Edwin Hubble, after whom the Hubble Space Telescope (HST) is named, discovered something really important about 100 years ago — that the universe seems to be expanding. Coincidentally, Albert Einstein was working at roughly the same time on explaining the universal laws of gravitation, something we now call general relativity. Hubble drew a line on a plot he had made and calculated the rate at which the universe was expanding. Einstein came up with an equation that said the universe was most likely either expanding or contracting — staying the same was virtually impossible. Einstein, though, believed the universe was not expanding nor contracting so he added a term to his equation, now called the cosmological constant. When Einstein learned that the universe was expanding he called his addition of the cosmological constant his greatest blunder.
With me so far? Hubble and Einstein independently “discovered” the same thing at roughly the same time — the universe is expanding.
The thing is, the expansion is hard to explain. Given what we know of the universe and the Big Bang, the universe should be contracting. Gravity should be winning its tug-of-war with the initial expansion of the Big Bang. There must be some force causing it to expand, what Einstein called the cosmological constant. We don’t know what it is but we call it Dark Energy. The name is not meant to be as mysterious as it sounds — it just means energy we haven’t detected yet. It might be one thing or many things, new or known, that we just haven’t put our finger on yet.
Now new research has suggested that the cosmological constant may not be constant. Says Phil Plait on the previous hyperlink:
Itâ€™s weird enough that the Universe is accelerating, but if that acceleration is itself accelerating, that makes things a whole lot weirder.
This is one tidbit I picked up while attending a recent meeting of the American Astronomical Society in Washington, D.C.
It’s amazing the things we can learn about the universe and how we learn it. It’s interesting to me to read about the work of people, like Hubble and Einstein, who are trying to figure out the very origin and fate of the universe as a whole.