Tuesday, June 30, 2009

MOND

The UNESCO palace, site of the "Invisible Universe" conference, is across from Ecole Militaire and within sight of the Eiffel Tower. Today there was time for a visit to the War Museum and Napoleon's tomb between talks. Last night I shared a table with Mordecai Milgrom and his wife. This afternoon Milgrom gave a 45-minute talk on MOND, modified Newtonian gravity.

While scientists since Fritz Zwicky and Vera Rubin have looked for "dark matter," Mordecai and colleagues have been developing MOND as an alternative for the last 25 years. Since DM has never been directly observed, the field is open to alternatives. He claims that MOND can match the predictions of DM. The theory is far from complete, Milgrom admits, but today he was able to present before an international audience.

Though they sound similiar, "dark matter" and "dark energy" would be quite different if they both existed. One would attract and the other repel. They possibly share the quality of being misnamed. DM could be made of Black Holes that have never been matter at all. DE can be explained by a changing speed of light. They are both inferences that have never been directly observed.

One of Mordecai's slides had an interesting equation:
a ~ cHo
This is remarkably similar to R = ct, suggesting that they are on to something. (Thanks to nige for pointing out the correct form, which he has pointed out before.) It is good that alternative ideas are being heard.

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7 Comments:

Blogger CarlBrannen said...

When I was just starting out doing physics, I sent a paper proposing an explanation of MOND to Milgrom. He was very kind. I'm sure he listened to you carefully.

I still believe that the graviton theory I'm working on will give MOND as a side effect.

Essentially, there is a difference between the emission and absorption of gravity. One comes with a factor sqrt(n+1), the other with a factor sqrt(n), just as with stimulated emission and absorption of photons (laser effect). The result is that for large n, emission and absorption are nearly equal but at small n, there effects that cause stimulated emission, which is therefore stronger than expected gravity.

9:40 PM  
Blogger nige said...

"adot ~ cHo"

Louise,

a = cH

= 6*10^{-10} ms^{-2}

is the acceleration of the universe. I published the theory predicting that equation, with that acceleration predicted, in a 1996 paper (p896 of the October 1996 issue of "Electronics World"; published in full in the February 1997 issue of "Science World" ISSN 1367-6172).

It was totally suppressed by New Scientist, Nature, Classical and Quantum Gravity, and others, both before during and after Perlmutter observationally confirmed the prediction of thye acceleration of the universe. (I just got elitist sneers of precisely the same sort I got as a kid with a speech defect when I tried to say anything. Nobody wanted to listen. Fortunately my experience with sneering as a kid gave me an understanding of how groupthink works, and I expect any advance to be proudly attacked by mainstream morons nowadays.)

The "secret" to that prediction is that Hubble's empirical recession law

v = HR

can be expressed with R = cT where T is time past:

v = HcT

Now when you observe a supernova at any particular distance, R, it is T seconds in your past and it is also t seconds itself from the big bang instant (at the time it emitted the light that you see T seconds later):

t + T = 13,700,000,000 light years

= 1/H in flat spacetime

Thus we have the equation

t + T = 1/H

This is not present in modern non-quantum (classical) cosmology, which is confused by classical GR metrics and can't address simple facts with simple equations anymore. The value of this equation is that it relates the time past for the observer of any observed event to the time after the big bang for that event.

Hence, T = (1/H) - t

So:

v = HR = HcT = Hc[(1/H) - t] = c – (Hct)

Differentiating v we predicted the cosmological acceleration:

a = dv/dt = d[c - (Hct)]/dt = -Hc = 6 × 10^{-10} ms^{-2}

I recall that the only person who made any kind of scientific comment on this prediction in 1996 was Mike Renardson, MSc (physics), a fellow "Electronics World" writer. He wrote that the acceleration was too small to ever detect, and he couldn't see how such a small acceleration could be connected to gravitation. (Actually, you multiply that outward acceleration by the mass of the universe, and that gives you a very large outward force F = ma.) When I explained the facts, he then sent a letter asking if I seriously expected him to stop "believing" in general relativity metrics. It's pretty obvious that fashionable consensus and groupthink are more important than facts to the indoctrinated.

12:55 AM  
Blogger nige said...

One good thing about MOND is that it provides me with a reference to the acceleration of the universe. You know the mainstream is crazy when they publish 25 books and 200 articles about the discovery of the acceleration of the universe without ever stating what the acceleration of the universe is!

Because of MOND, Professor Lee Smolin did finally publish the number in the chapter ‘Surprises from the Real World’ in his 2006 book The Trouble with Physics: The Rise of String Theory, the fall of a Science, and What Comes next (Allen Lane, London), page 209:

‘... (c^2)/R [which for R = ct = c/H gives a = (c^2)/(ct) = Hc, the a = cH for the cosmological acceleration result predicted theoretically in 1996, unlike Smolin's ad hoc dimensional analysis numerological approximation a Hc dated 2006] ... is in fact the acceleration by which the rate of expansion of the universe is increasing – that is, the acceleration produced by the cosmological constant.’

1:06 AM  
Blogger L. Riofrio said...

Hi nige: Writing from the Unesco Palace, it is promising when ideas like yours are being considered. I should remove the dot atop a to make it look like the equation you wrote.

These adventures show that an idea can be heard, even if it is rejected by journals.

1:18 AM  
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11:27 PM  
Anonymous Bjoern said...

@Nige:
1) Why do you call the product of c and H (you probably mean the Hubble parameter here) "the acceleration of the universe"? The expansion of the universe can't be expressed as a speed (i. e. with units of meters per seconds), since the speed of an object depends on its distance to us (v = HR, as you yourself say), but only as a rate (i. e. with units of one per second) - in essence, the Hubble parameter H. Hence the acceleration of the expansion should have units of one per second squared, not meters per second squared.

2) Why should R = cT hold? With R, you apparently mean the (current) distance of an object to us. Why should this distance be equal to the length of the path which light from that object traveled to reach us? After all, the universe expanded in the time which the light needed to reach us, so the considered object should now be *further* away from us than simply c times T.

3) Why should 1/H in flat space-time give the age of the universe? Solving the Friedmann equations, you get 2/3H for the age of a flat universe.

4) When you do the calculation a = dv/dt = d[c - (Hct)]/dt = -H, you apparently use dc/dt = 0 - in other words, you say that c does not depend on time, i. e. you disagree with Louise's proposal of a changing speed of light. Right?

5) You cite Smolin - but unfortunately you don't tell us what exactly he means by R, and what model of the universe (flat, open, closed, with or without Dark Energy etc.) he uses here. You only say that this is based on a "dimensional analysis" - could you elaborate further, please? As I pointed out above in (1), dimensional analysis should lead to an expression with the units of one per second squared, not meters per second squared.

3:06 AM  
Anonymous Bjoern said...

@CarlBrannen: Is n the number of gravitons, or what?

6:17 AM  

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