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.

In science, detective movies, love or any other area of life, when one is confronted with a situation in which the old assumptions are no longer working as they used to, it is perhaps time to look for new questions to ask.

[T]he ether … is now redundant…. In the absence of radiation and ponderable matter there is no substance, there is empty space.

That he may have missed the target in his speculations, as, for example, in his hypothesis of light quanta, cannot really be held too much against him, for it is not possible to introduce really new ideas even in the most exact science without sometimes taking a risk.

[T]he origin of inertia is and remains the most obscure subject in the theory of particles and fields.

Today an individual galaxy is considered as a local disturbance of a distribution which is indeed isotropic and homogeneous, to a degree which itself demands explanation. Einstein had no such physical grounds for assuming these two properties ….

That fellow Einstein suits his convenience. Every year he retracts what he wrote the year before.