270 The Quantum Structure of Space and Time
that exploded onto the scene of physics at about the same time. This totally
unpredictable decay of atoms seemed to threaten determinism. Radioactivity was
totally random, unaffected by any physical perturbation of the atomic systems and
seemed to violate both determinism and energy conservation. But, if you go back
and look at the discussions at the first Solvay Conference they totally focused on
quanta and radiation. There was almost no discussion of radioactivity, which was
much more of a threat to classical physics.
We too have discussed, during this conference, many areas in which we are
confused, and where revolutionary ways of thinking might be called for. One area
has to do with space and time and the threats to our classical, quantum mechanical,
field theoretical, traditional notions of space and time. We have heard at great
length about many new discoveries within quantum gravity and string theory that
hint that we are going to have to modify in a profound way our notions of space
and time. But it is as unclear today how the final picture will look in 94 years from
now, as it was unclear back in 1911 how the dual pictures of waves and particles
would be reconciled.
But there is another profound change that is looming over us, one that was
discussed in the last session, namely, the scope of science and its predictability: are
the basic laws, constants, parameters, and everything else up for grabs? Must we
resort to the anthropic principle? At the first Solvay Conference physicists were
perplexed by quanta and radiation on the one hand and by radioactivity on the
other hand. We have emergent space-time on the one hand and the anthropic
principle on the other hand. How should we draw the analogy? I believe that the
discussion of emergent space-time is similar to the discussion about quanta and
radiation, whereas the anthropic revolution - and I do regard it as a revolutionary
change in how we do physics, if true - is more analogous to the way people might
have tried to deal with radioactivity back in 19ll(which they were smart enough
not to mention).
I would like to make it clear that I do not regard the anthopic principle as evil.
It can lead to good science. What I found most interesting in Joe pol chin ski)'^
talk were the new questions that he was asking in the framework of string theoryand cosmology that were stimulated by thinking anthropically. So I don’t think
anthropic arguments are evil, they can stimulate people to do good physics.
What really bothers me about anthropic arguments was well expressed by Paul
(Steinhardt)’s challenge to the people who believe in the anthropic principle to make
a prediction; and by Steven (Weinberg)% answer that we cannot make a prediction
until you tell us which parameters are anthropically determined. Let me say why
this disturbs me. What disturbs me about anthropic arguments is that they sound
too much like “just so” stories. First, you have to know what it is that you are
allowed to discuss anthropically. For instance, if you try to argue that the hierarchy
scale is something that is determined anthropically, and therefore it is okay to fine
tune it - life picks out the scale - and then it turns out that we learn from the LHC