“The most profound puzzle of contemporary physics” is how Benjamin Granett and colleagues from the University of Hawaii in Honolulu describe the problem of dark energy. And they’re not kidding.
What we have is the extraordinary observation that type 1a supernovas in the most distant galaxies in the universe are dimmer than they ought to be.
Nobody disputes this evidence; the challenge is to explain it and astronomers have been falling over themselves to construct various fascinating theories.
The astronomers’ darling is that the cosmos is filled with a mysterious “dark energy” that is pushing the universe apart. This causes the most distant galaxies to accelerate away from us faster than they would otherwise do. And since they are further away, the supernovas they contain are dimmer.
Recently, astronomers have suggested that if that is the case, then there ought to be other evidence for dark matter too. In particular, they say that this acceleration should change the way photons are influenced by the gravitational fields associated with superclusters of galaxies and the supervoids between them.
Photons should be “heated” and cooled” as they pass through the crests and troughs of these structures (in other words their energy should depend in a small way on the journey they’ve taken).
So a map of the universe according to photon temperature ought to coincide with the large scale structure of superclusters and supervoids in the universe we see (a phenomena known as the late-time integrated Sachs-Wolfe effect).
It turns out we already have just such a map in the form of the cosmic microwave background data taken by the WMAP spacecraft. But until now the variations of this map have only been weakly linked to the superclusters and supervoids we can see.
Today, Granett and pals have taken this work a step further and presented the first strong statistical link between the structure of the universe as we see it today and photon temperature.
What’s more they say their findings may help to explain a mysterious cold spot in this map that astronomers have been puzzling over for a while now. The cold spot is the result of supervoids they say.
This is interesting work but the question of course is: how robust is their statistical analysis? These kinds of findings are notoriously sensitive to the way in which the data is selected.
Now we see it. But next week, who knows?
Ref: arxiv.org/abs/0805.2974: Dark Energy Detected with Supervoids and Superclusters