Ask Ethan: Can The Universe Still End In A Big Crunch? (Synopsis) [Starts With A Bang]

“It’s everywhere, really. It’s between the galaxies. It is in this room. We believe that everywhere that you have space, empty space, that you cannot avoid having some of this dark energy.” -Adam Riess

Have you heard about the accelerating Universe? What about dark energy, vacuum energy, or a cosmological constant? These are terms we throw around to talk about one of the strangest observations ever made in the Universe: that the more distant a galaxy is from us, the faster it appears to be receding from us. Not only that, but the rate of recession appears to actually increase over time, which is the biggest puzzle of all.

Possible fates of the expanding Universe. Notice the differences of different models in the past. Image credit: The Cosmic Perspective / Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider and Mark Voit..

But what does this mean for the expansion rate of the Universe? While you might think, as many do, that this means the expansion rate itself is accelerating, that’s not how it works at all. The expansion rate is dropping today, and will continue to drop, eventually asymptoting to a constant value. So how does this cause acceleration, and what does that mean for the fate of the Universe?

When astronomers first realized the universe was accelerating, the conventional wisdom was that it would expand forever. However, until we better understand the nature of dark energy other scenarios for the fate of the universe are possible. This diagram outlines these possible fates. Image credit: NASA/ESA and A. Riess (STScI).

Find out on this week’s Ask Ethan, and learn how a Big Crunch and a Big Rip are not only still possibilities, but how we’re going to attempt to find out whether either one might be real!

from ScienceBlogs http://ift.tt/2r436Zp

“It’s everywhere, really. It’s between the galaxies. It is in this room. We believe that everywhere that you have space, empty space, that you cannot avoid having some of this dark energy.” -Adam Riess

Have you heard about the accelerating Universe? What about dark energy, vacuum energy, or a cosmological constant? These are terms we throw around to talk about one of the strangest observations ever made in the Universe: that the more distant a galaxy is from us, the faster it appears to be receding from us. Not only that, but the rate of recession appears to actually increase over time, which is the biggest puzzle of all.

Possible fates of the expanding Universe. Notice the differences of different models in the past. Image credit: The Cosmic Perspective / Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider and Mark Voit..

But what does this mean for the expansion rate of the Universe? While you might think, as many do, that this means the expansion rate itself is accelerating, that’s not how it works at all. The expansion rate is dropping today, and will continue to drop, eventually asymptoting to a constant value. So how does this cause acceleration, and what does that mean for the fate of the Universe?

When astronomers first realized the universe was accelerating, the conventional wisdom was that it would expand forever. However, until we better understand the nature of dark energy other scenarios for the fate of the universe are possible. This diagram outlines these possible fates. Image credit: NASA/ESA and A. Riess (STScI).

Find out on this week’s Ask Ethan, and learn how a Big Crunch and a Big Rip are not only still possibilities, but how we’re going to attempt to find out whether either one might be real!

from ScienceBlogs http://ift.tt/2r436Zp