get this: space isn’t just some gin-clear ghostly elastic jelly with pressure gradients in it. The whole shebang is under pressure too. It’s like the whole universe is some squeezed-down stress-ball, only you’ve opened your fist. So it expands, like the raisin-cake analogy, something like this:

    Please Register or Log in to view the hidden image!



    Note that the squares aren’t flattened, so there’s no overall gravitational field in the expanding universe. And remember what Einstein said: a gravitational field is a state of space. It isn’t something that sucks space in, so the universe was never going to collapse under its own gravity. Also note that conservation of energy tells you that the cosmological constant can’t stay constant over time, because it’s "the energy density of the vacuum of space". This is obvious once you know about "the strength of space", which is mentioned on page 5 of this paper. If you’ve ever watched the Discovery Channel you’ll have seen the balloon analogy. Think "bag model" and remember the tension. Think of a balloon in a vacuum. A balloon is the size that it is because the pressure inside is balanced by the tension in the skin. But the expanding universe is likened to an inflating balloon, where air is being added. That's not good, because adding air is like adding energy, and conservation of energy is one of the most important laws of physics. A better analogy would be a bubble-gum balloon. Or a balloon made out of silly putty. The skin relaxes a little so it expands a little. But as it expands, the skin gets thinner and weaker. The tensile strength reduces. The dimensionality of energy is pressure x volume. The pressure drops, tension is negative pressure and that drops too, but the volume increases so energy is conserved. Only the balloon doesn’t stop expanding, because the skin gets weaker and weaker. Instead it expands faster and faster.

    It’s all pretty simple when you see it right. You appreciate that the pressure and shear stress in Einstein’s stress-energy tensor is there for a reason. Because space really is like some ghostly gin-clear elastic. You also appreciate that it's the stress-energy tensor because stress is directional pressure and it isn't a million miles away from Kip Thorne's elastodynamics. You appreciate at last that energy tells space how to curve because it's like injecting jelly into jelly.

    Yes, it's all pretty simple when you appreciate that you can't separate space from energy. And that there's a lot of it about. And that space, of course, is dark.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. PhysBang Valued Senior Member

    Messages:
    2,422
    Indeed, if you read Einstein, then you know about the cosmological constant, which is pretty much what we call dark energy today.

    This is clearly an alternative theory, since it disagrees with everything that contemporary physicists and astronomers say.

    Here is another example of Farsight's abuse: he has been told that alternative theories belong in another section, yet he demands recognition as providing mainstream physics, so he is willing to violate rules in order to seek this attention. Sad.

    Please provide a direct citation and the mathematical details that Einstein worked out to do this. And could you compare this to the cosmological model that Einstein worked out where he added a cosmological constant separate from the GR he previously and then later endorsed?

    Please show us where Einstein worked this out. Please also show us where in the WMAP papers they have made the error in measuring the state function of dark energy that indicates that it likely does not change over time.

    Since this is a purely Newtonian paper of an alternative theory that most physicists reject, why should we accept one cherrry-picked statement from this paper?
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. origin In a democracy you deserve the leaders you elect. Valued Senior Member

    Messages:
    10,907
    Farsight does not even appear to understand why dark energy is theorized in the first place and yet he 'explains' dark energy. His explanation has nothing to do with the major observation that result from dark energy. Pretty odd.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Beer w/Straw Transcendental Ignorance! Valued Senior Member

    Messages:
    5,036
    No one understands Dark Energy...
     
  8. Farsight

    Messages:
    3,492
    It's an interesting story. Einstein usually was very bullish about his theory, taking the view that if the theory disagrees with the experiment, the experiment must be wrong. But somehow things went wrong when it came to cosmology. He used a "dusty" universe instead of a universe consisting of space alone. Then he added the cosmological constant to counterbalance the gravitational collapse of the dust. But ended up with a static universe that was like a pencil balanced on its point. He knew that a gravitational field was inhomogeneous space (see his Leyden Address) so he must have know that a de Sitter universe that was homogeneous space had no overall gravitational field. He must have known that the FLRW metric "starts with the assumption of homogeneity and isotropy of space" and so assumes no overall gravitational field. He must have known that space was "flat". And yet he proposed a hypersphere universe. I can't explain why Einstein suffered this "greatest blunder". It's as if he lost some of his spark after about 1920. Maybe it was because he became famous and rested on his laurels. Maybe it was because he wrote so many letters thereafter. I just don't know.

    It doesn't. The universe expands. Dark energy exists. There's a negative pressure. Negative pressure really is tension. Don't blame me if contemporary cosmologists refer to the balloon analogy but not the bag model or the tension that opposes the pressure or conservation of energy.

    Point out what's wrong with what I've said instead of making such naysayer claims.

    It's in the OP. Follow the link to http://www.rain.org/~karpeles/einsteindis.html and look at the paragraph headed "Expanding the theory".

    See my first paragraph above where I talked about Einstein's greatest blunder. He described a dusty hypersphere universe in Cosmological considerations on the general theory of relativity. That's in The Principle of Relativity and doubtless elsewhere.

    He didn't. But conservation of energy is not something we challenge. Not unless we believe in perpetual motion machines and similar magick.

    I can't. All I can do is refer you to conservation of energy.

    You don't have to. Do your own research. Google on f(R) gravity and elasticity, and don't forget the rubber-sheet analogy. Remember that I'm just telling you things you don't know about. I'm not some my-theory guy who makes things up.
     
  9. Farsight

    Messages:
    3,492
    Of course I do. Surely everybody does? A moment's work takes you to the Wikipedia article, which is pretty good:

    "...dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe.[1] Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate".

    See the section heading which includes a small constant negative pressure of vacuum then google on negative pressure tension. Negative pressure is tension. Again, do your own research. Check out what I say. You'll find it checks out.

    Yes it does. The expansion of the universe is increasing because the tension is reducing. Go get some silly putty and watch it droop faster and faster.

    I give the physics with the references to back up what I'm saying. But if you just dismiss it because it's unfamiliar to you, you'll never learn any physics. Now go and do your own research. Go and think for yourself.

    I do. Like I said, it's easy. See the OP. But if you'd rather not, if you're happier with a "magisterium" and would rather be some kind of "custodian of ignorance", you might find some other forum more to your liking.

    NB: See this from the NASA article wellwisher referred to on post #37 on the other thread:

    "One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood..."
     
  10. PhysBang Valued Senior Member

    Messages:
    2,422
    Sure, he used a universe that had matter in it rather than one that did not. The use of "Dust" models means models where the matter does not significantly interact in any means other than gravity, just like matter at cosmological scales to a first approximation. There is nothing incorrect about trying to model the universe as if there were things in the universe.

    That is a lie. In his address, he makes a clear reference to a series of equations (equations that you seem unable to use or understand) that relate the presence of matter and energy to the behaviour of spacetime. Einstein was well aware that "space" is something that is defined by a chosen metric.

    He would not have known something so obviously false. Can you show us where in de Sitter's paper he makes a mistake?

    Given that there is no gravitational field in such a model, what role did Einstein assign to GR in his homogeneous and isotropic model?

    Contemporary cosmologists do not use either analogy in their work. Given that you just admitted that you are not doing the same thing that contmporary cosmologists are doing, it seems that you are admitting that you are presenting an alternative theory.

    That insult aside, Can you demonstrate that the so-called "energy of the gravitational field" produces the same measurable dynamics as the cosmological constant?
    Can you please point to exactly where, in Einstein's work, he shows that the universe cannot collapse because of the presence of matter? The link that you provided does not cover that issue in the paragraph that you identify. Please do not duck this issue again.

    You have not provided any mathematical detials. What you have said gainsays the many, many books on the subject I have nearby. Einstein never abandoned dust-models for cosmology, but he did abandon the cosmological constant and the dynamics that it produces.

    So, please, show us how your alternative theory works, what Einstein missed about GR, and how GR alone produces the cosmological constant behaviour observed and measured very robustly. You can even show us in the toy model of your choice; you must have some alternative model in mind other than a dust model. If this model is effective, surely it would advance contemporary cosmology to see how it works.

    Ao you are admitting again that you are presenting your alternative idea, not Einstein's.
    Can you please explain what conservation of energy means in GR in a global context? Then can you please explain how this is violated by a cosmological constant? Can you please explain how to create a perpetual motion machine using the cosmological constant?
    So you trust wikipedia over the measurement results of dozens of scientists in many different projects?

    No, you seem to be some other type of guy that makes stuff up. You cited the MOND paper as if it is an authority; we should be able to ask why it is a reasonable authority. Did you work through the paper to ensure that the statement you took from the paper is acceptable, or did you take it because you liked the conclusion?

    These are important questions to figure out your scientific method; we need to work through your alternative proposal to see if it is worth believing.
     
  11. PhysBang Valued Senior Member

    Messages:
    2,422
    This "answer by google" does not actually provide an answer. There is no clear evidence, Farsight, that you have done your research.
    Case in point: can you demonstrate that some supposed tension in space can produce the same measured results that we see in available observations? One could just as easily say that there is an expansion of space because there are less and less Norse giants holding space back. Without the explicit link between explanation and measurement, it is just fantasy.


    That isn't true: the physics is in how one can apply your ideas and you need to demonstrate that.
    If it is easy and you are not merely trying to make yourself look imporatant at the expense of others, you should be able to give some simple demonstration of how your theory governs the dynamics of the universe. Remember, as you point out, no contemproary cosmologist is doing things your way.
     
  12. Farsight

    Messages:
    3,492
    There is when it leads to one's "greatest blunder". There's no dust in de Sitter space. In his 1920 Leyden Address he said the contrast between ether [=space] and matter would fade away. So when I read my hero Einstein talking cosmology, it's like I'm shouting "Albert! Lose the dust!"

    Sorry, I have to go. I'll get back to you later.
     
  13. brucep Valued Senior Member

    Messages:
    4,098
    Based on the WMAP prediction the 'dark energy' is the cosmological constant. That Einstein guy was kinda prophetic. Kinda like all them 'other' great scientists.
     
  14. Beer w/Straw Transcendental Ignorance! Valued Senior Member

    Messages:
    5,036
    Or, James Clerk Maxwell was a great scientist.
     
  15. cosmictraveler Be kind to yourself always. Valued Senior Member

    Messages:
    33,264
    Just wondering if dark matter might be spacetime? It is always moving and we know it exists.
     
  16. brucep Valued Senior Member

    Messages:
    4,098
    Farsight has demonstrated he doesn't 'have a way'. With his appeal to authority we know 'for sure' Farsight doesn't have a way to do science. Ipetrich cast Farsight as equivalent to 'a theologian' so I'm not surprised Farsight wants to send 'you' [Physbang] to that particular 'some other forum'. He might be a moderator there.
     
  17. brucep Valued Senior Member

    Messages:
    4,098
    You should read about what science is doing to indirectly verify and measure, and the ongoing experiments to directly detect dark matter particles. A good place to start is how WMAP made the prediction for dark matter and cosmological constant components of the total mass of the universe. It sounds like it's a big assignment when it's just a little reading with you coming out of it reasonably informed. But the simple answer is no. Dark matter has mass, and it's a particle of some kind, so it contributes to the local spacetime geometry like matter does gravitationally. Possibly some very weak 'interaction' electromagnetically if you read about the 'Mirror Dark Matter' theory by Robert Foote. His original paper hit me a bit like the the feeling I got when I understood Guth and Linde's idea for inflation. Once again these folks are on the top rung of my 'other great' scientist list. Just to be clear [but irrelevant] Newton and Galileo are at the pinnacle of my 'other' great scientist list. Spewing crank nonsense about 'the work' they did pisses me off. That was meant for the trolls. IE: Farsight and his band of knuckleheads.
     
  18. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    Moderator Note:
    For someone who spends so much time complaining about the trolling of others, you waste an awful lot of bandwidth on invective rhetoric.
     
  19. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    My recollection, such as it is, is that Relativity predicted that the universe should either be expanding or contracting and Einstein didn't like either idea, he was in the static universe camp, so, he added the cosmological constant and adjusted it accordingly.
     
  20. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

    Messages:
    5,105
    You can read more about that on this link:

    Please Register or Log in to view the hidden image!

    Please Register or Log in to view the hidden image!

    http://en.wikipedia.org/wiki/Fudge_factor
     
  21. Farsight

    Messages:
    3,492
    Trippy: again, you've moved a good physics discussion to "on the fringe". And you have not moderated brucep's post above where he says this:

    "...Spewing crank nonsense about 'the work' they did pisses me off. That was meant for the trolls. IE: Farsight and his band of knuckleheads..."
     
  22. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    I've already deleted one of Bruce P's posts and I am of the opinion that the post you're complaining about is largely on-topic with an unfortunate rejoinder at the end of it, much like your post here. If I moderated one post, I would feel compelled to moderate both posts - this is something that Undefined was never able to understand.
     
  23. Farsight

    Messages:
    3,492
    Origin had not read the OP and was mudslinging. Mine was a valid point. There are people here who seek to stifle discussion.

    And as you know full well, I will not carry on a discussion that has been stigmatised as "on the fringe alternative theories". So that's the end of this conversation for me.
     

Share This Page