[guygurari]

It is hard to overstate how important the resolution of this question is to physics, and in particular to theoretical physics. The “cosmological constant problem”, that is the problem explaining the cosmological acceleration (if it exists), is arguably the most important and hardest question in high energy theoretical physics. Many theoreticians have spent significant effort studying this question, working under the assumption that the empirical evidence is solid. If this is not the case, it changes the landscape of cutting edge physics research.

There are several reasons why explaining the observed acceleration is so hard. The cosmological constant (the measure of how much dark energy there is) is a tiny positive number which seems to require a lot of “fine tuning” to explain theoretically. We can easily include it in general relativity, but our best understanding of quantum physics says that if it is there then it should be much larger. This means there probably is something we don’t understand about its microscopic origins. If we try to build a microscopic model that has this small constant using string theory (our best guest at a complete theory), we find that such models are hard to create. In fact, it is not clear that any model that includes dark energy is even valid in string theory! Any way we look at it, it seems more difficult to explain this number if it is tiny and positive than if it is strictly zero (no acceleration).

Finally, theoreticians don’t have much to go on when explaining this phenomenon besides this one single number — there aren’t closely related experiments we can combine to come up with a coherent picture of what’s happening. Combine this with particle physics, where accelerators provide us with an abundance of data. It is a single tiny number that has puzzled theoreticians for decades.

[RookyNumbas]

Do you know if these measurements were possible in the past, and no one thought of doing them? Or are they only recently possible, enabled by new technology?

[BoiledCabbage]

What's more mind-boggling to me is all these thousands of scientists running around looking at the extreme oddity of multi-dimensional string theory, and nobody bothered to check if the cosmological constant is actually real.

It seems like physics is really being held back by perverse incentives.

And of course my pocket view that string theory will turn out to be the single largest waste of brilliant human minds in history.

[eloff]

I'm not a physicist, but I don't think string theory is a total waste. It agrees with our existing theories and predictions, so it can be viewed as just an alternative mathematical abstraction, and there is value in that.

Whether or not tiny vibrating strings are really at the heart of things is neither here nor there. It's about as relevant to science as god.

[tylerjwilk00]

The problem with string theory is that there are limitless physics universes you can create within its framework so saying that ours fits in it is not saying a lot. Many universes could be described by it.