/sci/ - Science & Math

First of all, the law is
>In inertial frames of reference, F=m·a.
Note that a statement like "Newtons second law only holds in an inertial frames of reference" is a faux pas.

Secondly, it's not a definition akin v=dr/dt because when you use the mechanical theory to make a prediction, you always also need to provide a force expression F too. Say F=-mM/r^2 or F=-kr.

Lastly, the sense in which those laws set up the theory is different from how Newton thought physics works. Without a fixed star reference point, i.e. without knowing how you yourself move or are possibly affected by forces, the 3 laws don't actually give you a chance to know if no force is acting on an object.

>>6946293
I must say I don't really understand you two-way speed emphasis, but I guess it's related to how the mirroring in the experiments measure light.
Regardless, I personally have no problem (maybe educated away) with constant speed of light of QM non-intuiveness, so I don't actually feel the need to explain any why here - just correct the faults in that are there and understand the models better. I'm not into phenomenology - shut up and calculate - either, but you want to replace something just because you have a hunch it could be better.
But to that, your claim that people don't think at all about the behinds of theories is just not true. People try to expand some theories in the obvious ways (this are the "uncreative accounts", if you will), see e.g.
http://en.wikipedia.org/wiki/Alternatives_to_general_relativity
The notion of time in loop quantum gravity is very beautiful, to me, and I also don't blame the people who work out strings since 40 years, the geometry is pretty fine too.
But then there are also more radical approaches like Cellular Automaton approaches to the workings behind the behaviour of the universe etc. I'd say people like Christopher Isham are also creative physicists, who try to apply cool tools to shake some of the foundations.
And
>>6946375
is right, the axioms don't come first for physicists - they use the tools they need (and know of) on the fly, or the good people introduce some.

Related to the thread, but of course not in your spirit, there is a logical treatment of special relativity out there, pretty syntetic, see
http://arxiv.org/pdf/1005.0973v1.pdf