[W]e now have in our possession laws that can describe correctly every experiment we have been able to invent.

According to general relativity every bit of the collapsed star and every particle that falls afterwards into the black hole will end up at a last moment of time, at which the density of matter and strength of the gravitational field become infinite.

One can … always ask, why is the universe where it is, rather than ten feet to the left, or rotated 30 degrees? Or, why did the universe not start five minutes later? This is sometimes called the problem of under-determination: nothing in the laws of physics answers the question of why the universe is where it is, rather than translated or rotated.

It should also be said that for physicists relationalism is a strategy. As we shall see, theories may be partly relational, i.e., they can have varying amounts of background structure.

It is becoming clearer and clearer that the hardest problem faced by theoretical physics is the problem of accounting for the small value of the cosmological constant.

What is the universe? Is it infinite, or finite?

The problem of how to make a theory of a whole universe is thus the problem of how to construct a theory without making any reference to anything that exists … outside of the system we are describing.

No matter how smart she is, no matter how modern her methods and how tricky her reasoning, a detective cannot be a good detective unless in the end the bad guys are found out. It is the same with science.

At present … the question of what happens inside of a black hole when quantum effects are taken into account remains unresolved.