Einstein theory on bending of space

1. Einstein says it is the bending (more precisely, curvature) of space-time, not just space, that is responsible for gravity.
2. Einstein's theory of gravity is very complex, involving advanced mathematical concepts that would be inaccessible to a high school student or beginning college student. So unless you want to teach the students nothing about gravity until they are junior or senior undergraduate level physics students or higher, you are stuck teaching Newton's theory of gravity.
3. Newton's theory of gravity is an excellent approximation and works very well for almost all aspects of gravity that we encounter in every day life, including predicting all of the orbits of the planets to very high accuracy. The largest inaccuracy for predicting things in our solar system of Newton's theory is the perihelion precession of Mercury. Even then, the precession rate that is predicted by General Relativity over Newtonian theory is a mere 43 arc-seconds per century.
4. School is not about teaching the students the state-of-the-art in every science. If you wanted to do that, you better become a researcher in that area of science. It's about giving the student a database of working knowledge. As such, there is no reason to teach Einstein's general relativity unless you specialize to that area.

 

Gravitational force isn't exactly incorrect, it just depends on your point of view. From the point of view of bodies within space-time that can't "see" the curvature, there does seem to be a force attracting bodies together. This force is capable of accelerating masses and can be measured with F = ma like any other force. If you could adopt a "god's eye view" however and see space-time from the outside (somehow!), you'd be able to see that bodies are just following geodesics - the shortest possible paths they can take through space-time. General relativity doesn't replace gravitational force, it explains the origin of that force as curved space-time.

Besides, Newton's theory of gravitational force is a lot simpler than Einstein's. You may protest that Newton's theory of gravity is wrong, and therefore we should never teach it. But Einstein's theory of gravity is also wrong! That's because, as Isaac Asimov said, scientific theories are not so much wrong as incomplete. (I highly recommend this essay if you're struggling with this concept!)

Scientific theories are never the whole truth - only approximations to the truth. Einstein's theory is a better approximation to the truth than Newton's, but neither theories are the absolute truth. General relativity breaks down under super-extreme conditions anyway - like the earliest moments of the Big Bang, or the centre of a black hole - and it's incompatible with quantum mechanics, so we already know that Einstein isn't the last word and a better theory of gravity is needed! When we get that theory though it won't replace curved space-time - a phenomenon we know exists - it'll just provide a deeper explanation for why matter-energy curves space-time, and will presumably be compatible with quantum mechanics and its equations will work inside a black hole or close to the Big Bang. The equations of general relativity, and the phenomenon of curved space-time, will still of course be very useful, and when we aren't dealing with those super-extreme conditions, general relativity will still be used for other purposes.

In the same way curved space-time didn't replace the force of gravity - only provided a deeper and more satisfying explanation for why the force exists, and provided better answers to calculations for the extreme conditions Newton's theory breaks down in (e.g. high speeds, large distances and strong gravitational fields like the Sun's gravity near the orbit of Mercury). But Newton's equation for gravitational force is still useful for most purposes, and the phenomenon of gravitational force is still a very useful concept. General relativity does provide a deeper understanding of gravity than Newton's theory, but it's still not necessary for the vast majority of purposes, up to and including sending a space probe to Neptune.

I do agree with you it'd be interesting if we introduced the concept of curved space-time earlier on in education - it's cool, and while the detailed mathematics of general relativity is horrendously complicated, the general concept of curved space isn't too difficult for secondary school aged kids to wrap their minds around! But they'd need to know what gravity is first. Newton's a necessary stepping stone along the way to Einstein. Schools have to teach gravitational force first - then later let the students find out about the curved space-time that underlies it all - and later still, maybe one of them will help create that future, all-encompassing quantum theory of gravity that will do for Einstein what Einstein did for Newton - not replace his theory or render it obsolete, but explain why his theory works, fill in the gaps and patch up the problems, and set it in a broader and deeper physical context. Long live both Newton and Einstein!

(Electrons orbiting the nucleus inside an atom like planets orbiting a star... now there's something that's just plain wrong and shouldn't be taught in schools!)

 

So, do you think that if you place two magnets close together in outer space, not touching but close together, that they will not attract/repel each other? That's the clear implication of your statement "force can't travel in vacuum"

 

Point noted, thanks for the clarification! I was referring to "force" in the Newtonian sense. General relativity (in which as you point out gravity doesn't produce proper acceleration, but does produce coordinate "acceleration") explains why there appears to be a gravitational force in the Newtonian model, which is still useful for most intents and purposes, and must be discussed in schools before students can begin to understand GR. So I still stand by my statement that GR explains the source of Newton's gravitational force, even if gravity is no longer considered a force within GR. (Note also that the word "force" is also used in a rather loose sense by particle physicists to mean "interaction" in general, e.g. "the four fundamental forces." Outside of the context of Newtonian mechanics "force" is a pretty imprecise term!)

 

The way I see it, classical physics( Newtons Laws,Maxwells laws etc.) isn't wrong. Its just that the theories of relativity and quantum physics provide a more accurate picture of the universe.

 

They can't be "wrong",... Newton found us many planets and so on....
He was just unable to give correct numbers to more accurate measurements performed later on... as such, it's a good theory that works in some region [and it's much more easy to handle when you want to work in that region] ... I would say Newton was incomplete....So it's only natural to be taught. If we want to teach only the correct over all regions theories, we should start looking at Quantum Gravity and so on... because GR is also not expandable to all "regions" of "reality".
The rest problems from clashes between GR and Newton, come from interpretations and how you see the world...

 

ronric,

I think Amaterasu21 explained it well, with support from PF staff and others of course. I rank Asimov up there with Feynman as a great teacher. Asimov was not only an imaginative, prolific writer, but a prolific deep thinker as well.

Something will eventually have to give as Peter mentioned. Somebody will have to ask the right questions to reconcile Quantum Mechanics (QM) with General Relativity (GR). And the "intruding" conjecture will have to do for both what GR did for Newtons Classical Mechanics, at least in the respect that GR encompassed Newtonian views, yet vastly improved them. Therefore the new perspective will very closely have to basically agree with both QM and GR without totally invalidating either.

QM and GR are both too good to be wrong... but one foundation may have to reluctantly give more than the other. After all this time has passed, the new perspective, historically seen as an intruder of current science by nature, will likely have to be radical... but still fit like a fine glove. When it dawns upon us, we will probably marvel at it's simplicity... and wonder why we didn't think of it sooner.

With luck, we won't have to redefine too many physics terms again. Redefinition is a messy ad hoc business. The simplest explanation is generally the best explanation, aka http://en.wikipedia.org/wiki/Occam's_razor][/PLAIN] [Broken] Occam's razor .

Wes
...

 

Yes, indeed - and that is also the way Einstein used used those words in his theory. In contrast, Peterdonis is referring to modern GR.

 

Grrrrrr

 

I eat vets for breakfast and !