Search for the Missing Universe

Chris Gondek writes "The Sydney Morning Herald has reported that one of the greatest discoveries of our time could be made under the Yorkshire moors. Deep in a Yorkshire mine, scientists are toiling to solve a cosmic puzzle that has baffled astronomers for 70 years: about 90 per cent of the universe is missing. Analyse the movements of stars and you can work out how much matter is making them swirl round in galactic islands and how much makes galaxies cluster together as they do - in other words, you can work out how much mass makes the universe look the way it does. But measurements suggest that the universe is not what it appears."

Comments

Historical Analogues

[Farley Mullet]

Back in the 19th century, astronomers had noticed that there was a minute procession in the perihelion of Mercury (in other words, the point in Mercury's orbit that is closest to the sun kept moving forward) that they couldn't account for using the Keplerian/Newtonian model of celestial dynamics. Astronomers thought that it must have reflected the influence of some massive, distant unknown planet; predictions were made about where this planet was and what its mass was, but astronomers couldn't find it. Then all of a sudden General Relativity came along, and our understanding of mechanics in gravitational fields was improved, and the procession was easily predicted (within an incredibly small margin, as I recall). So it seems just as likely that the "missing mass" is due to a theoretical deficit as it is due to an observational deficit.

Stephen Hawking's wishful thinking

[kindofblue]

In his book, A Brief History of Time, I think he said something to the effect that he believes that we'll figure out most of the big questions about the nature of the universe within 10 years or so. That was about 15 years ago. Does anybody remember reading this?

When I saw that, I remember thinking that's naive and contrary to the entire history of scientific research. Anyway, it reminds me that even some of the best minds say some of the stupidest things. Especially in physics.

I'm not a physicist but I'm pretty damn sure that Stephen Wolfram and Roger Penrose have had some pretty wacky theories when they venture away from straight physics, like into cellular biology, free will, philosophy, ...

Not True

[efuseekay]

Not true.

Gravity is only tested to solar system scales, and in an indirect way, galactic cluster lensing effects.

At very large scales, say of the Hubble radius, we have no tests of gravity. Cosmological models are almost always based on the belief that Gravity works at the very large scales, an extrapolation of many orders of magnitude. There is no proof that this is a valid extrapolation, and there are hints that they are not. (Like they lead to an extremely highly unlike situation. Check out This Talk )

Large scale modifications of gravity may affect the smaller scales, but these effects are naturally suppressed (you can cook up theories where they are not suppressed, but then it is not "large scale" modifications anymore). So to discover these effects are hard.

We have experimental constraints of course, but they are not very strong.