Science on Sunday with John Duffield: Dark Matter

The evidence for dark matter is provided by flat galactic rotation curves, the orbital motion of galaxies in clusters, and gravitational lensing, such as that of the Bullet Cluster:

There’s just not enough visible matter to account for all the gravity. Strictly speaking this might be because gravity doesn’t quite work the way people think, as per Mordehai Milgrom’s MoND. Or it might be because there’s a lot of ordinary matter out there that we just can’t see. Neutrinos are ordinary matter, and they are dark matter of sorts. So are orphan planets far from any sun, along with other MACHOs such as black holes. We’re fairly confident that such things are out there, for example there’s a supermassive black hole in the middle of our galaxy, and we can’t see it. But most cosmologists think there’s not enough ordinary matter to account for dark matter, and most don’t favour MOND. Instead they favour the idea that dark matter consists of exotic particles called WIMPs.

However there’s a problem. WIMPs are predicted by supersymmetry, which has been around for fifty years. And none of the particles predicted by supersymmetry have been observed. None. Hence nowadays supersymmetry is a busted flush. Google on death of supersymmetry. Soon it will get a stake through the heart, then they’ll bury it deep. Meanwhile the WIMP is a dead man walking. It isn’t long for this world.

So if dark matter is none of the above, what is it? If you know a bit about relativity and conservation of energy you can work it out. You start off with the rubber sheet analogy. There’s a bowling ball sitting on the rubber sheet to represent a massive galaxy. The bowling ball causes the rubber sheet to sag, and this represents the galaxy’s gravitational field. Only the universe expands, so the rubber sheet gets bigger. Think about it. If you had a rubber sheet that started off 1m in diameter and ended up 2m in diameter, what’s got to happen? The rubber sheet has to get thinner, that’s what. So the bowling ball sags down lower, like this:

bowlingballgravity

If you didn’t know your rubber sheet got thinner, you might think your bowling ball was heavier than it really was. In terms of its gravitational field, it’s now punching above its weight. Because of that, you might think that dark matter doesn’t exist.

Don’t.

Look closely at the depiction above, and remember this: space expands between the galaxies but not within. So in our analogy, the rubber sheet doesn’t get thinner where the bowling ball is. So the bowling ball ends up nestled in a still-thick portion of the rubber sheet. A heavy portion, that causes the bowling ball to sag even lower. That’s your dark matter.

Of course, the rubber-sheet analogy isn’t ideal. It’s better to think of space as a ghostly gin-clear block of jelly. Like I was saying a couple of weeks back, when you inject more jelly in the middle you create a pressure gradient in the surrounding jelly. Curved spacetime is essentially a plot of this pressure gradient, and as John Baez said, curved spacetime isn’t curved space. Space isn’t curved in a gravitational field. Instead, like Einstein said, it’s inhomogeneous.

OK, let’s take a look at some galaxies, courtesy of NASA. We start with two galaxies close together and take a slice through the middle to avoid getting confused by round things. Then we depict their gravitational fields as inhomogeneous space, like so:

 galaxystrip1

galaxystrip2

Then we let the universe expand, so the galaxies get further apart, like the raisin cake analogy. Galaxies are gravitationally bound, so space expands between the galaxies but not within. So the energy density of space between the galaxies reduces by virtue of conservation of energy, whilst within the galaxies, it doesn’t. So the inhomogeneity of space increases. And what’s a gravitational field? Inhomogeneous space. So the galaxies end up with deeper gravitational fields than they had previously:

 galaxystrip3 galaxystrip4

The depiction for one galaxy is something like looking at the rubber sheet from above. The energy density of space within the galaxy didn’t reduce, and like Einstein said, E=mc². That energy has a mass equivalence, so the energy of space acts just like energy tied up in the form of matter. It has a gravitational effect. It’s like the still-thick portion of the rubber sheet causing it to sag further. So the galaxies have even deeper gravitational fields. So gravity is “modified”. Which means there is a sense wherein Milgrom has always been on the right lines. And the same goes for his competition, the guys who talk about dark matter.

So what is dark matter? It’s inhomogeneous vacuum energy. Or inhomogeneous dark energy. Or take your pick, because 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”. The space where a gravitational field is, has a higher energy density than free space, so it has a gravitational effect. So it’s dark matter. That might come as a surprise, but remember that jelly analogy. The jelly represents space, and you inject more jelly to represent energy, so at the fundamental level, energy and space are the same thing. And what’s matter made out of?

This is where you wash up when you read what Einstein said. He talked about space as the aether of general relativity, and how the contrast between aether and matter would fade away. And that a field is a state of space. What’s a quantum field? A state of space. What’s field energy? Spatial energy. What’s dark energy? Spatial energy. What’s dark matter? Inhomogeneous spatial energy. What’s a gravitational field? Inhomogeneous spatial energy. What’s matter made of? Energy. What’s space made of? Energy. What’s energy made of? Space. It reminds me of Chinatown: She’s my sister. Slap. She’s my daughter. Slap. She’s my sister and my daughter.

What goes round comes round. Space is dark, and there’s a lot of it about.

15 comments on “Science on Sunday with John Duffield: Dark Matter

  1. dr
    November 3, 2013 at 6:55 pm #

    Its highly likely that the person or team that “discovers” or observes “dark matter” will win the Nobel Prize.
    Since you have explained things here, Mr Duffield, I suggest that you publish the mathematical formulation of these ideas in a scientific journal as soon as possible, and wait for the notification letter to hit your doormat.

    • therealguyfaux
      November 3, 2013 at 9:47 pm #

      Presumably a Nobel in Physics carries more weight (and velocity?) than the Peace or Economics iterations.

      One would think a demonstrable and replicable phenomenon would be required as the basis of such an award, and that it would not simply reflect the bent of the Prize Committee.

      Mind, it still might require politicking for someone to get it– I read these columns, and as science, they’re Double Dutch to me, but as a reflection of human psychology, “My theory can kick your theory’s ass!” is fun to read about. Such internecine intramural squabbling occurring, even in the sciences– who’d’a thunk it?

  2. duffieldjohn
    November 3, 2013 at 8:58 pm #

    Easier said than done. Note that what I’ve said here isn’t something entirely new or unique. Some of it goes back a hundred years, and see for example http://arxiv.org/abs/1209.0563. It’s just unfamiliar to most because the WIMP hypothesis has won the “marketing battle”. Sabine Hossenfelder touched on that in her blog at http://backreaction.blogspot.co.uk/2013/10/science-marketing-needs-consumer.html. People promote the theory they’re involved in, and try to impose a consensus at the expense of the competition even when there’s no supporting evidence. By the way I thought Matt Strassler gave a fair account of dark matter and LUX in his blog:

    http://profmattstrassler.com/2013/10/31/questions-and-answers-about-dark-matter-post-lux/

    Note this bit: “Do we know dark matter is made from particles (i.e. ultra-microscopic objects with uniform properties)? No, that’s not certain. Particles would do the job, but that’s not a proof it is made from particles”.

    • B. Prior
      November 4, 2013 at 1:24 pm #

      “So if dark matter is none of the above, what is it?”
      It’s true that WIMPs from supersymmetry are looking in poor shape, especially after the LUX results you mentioned later. However they aren’t the only cold dark matter candidates. The axion is an alternative, as is a sufficiently heavy sterile neutrino.

      “If you know a bit about relativity and conservation of energy you can work it out.”
      Here I’m afraid you’re going off the rails. You are reading things into what Einstein may have said in some lectures and reading things into some rather poor analogies. The facts of general relativity, expressed in Einstein’s equations, are clear.

      Space isn’t a rubber sheet. It doesn’t get thin when it expands. Potential wells don’t get deeper because of the expansion of space (which isn’t to say that the don’t evolve in other ways as time passes, e.g. by structure formation).

      If this explanation of yours *were* dark matter we could tell what was up by simply calculating the gravity from GR rather than using a Newtonian approximation. It doesn’t help – if you do it you’ll still need extra matter. Your explanation also fails to explain the difference in distribution between baryonic and dark matter (especially that dark matter distributes more widely than baryonic matter), and fails to explain why solar system dynamics or certain systems on other scales don’t show any evidence for dark matter. It doesn’t explain why early in the universe when potential wells weren’t so deep that dark matter was apparently still at work (without it you won’t get things to collapse fast enough to form galaxies).

      “Galaxies are gravitationally bound, so space expands between the galaxies but not within. So the energy density of space between the galaxies reduces by virtue of conservation of energy, whilst within the galaxies, it doesn’t. So the inhomogeneity of space increases. And what’s a gravitational field? Inhomogeneous space.”
      No, try doing the calculations rather than doing it by analogy. Also, gravitational effects don’t require inhomogeneity of space. You can have both gravitational effects in flat space (a flat cosmology is the obvious example, where there is both matter and dark energy in the right proportion to the expansion rate), and also a space of constant curvature (which is therefore homogeneous).

      “So what is dark matter? It’s inhomogeneous vacuum energy. Or inhomogeneous dark energy. Or take your pick, because 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”. The space where a gravitational field is, has a higher energy density than free space, so it has a gravitational effect. So it’s dark matter. That might come as a surprise, but remember that jelly analogy. The jelly represents space, and you inject more jelly to represent energy, so at the fundamental level, energy and space are the same thing. And what’s matter made out of?”
      No, dark matter has zero pressure (or very nearly so), and dark energy has negative pressure. The two are not the same, and they aren’t the non-linear effects of energy in the gravitational field. If you want to claim this, you need to be able to reproduce, as I said above, the apparent distribution of dark matter from that of baryonic, and explain the proportion of dark energy to dark matter, and a lot more.

      The De-Santiago et al paper you reference in your comments does not represent the same sort of ideas you are trying to put forward here. They look at dark energy that may interact with the matter components in ways other than gravitationally. It in no way supports the idea that dark matter is just some effect of general relativity that everyone has been ignoring. I don’t know why you’ve picked up on it other than that it may contain some keywords you like.

  3. duffieldjohn
    November 4, 2013 at 9:03 pm #

    With respect, I must urge you to read what Einstein said. Space isn’t nothing. A field is a state of space. A gravitational field is inhomogeneous space. Thus if space expands in a non-uniform fashion the state of space changes, and you know full well that the universe expands but galaxies are gravitationally bound. No, space isn’t a rubber sheet, but there is that shear stress in the stress-energy tensor. You cannot calculate the gravity from GR because the vacuum catastrophe stands in the way and space has expanded a thousandfold since the CMBR. Dark “matter” is distributed more widely than baryonic matter because the latter binds it like a stitch. The solar system shows no evidence for dark matter because the space within the galaxy hasn’t expanded. Gravitational effects do require inhomogeneous space because that’s what a gravitational field is. Curved space is electromagnetism, and you are confusing space and spacetime. Dark energy doesn’t have a negative pressure, last week you confused positive pressure with opposing negative pressure which is the tension in the balloon skin, which relates to the strong force. The paper I mentioned was merely indicative. Another one you will find of interest is http://iopscience.iop.org/0256-307X/25/5/014 along with http://arxiv.org/abs/physics/0204044. Also read these previous blog entries with care:

    http://bogpaper.com/2013/09/29/science-sundays-with-john-duffield-time-travel/
    http://bogpaper.com/2013/10/06/science-sundays-with-john-duffield-speed-of-light/
    http://bogpaper.com/2013/10/13/science-on-sunday-with-john-duffield-gravity/

    Whilst 2 out of 3 authors of MTW did/do believe in time travel, the first of the above blogs hopefully presents no issues to you. If the second one does, talk to Don Koks at Adelaide. Once you’re reconciled with that, there’s no escaping the third. I hope thereafter you will have a better understanding of what I’m saying here. As I said last week, I’m not making this up, and nor was Einstein.

    • B. Prior
      November 4, 2013 at 9:51 pm #

      Einstein entirely and precisely specified GR with one equation. Why don’t you use that and demonstrate mathematically your claim?
      What he said in less formal context is irrelevant.

      • duffieldjohn
        November 4, 2013 at 11:21 pm #

        Don’t dismiss what Einstein said as irrelevant. What he said isn’t irrelevant. Read what he said. Understand what he said. Then you’ll understand that equation. And read that other material too instead of playing the “demonstrate mathematically” naysayer card. Understand time, understand the speed of light, understand gravity. What would you rather do? Dismiss Einstein along with the hard scientific evidence because you’d rather believe in WIMPs and axions that have no evidential support whatsoever? When general relativity is one of the best-tested* theories we’ve got?

        Please don’t hesitate to ask your supervisor to comment, whereupon I will advise and inform accordingly.

        * http://arxiv.org/abs/gr-qc/0510072

      • B. Prior
        November 5, 2013 at 10:42 am #

        I fully support Einstein’s GR as a good model of gravity on all scales tested to date. I understand better than most how that model works and what the observed data combined with that model suggest. It’s disingenuous of you to suggest I’m going against Einstein, or that thinking some kind of dark matter particle (I don’t have a strong opinion on what that is likely to be) probably exists is somehow going against GR.

        I am claiming you have a very poor understanding and that the many of the things you present are not representative of Einstein’s theory, and it is a real shame you are misleading people here with your posts.

      • duffieldjohn
        November 8, 2013 at 1:07 pm #

        I’m the one giving the Einstein quotes here. It isn’t me who’s been misleading people. The people who do that peddle an ersatz version of relativity and appeal to Einstein’s authority, even though they contradict what he said. Then they dismiss what he said as “irrelevant”, along with the hard scientific evidence like optical clocks and Shapiro. For example Einstein said repeatedly that the speed of light is not constant*. But all we get is “Einstein told us the speed of light is constant”. It can’t go on, B.

        * http://bogpaper.com/2013/10/06/science-sundays-with-john-duffield-speed-of-light/

  4. shorelark
    November 7, 2013 at 10:53 am #

    Hi all

    I thought this was SCIENCE on Sundays, not theology. What we know in classical mechanics is that points of a rotating rigid body have a speed proportional to their distance from its axis, while the speed of orbiting bodies varies inversely with the square root of the distance from the attractor. Examples might be the rotation of the moon and its orbital motion around the earth, while the rings of Saturn illustrate the case of a multitude of independently orbiting particles.

    To generalise, cases intermediate between orbital and rotational motion involve a stiffening of the mix, again represented by some power of the distance. The outer layer of the sun is of special interest, where gravity and matter take second place to electromagnetic fields and plasma currents.

    Thinking in these terms, what stiffening of the outer arms of the galaxy would produce the observed galactic speed anomaly, representing a power of zero? My answer would be to look for more of the same, exhausting the resources of classical theories before looking further afield.

    To the best of my knowledge Newtonian mechanics and plasma physics are valid on the scale of the galaxy, and should require no fudging to fit. I don’t know whether the project is feasible, but many physicists believe it is, and a few have already claimed some success.

    • B. Prior
      November 7, 2013 at 9:13 pm #

      Trying to invoke electromagnetic forces really doesn’t work. You can measure the magnetic fields in galaxies for one thing, and therefore estimate their maximum possible effect. You can observe that the forces don’t seem to be be affected by the ionisation state of the matter. You can also observe that gravitational lensing happens in the right size for it to be a gravitational effect and not electromagnetic effects that make up the difference between the prediction from gravity of visible matter and what is observed. You will also find it doesn’t help explain the Bullet Cluster and similar results, nor the fact that the limits on baryons are rather low, and yet the universe does not have an open geometry.
      We’d love it if we could do it without extra ingredients, but it cannot be done.

      • shorelark
        November 9, 2013 at 10:10 am #

        Hi BP

        There is a big difference between science (physics) and cosmology (astronomy) in what passes for proof. Consider; some astronomers have figured out a procedure (weak gravitational lensing) for estimating the quantity and distribution of dark mass in the Bullet Cluster. I can’t make head nor tail of this. I am not going to try.

        As far as I am concerned, their findings should be taken with a large pinch of salt, since they have no means of validating their procedures. They might, for example, have swept out all the dark matter from the vicinity, to observe the residual lensing effects of the ordinary matter. Or maybe they could just have collected some of the dark stuff in a jar?

        Don’t you think it’s strange though, that the only effect of dark matter in the cosmos is to create oddities that advertise its existence?

        Regards

    • John Duffield
      November 8, 2013 at 12:47 pm #

      Shorelark: what I’ve told you about here is something Newton would have been happy with. I’m a big fan of Newton, see my “Mr Newton’s Classroom” in physicsworld*. Also see the Newton quote in the gravity* article and make sure you read Einstein’s Leyden Address*. Light veers left if space is “denser” on the left. Then when you know about the wave nature of matter you can understand why the electron falls down, and it’s only a short step from there to orbital mechanics then stars in galaxies. It isn’t quite Newtonian mechanics, but it’s plain-vanilla stuff, and it’s still relativity. Mind you when you read about this sort of thing from guys like Albrecht Giese* he says things like “relativity with Einstein”. I’ve nagged him about that and told him to read Einstein’s Leyden Address, but he hasn’t changed his website.

      * http://mag.digitalpc.co.uk/olive/ode/physicsworld/LandingPage/LandingPage.aspx?href=UEhZU1dvZGUvMjAxMC8wNy8wMQ..&pageno=NTA.&entity=QXIwNTAwMA..&view=ZW50aXR5

      * http://bogpaper.com/2013/10/13/science-on-sunday-with-john-duffield-gravity/

      * http://www-history.mcs.st-nd.ac.uk/Extras/Einstein_ether.html

      * http://ag-physics.org/gravity/

  5. duffieldjohn
    November 8, 2013 at 12:50 pm #

    The link above doesn’t work, google on physicsworld Duffield “Mr Newton’s Classroom”.

  6. Zephir
    July 25, 2016 at 8:20 pm #

    Dark matter is formed with scalar waves of Nicola Tesla https://www.reddit.com/r/Physics_AWT/comments/4tycm7/scientists_looking_for_invisible_dark_matter_cant/

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: