16 upvotes, 6 direct replies (showing 6)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
is it likely there will be a point where physics is 'finished'? where we perfectly understand all the mechanisms of the universe, its history and future. On a scale of 0% understanding of physics (pre cavemen or something) to 100% perfect and complete understanding, how far along do you think we are?
edit: by saying know it's future I don't mean know everything that will happen in the universe in the future, more know what is likely to happen to the universe at a large scale
Comment by SonOfOnett at 20/07/2022 at 15:28 UTC
27 upvotes, 2 direct replies
Here’s a partial answer to your question: even if we perfectly understood all the rules governing how the universe behaved we would still not be able to predict the future or know the past perfectly. What we know of Physics already prevents perfect Determinism. A couple of reasons for this are you 1) quantum phenomena which shows they universe has true randomness and 2) many complex systems are chaotic, meaning they are highly dependent on initial conditions
Comment by zadagat at 20/07/2022 at 19:27 UTC
4 upvotes, 0 direct replies
I think we could one day reach a point where physics is finished, though as another commenter pointed out, we may never give up finding a better model for some definition of better. To have a compete model that replicates our universe up to quantum or measurement uncertainties seems feasible.
As for how close we are, that's really really hard to say. At the turn of the 20th century, if I recall, we were supposedly close to finishing physics, we just had a few pesky details in the photoelectric effect, blackbody radiation, and Mercury's orbit to handle. Those exploded into quantum mechanics and relativity and now we seem farther from knowing everything than ever before, given all the known anomalies, and yet we're undeniably closer. I'd say 50%
Comment by drhunny at 22/07/2022 at 23:18 UTC
2 upvotes, 1 direct replies
Definitively NO
We have a really good understanding of physics at energy, time, and length scales that are ... human.
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There's some story, maybe apocryphal, that some giant of classical physics (don't remember who) told a young Einstein that he should do something else because the classical theories (Newton + Maxwell + classical stat phys) completely explained everything they could measure, so physics was completely understood. But, that guy hadn't thought about the possibility that engineering in the early 20th century would improve enough that experiments could be run that would test those theories in new conditions.
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We have a good understanding of physics at scales that are: energies like in the middle of the sun, times that are in the picoseconds, and lengths that are in the femtometers. But there has been and will always be scales that we can't test our theories at. Even if we develop and test a theory of physics that goes all the way into Planck scale, that theory will not be tested at some even higher / lower scale. There will *always* be a scale that the theory hasn't been tested at. And we'll have to say "we don't know if the physics changes at that scale"
Comment by Brickleberried at 20/07/2022 at 17:50 UTC
2 upvotes, 1 direct replies
As someone already said, we can't perfectly know the past and future because determinism doesn't work.
However, let's say we DO understand all physics perfectly. How would we actually know that there wasn't more? We never would.
Comment by KristinnK at 20/07/2022 at 23:42 UTC
1 upvotes, 0 direct replies
As someone with a Ph.D. in physics, the off-the-top-of-my-head, guesstimate, intuition based answer would be that physics is 95% complete. The only things really missing in physics is the unification of relativity and high-energy physics, larger cosmological questions like the ultimate fate of the universe, and what the hell dark matter and dark energy is. Compared to all that we do know that's not really a lot of things.
Comment by RudeHero at 21/07/2022 at 01:44 UTC
1 upvotes, 0 direct replies
is it likely there will be a point where physics is 'finished'?
depends on the definition of "finished!"
physics is the eternal question of "why". or "how", or "what", however you want to put it.
every answer we get immediately produces another question- "why is it that way?"
so, in that sense, i think physics will never be finished, no matter what.
but we may reach a practical limit for humanity. we'll be out of time or space or energy or fine manipulation