Dark energy highlights continued

Here is a great dark energy FAQ from Sean Carroll, a physicist at CalTech.

Einstein's greatest blunder (?)

In 1917 Einstein added a fudge factor, the cosmological constant, to the equations in his theory of general relativity. Before adding the constant, his equations showed the attractive force of gravity would cause the universe to implode in a Big Crunch. The constant kept Einstein's picture of the universe static – neither expanding nor contracting.

When Edwin Hubble discovered that the universe was expanding (the rate of expansion is what won this year's Nobel Prize), Einstein threw out the cosmological constant, declaring it his greatest blunder.

But the cosmological constant may still work. In fact, without the constant, the age of the universe is calculated to be much younger than the oldest observed stars. Since this makes no sense, the constant may hold validity.

How do spacetime and quantum field theory ultimately fit together? That has been the big looming question. One proposed “quantum correction” to classical mechanics is quantum mechanical vacuum energy. If there is such a vacuum energy, it may be associated with the cosmological constant.

But there is still an incredibly gaping margin of error: when physicists calculated the vacuum energy they came up with an answer 120 orders of magnitude (10^120 times) greater than what we actually observe. It would take me 2 minutes just to write out all those zeroes.

(hey you physics people, want to delve further?)

With all the advances in modern physics and the accomplishments highlighted by this year's Nobel Prize, there still remains an entire universe (or perhaps multiverses?) of mysteries.

Into the Future...

For the time being, budget cuts caused NASA to scrap its projects investigating dark energy using the James Webb Telescope. Fortunately, in 2019 the European Space Agency plans to step in with its Euclid mission.

The Large Synoptic Survey Telescope (LSST) in Chile will become another source of data for dark energy research.