Sunday, July 29, 2007

Lunar Observatory


Not long ago talk about a changing speed of light was verboten. "Dark energy" was to be the new paradigm for physics. The flagship of astrophysics was to be a Joint Dark Energy Mission (JDEM) for which the leading concept was Supernova Acceleration Probe. SNAP was to be a 2-meter infrared telescope at the Earth-Sun L2 point, whose mission was to discover more "dark energy." DE was going to create new missions, careers, prizes and loot for big science.

Steinn Siggurdson has been chronicling the slow sinking of NASA's astrophysics program. One trouble is that NASA already is sending an infrared instrument to L2. The huge cost of James Webb Space Telescope is increasing every day, leaving little room for another similiar mission. With no NASA center supporting it, things are looking bad for "dark energy."

Astronomers should not despair of the Vision. As with many problems, the solution is staring us in the face every night. The Moon is a providential location for observatories. For radio astronomy, the lunar farside is shielded from Earth's radio racket. For interferometers and gravity wave experiments, putting instruments on the Moon avoids the problems of formation flying. For deep surveys, placing a telescope on the lunar South Pole allows one sector of sky to be watched for indefinite periods of time. All this can be done for surprisingly little cost.

In California's Silicon Valley, campuses with names like Google and Cisco line the roads like theatre marquees. Friday representatives of some of these companies attended a meeting of the International Lunar Observatory Association. ILO would be a 2-meter multi-wavelength telescope on the lunar South Pole. With the same mirror diameter as SNAP, it could search for supernovae and many other phenomena. Surveys in many areas of the spectrum would create a database that astronomers could mine for years. ILO would be launched on a Russian Dniepr booster, using technology demonstrated by the Cubesat program.

ILO could be built within 2 years of getting funding. Cost would be barely a tenth of SNAP, about 35-50 million US. This project is inexpensive enough to be financed by wealthy individuals. The William Keck Observatory on Mauna Kea was funded this way. Bill Gates Telescope, anyone? Sergei Brin Telescope? Observations from ILO would be available to the world via the web.

An International Lunar Observatory is an inexpensive project that would benefit all humanity. See the figure in the clunky old-fashioned spacesuit? Like Hubble, a telescope on the Moon will need to be serviced by humans. Tomorrow we'll see how that may be done.

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17 Comments:

Blogger Kea said...

Fantastic! I can almost imagine being there! Thanks for a never ending stream of interesting posts.

7:04 PM  
Anonymous Anonymous said...

Louise, you said:
"... DE was going to create new missions, careers, prizes and loot for big science. ... With no NASA center supporting it, things are looking bad for "dark energy." ... ILO could be built within 2 years of getting funding. Cost would be barely a tenth of SNAP, about 35-50 million US. ...".

Over on Cosmic Variance, back in July 2006, JoAnne Hewett blogged about her participation in the High Energy Physics Advisory Panel (HEPAP) and mentioned "... Investment in a phased program to study dark matter, dark energy, and neutrino interactions ...".
In a comment, I suggested a Dark Energy related experimental program that would cost on the order of half a million dollars.
JoAnne replied, saying "... our committee is only charged at looking at experiments that cost $20 Million or more. Anything as inexpensive as you mention is way below our radar screen. ...".

So, your 35-50 Million US$ ILO project may be big enough to be looked at by the Big Shots that run physics in the USA, but still may be dangerously cheap for them to give it serious consideration.

Maybe it is needless to say, but the situation where a possibly useful experiment is rejected as too cheap seems absurd to me. (Happily, the UK is not quite as messed up as the USA, and EPSCR is now actually funding similar work at UCL.)

Tony Smith

PS - I should make clear what I mean by Dark Energy (especially since I mentioned it recently in a comment over on Arcadian Functor). I see Dark Energy as being due to the 4 special conformal generators of the 15-dimensional conformal group Spin(2,4) = SU(2,2).
Since the special conformal transformations deform spacetime, they might be viewed as varying the speed of light, which in my view is consistent with your varying speed of light model.
The main reason that I talk about it as Dark Energy rather than varying c is to try to state the physics in the same terms used by most of the physics community, in the ( unfullfilled in my blacklisted case ) hope that they might understand it.

7:48 PM  
Anonymous Anonymous said...

Sorry that I used a dollar sign that messed up the appearance of my previous comment.

I should have written that paragraph as:

So, your 35-50 Million USdollar ILO project may be big enough to be looked at by the Big Shots that run physics in the USA, but still may be dangerously cheap for them to give it serious consideration.

Tony Smith

7:52 PM  
Anonymous Anonymous said...

Sorry, I used a dollar sign twice, not just the one time that I just corrected.
Here are both paragraphs corrected:

JoAnne replied, saying "... our committee is only charged at looking at experiments that cost US dollars 20 Million or more. Anything as inexpensive as you mention is way below our radar screen. ...".

So, your 35-50 Million US dollars ILO project may be big enough to be looked at by the Big Shots that run physics in the USA, but still may be dangerously cheap for them to give it serious consideration.

Tony Smith

PS - I know the US dollar is perilously problematic in many ways, but I did not realize that it was a troublemaker in blogging software.

7:57 PM  
Blogger L. Riofrio said...

Yes, that pesky dollar sign causes trouble on blogger! My own experimental program has cost less than half a million. It found multiple lines of data from independent sources (including lunar experiments) showing that c has changed. Putting people on the Moon has already been a great aid to astrophysics.

8:33 PM  
Anonymous alex said...

Hello,
How dark energy can be observed in the telescope?
Is it a chance,that instead a changing speed of light or a dark energy the factor which changing is a gravitational constant?

9:48 PM  
Anonymous Anonymous said...

Maybe I should be more explicit about varying c, conformal transformations, and Dark Energy.

If you consider the gravity sector of physics as coming from a modified MacDowell-Mansouri mechanism using the 15-generator Conformal Group,
and
if you let its 4+6 = 10-generator subgroup made up of the 4 special conformal generators plus the 6 Lorentz generators be the subgroup that governs the expansion of our universe,
then
you see that it is the subgroup that varies c, as follows:
The special conformal + Lorentz subgroup preserves light-cones, i.e., maps light-cone to light-cone.
c is determined by the angle of the light-cone, such as, for example,
a 45-degree light-cone corresponds to c = 1,
a 60-degree light-cone corresponds to c = sqrt(3),
a theta-degree light-cone corresponds to c = tan(theta),
so
varying c is equivalent to a conformal map from light-cone to light-cone, changing its angle,
and
you can set up a dictionary between your varying-c physics and the more conventional Dark Energy language. If you do that, then it should be obvious to any fair-minded intelligent person that the wrong-and-simple-minded slogan "varying c is crazy and anyone doing it must be crackpot" used by your critics is really in fact wrong-and-simple-minded.

Further, when you compare that 10-generator subgroup to the total 15-generator conformal group,
you see that the varying-c subgroup makes up 10/15 = 2/3 of the whole conformal group, and that is roughly the fraction that is commonly thought of now as Dark Energy.

Tony Smith

PS - As to the other 5 generators of conformal Spin(2,4), physically you have:

1 dilation that looks like a scalar Higgs field, so it should be what gives rise to the mass of Ordinary Matter, which should make up roughly 1/15 = 6.7 per cent of the total

and

4 translations that describe 4-dim spacetime whose basic singularities are primordial black holes, which should be Dark Matter making up roughly 4/15 = 27 per cent of the total

so that the DE : DM : OM ratio is roughly estimated to be
67 : 27 : 6.7

When you take into account that expansion of the universe itself changes the relative densities, you see that the ratio varies with the age of the universe, and that at its present age the ratio is calculated to be about
75.3 : 20.2 : 4.5
which is substantially what WMAP observed.

4:28 AM  
Blogger Kea said...

Interesting comments, Tony. But I think using the term 'Dark Energy' would only confuse the issue (as to what we actually meant by it) and I cannot imagine it would lead to people taking all this seriously! And Louise has already derived the 'DE' and baryonic mass fractions.

1:01 PM  
Anonymous Lubos Motl said...

You mean "derived". I've yet to see anything really derived here!

Best
Lubos

4:52 PM  
Anonymous Anonymous said...

I understand that Louise has already derived the
DE : DM : OM ratio,
using
the ratio 2 pi / 6 of critical density / nonbaryonic density to get the baryonic OM / Total part,
based on a spherical Riemann Universe of volume 2 pi pi R R R representing the universe prior to formation of baryonic OM,
and
for the DE / Total part using a Gaussian distribution to assign 68% as regions of overdensity that would, due to collapse, correspond to voids.

Since "... a Riemann universe ... admits of a continuous group of conformal transformations ... a 15-parameter group in a spherical de Sitter universe ..." (according to a paper by Chernikov and Shavokhina in Russ. Phys. J. 41, No.10, 1055-1060 (1998)),
Louise's calculation of baryonic OM uses conformal structure and should be (as it is) consistent with the conformal structure calculation that I use.

Since the Gaussian distribution is an approximation to the Binomial distribution, and since the 15 generators of conformal Spin(2,4) have an almost-Binomial graded structure
1 4 6 4 -
where the Lorentz 6 and the special conformal 4 make up the 10 Dark Energy generators
and
where the Gaussian 68% would correspond to the 6 and half of each of the 4s
- 2 6 2 -
which also gives 10 generators
it is clear that Louise's calculation of DE is also consistent with the conformal structure that I use.

I am only trying to point out that you get the same results and the same basic physics as Louise's from the conformal group point of view,
and
that conformal transformations are implicitly in Louise's picture of two regions of spacetime with two different values of c
because
the transformation between them that preserves light-cone structure is a conformal transformation,
so
I thought that presenting the same results in a conformal way might lead to wider acceptance of Louise's model.

My apologies if I misrepresented anything, and if I am wrong thinking that it might lead to wider acceptance.

Tony Smith

6:19 PM  
Anonymous alex said...

how about a more popular explanation?

7:51 PM  
Blogger L. Riofrio said...

Alex, a varying G has been exsplored by Dirac and many others. It is ruled out by many experiments, even data from the Viking lander. If G changed, planetary orbits would not be stable and life would not have evolved on Earth.

Kea is right that "dark energy" is an unfortunate and misleading term. The idea of a repulsive energy is a lot like the emperor's New Clothes. Claiming an energy that doesn't exist is going to ruin the reputation of physics.

Lubos, you are welcome to peruse the papers and calculations available through this site. Since the 2004 paper I have explored sinusoidal rather than Gaussian distributions. This would lead to 71.62% of mass in "voids," 23.87% dark mass, and remain with 4.507034% baryons.

8:10 PM  
Blogger Kea said...

OK, thanks, Tony. Actually, I really like your conformal point of view because it fits with some twistor thinking that I'm fond of, but I simply disagree that we should adopt the term 'DE' just to make people happy.

1:21 PM  
Anonymous Anonymous said...

Kea, I don't use the term "Dark Energy" "... just to make people happy ...".
In fact, I was not happy a few years ago when "Dark Energy" became the term that replaced "Cosmological Constant",
but
somehow it became the commonly used term for that phenomenon. For example, in the 19 July 2007 issue of Nature, there is a News Feature on "Unseen Universe" in which Michael Turner is quoted as saying
"Dark energy seemed to be the piece that made everything else work."
and
in which there is a density v. equation-of-state diagram entitled "Closing In On Dark Energy".

Although I don't like the term "Dark Energy", I use it because it is the present-day common-language label for the phenomenon, and if I use another term, a lot of people (such as most readers of Nature) will not know what I am talking.
Even so, an unconventional model like mine has very few readers.

What term would you prefer for the phenomenon causing apparent acceleration of expansion of the Universe ?

"Varying-c" and "conformal gravity" and "twistor gravity" are three possible candidates, but any of them would require a sort-of-lengthy explanation to explain to a typical Nature reader how and why such a term corresponds to what most people now call "Dark Energy", and many such readers might not be patient enough to listen to or read about such an explanation.

Whatever you call it, it seems that there are different regions in the spacetime of our universe in which c ( or conformal structure or twistor structure ) takes different values,
and
so there may be phase transitions at the boundary of such regions.
One such region might be roughly a sphere around our Sun at the orbit of Uranus,
and
such a phase transition seems to account quantitatively for the Pioneer anomalous acceleration (according to calculations I did using the conformal language - there should be equivalent calculations in varying-c and twistor languages).

Since calculations (in all those languages) also give accurate values of what is known as the ratio
DE : DM : OM (sorry for use of that terminology)
the approach that Louise and you and I use solves not only cosmological issues, but also the Pioneer Anomaly.
I wish that a significant part of the physics establishment would pay attention.

It is very frustrating to read things like the Nature article that says there is
"... no clear explanation of something that could be up to three-quarters of everything out there ..."
and
"... In general, the theoretical side of the debate is not a pretty thing. "We've tried a whole bunch of things and nothing has sprung forward", says Sean Carroll, a theoretical physicist at the California Institute of Technology in Pasadena. ...".

In fact, Louise and you and I have put forward things that work, and it is maddening that they are not only ignored, even suppressed,
but
prominent spokemen for the field get away with saying that "nothing" that works has been put forward,
and Nature spreads the Big Lie.

Tony Smith

6:04 PM  
Anonymous Anonymous said...

I wish that a significant part of the physics establishment would pay attention.

The problem is that we are all so highly unrespectable. I get ignored, or called crazy (I was almost committed to a mental hospital for the second time by my own family on the hearsay of my 'colleagues'). Now I see more and more 'respectable' people heading this way, and even they get ignored or called crazy. But at least that's the next step in the process - in the next round there will be well-known people saying something along these lines. Patience wears thin, yes, and no doubt you'll never be given any credit, but let's face it - that's not really why you spent so many years thinking about these things...

6:39 PM  
Blogger L. Riofrio said...

I definitely sympathise with you Tony. Humans act out of self-interest, and the old guard wants to keep their cushy jobs. The good news is that more and more people are getting our message.

If one side peddles a Universe dominated by invisible energies and confesses that they have no explanation anyway, who is the crackpot?

7:15 PM  
Anonymous Anonymous said...

To my knowledge, ILO has never presented itself as any more than a microwave telescope. Not a near- infrared telescope. You aren't going to see supernova with a warm microwave telescope.

Get real, though. The Moon is hardly a "providential location" for observatories. It is dirty, and has gravity. You can find niches of astronomical value there, but rather little of use compared with free space for what astronomers consider priority science.

And give me a break. "All this can be done for surprisingly little cost"? Go ahead, surprise me. Give me some dollar numbers. Farside radio astronomy, interferometers, and polar zenith telescopes are not cheap by any stretch of the imagination. ILO might look cheap, but, ahem, on the basis of what little the developers want to tell us about it, ILO can't do hardly anything.

4:45 PM  

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