Magazine article Science News

The Cosmos' Fate: World without End

Magazine article Science News

The Cosmos' Fate: World without End

Article excerpt

Will the universe expand forever, or will it eventually contract into a Big Crunch? Observing the fireworks from distant, exploding stars, two independent research groups have found evidence suggesting that the cosmos will balloon indefinitely.

The density of matter may simply be too low for gravity to halt the expansion that began with the birth of the universe--the Big Bang--some 15 billion years ago. Although other studies over the past several years have hinted at the same conclusion, the technique employed in the two new reports is a particularly promising method of determining the fate of the cosmos, researchers say.

If further observations support the notion of perpetual expansion, cosmologists may have to rethink their options. The widely accepted theory known as inflation explains why the structure of the universe looks the same in all directions, but it also predicts that the cosmos has exactly the right density to bring expansion to an eventual halt (SN: 6/7/97, p. 354). Reconciling this theory with endless expansion may require cosmologists to resurrect the so-called cosmological constant--an antigravity term in the equations of general relativity.

The new results are based on measurements of the brightness and recession velocity of a special class of supernovas, or exploded stars. Known as type la, these supernovas are the brightest in the cosmos and can be seen from great distances. Moreover, they all have about the same intrinsic brightness.

The most distant la supernova observed with the Hubble Space Telescope provides a glimpse of the cosmos when it was half its current age. The rate at which the universe was expanding in the past determines how far away a supernova with a given recession velocity lies. By comparing observations of faraway supernovas to those of nearby ones, astronomers can infer the rate at which cosmic expansion may be slowing down. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.