Actually, until fairly recently (my student days!) many astronomers, myself included, believed the universe to be infinite in both space and time. Not only infinite, but homogeneous and unchanging; i.e., no matter where or when you were in the universe, a look around would show you pretty much the same mix of galaxies, etc at pretty much the same density and state of evolution, for as far as one could see. As the universe expanded, hydrogen atoms were created from nothingness (Fred Hoyle calculated a rate of about 1 per cubic meter per year), just enough to keep the overall density constant. Miraculous creation of matter was what allowed the Steady-State theory to avoid having to face the concept of a beginning in time and a singularity in space--the Big Bang--and all the philosophical problems that brought up. An infintely large, infinitely old and eternal and unchanging universe was actually the "instinctive" reaction for most scientists. It made more sense than a beginning, an end, and a size.

As is often the case, the observations led in another direction. The discovery of the 3 degree background radiation in the 60s confirmed that the Big Bang theory (which had predicted just such a residual effect as a trace of the initial explosion) forced astronomers to go to the concept of an evolving universe, with a beginning in time and an unknown future. Modern observations with the mega-telescopes of the last half-century also began to reveal that at great distances, near the "edge", objects were different than those nearby, they seemed less evolved, younger. As we look very far away we look way back in time, and into the Universe's early days; when everything was young, things indeed looked different.

A finitely aged universe immediately suggested a finitely sized one, but this doesn't mean that there's a wall of crystal out there, holding it all together. The universe seemed to be finite and unbounded, that is, it had a size, but not an edge. If you could build a big enough telescope, and looked out, eventually you would see...the back of your head! (Assuming everything was old enough for the light to have time to get back to you.) Or to think of it another way, if you had an FTL spaceship and took off in one direction, eventually you'd go around the universe and come back to where you started, just as if you started walking around the earth you'd comeback, after a complete circumnavigation, to where you began.

These issues are by no means settled, and only more observations can do that. This is why cosmologists need bigger telescopes, and preferably in orbit. I can think of no better way to spend our money than to use it to learn our place in the universe, and its history and its destiny.