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Wednesday, 1 April 2015

Can clouds of atoms pin down dark energy?

Dark energy: It's one of cosmology's big mysteries. It also proves that scientists can  do a cool name if they try - it sounds sexy as hell and it's been name checked in all the cool sci-fi movies. But we don't have a clue what it actually is.

Above: In the Marvel movie universe it's embodied by this big glowing dice. Real world cosmologists would find that much more convenient to study I suspect...

While the nature of dark energy isn't a matter of immediate panic it is a source of long term worry, as it's  tearing the universe apart - if it keeps accelerating the expansion of space all the other galaxies will eventually disappear at faster than light speeds*. It's slightly embarrassing to be facing  the end of creation as we know it without a clue as to why, so it's something we'd like to get a handle on. For a slightly less melodramatic explanation here's the big brains at Imperial College (warning, this is a full blown physics lecture, so put a cup of tea/coffee on):

One of the suspects in our man hunt is called  a 'chameleon field'. The chameleon field would be a kind of dark energy that is suppressed by matter (or large concentrations of energy) very well. This would explain some of the stranger aspects of dark energy, like why it seems to be very, very, powerful over very long distances, but can't be measured on Earth. On Earth all the dense matter suppresses it.

Above: Earth. Beautiful and, apparently, inconvenient for dark energy hunters. Courtesy of NASA

But Clare Burrage, Edmund J. Copelanda, and E. A. Hinds at the University of Nottingham have come up with an experiment that, maybe, could measure the dark energy field - if it is the chameleon type. The experiment would consist of a big vacuum chamber containing as much nothing as possible - since the chameleon field is suppressed by matter and energy an empty vessel  is the best chance of bringing it up to detectable levels. A stream of cooled rubidium atoms would be fired through the chamber, while it was weightless. Any unexplained deflection of the atoms could be evidence of the chameleon force. This sort of approach is already used to measure fundamental constants like gravity, so the team has been able to put some upper limits on how big the chameleon field might be. Here's the paper. I'll be interested to see if anything comes of it...

Elsewhere in the universe:

Galaxies in this universe cluster together like... like... well, like galaxies clustering. Things that huge can't really be like much except themselves. But how did galaxy clusters begin? The Herschel and Plank space telescopes have teamed up to look waaaay back in time and find the answer.

Above: The image in the centre is the Plank all sky map, and the little images are the Herschel images of possible galaxy cluster seeds. Courtesy of ESA.

Elsewhere on the internet:


Suck on this Tatooine

Mapping cosmic rays

An attempt to make robots conscious?

Graphene sandwich produces new form of ice

Radio bursts - alien messages?

*Yes that sounds crazy. Yes it's true: The rules let you do faster than light if space is the thing that's moving rather than you.

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