NASA Insignia
Imagine the Universe!

WMAP Special Exhibit

Fate of the universe

Will the universe continue to expand at such a hurried pace? Will the expansion teeter out, or will the universe collapse back in on itself under the pull of gravity? These are the big questions about the fate of the universe that WMAP worked to answer.

The fate of the universe depends on its contents: how much matter and energy there is. If there is a lot of matter, then gravity will dominate, slowly reigning in the expansion and pulling all matter together back to one point. Some call this the Big Crunch. If there is not so much matter but rather dark energy – that force that acts like anti-gravity – then the universe will continue to expand until every single speck of matter is pulled infinitely apart from each other.

Graph of possible fates of the universe

The ultimate fate of universe depends on the density density of the universe. If the density of the universe is less than the critical density, then the universe will expand forever, like the green or blue curves in the graph above. However, if the density of the universe is greater than the critical density, then gravity will eventually win and the universe will collapse back on itself, the so called “Big Crunch”, like the graph's orange curve. (Credit: NASA/WMAP Science Team)

Both scenarios sound scary, but neither would happen for trillions upon trillions of years. A more pleasant notion is the situation where the universe has just the right amount of matter and dark energy to keep it from flying apart or crashing in.

WMAP measured the ratio of ordinary matter, dark matter and dark energy. Scientists refer to the density of matter as ω and the contribution of dark energy as the cosmological constant, denoted by λ. Knowing lambda and omega will provide a hint of what's in store for the next 10100 years. Will life still exist? It will be difficult, to say the least. If the universe continues to expand, stars will all but disappear after 1014 years. And protons are thought to decay after 1050 years. It is hard to think about life without protons. That's 100 trillion trillion trillion trillion years or, in less scientific terms, a real long time.

Published: July 2001
Text Reviewed: September 2018