On Tuesday, February 19, 2019 at 6:41:52 AM UTC-7, John Clark wrote: > > On Mon, Feb 18, 2019 at 5:30 PM <[email protected] <javascript:>> wrote: > > *> Sure, but why does this obvious fact force us to merge space and time >> in one concept, aka a manifold?* >> > > If you want to meet me in Manhattan you're going to have to give me 4 > numbers (aka dimensions); 2 of them will give me the street corner, another > one will tell me what floor to get off the elevator, and the fourth will > give me the time of the meeting. >
*You seem to have a firm grasp of the obvious. Perhaps the reason space and time must be merged is for a much deeper reason; namely, only by merging them can we get a curvature of the result. AG * > > >> *> Also, why is it that Newton's law of gravity is not Lorentz invariant, >> yet it seems to work in all inertial frames? TIA, AG * >> > > Newton's law of gravity only approximately works, although the > approximation is quite good provided the speeds involved are not too large > and the spacetime curvature (aka gravity) is not too great. Newton's world > was not Lorentz invariant because there was no limit on how fast you could > go, so the laws of physics would look different depending on how fast you > were going; if you could move at the speed of light in a closed elevator > you could tell you were moving because a beam of light would look frozen > in violation of Maxwell's Equations which says light always moves at the > same speed. Therefore if things are Lorentz invariant you can't move at the > speed of light in a closed elevator. > > By the way, when Maxwell came up with his theory some thought the one flaw > in the idea was that the speed of light that the theory produced with did > not say the speed relative to what. But Einstein realized that Maxwell's > greatest flaw was really his greatest triumph. > *Can you cite any statement by Einstein to this effect? AG * > > > *> So how does GR explain motion? That is, how does curvature of >> space-time result in motion? AG* >> > > Motion is how a change in time relates to a change in space, if spacetime > is flat a given instance in time corresponds to a particular point in > space, if spacetime is curved that same instance in time would correspond > to a different point in space. > *Please elaborate. I don't understand how curvature in itself produces accelerated motion. AG * > > *> What would baseball look like without that tiny curvature? AG * >> > > Imagine a baseball game played on the International Space Station. > *It's strange that such a small change in curvature, produces such a hugely different result. AG * > > John K Clark > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
