On Mon, Dec 11, 2017 at 5:11 PM, <[email protected]> wrote:
>> >> The Equivalence Principle says if >> you >> ignore tidal effects and you're in a windowless elevator cab there is no >> way to know if you're sitting on the Earth in a gravitational field or in >> deep intergalactic space being accelerated by a rocket upward at 1G. If you >> feel zero G and fire a Laser pointer from one wall >> to the other >> it will go in a straight line and hit the exact opposite side on the >> other wall. But if you were being accelerated upward the elevator cab will >> move >> slightly >> upward in the time it takes for the light to go from one wall to the >> other so the spot the laser makes on the other wall will be slightly lower >> than it was when you were in zero G, you see the laser beam follow a curve. >> > > > > At rest on Earth is not a situation of zero G; it's 1G. Or, say, if you > want a straight beam, one can assume an inertial frame, > The surface of the Earth is in a gravitational field and so it is *NOT* a inertial frame, and so light from a Laser pointer does curve, although not by a lot. The interior of an elevator in which the cable has been cut would be a inertial frame, until it hit the ground. >> >> A curved line from one wall to the other is longer than a straight line >> , >> and yet when you measure the time it takes for light to do this with your >> very accurate clock you notice its exactly the same. You already know the >> measured speed of light never changes so >> if something is moving at the same speed and moves a greater distance in >> the same number of clock ticks then >> you'd have to conclude that being accelerated makes your clock run slow. >> > > > > I think most of last paragraph incorrect. In experiments with GPS clocks, > the ground clock, in the stronger gravity field, runs slower than an > orbiting clock. > T he GPS satellite is moving very fast so due to Special Relativity the satellite's clock will LOSE 7210 nanoseconds a day, but the satellite's clock is in a weaker gravitational field than the clock on the ground because it is further from the Earth's center, so due to GENERAL RELATIVITY the clock will GAIN 45850 nanoseconds a day. Taking these 2 factors into account the satellite's clocks gains 45850 −7210 = 38,640 nanoseconds a day relative to a clock on the ground. If this were not taken into account the GPS system would drift off by 6 miles a day. > > > Fewer ticks in ground clock > Yes, a clock on the ground in a 1G gravitational field or a clock in deep space being accelerated by a rocket at 1G will record fewer ticks than a non-accelerating clock in no gravitational field. > > In your elevator example, where zero G can be interpreted as being in an > inertial frame, you claim the elapsed time duration using ticks, is > identical for both beams. I'm not sure which 2 beams you're talking about. The interior of the elevator sitting on the ground and the elevator in deep space being accelerated by a rocket are identical. The elevator with the broken cable near the earth and the elevator with no rocket in deep space are identical. 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.
