Page 71 - A Brief History of Time - Stephen Hawking

A Brief History of Time - Stephen Hawking... Chapter 8
additional red shift.

Further predictions of the no boundary condition are currently being worked out. A particularly interesting problem is
the size of the small departures from uniform density in the early universe that caused the formation first of the
galaxies, then of stars, and finally of us. The uncertainty principle implies that the early universe cannot have been
completely uniform because there must have been some uncertainties or fluctuations in the positions and velocities
of the particles. Using the no boundary condition, we find that the universe must in fact have started off with just the
minimum possible non-uniformity allowed by the uncertainty principle. The universe would have then undergone a
period of rapid expansion, as in the inflationary models. During this period, the initial non-uniformities would have
been amplified until they were big enough to explain the origin of the structures we observe around us. In 1992 the
Cosmic Background Explorer satellite (COBE) first detected very slight variations in the intensity of the microwave
background with direction. The way these non-uniformities depend on direction seems to agree with the predictions
of the inflationary model and the no boundary proposal. Thus the no boundary proposal is a good scientific theory in
the sense of Karl Popper: it could have been falsified by observations but instead its predictions have been
confirmed. In an expanding universe in which the density of matter varied slightly from place to place, gravity would
have caused the denser regions to slow down their expansion and start contracting. This would lead to the formation
of galaxies, stars, and eventually even insignificant creatures like ourselves. Thus all the complicated structures that
we see in the universe might be explained by the no boundary condition for the universe together with the uncertainty
principle of quantum mechanics.

The idea that space and time may form a closed surface without boundary also has profound implications for the role
of God in the affairs of the universe. With the success of scientific theories in describing events, most people have
come to believe that God allows the universe to evolve according to a set of laws and does not intervene in the
universe to break these laws. However, the laws do not tell us what the universe should have looked like when it
started – it would still be up to God to wind up the clockwork and choose how to start it off. So long as the universe
had a beginning, we could suppose it had a creator. But if the universe is really completely self-contained, having no
boundary or edge, it would have neither beginning nor end: it would simply be. What place, then, for a creator?

PREVIOUS NEXT

file:///C|/WINDOWS/Desktop/blahh/Stephen Hawking - A brief history of time/g.html (11 of 11) [2/20/2001 3:15:29 AM]