Data and Discovery
This plot shows our supernova data. Across the Bottom axis is Distance (or equivalently time since the SN exploded). The side axis shows change in the Expansion rate from its current rate. As you can see the points do not show the Universe slowing down enough to have a gnaB giB. Furthermore, they do not even seem to show the Universe coasting, rather they show that the Universe is accelerating!
So what could make the Universe
accelerate? It turns out one possibility is a form of matter/energy invented
by Einstein in the 1920s to make sure his equations of General Relativity
did not predict the Expansion of the Universe. Although Einstein was willing
to predict several things with his equations of General Relativity, he
obviously thought an expanding Universe was too much, and so he invented
the Cosmological Constant, which repels itself, and was meant to balance
the force of gravity, and make the Universe static. He later called this
the greatest mistake of his life.
Here we show how much cosmological constant and normal matter (that is the stuff you and I and everything around us that we see is made out of) there is in the Universe. The darker the color, the likely a particular combination of the two types of matter is. The numbers are plotted as the greek letter Omega which is the symbol we use to represent the fraction of the Universe made out of matter relative to the amount necessary to make space flat. (i.e., if Omega = 1 then there is just enough matter to make the Universe flat). As you can see, it appears that the total amount of normal matter in the Universe is quite small - Omega is less than 1 for normal matter, and the amount of cosmological constant is reasonably large - Omega greater than 0 for the cosmological constant.
Supernovae are not
the only way to make such a diagram. Another way is to look at the Universe
when it was very young, and glowed like the sun. This radiation is the
furthest thing we can see in the Universe, and is known as the Cosmic
Microwave Background. By observing how the lumps and bumps in this background
are distributed, it is possible to measure the amount of matter in the
Universe. New measurements from this method give their own measurement
of Matter and Cosmological Constant.
If we combine the two measurement into one diagram, we can figure out what both methods together are telling us right now. As you can see the best values (the hashed red and white area where the two methods overlap) are having normal matter 0.2 of the critical value, and the cosmological constant about 0.8 of the critical value.
is actually quite amazing because many theorists want the sum of Omegas
in all types of matter to be one - this is the prediction of a theory
called Inflation - and these results suggest that it just might be.
We hope and believe it is the first alternative, but we have to work hard and test to see if it isn't the second or third alternative. Checking these two other alternatives is a major focus of our current work.