The Lorne Trottier Public Science Symposium (link to poster)

A COSMIC COINCIDENCE: WHY IS THE UNIVERSE JUST RIGHT FOR LIFE?

January 25, 2007
5:00 p.m. — 7:00 p.m.
Stephen Leacock Building, McGill University
(Montreal, Quebec, Canada)

Panel: Paul Davies, George Efstathiou, David Gross, Leonard Susskind

Moderator: Victoria Kaspi (McGill, Astrophysics)

Also I have come across papers by Peebles, Damour, Visser (and perhaps others)
which talk about dark matter with scalar interactions, or dark matter with non-zero pressures
and many other exotic models for dark matter.

If this is really true, then of course the distinction between dark matter and modified gravity
becomes much more blurred and then whether you call it dark matter or modified gravity
or both is only a pedantic question. Do you agree?
Thanks

I am afraid I brought this epoch making news down to street level. My apology to scientists.

“We’ll find dark matter when pigs fly?”

As DM gets clumpier and collapses more, will they someday find literally pitch dark black holes/clusters?? A total amateur ponders, probably a totally dumb question.

Cheers.

Allyson, I’m happy to come to JPL to give a talk. But not about this! See above.

“…most of the dark matter concentrations are indeed found where ordinary matter is. But (apparently) some of the smaller ones [concentrations] are not.”

Let me pose two questions regarding this statement:
1) What is the current estimated breakdown between “clothed” dark matter (meaning dark matter draped in ordinary matter) and “naked” dark matter (meaning dark matter not draped in ordinary matter)?
2) From looking at this 3-D image, how’s one to distinguish between what clumpy shapes/colors represent “clothed” dark matter, and–on the other hand–what clumpy shapes/colors represent “naked” dark matter? In other words, is the difference between “clothed” and “naked” expressed in , for instance, contrasting colors and/or contrasting shapes?

By the way, I’m aware of the evolution of time (the cosmic arrow of time, so to speak) within this 3-D image. To me, however, this 3-D image just doesn’t seem to convey this issue of “clothed” versus “naked” dark matter…

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kapakapa

You are not alone. The entire picture looks to me like a cluster of flying pigs. (“We’ll find dark matter when pigs fly?”)

Diagram of the Lagrange Point gravitational forces associated with the Sun-Earth system.

The example of “how one may see” is further expounded upon to show how dark matter and dark energy are in action as a 90% aspect of the cosmos, while the remaining 10% is a discrete measure of what is cosmologically matter orientated. We don’t loose sight of these relationships, but are helped to further develop them in terms of this gravitational relationship.

I think that yes, negative energies could give rise to a simliar dispersive effect as underdense regions. If you found that they only way to fit the data was to invoke negative energies — well, that would be interesting.

Thanks. Nah, I’m not fitting any data (so far), just wanted to make sure.

You are mentioning the Jeans inst. to say a uniform gas wouldn’t stay uniform? My argument doesn’t rely on the negative density to be uniformly distributed (I just used that for an easy example). In fact, I’d want it to clump like ordinary matter. As mentioned above, such a distribution when left alone would make a diffraction lensing which is hard to detect, but in some configurations it would act just like a gravitational lens.

Hi ovido,

I think that B’s first question (comment #4) is about the sheet-mass degeneracy. Does anyone want to answer that question?

Never heard of the sheet-mass degeneracy, but if anyone wants to explain it to me – go ahead!

Best,

B.

It may be simply a logic fact that we need DM and it’s lensing properties in order to factor where our Galaxy ends, and other Galaxies begin?

Am I the only one who sees an ensconced cosmic-hippo happily surrounded by a jugon, a flying pig, a manta ray and even a floating peace of chocolate?

I’ll get me a coat.

Sean, I am really sorry I missed you. I suspect Jennifer can fill you in.