uhm...how is it not. I know that F=ma breaks down at extreme values -- but it has still helped develop all of our basic physics, and is still applicable almost anywhere in mechanics provided that there are no extreme values.

There is also the fact that you can't prove that what you're seeing/feeling is what is actually there, or even real. For example, how do you know that life itself isn't one big illusion?

However, we have to make *some* assumptions, otherwise we would get nowhere. Yes, everything we are doing could mean absolutely nothing in the grand scheme of things, but we just have to assume that everything is real, and that everything observed by our senses is real. If you see a person flying, then in your eyes, people can fly (weird example ) since you observed it with your own senses (although there could be a logical explanation for it, I guess). Everyone else will think you're mad, but you will be convinced of that fact.




It could just be a coincidence that our view of physics "works", and we might be missing the whole picture (i.e. we know what happens at values that we can observe, but with values that are much higher than we can observe, it might completely fall apart).

If it was possible to out and out prove Newton's laws, we probably wouldn't even be having this conversation. We have to just go on and assume they are correct though, since they have served us well this far, and we don't exactly want to start back at square one.

i am not saying that it is not useful, i am very aware of newton's wisdom, but pullamies' attitude is just pissing me off, you will agree with me once you read his threads and his replies



F=ma is useful, but not the basis everything in physic at our level of observation, for example it doesnt comment on heat/energy transfer, it doesnt comment on how electric/magnetic field work, which are both useful.

if you are just talking mechanics, it takes 1/3 of the importance, because there are two other laws of newton that are as important

This post was edited by hk_nobody on Jan 24 2009 06:48am

Here's my 5 cents:

I own a copy of Newton's Principia, and in there, these three laws are part of Newton's axioms (facts not logically reducible to simpler principles). With these and other physical axioms, as well as a lot of heavy geometrical reasoning, he is able to derive the inverse square law for the gravitational attraction of two bodies.

That said, I don't think the question needs to be considered very much longer.. whether these principles are provable depends on the philosophy of physics (and not applied mathematics). Most people accept these to be reasonable and readily verifiable classical mechanics laws, others have to scratch their heads a while and convince themselves that classical mechanics cannot be any other way. These axioms have successfully caused the prediction of many empirical phenomena, and today lots of people accept them based on the fact that they have been used successfully for a very long time.

For myself, I would like to hear a physicist speak on this topic, but as a mathematician, I can say simply that axioms need no proof (and that is what Newtons three 'Laws' are).

well, like how would one prove that if there are no forces acting on an object (inertia etc) then the object would keep going straight.

*or remain in a state of rest

And I'm not altogether sure anymore... physical proof is a lot murkier than mathematical proof.

This post was edited by just_shotmikew1 on Jan 24 2009 06:22pm

go ice skating, then go really really fast, then stop all of a sudden and fall.. but slide a couple feet.

thats not the best way to describe it but thats newton's law of inertia in a very simple way.

... Stupidass thread.

100% agree

I doubt we will ever be able to prove this.

You can only break something down so much...

We just know it works. So either its right or close enough that we dont give a shit

This should go in my profile.