Einstein equations don't work at large scale?

[Dale]

How universe works that way if we find that relativity don't works at large scale and quantum world?

Because we have found experimentally that it does work at scales like 4 m and 50 km/h to 200 km/h. If we eventually find that it doesn’t work at cosmological scales that will not change the experimental fact that it does work at the everyday scales you mentioned.

 

[sbrothy]

Maybe better word is logic , instead intuition.


Will Newton laws still be just approximation if one day we find that time is absolute?

If gravity is correct we will not have these problems today.

Maybe one day we will find theory that is correct from 10^-35m to 10^27m

I guess that's the dream!

 

[Ibix]

Will Newton laws still be just approximation if one day we find that time is absolute?

Of course. We have observational and experimental evidence (a lot of it!) of Newton's laws being violated, some of it pre-dating the discovery of relativity. You can't wish that away.

 

[gen x]

Of course. We have observational and experimental evidence (a lot of it!) of Newton's laws being violated, some of it pre-dating the discovery of relativity. You can't wish that away.

What are all reasons why newton laws fail? exclude quantum physics

 

[Sagittarius A-Star]

What are all reasons why newton laws fail? exclude quantum physics

Newton's law of gravitation predicts a too slow precession of planet Mercury’s orbit, mainly because it did not include spacetime curvature.

Walter Ritz wrote in 1909:

Astronomical observations carried out over many centuries have revealed some deviations between observation and calculation, which cannot be explained by Newton’s law up to now, and which a new theory will have to explain. Of these anomalies by far the largest is of the planet Mercury, whose ellipse precesses slowly, under the effect of the remaining planets; but the observed precession is larger by approximately 42 arc-seconds per century than the computed. The difference is small, but nevertheless unquestionable and unexplained.

Source:
https://www.mathpages.com/rr/s8-10/8-10.htm

 

[Ibix]

What are all reasons why newton laws fail? exclude quantum physics

All of them? Seriously?

For starters there's the anomalous precession of Mercury (and the other planets). There's GPS time dilation. Accelerator experiments such as Bertozzi's (on YouTube). Gravitational lensing of light. Fizeau's experiments with light in water. Anything that shows the invariance and source independence of light speed. The existence of magnetic fields around current carrying wires.

The fundamental reason for all of this is that the fundamental forces appear to be Lorentz covariant, not Galileo covariant. Thus literally every physical interaction (except gravity) obeys SR, not Newton, and gravity obeys GR. Exactly how GR and quantum theory fit together is the big question - everything else fits in.

 

[gen x]

All of them? Seriously?

I didnt mean all examples of where Newton physics cant be used, I mean reasons why theory is wrong..
So he use absolute space and time, dont have finite speed etc...

 

[Ibix]

So he use absolute space and time, dont have finite speed etc...

He (implicitly) assumed the invariant speed was infinite. Einstein realised it must be finite and equal to light speed. All the other differences stem from that.

 

[gen x]

He (implicitly) assumed the invariant speed was infinite. Einstein realised it must be finite and equal to light speed. All the other differences stem from that.

Einstein already knew that speed of light is constant from past experiments.

<edited by mentor>

 

[Ibix]

He (implicitly) assumed the invariant speed was infinite. Einstein realised it must be finite and equal to light speed. All the other differences stem from that.

Note that this is very much a modern retrospective view of it. The actual history is somewhat more tangled, and I very much doubt Newton thought in such terms. Interestingly, had he done so, the mathematical tools to discover relativity were available to him (although due to experimental limitations he would only have been able to say that if the invariant speed is finite it is much larger than anything he could measure).

 

[Ibix]

Einstein already knew that speed of light is constant from past experiments.

Sort of. There were a lot of patches to electromagnetic theory that amounted to SR, but they had not been recognised as such. Poincaré famously published the complete maths for relativity in 1904, but still clearly saw it as a bunch of weird fixes to Maxwell's equations. Einstein's insight was to realise that they weren't fixes to Maxwell, they were a replacement for Newton, and to rederive them from what we would now call symmetry considerations rather than (highly precise!) empirical bodging.

Do you think Newton work is greater then Einstein?

I don't know of a meaningful way to compare them.

 

[PeterDonis]

Einstein already knew that speed of light is constant from past experiments.

Newton didn't when he developed his mechanics, which he did in the mid-1660s, but didn't publish until his friend Edmund Halley badgered him into it in the 1680s. The Michelson Morley experiment, which was the first indication that the prevailing theory of light, which predicted that its speed should vary depending on your motion relative to "absolute space", might be wrong, did not happen until the 1880s.

 

[Dale]

Of course. We have observational and experimental evidence (a lot of it!) of Newton's laws being violated, some of it pre-dating the discovery of relativity. You can't wish that away.

Yes, and we also have lots of evidence validating Newton’s laws. We can’t wish that away either. The existence of that evidence is why Newton’s laws are still valid in the classical domain.

A lot of people in the OP’s position struggle because of an overly simplistic black and white view of scientific theories. The fact is that subsequent data does not undo previous data. Relativity will always be valid where experiments have already confirmed it, just as Newton’s laws will always remain valid where experiments have already confirmed it.

 

[Dale]

I mean reasons why theory is wrong.

The only way to know that a theory is wrong is to obtain measurements that contradict it.

So he use absolute space and time, dont have finite speed etc.

Those are reasons why Newtonian physics differs from relativity. But the reason why it is wrong is not because it differs from relativity. It is wrong only insofar as it differs from experimental observations.

What we can say is that where Newtonian physics differs from relativity, it also differs from the evidence. And where it matches the evidence it also matches relativity. So where Newtonian physics is right, relativity is also right. But the reverse is not always true.

 

[gen x]

Yes, and we also have lots of evidence validating Newton’s laws. We can’t wish that away either. The existence of that evidence is why Newton’s laws are still valid in the classical domain.

A lot of people in the OP’s position struggle because of an overly simplistic black and white view of scientific theories. The fact is that subsequent data does not undo previous data. Relativity will always be valid where experiments have already confirmed it, just as Newton’s laws will always remain valid where experiments have already confirmed it.

When you said valid, you mean accurate enough? So F= 40 N instead F=40.000000001 N

 

[Dale]

When you said valid, you mean accurate enough? So F= 40 N instead F=40.000000001 N

I mean accurate to within the experimental precision.

 

[gen x]

I mean accurate to within the experimental precision.

Experimental devices for engineering & technology in low every day speeds, can't even show relativistics results, because they are so small?

 

[PeterDonis]

Experimental devices for engineering & technology in low every day speeds, can't even show relativistics results, because they are so small?

We have plenty of experimental devices that can show relativistic effects. Indeed, we have "everyday" engineering and technology that would not work if we did not correctly take such effects into account, such as GPS.

 

[gen x]

We have plenty of experimental devices that can show relativistic effects. Indeed, we have "everyday" engineering and technology that would not work if we did not correctly take such effects into account, such as GPS.

99% of engineering & technology use Newtonian physics, only small part use Einstein?

 

[Sagittarius A-Star]

99% of engineering & technology use Newtonian physics, only small part use Einstein?

100% of engineering & technology use Einsteinean physics, but in > 99% of the use cases Newtons laws of classical mechanics are accurate enough.

 

[Dale]

Experimental devices for engineering & technology in low every day speeds, can't even show relativistics results, because they are so small?

We have clocks that are sufficiently precise to measure relativistic effects at human speeds (jogging or biking). So the issue is the combination of the experimental precision and the size of the effect. Not just the size of the effect.

99% of engineering & technology use Newtonian physics, only small part use Einstein?

I don’t know the percentage but “a lot”.

 

[gen x]

100% of engineering & technology use Einsteinean physics, but in 99% of the use cases Newtons laws of classical mechanics are accurate enough.

Where do you find this information? Why would they use relativistics physics for engineering like automobile, naval, structure industry, weather forecast, aerodynamics (navier stokes ), etc?

In technical university for engineering we didnt mention relativity even once, in 5 years of study...

 

[PeterDonis]

99% of engineering & technology use Newtonian physics, only small part use Einstein?

Engineering and technology use whatever they need to to work. If Newtonian models are accurate enough for the engineering and technology to work, that's what they use. If they need the grerater accuracy of relativity, they use that.

I think you are belaboring this way beyond what's necessary.

 

[Sagittarius A-Star]

Where do you find this information? Why would they use relativistics physics for engineering like automobile, naval, structure industry, weather forecast, aerodynamics (navier stokes ), etc?

In technical university for engineering we didnt mention relativity even once, in 5 years of study...

I mean, you have relativistic effects even for small $v/c$. But usually they are so small that they can be and are neglected by using Newtons formulas.

 

[javisot]

What are all reasons why newton laws fail? exclude quantum physics

Newton's laws are not general, given that Newton was a man of the 17th century with virtually no technology at his disposal. He did not explore or observe beyond the limits imposed by the technology available to him. He formulated laws that he considered universal because they could be verified by his contemporaries using similar technology

 

[Histspec]

In technical university for engineering we didnt mention relativity even once, in 5 years of study...

You may be interested in the following paper:

Relativity for Retired Engineers
https://arxiv.org/abs/2605.21660

 

[Ibix]

A lot of people in the OP’s position struggle because of an overly simplistic black and white view of scientific theories. The fact is that subsequent data does not undo previous data.

I think we disagree in our views on what the OP's position is. I think they're hoping to wave "absolute time" like a magic wand and have Newton's laws come back as the real physics with relativity as a misunderstanding. The point I was trying to make was that there were known theoretical and observational problems with Newtonian physics before Einstein (before "relative time"), so that won't happen even if the next theory of gravity turns out to be some Lorentz Ether-esque 3d universe. If I thought the OP was simply struggling with the correspondence principle I'd be closer to your position.

 

[Ibix]

Where do you find this information? Why would they use relativistics physics for engineering like automobile, naval, structure industry, weather forecast, aerodynamics (navier stokes ), etc?

In technical university for engineering we didnt mention relativity even once, in 5 years of study...

If I say I'm driving at 30mph you know that by convention I mean "relative to the local surface of the Earth". In every day life, even in law, we use this convention and it's fine. Nobody even thinks about the convention. Except physicists, because we frequently deal in circumstances where the convention doesn't or cannot apply. "I'm driving at 30mph" is, in physics terms, an incomplete sentence. It needs the "relative to" bit to complete it.

Any time you say "kinetic energy is $\frac 12mv^2$", this is an incorrect statement, strictly speaking. A correct statement would be "kinetic energy is $\frac 12mv^2$ using the Newtonian approximation", or "kinetic energy is $\frac 12mv^2$ plus terms of order $v^4/c^2$ that are negligible for our purposes". Of course, nobody does this, and for much the same reason that we say "I was driving at 30mph" and not "I was driving at 30mph relative to the local Earth's surface" - most people don't understand ennough physics to know why the qualifier is needed, and the rest understand that there is a conventional qualifier that we assume when one is omitted and it is safe to do so.

Engineers will use the Newtonian approximation without acknowledging that they are doing so because (outside some very specialist areas) they will always be able to neglect the relativistic effects, so acknowledging it in every formula would be a waste of time. But you want to step beyond engineering into fundamental physics, and in that context all your post says is "engineers don't realise they are using relativity albeit approximated". It doesn't mean they aren't, implicitly, using it.

There's absolutely nothing wrong with engineers usinbg Newton's formulae without understanding they are an approximation, by the way. For engineering purposes it's perfectly fine. But you aren't doing engineering here, and ignoring that something is an approximation because you personally would like it to be exact is a problem for you, IMO.

 

[gen x]

I think we disagree in our views on what the OP's position is. I think they're hoping to wave "absolute time" like a magic wand and have Newton's laws come back as the real physics with relativity as a misunderstanding. The point I was trying to make was that there were known theoretical and observational problems with Newtonian physics before Einstein (before "relative time"), so that won't happen even if the next theory of gravity turns out to be some Lorentz Ether-esque 3d universe. If I thought the OP was simply struggling with the correspondence principle I'd be closer to your position.

I don't like that every few hundreds years it turns out that our theories are not complete(polite expression of wrong). I would like that theories are always 100% truth just like in math.

In university we didnt even touch relativity, so I was shocked when I find that everything we learned was not 100% correct. But I understand that Newton physics is accurate enough for every day jobs.
I also understand that Newton with math, experimental devices and knoweldege from 17th century cant see everything that we can see today.

 

[Ibix]

I don't like that every few hundreds years it turns out that our theories are not complete(polite expression of wrong).

Unfortunately it's the nature of the beast. Physics isn't given to us by revelation and we can only work with the information we have. We can see that what we have is incomplete, but we haven't any solid leads on which way to proceed from here.