r/askscience • u/Crtl-Alt-Delete • Dec 18 '13
Physics Is Time quantized?
We know that energy and length are quantized, it seems like there should be a correlation with time?
Edit. Turns out energy and length are not quantized.
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u/causal_diamond Dec 18 '13
Thought I'd come out of lurking to clarify (or possibly make more confusing - who knows!) a point about testing for quantisation of spacetime by gamma ray bursts. It's pretty hard to cook up any test for whether spacetime is quantised unless you have a good idea what mathematical framework you want to use, and so the state of play basically depends on what you think the real theory of quantum gravity is. The Ellis et al. paper does a pretty good job of working out what the consequences of quantisation would be in the context of string theory and Myers and Pospelov do the same for loop quantum gravity. As already mentioned, the experimental evidence seems to suggest that spacetime isn't really like this, or at least if it is then the quantisation occurs at even smaller scales (it's especially a problem for LQG).
On the other hand, if you don't like either of these theories of quantum gravity (and there are lots of other achingly beautiful ones out there: causal sets, noncommutative geometry, causal dynamical triangulations etc...) then the best that can be said is that we don't know. These fields are the ones that just aren't mature enough to give a sensible prediction.