system
Given the following post, respond as if you're commenting on Reddit:
human
What is the current status on String Theory / M Theory?
gpt
It's still highly speculative. Optimistic estimates say that some of its predictions (to what extent there are any, as there are a lot of different ways to realize string/M theory) may be testable in our lifetimes - almost certainly in the sky rather than in particle accelerators - but that's no guarantee.

How would string theory be testable in the sky? The Universe in its earliest moments naturally produced energies far exceeding those we can create in a particle collider on Earth. The further back in time we can probe the Universe, the higher the energies are, and the more likely string theory (or whichever theory of quantum gravity is right) is to be relevant. Right now, the earliest era we can probe in the Universe is about a second after the Big Bang, through the abundances of light elements like helium produced then, but the relevant energies are more comparable to those produced in a nuclear reactor than in a high-tech accelerator like the LHC. So that tells us more about the conditions of the Universe at that time (e.g., were fundamental constants much different back then?) than about physics at those energies.

Going into the future, the cosmic microwave background is set to provide some key tests of inflation, one of the earliest eras in cosmic history. Look for the results from the Planck satellite in 2013 or 2014 which may very provide some bombastic news on inflation. Inflation is believed to have taken place at very high energies, so it could very well tell us something about supersymmetry or even string theory. Going further ahead, because gravity is so weak, gravity waves produced in the very early universe, right around the time string theory mattered, have been running around the Universe almost completely unimpeded. If we can detect this gravitational wave background, we'll have a direct window onto the very early universe and possibly the string era, just as the cosmic microwave background probes back to the era (380,000 years after the Big Bang) when light stopped bouncing around from atom to atom. Unfortunately this is a ways off, and the situation is only getting bleaker. We'll need one or even two generations of space-based gravity wave detectors before we're likely to find this early universe background, but the first generation - a probe once called LISA - was recently gutted and delayed when the US pulled its funding, leaving it to the Europeans to fly a less potent version at a later date. So if you want to know more, go bug your Congressman!

In the theoretical physics community, at least, string/M theory are viewed with a range of opinions ranging from skepticism to, well, something more credulous, but it's pretty widely seen as at least the most likely quantum gravity theory of the ones we've come up with. So there's a mountain of work on it still ongoing (as there should be - how will we know whether we can test it if we don't try to work out its predictions?), and it's often used - rightly or wrongly - as a motivation for investigating various models. "Potentials of this type are believed to arise from moduli compatification in string theory" sounds much nicer than "no one's looked at this function before, so now we're going to do that."