Is the Universe infinite in volume? Looking at the night sky one may be led to believe so. As out technology improves we are able to look farther and farther into space. But is it really infinite? Could it be finite in volume? How? Ancient astronomers argued that if the Universe is finite in volume then there should be an edge to the Universe...but then, what is on the other side of the edge?

The european astronomer Thomas Digges (1546-1595) was the first scientist to claim that the Universe was infinite in size. Before him, there was the "Paradise" and the domain of the "Prime Mover" beyond the shell of stars.

Giordano Bruno (1548-1600) took the idea a step farther and claimed that there must exist infinitely many Worlds and Solar Systems, populated by other intelligent beings, in the Universe. He was burned alive for this.

From the teachings of Copernicus, Galileo, Kepler, Newton and Einstein we have learned much about the laws of the Universe and how the Universe works and how it was born. Their theories, specially Einstein's general theory of relativity, explain the Geometry of the Universe. However, none of these laws say anything about the Topology of the Universe.

Moreover, from Einstein's work we know that light travels at a constant speed, and nothing can travel faster than light. Since the Universe had a beginning (according to the theory of the Big Bang) and it is about 10 to 20 billion years old, we can only see as far as 10 to 20 billion light-years away. This implies that necessarily, our Visible Universe is finite. But the Visible Universe should not be confused with the Actual Universe. In fact, if the Universe is infinite in volume, the visible Universe (finite) is not more than a 0% of the total of the Universe!

Finally, another question: if the Universe is infinite, should we expect that the Universe looks alike everywhere? The answer seems to be *no*. The Theory of Inflation predicts different conditions in different parts of the Universe, which could even mean that different parts (or bubbles) of the Universe are ruled under different values of the most usual constants.

"It may seem rather rash indeed to draw conclusions valid for the whole universe from what we can see from the small corner to which we are confined. Who knows that the whole visible universe is not like a drop of water at the surface of the Earth? Inhabitants of that drop of water, as small relative to it as we are relative to the Milky Way, could not possibly imagine that beside the drop of water there might be a piece of iron or a living tissue in which the properties of matter are entirely different". - Emile Borel (1922).