It took centuries, but we now know the size of the Universe.
Adam Rifkin stashed this in The Universe
This is rather humbling.
Over the last 13.8 billion years, the Universe has been continually expanding – and at first it did so very rapidly. Taking that into account, astronomers have worked out that the galaxies right on the edge of the observable Universe, whose light has taken 13.8 billion years to reach us, must now be 46.5 billion light years away.
That is our best measurement for the radius of the observable Universe. Doubling it, of course, gives the diameter: 93 billion light years.
This figure rests on many other measurements and bits of science, and it is the culmination of centuries of work. But, as Casey notes, it is still a little rough.
For one thing, given the complexity of some of the oldest galaxies we can detect, it is not clear how they were able to form so quickly after the Big Bang. One possibility is that, somewhere, a few of our calculations are not quite right.
"If one of the rungs of the cosmic distance ladder is off by 10%, then everything's off by 10%, because they rely on each other," says Casey.
And where things get really complex is when we try to think about the Universe beyond that which is observable. The "whole" Universe, as it were. Depending on which theory of the shape of the Universe you prefer, the whole Universe could actually be finite or infinite.
Recently, Mihran Vardanyan and colleagues at the University of Oxford in the UK analysed known data about objects in the observable Universe, to see if they could work out anything about the shape of the whole Universe.
The result, after using computer algorithms to look for meaningful patterns in the data, was a new estimate. The whole Universe is at least 250 times as large as the observable Universe.