Just curious - Lets assume that sometime soon physics is able to unify all the various magnetic-atomic-electrical-gravitational forces into a grand unified “Theory of Everything”. It’s my layman’s understanding we’ve got most everything sussed except for how gravity works and some of the more exotic atomic interactions.
Assuming we’re able to do this what (prospectively) would this really get us in terms of better machines, batteries, power generation etc.? Is knowing how gravity works on a fundamental level really going to make a difference in any practical applications?
Nobody thought relativity or quantum mechanics would ever mean anything in terms of “making stuff”. Yet almost all technologies today, from lasers to GPS systems, exist only because we now know how to exploit them.
That took 30 to 50 years. If we come up with a ToE tomorrow don’t expect to have new technology in the stores by Friday.
It will take decades and be something that can’t be predicted now. You really can’t answer this question today. You couldn’t even if we knew what form a ToE would take, and we don’t know that, so it makes the question doubly unanswerable.
I think the best answer is: Probably, but we’re not really sure. After all, most physicists are too clumsy to hold on to their crystal balls without dropping them onto the particle accelerator, breaking both accelerator and crystal ball (and producing a false positive Higgs sighting), so they don’t know if their work will end up providing the foundation behind Joe’s Ultra Cool Gizmo.
On the other hand, if history has been any guide, advances in physics have produced very tangible benefits. Fast neutron therapy, for example, is a useful cancer treatment. Heavy ion beams probably had a role in producing the computer chips through which this text traveled not too long ago. And finally, linacs can be used to convert nuclear waste with long half-lives to something less dangerous and less long-lived. Granted, a lot of this tech is a couple decades old (and I was just looking at particle accelerators to compile that short list)—but research doesn’t always get you instant “practical” applications. That’s the part that takes time, and investors.
I have three answers. First, as Ben Franklin may or may not have said, of what use is a newborn baby? Once we have this new science, we’ll surely find plenty of uses for it, but most of those uses, we won’t even be able to conceive of until we have the science in hand.
Second, if you really insist on specifics, one possible product of a theory of everything would be the production of laboratory-scale black holes, and there are at least three different ways of using black holes as super-efficient energy sources that can take anything at all as fuel and produce energy outputs that put even fusion to shame. There will probably be many other uses for black holes, too, but I expect that you’ll probably consider limitless energy to be “practical”.
Thirdly and most importantly, though, I think you’re asking the wrong question. Turn it around: I would instead ask, what good is making stuff re gaining us a greater understanding of the Universe? I view knowledge and understanding as a goal in its own right, with everything else just being a means to that end. Or as Feynman put it, science is like sex: It may lead to practical results, but that’s not why we do it.
We can only speculate of course, but the biggest obvious benefit in knowing the connection between gravity and the other forces is that we’d have a way to manipulate gravity. I imagine various radiative technologies (medical, imaging, communications) would get a boost.
Don’t get your hopes up on this score. We understand electromagnetism better than we understand anything else in the Universe (not hyperbole), and the way we manipulate electromagnetism is to move charges around. The analogous process for gravity would be to move masses around, which would require impractically large masses. Now, it’s possible that there are some big surprises waiting for us when we do get quantum gravity figured out, but being surprises, we don’t know what those are.
For the first few decades of the study of electricity it was considered a purely theoretical science with no practical applications. Obviously moving electrons around now has a major role in our economy.
Same thing with a “theory of everything”. It appears like useless now but who can guess what practical applications may arise from it once we’ve got it?
That’s not really relevant - we understand gravity somewhat by itself too. What would be relevant is the question of do we understand the relationship between any two forces, and has that led to any important technologies?
I think you’re selling short what moving charges around can accomplish. I was just woken up by moving charges, which also helped heat the water for my shower, lit the room, moved a whole train of people to get me to work, lit my office, and allowed me to read your words (and send these words out).
Now, I’m not saying that moving masses around will enable similarly far-reaching and impressive technology, but it well might get us something cool.
Not at all-- Practically everything in human experience is ultimately electromagnetic. My point is just that that doesn’t carry over well to gravity.
Electromagnetism is pretty much completely unified with the weak force: The relationships between the photon and the W and Z particles (which mediate the weak force) are well-understood, and they behave in much the same way (the Z is basically a massive photon). In fact, it’s not even possible to describe the weak force without also describing electromagnetism in the process. There are sound experimental reasons to suspect that the electroweak force can be unified with the strong force, as well: The coupling constants for E&M, weak, and strong all vary with energy, and they appear to all converge on exactly the same value at some particular (very high) energy. As a result, nobody has strong doubts that the strong and electroweak forces can be unified; the question is just how.
For gravity, though, we have no real reason to believe that it can be unified with the others, other than wishful thinking and the fact that it looks like the String Model might be able to accomplish it (if we can ever figure out how to accomplish anything with the String Model). There must be some way of describing gravity at the quantum level, but that description of gravity might well be completely unrelated to the other forces (Loop Quantum Gravity, for instance, a rival model to the String Model, makes no pretense of unification). For this reason, it makes sense to distinguish between a GUT which unifies the strong and electroweak forces (which we suspect really is out there, and we just have to find it) from a TOE which brings gravity into the fold as well (which might turn out to just be a wild goose chase).
It’s a question of scale. The relatively small amount of charge needed to pump the water high enough to drop on you for a shower defeated a whole plant’s worth of mass in the process.
But the difference is (and the point Chronos was trying to make) is that it is very easy to move electric charges around in a way that influences the electromagnetic plenum, thereby making it very easy to use them to do work, even though we can’t change the fundamental value of the electric charge. However, for mass, it takes a heck of a lot of it (the size of a small planet) to have a perceivable influence upon other masses, and there is no practical means to focus or direct gravity. In order to be useful we would need to be able to polarize or make coherent “beams” of gravity, or alter the inertial value of mass, which are beyond our theoretical grasp of gravity. (There are a few cool things you can do with very large, very concentrated, very fast spinning masses, but again we’re dealing with energy levels that would cause your ConEd bill to bankrupt a major industrial nation, and that is just to turn on the lights.)
Personally, I’d be happy if we could just isolate and control individual magnetic charges. There are so many cool pranks you can play with magnetic monopoles.
You are mistaken. Grand Unified Theories (which is a general label for a number of non-gravitational unified field theories) always combined the strong, weak, and electromagnetic fields into one comprehensive theory. GUTs have never addressed gravity, partially for historical reasons (Einstein’s treatment of gravity as a geometric effective of curved spacetime) and partially for practical reasons (we’ve never seen or even indirectly measured the influence of an individual “graviton”, and gravity isn’t renormalizable, making it inconsistent with the normal approaches to the Standard Model of particle physics. Integrating gravity into a unified field theory with the other forces has required a completely different set of approaches like superstring theory, M-theory, and quantum loop gravity, none of which are very satisfying or complete at the present time.
As for what good a GUT or TOE would be for practical application, one might as well ask a caveman what use he has for a CAT scanner or an iPhone. Hard science fiction (such as that written by Charles Sheffield, Frederik Pohl, and Stephen Baxter) abounds with possibilities, most of which are probably physically impossible and all of which certainly fail to predict the next “killer app” that will revolutionize human existence the same way that Neolithic agriculture, public sanitation, and the printing press have.
I would be so bold as to say that humans or our descendants will never measure individual gravitons. That’s the sort of thing that a Kardashev Type III civilization might do as a technological tour de force, and any given species will probably never get that far. Now, streams of a very great number of gravitons are a different story: We’ll probably detect those within 5-10 years. But that doesn’t really get us any closer to quantum gravity.
