Current paradoxes in cosmology  FEB 04 2015

From the Physics arXiv Blog, a list of paradoxes in modern cosmological physics, i.e. areas where theory and observation disagree, sometimes by a whopping 120 orders of magnitude.

Perhaps the most dramatic, and potentially most important, of these paradoxes comes from the idea that the universe is expanding, one of the great successes of modern cosmology. It is based on a number of different observations.

The first is that other galaxies are all moving away from us. The evidence for this is that light from these galaxies is red-shifted. And the greater the distance, the bigger this red-shift.

Astrophysicists interpret this as evidence that more distant galaxies are travelling away from us more quickly. Indeed, the most recent evidence is that the expansion is accelerating.

What's curious about this expansion is that space, and the vacuum associated with it, must somehow be created in this process. And yet how this can occur is not at all clear. "The creation of space is a new cosmological phenomenon, which has not been tested yet in physical laboratory," says Baryshev.

What's more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that this energy must increase as well. And yet physicists generally think that energy creation is forbidden.

Baryshev quotes the British cosmologist, Ted Harrison, on this topic: "The conclusion, whether we like it or not, is obvious: energy in the universe is not conserved," says Harrison.

This is a problem that cosmologists are well aware of. And yet ask them about it and they shuffle their feet and stare at the ground. Clearly, any theorist who can solve this paradox will have a bright future in cosmology.

Luckily, these paradoxes are an opportunity to do some great science.

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