The science of expansion: Andromeda, gravity, and the ‘Big Rip’ | Michelle Thaller

If the universe is expanding in all directions, why is Andromeda hurtling toward the Milky Way?

- The Andromeda Galaxy and our Milky Way are on a collision course that will obliterate life on Earth 4.5 billion years from now.

- The universe is expanding in all directions, all at once – so why are Andromeda and the Milky Way drawing nearer? The gravity between them is a stronger force than expansion.

- The rate of expansion is accelerating. If it continues to speed up, its force may become strong enough pull things apart that are currently held together by superior forces: Our galaxy, the solar system, and even the atoms in our bodies. That possible ending to the universe is known as the 'Big Rip'.


Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit NASA.gov

Read more at BigThink.com: https://bigthink.com/videos/the-science-of-expansion-andromeda-gravity-and-the-big-rip

Follow Big Think here:
YouTube: http://goo.gl/CPTsV5
Facebook: https://www.facebook.com/BigThinkdotcom
Twitter: https://twitter.com/bigthink

One of the questions I get asked most commonly as an astronomer is if almost all the galaxies in the universe are flying away from us in space, why is the Andromeda Galaxy getting closer to us? Does that somehow mean that the Big Bang works differently in different parts of the universe? And the answer simply is: no. Space is expanding because of the Big Bang. All of space is expanding in every direction all at once and from our viewpoint that means that it looks like all the other galaxies are moving away from us. But not all the universe around us appears to be expanding. For example, the Earth doesn't seem to be getting any farther away from the Sun. The Sun is not getting any farther away from our galaxy. Thank about smaller scales, like your body; your body (luckily) is not expanding along with the universe. And the reason is that the expansion of the universe is actually a pretty gentle force; you really only notice it out in the middle of nowhere in the vast reaches of space between the galaxies. There's a lot of space out of there, so there is a lot of space to expand and so you really notice this expansion.

But there are things that are stronger than the expansion force. For example, my body is held together by chemical forces and by electrical forces. That is much, much stronger than the tiny little push that space has to expand inside me. I hold together very well. One of the analogies I think about is: You could try to push over the Empire State Building by blowing on it. You are actually exerting a force on the Empire State Building by blowing on it, you can measure that force, but you're not going to blow over the Empire State Building. There are things that are much stronger than this omnipresent but gentle force of the expansion of the universe. The gravity between the Sun and the Earth is stronger than space's pressure to expand over that scale. The force of gravity is stronger than the outward push of the expansion of the universe. That's also true of the galaxy, we are held in orbit around the center of the galaxy. Gravitationally, that's much stronger than any expansion force...