A Quote by Edward Witten
There was a long history of speculation that in quantum gravity, unlike Einstein's classical theory, it might be possible for the topology of spacetime to change.
Related Quotes
In Einstein's general relativity the structure of space can change but not its topology. Topology is the property of something that doesn't change when you bend it or stretch it as long as you don't break anything.
I am not aware of any sensible theory of how classical gravity could interact with quantum matter, and I can't imagine how such a theory might work.
Einstein comes along and says, space and time can warp and curve, that's what gravity is. Now string theory comes along and says, yes, gravity, quantum mechanics, electromagnetism - all together in one package, but only if the universe has more dimensions than the ones that we see.
The supposed astronomical proofs of the theory [of relativity], as cited and claimed by Einstein, do not exist. He is a confusionist. The Einstein theory is a fallacy. The theory that ether does not exist, and that gravity is not a force but a property of space can only be described as a crazy vagary, a disgrace to our age.
On the other hand, we don't understand the theory too completely, and because of this fuzziness of spacetime, the very concept of spacetime and spacetime dimensions isn't precisely defined.
Classical physics has been superseded by quantum theory: quantum theory is verified by experiments. Experiments must be described in terms of classical physics.
The Theory of Relativity confers an absolute meaning on a magnitude which in classical theory has only a relative significance: the velocity of light. The velocity of light is to the Theory of Relativity as the elementary quantum of action is to the Quantum Theory: it is its absolute core.
It is a remarkable fact that the second law of thermodynamics has played in the history of science a fundamental role far beyond its original scope. Suffice it to mention Boltzmann's work on kinetic theory, Planck's discovery of quantum theory or Einstein's theory of spontaneous emission, which were all based on the second law of thermodynamics.
In many ways, string theory attempts to go beyond Einstein's dream... an all-encompassing description of nature that works at large distances where gravity becomes important as well as small distances where quantum mechanics is important.
If we do get a quantum theory of spacetime, it should answer some of the deepest philosophical questions that we have, like what happened before the big bang?
In Darwin's theory, you just have to substitute 'mutations' for his 'slight accidental variations' (just as quantum theory substitutes 'quantum jump' for 'continuous transfer of energy'). In all other respects little change was necessary in Darwin's theory...
We're going to need a definitive quantum theory of gravity, which is part of a grand unified theory - it's the main missing piece.
We could tell them [alien civilization] things that we have discovered in the realm of mathematical physics, but there is stuff that I would like to know. There are some famous problems like how to bring gravitation and quantum physics together, the long-sought-after theory of quantum gravity. But it may be hard to understand the answer that comes back.
One of the main successes of string theory is that it has been able to unify the general theory of relativity, which describes gravity, and quantum mechanics.
The most important single thing about string theory is that it's a highly mathematical theory, and the mathematics holds together in a very tight and consistent way. It contains in its basic structure both quantum mechanics and the theory of gravity. That's big news.
Scientific realism in classical (i.e. pre-quantum) physics has remained compatible with the naive realism of everyday thinking on the whole; whereas it has proven impossible to find any consistent way to visualize the world underlying quantum theory in terms of our pictures in the everyday world. The general conclusion is that in quantum theory naive realism, although necessary at the level of observations, fails at the microscopic level.
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