Sounding out the universe: How big, how old?
Astronomers peering deeply into space - hence, far back in time - have recently reported significant new facets of the early universe. But they still can't decide how old and how big the cosmos actually is.Skip to next paragraph
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An astronomical team at the University of California (Berkeley) has published a list of the most distant galaxies yet known. One of them is calculated to be 12 billion light-years from Earth. The astronomers say they may be seeing this galaxy as it was when the universe was only one-third as old as it is today. This presumes the universe was born in a vast primordial explosion of energy - the Big Bang - some 18 billion to 20 billion years ago. Some astronomers would dispute such a hoary age.
Meanwhile, British observers have found new members of the family of objects known as quasars (quasi-stellar radio sources) out near the edge of the observable universe, where few such objects were expected to be. Astronomers now may have to revise their notion of the makeup of the very distant, very early universe.
In reporting their quest for our cosmic history, the astronomers' use of words is important. Words referring to time and distance are virtually synonymous. The radiation by which we observe an object a billion light-years away left that object a billion years ago. We see it now as it was then. Likewise, qualifiers such as ''may'' or ''observable'' reflect the underlying uncertainties of this research enterprise. Astronomers can deal only with what can, at least in theory, be observed from Earth.
They speak tentatively of the implications of their findings because they aren't even sure they know what they are talking about when they speak of the distance of an object or the age of the universe. Theoretical assumptions are built into the determination of such things. Thus, when a research team says a galaxy is 12 billion light-years distant, with an age one-third of that of the present universe, its members are in open disagreement with astronomers who believe the ''observable'' universe to be only 10 billion years old.
It is from this perspective that the newly reported findings should be viewed.
The galaxy distances were determined by Hyron Spinrad and Stanislav Djorgovski in California. The galaxies themselves have been known for some time as sources of radio noise. Spinrad and Djorgovski identified these sources with optically visible galaxies. They then measured the light spectra from the galaxies and, from these, derived their distances.
Distant objects are retreating from Earth as part of the general expansion of the universe. The farther they are, the faster they recede. Their speed is reflected in the light they emit. Light of different wavelengths appears longer (redder) than it would if the source were not moving. Also, the faster an object moves away, the redder its light appears. Thus faster speeds, which imply larger distances, are associated with greater red shifts.