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As I know Newton physics is used for most engineering, aerospace, mechanical, naval etc.

Where we must use Theory of Special Relativity and Theory of General Relativity to get correct results, only for astronomy, big distances/objects etc?

Qmechanic
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user707264
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    Does GPS count? Also https://en.wikipedia.org/wiki/International_Atomic_Time – PM 2Ring Oct 15 '23 at 12:48
  • @PM2Ring For sure. – user707264 Oct 15 '23 at 12:49
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    Also, you can't do nuclear physics without $E=mc^2$, etc. – PM 2Ring Oct 15 '23 at 12:52
  • This post (v1) seems too broad. To reopen it, consider to limit the question to only one aspect of Einstein's work, e.g. general relativity. – Qmechanic Oct 15 '23 at 13:09
  • @Qmechanic I edited. – user707264 Oct 15 '23 at 13:12
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    for the GPS see https://www.astronomy.ohio-state.edu/pogge.1/Ast162/Unit5/gps.html – anna v Oct 15 '23 at 15:07
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    @Qmechanic is't not a great idea to edit a question after it already received answers. It can make the answer - which now might not be suitable for the modified question - look stupid and worthy of down-voting. – Nadav Har'El Oct 15 '23 at 16:34
  • @Nadav Har'El: Fair point. – Qmechanic Oct 15 '23 at 17:14
  • @PM2Ring In reality, the use of general relativity in GPS is a misunderstanding. The real operation of satellites does not involve relativistic corrections. – Pipe Oct 17 '23 at 21:31
  • @Pipe GR time dilation is taken into account in the GPS system, but there are some subtleties. We have numerous questions on this topic, eg https://physics.stackexchange.com/q/402758/123208 & links therein. – PM 2Ring Oct 18 '23 at 02:34
  • @PM2Ring I have read many questions and answers both on the site and related links. I agree that GPS satellites can be used to verify some relativistic effects. However, I have not found any technical documents from the GPS reports that makes explicit mention of relativistic effects for their operation. – Pipe Oct 18 '23 at 03:27

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I'm going to add:

  1. Space craft attitude control (star trackers). They account for stellar aberrations which are a form of the relativistic Doppler shift.

  2. Radiation oncology uses the relativistic form of the Bethe-Bloch eq (1932): https://en.wikipedia.org/wiki/Bethe_formula

  3. PET scans, since they involve annihilating your body's electrons with positrons it's inherently relativistic and quantum.

JEB
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Einstein was so prolific, that by "Einstein Physics" you may be referring to three different things:

  1. Einstein's Theory of Special Relativity.
  2. Einstein's Theory of General Relativity.
  3. Einstein's discoveries about the photoelectric effects that led to the development of Quantum Mechanics.

Quantum Mechanics - which was only started by Einstein but then fully developed by others (Planck, Bohr, Schrodinger, Dirac, Fermi, and many many others), is super-important in many areas of practical engineering, including the invention of the transistor in the 1940s which allowed modern computers, LED lighting, LASER (light amplification by stimulated emission of radiation), superconducting magnets, and a lot lot more.

The theory of special relativity effects calculation of extremely fast-moving objects, and isn't used for most "normal" engineering (e.g., isn't relevant when calculating trajectories of bullets or airplanes), but was very important for the development of the GPS (global positioning satellites) system. In the GPS system, we need to calculate the movement of satellites and electromagnetic beams coming from them very very accurately, to achieve good accuracy of the position on the ground. It turns out that without including special relativity (because these satellites are moving quickly around the earth), the calculations are not accurate enough.

It turns out that the GPS system also needs general relativity: Among other things, general relativity predicts that time slows down near a massive object. Because of general relativity, the time flows a bit more slowly on Earth than it does on the GPS satellites, and if this is not taken into account - the GPS calculations would not turn out to be accurate. Note that this is a separate effect than the velocity-related time dilation I mentioned above (due to special relativity), and both were needed to achieve good accuracy with GPS.

Nadav Har'El
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  • And as others noted, nuclear engineering (everything from building nuclear bombs to nuclear power plants) also needs both quantum mechanics and special relativity (which are unified as quantum field theory; sadly we don't have a unification of quantum mechanics and general relativity yet). – Nadav Har'El Oct 15 '23 at 13:04
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    By the way, there's an old answer https://physics.stackexchange.com/a/128951/219989 which claims that although GPS can be used to demonstrate the truth of General Relativity, it doesn't really depend highly on it, and neglecting general relativity would make the position estimates off by at most a meter. Maybe someone familiar with GPS software can comment: Does it, or does it not, take GR into account? – Nadav Har'El Oct 15 '23 at 13:11
  • But Einstein dont accept today quantum physics, he is determinist dont believe that effect is before cause etc... – user707264 Oct 15 '23 at 13:11
  • Einstein found it hard to accept the interpretation of quantum mechanics, but not the calculations which yielded very good testable results. Moreover, really "modern" quantum mechanics, i.e., quantum field theory, has quantum mechanics fully integrated with special relativity - you can't really do one without the other. In any case, none of this is "Newtonian" physics, and I understood the original question as also being about how post-Newtonian physics is relevant to practical engineering. – Nadav Har'El Oct 15 '23 at 15:07
  • Note to readers (and whomever downvoted by answer): The original question was edited heavily after I wrote my answer. The original question read: "As I know Newton physics is used for most engineering, aerospace, mechanical, naval etc.Where we must use "Einstein physics" to get correct results, only for astronomy, big distances/objects etc?".

    This is why in my answer I used the weird phrase "Einstein physics", and discussed all physics that Einstein was a contributor to - not just relativity.

     – Nadav Har'El Oct 15 '23 at 16:29
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    I was forced to edited because he closed the question – user707264 Oct 15 '23 at 16:36