The Beginning of Time

What has a beginning but no end? Time. At least this is the consensus of the most accepted hypothesis about the origin of the Universe. This is the hypothesis of the "Big Bang" theory which postulates that the Universe was created about 10 billion years ago. For us, time began then, for it is meaningless to ask what happened before that point in time. It is thought that the Universe exploded into existence from a state of near-infinite density and temperature, so there is no possible way that information of prior events could have propagated past the moment of creation.

Why do we believe the University originated from such a cataclysmic event? There are two compelling reasons: first, we notice distant galaxies are all receding from us and from each other, and that the velocity of recession increases with increasing distance. If we trace their motion back in time, the galaxies appear to have originated from a single point at a single time. The second reason is that the equations of gravitation, or of general relativity, which describe all large-scale motions demand a non-static Universe. If we observe an expanding Universe today, the equations of relativity say that the Universe must have originated from a singular point in space-time.

The next question is whether there is an end to time: will the University exist forever into the future? This depends on how much matter and energy there is in the Universe. If there is more than a critical amount, the Universe is closed and will re-collapse in another 40 billion years. If there is less than the critical amount of matter and energy, the Universe will expand forever. Only one-tenth of the matter necessary for re-collapse has been observed, so present evidence points towards continued expansion.

Hence, time will run on forever.