Three Roads To Quantum Gravity

148 THREE ROADS TO QUANTUM GRAVITY
been able to solve it. Einstein had to ask a friend who knew
the right mathematics.
The textbooks go on to say that once one understands the
curvature tensor, one is very close to Einstein's theory of
gravity. The questions Einstein is asking should lead him to
invent the theory in half a page. There are only two steps to
take, and one can see from this notebook that Einstein has all
the ingredients. But could he do it? Apparently not. He starts
out promisingly, then he makes a mistake. To explain why his
mistake is not a mistake he invents a very clever argument.
With falling hearts, we, reading his notebook, recognize his
argument as one that was held up to us as an example of how
not to think about the problem. As good students of the
subject we know that the argument being used by Einstein is
not only wrong but absurd, but no one told us it was Einstein
himself who invented it. By the end of the notebook he has
convinced himself of the truth of a theory that we, with more
experience of this kind of stuff than he or anyone could have
had at the time, can see is not even mathematically consistent.
Still, he convinced himself and several others of its promise,
and for the next two years they pursued this wrong theory.
Actually the right equation was written down, almost
accidentally, on one page of the notebook we looked at it.
But Einstein failed to recognize it for what it was, and only
after following a false trail for two years did he ®nd his way
back to it. When he did, it was questions his good friends
asked him that ®nally made him see where he had gone
wrong.
Nothing in this notebook leads us to doubt Einstein's
greatness ± quite the contrary, for in this notebook we can
see the trail followed by a great human being whose courage
and judgement are strong enough to pull him through a
thicket of confusion from which few others could have
emerged. Rather, the lesson is that trying to invent new laws
of physics is hard. Really hard. No one knew better than
Einstein that it requires not only intelligence and hard work,
but equal helpings of insight, stubbornness, patience and
character. This is why all scientists work in communities.
And that makes the history of science a human story. There