Tuesday, October 27, 1998 Published at 14:08 GMT
Hubble v Big Bang
Through a lens clearly - multiple images from across the universe
By our Science Editor David Whitehouse
New observations made by the Hubble space telescope suggest that some of our ideas about the Big Bang, the explosion that started the universe, may need revising.
A team from the University of Arizona has obtained a Hubble image of a distant galaxy, designated PG 115+080, seen through a much nearer galaxy.
PG 115+080 is eight billion light years away. The closer galaxy, three billion light years distant, acts as a 'gravitational lens' bending light so that the picture we see of PG 115+080 consists of several distorted images.
This is useful to astronomers because it gives them the chance to do some simple geometry to measure distances across the universe based on the path that the light in each image has travelled
The good news is that using the new Hubble image, it is possible to measure how fast the universe is expanding. The new figure agrees with previous estimates.
The bad news is that the big bang cannot easily explain this observed rate of expansion with the matter the cosmos seems to contain.
So it seems that the Big Bang theory needs patching up. There are three possible ways to do this but each adjustment is unpalatable to astronomers.
Earlier this century, before it was discovered that the universe was expanding, Einstein tried to explain why it did not collapse. He came up with an anti-gravity force that holds it up.
When it was discovered in the 1920's that the cosmos expands, Einstein's new force was dropped. However some astronomers, while still not liking the idea, point out that it could come in useful today to explain a few things about the universe.
Despite these problems it is clear that the fundamental basis of the Big Bang theory, that the universe began in an explosion of time and space about 13 billion years ago, is not in dispute.
It is just that we do not understand what came next as well as we thought we did.