Do you believe in the Multiverse?

Great review article of cosmology by Martin Rees, the British Astronomer Royal  : One universe among many? 

Some people complain that scientists should be wary of assuming everything in their math exists physically in our world. Very right, however, they should be just as careful to assume they know what ‘exists’ means and what can be true based on some notion of what makes sense to them. A good example from physics of crazy math leading to a real thing is that the idea of anti-matter first occurred to scientists only as a theoretical concept because some equation had both a negative and a positive root for the energy of an electron. Everyone assumed the negative root couldn’t possibly be ‘real’…until they discovered the positron which is now used in your local hospital and the smoke detector in your house.

I’m no physicist, but I think it’s inevitable that some form of multiverse explanation for reality will be required to explain the fundamental cosmological questions physics is looking at.  One thing I always wonder though is why so often people seem to mean a single, infinitely large universe with all possible events in it as the multiverse rather than an infinite number of separated universes which do not interact. The single approach isn’t really a multiverse isn’t really a multiverse it just something large enough to disallow communication, seems like a bit of a hack to me. But there could be some good theoretical reason in the physics that this is preferable to the ‘parallel dimensions’ approach.

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A Dark Source for our Familiar Myths

Just a quick comment on this fascinating story up at the newscientist about the  possible dark matter original of our familar bright constellation stars. I’m quite interested in astronomy and I didn’t know that most of the bright stars that make up the most familiar constellations in our skies (Orion, canis major, the souther cross, perseus, scorpius etc) are part of an identifiable belt of large, young, hot stars (this is astronomy people not hollywood, calm down!) that are not part of the normal spiral structure of our galaxy.  They can be identified as a seperate line of stars formed at an odd angle to the plane of the galaxy, its called Gould’s belt, and astronomers are still not sure why its there.

So, that’s the first interesting thing.  The second thing is that there is a theory gaining more and more credibility that Gould’s belt was formed by a cloud of dark matter passing through our galaxy, get this, around 30 million years ago.  If that doesn’t blow you mind you need to go refresh you memory about the ages of planets, stars, galaxies etc.  Thirty million years is literally nothing in astronomical terms.  The dinosaurs died out twice as long ago as this.  Which means the dinosaurs wouldn’t have seen Orion in the sky.  (Of course, the stars also move, so the constellations would have been very different millions of years ago, but these bright stars weren’t even born at that time).  The thing that seems fascinating about it is the possibility that all of these stars were created at once due to the impact of a passing cloud of dark matter.

This is important culturally and scientifically.  Culturally, these bright stars form the backbone of the constellations that were incredibly influential in the formation of human culture.  The Egyptians and the Greeks (for example) would surely have found other things to look at if they were not there, but the sky would have been significantly less interesting without the stars of Gould’s belt.

Scientifically, it turn out that these bright stars may help us locate a nearby cloud of passing dark matter that can be studied because, oh yeah, we have absolutely no idea what dark matter actually is.

Anyways, I just thought it makes a good story, it ties together our modern attempts to understand the makeup of the universe with our ancient attempts to understand the makeup of the universe.  The great Orion  and Perseus may yet lead us to the ultimate Truths.

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