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Q & A: relativity and Newton's 3d law

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Most recent answer: 04/13/2013
Q:
How does Newton's third law of motion equate to Einstein's relativity theory? Secondly, why is Einstein's theory not a law? I am an Einstein sceptic and believe that, whilst he might have been right given the technology of his day, is increasingly likely to be wrong as technology develops and I believe that if mankind progresses at the same rate that it has been, we will see light speed travel inside the next 100 years.
- Michael Downs (age 63)
Dimboola, Victoria, Australia
A:
Today we usually just refer to Newton's 3d law as "conservation of momentum". Thanks to Noether's theorem, we think of that as logically the same as saying that the laws of physics work the same in different places. It's related to relativity, both the old-fashioned Galileo-Descartes type and the more modern Einstein version, in that both reflect symmetries, ways the universe follows the same rules as seen same from different viewpoints.

I guess general relativity is still sometimes called the "theory of general relativity" rather than "the law of general relativity" because in the actual practice of science nobody really cares enough about that sort of naming convention to bother to say things differently.

Your take on the implications of technology for general relativity looks exactly backwards to me. When Einstein and Hilbert came up with the initial formulation, there was almost no evidence except a slight anomaly in the orbit of Mercury. Eddington's confirmation of the predicted light curvature in 1919 stood alone for a long time. As technology improved, we've now gotten a flood of highly accurate confirmations of the theory, starting with the Pound-Rebka clock effect (1960). Now it's way too many to list: black holes, GPS timing, Shapiro time delays, frame-dragging, pulsar gravity waves, confirmation of the theoretical prediction of a naked singularity (Big Bang).......
See for starters.
As for special relativity, which gives the local speed limit, it's so deeply built into the whole structure of modern physics and into most of its accurate predictions that it's hard to even imagine how it could be violated.

Deep revolutions in science do happen, but not just by bigger engines running past fundamental laws.

Mike W.

(published on 04/12/2013)

Follow-Up #1: scientific progress

Q:
Thank you Mike W, you've given me some additional research; but I'm still not convinced about the speed limit, science has been wrong before.
- Michael Downs (age 63)
Dimboola, Victoria, Australia
A:
We'll be wrong again, too.

Mike W.

(published on 04/13/2013)

Follow-up on this answer.