4 ms·

We should bear in mind that, if the history of science is any guide, in 250 years' time relativity will probably seem pretty badly flawed as well leading some f

We should bear in mind that, if the history of science is any guide, in 250 years' time relativity will probably seem pretty badly flawed as well leading some future person to criticize our science for "getting to a correct answer by incorrect reasoning." (If we're lucky. It might just seem wrong.) So we'd do well to be charitable in crediting our predecessors' achievements.

lapetitejort 5y ago
Relativity will probably suffer the same fate as classical mechanics: true for small values of v. In relativity's case, the small value will probably be about 0.99999999c.
- pdonis 5y ago
  I don't know where you're getting this from. We have a relativistic quantum field theory of light itself.
- tsimionescu 5y ago
  Given what we know today, it seems that it's much more likely that special relativity will remain more or less as we know it today (a good approximation for relatively flat regions of space-time and non-accelerating bodies), and that GR will be a good approximation for something like large regions of space-time and huge masses (where "large regions" may mean anything larger than a few Planck lengths, and "huge masses" may mean anything greater than a few micrograms).
  - raattgift 5y ago
    > non-accelerating bodies Accelerated bodies in flat spacetime (Minkowski space) are well-described by special relativity. One can even calculate usefully in accelerated reference frames. https://en.wikipedia.org/wiki/Acceleration_(special_relativity) https://en.wikipedia.org/wiki/Acceleration_(special_relativi... The Unruh effect can happen in flat spacetime, for example, and is a useful check on Hawking radiation (in a black hole curved spacetime). It's also interesting in understanding the weak equivalence principle in detail; very loosely, a small-mass object can rest quietly on the surface of a non-compact, non-spinning, spherical mass eternally, while it is at least very difficult to keep the same small-mass object accelerating uniformly in flat spacetime for even fairly short (compared to say the age of the universe, which is hardly eternal) finite times.
joe__f 5y ago
Your comment seems to imply that, for example, the current consensus is that Newtonian gravity is 'pretty badly flawed' now that we understand it to be superseded by general relativity. This is not true; Newtonian gravity is considered to be a very good approximate theory for low velocities and field strengths.
- xmprt 5y ago
  If we use relativity to explain certain phenomena and the theory fits but it turns out that in the future, there's a much more complete explanation then people will probably look back and say that relativity was the wrong steps to the right answer even though those "wrong" steps are serving us quite well right now.
soheil 5y ago
Completely agree. It's a textbook example of hindsight bias when people cannot "unsee" the currently accepted theory deemed to be "true" and fail to imagine that people in the past thought just like them before the new theory came along. I think it takes a good amount of marketing (eg. Einstein with Relativity) to change people's mind if a new improved theory is to be accepted and for majority to conform to it. So let's indeed be very charitable in crediting our predecessors' achievements.
- mr_mitm 5y ago
  What do you mean by marketing? Einstein didn't need much convincing, as he proposed experiments that would falsify or confirm general relativity. The theory is also not only mathematically sound but very elegant. Acutally, Hilbert arrived at the same equations using a competely different, more mathematical approach using the least action principle, which is another good sign it was correct. But the smoking gun was of course Edison's observation of gravitational lensing during an eclipse. But of course the topic in this subthread is special relativity. And I think the speed of light being constant and a maximum speed is one of the most fundamental and most assured fact about the universe that we know, because it's more than just some speed of some particle. It's a geometric property of spacetime, a Lorentzian manifold. I doubt it will ever be looked upon as some sort of horrible blunder, just like no one ever thinks less of Newton just because he only found an approximately correct theory. I think it's foolish to doubt it just to be contrarian. Could it be wrong? Sure, we look for violations of Lorentz invariance all the time. But the boundaries we have on it are extremely good. But if someone claims to have observed superluminal speeds, I'll doubt the experimenters more than I'll doubt special relativity, because of the strong priors we have on it. This happened by the way a few years ago, where some Italian lab claimed to have seen superluminal neutrinos. Most professional physicists didn't believe it. It turned out to be a faulty cable.
  - raattgift 5y ago
    > Edison's observation of gravitational lensing during an eclipse There may have been electric lights and phonographs on the ships, but it was the https://en.wikipedia.org/wiki/Eddington_experiment https://en.wikipedia.org/wiki/Eddington_experiment and while maybe you could say it was about gravitational lensing, the observatories (and Earth) was so far from any possible caustic that it's better to leave it at just deflection of light. Here's a pop-sci treatment of the gravitational lensing of our sun for astronomy -- tl;dr it involves lonnnnng distance travel, more than 500 astronomical units (Pluto is at ~ 30-50 au). https://blogs.scientificamerican.com/observations/using-the-sun-as-a-cosmic-telescope/ https://blogs.scientificamerican.com/observations/using-the-...

lapetitejort 5y ago

Relativity will probably suffer the same fate as classical mechanics: true for small values of v. In relativity's case, the small value will probably be about 0.99999999c.

pdonis 5y ago
I don't know where you're getting this from. We have a relativistic quantum field theory of light itself.
tsimionescu 5y ago
Given what we know today, it seems that it's much more likely that special relativity will remain more or less as we know it today (a good approximation for relatively flat regions of space-time and non-accelerating bodies), and that GR will be a good approximation for something like large regions of space-time and huge masses (where "large regions" may mean anything larger than a few Planck lengths, and "huge masses" may mean anything greater than a few micrograms).
- raattgift 5y ago
  > non-accelerating bodies Accelerated bodies in flat spacetime (Minkowski space) are well-described by special relativity. One can even calculate usefully in accelerated reference frames. https://en.wikipedia.org/wiki/Acceleration_(special_relativity) https://en.wikipedia.org/wiki/Acceleration_(special_relativi... The Unruh effect can happen in flat spacetime, for example, and is a useful check on Hawking radiation (in a black hole curved spacetime). It's also interesting in understanding the weak equivalence principle in detail; very loosely, a small-mass object can rest quietly on the surface of a non-compact, non-spinning, spherical mass eternally, while it is at least very difficult to keep the same small-mass object accelerating uniformly in flat spacetime for even fairly short (compared to say the age of the universe, which is hardly eternal) finite times.

joe__f 5y ago

Your comment seems to imply that, for example, the current consensus is that Newtonian gravity is 'pretty badly flawed' now that we understand it to be superseded by general relativity. This is not true; Newtonian gravity is considered to be a very good approximate theory for low velocities and field strengths.

xmprt 5y ago
If we use relativity to explain certain phenomena and the theory fits but it turns out that in the future, there's a much more complete explanation then people will probably look back and say that relativity was the wrong steps to the right answer even though those "wrong" steps are serving us quite well right now.

soheil 5y ago

Completely agree. It's a textbook example of hindsight bias when people cannot "unsee" the currently accepted theory deemed to be "true" and fail to imagine that people in the past thought just like them before the new theory came along. I think it takes a good amount of marketing (eg. Einstein with Relativity) to change people's mind if a new improved theory is to be accepted and for majority to conform to it. So let's indeed be very charitable in crediting our predecessors' achievements.

mr_mitm 5y ago
What do you mean by marketing? Einstein didn't need much convincing, as he proposed experiments that would falsify or confirm general relativity. The theory is also not only mathematically sound but very elegant. Acutally, Hilbert arrived at the same equations using a competely different, more mathematical approach using the least action principle, which is another good sign it was correct. But the smoking gun was of course Edison's observation of gravitational lensing during an eclipse. But of course the topic in this subthread is special relativity. And I think the speed of light being constant and a maximum speed is one of the most fundamental and most assured fact about the universe that we know, because it's more than just some speed of some particle. It's a geometric property of spacetime, a Lorentzian manifold. I doubt it will ever be looked upon as some sort of horrible blunder, just like no one ever thinks less of Newton just because he only found an approximately correct theory. I think it's foolish to doubt it just to be contrarian. Could it be wrong? Sure, we look for violations of Lorentz invariance all the time. But the boundaries we have on it are extremely good. But if someone claims to have observed superluminal speeds, I'll doubt the experimenters more than I'll doubt special relativity, because of the strong priors we have on it. This happened by the way a few years ago, where some Italian lab claimed to have seen superluminal neutrinos. Most professional physicists didn't believe it. It turned out to be a faulty cable.
- raattgift 5y ago
  > Edison's observation of gravitational lensing during an eclipse There may have been electric lights and phonographs on the ships, but it was the https://en.wikipedia.org/wiki/Eddington_experiment https://en.wikipedia.org/wiki/Eddington_experiment and while maybe you could say it was about gravitational lensing, the observatories (and Earth) was so far from any possible caustic that it's better to leave it at just deflection of light. Here's a pop-sci treatment of the gravitational lensing of our sun for astronomy -- tl;dr it involves lonnnnng distance travel, more than 500 astronomical units (Pluto is at ~ 30-50 au). https://blogs.scientificamerican.com/observations/using-the-sun-as-a-cosmic-telescope/ https://blogs.scientificamerican.com/observations/using-the-...