Now not to sound too pragmatic-minded, but I would really want to know. Let’s say that we get to the point where string theory has been confirmed/proven. What then?
Does that mean that we know “everything”? I don’t mean to be wry about it, but what impact will it have on everything else we know about in the workings of the universe?
I often hear that we haven’t yet cracked many aspect(s) of fluid dynamics. Will the solutions of string theory provide answers to other problems/questions we have about the universe such as these?
In short, will it provide the bridge from where we will be elevated to the status of “gods on earth”, where we can begin to cure diseases, create unimaginable technologies and make coffee in 0.5 minutes?
Seriously, what does it all lead to in the end if it does become a reality?
When we do have a quantum gravity model it will simply open up deeper more subtle questions we don’t even know we need to ask.
Fluid dynamics are more a question of getting a handle on non-linear equations that can be very dependant on initial conditions. I don’t see string theory helping there any more than the Standard model currently does.
Practically? Well I would suppose we could begin trying to create and control gravitons in a lab environment.
Look at it this way: We know that General Relativity and the Standard Model of elementary particles work really well for all the experimental situations we currently encounter. (Well, except for that pesky dark matter - but that’s only 90% of the universe so we can ignore it …?) Any string theory that works has to reproduce those results. So it won’t affect everyday life, our understanding of chemistry, medicine, electricity, etc.
Where it will help is with the extreme situations that current theory can’t touch: near a black hole, say, or near the Big Bang.
It’s not supposed to be a “theory of everything” in the sense that it provides the answers to any question you can ask. (“Will she go out with me, O great Theory?”) It’s a theory of what everything is made of on the lowest level. It might tell us something about dark matter. It definitely won’t tell us if the train will arrive on time.
It’s worth noting that the extreme situations where String Theory (or some other theory of quantum gravity) would be useful are far removed from anything we can currently observe. For instance, quantum gravity would be essential for understanding a black hole with a mass of a small fraction of a gram. But the smallest black holes we’ve ever detected are several times the mass of the Sun, and for those black holes, non-quantum GR seems to work just dandy.
Proving a theory does not mean you have control over the domain of that theory. The theory of gravity does not enable to us control gravity, just to understand it better. Likewise, a theory about how the universe works doesn’t enable us to control it directly, just to understand it.
The examples you gave are unlikely to be affected by our knowledge of string theory. We have more than enough knowledge of how matter works to understand coffee and disease. The barriers in our understanding don’t have anything to do with physics.