geordief

I think acceleration can just be an increase in speed if the direction does not change With the Moon ,isn't it in freefall? (so not accelerating)

Doesn't the orbit decay? I feel out of my depth as usual but if it doesn't decay doesn't that mean it is accelerating? And if it does decay ,then it is in freefall and so not accelerating. Maybe there is a difference in what acceleration means in Relativity and in Newtonian mechanics?? I hope I just answered your question too.

I always thought that a system was in acceleration because it was expending energy and that its acceleration could be maintained only so long as the energy lasted. The longer the acceleration was maintained the more the system dissipated and eventually it would vanish. On the other hand a system that was in motion wrt another system could maintain that state for ever.

Thanks. Appreciate your help and patience.

So it would give most of SR ? Can you give me an example of what it would fail to show in SR ?(I sound argumentative but am just curious) What additional requirement might allow it to completely derive SR?

So ,even the maximum separation speed **during inflation would be comparable to that obtaining now ,just many times higher?(so many ,many multiples of c) but the actual maximum speed then would likewise be the same as now ....ie c? *I think that is the term (or the term I am looking for) where on account of expansion objects recede (and become invisible) at speeds greater than c

I didn't know that the inflationary epoch was covered by GR. It is ,then?

If I was trying to arrange such a scenario I have the intuition that any such force would approach a limit in practical terms. Actually ,in the initial inflationary epoch ,I wonder if there were objects separating from each other and if there was a velocity attached to those separations? Did the term "speed" even apply to those conditions?

But the same spacetime interval ,no? The first event is the departure of the light from A and the second is its capture by B But only one spacetime interval,surely....

Could it be derived simply from assuming that the spacetime interval is the same for all observers? Perhaps there are two observers and A flashes a light pulse to B so that both A and B have 2 (identical events) Then perform the same operation with A accelerating towards B . Then repeat with the acceleration increasing linearly Then repeat with the last operation accelerating similarly wrt the last operation And so on ..(the distance between A and B the same on each occasion) Is the spacetime interval invariance a stand in for Einsteins's "physical laws are the same everywhere" postulate?

Apparently Feynman had his own method https://books.google.ie/books?id=G0paDwAAQBAJ&pg=PA87&lpg=PA87&dq="Einstein+himself,+of+course,+arrived+at+the+same+Lagrangian**+but+without+the+help+of+a+developed+field+theory,+and+I+must+admit+that+I+have+no+idea+of+how+he+ever+guessed+at+the+final+result.+We+have+had+troubles+enough+in+arriving+at+the+theory+--+but+I+feel+as+though+he+had+done+it+while+swimming+underwater,+blindfolded,+and+with+his+hands+tied+behind+his+back!&source=bl&ots=IGoZy4MI0z&sig=ACfU3U1pAweHTDVX73wpqtGr5ucyNNda5w&hl=en&sa=X&ved=2ahUKEwicjrzO0JXsAhUnSBUIHTTsDJsQ6AEwCHoECAkQAg#v=onepage&q=blindfolded&f=false ""Einstein himself, of course, arrived at the same Lagrangian** but without the help of a developed field theory, and I must admit that I have no idea of how he ever guessed at the final result. We have had troubles enough in arriving at the theory -- but I feel as though he had done it while swimming underwater, blindfolded, and with his hands tied behind his back!" How many distinct (not distinguished by methodology but really distinct) methods are there to derive relativity?

I've had them regularly for the past 25 years.At first I thought that Lyme's disease was only prevalent in N America and maybe mainland Europe until a friend in England got it. So I now wash my hands whenever I need to remove them from different ,sometimes alarming parts of my body. It feels like I should have built up an immunity but I don't know if that is what happens.

If anyone else tries this ,would they put it on Youtube?😆 Not taking the piss,just hard not to laugh.

Sounds suspicious . Like a trained tick. (they only fall off when they are full of blood sfaik)

Exactly.

Is this animal cruelty? I once sat on a nest of baby ticks . Turns out I was all their preferred host

Extrapolating now,if we take an event such as the death of Julius Caesar and we take the set of all ("subsequent") events (eg my typing this) can we say that ,provided these events occur after the initial event (as judged from that event's frame of reference ).... if all that is true then there is no event that is not connected by a spacetime interval? Must there be a chain(s?) of causation no matter how tenuous There are no "blind spots"....no "causation shields"(except black holes or gravitational waves)? The "causation cone" which is the set of events in the light cone is thus interconnected like a moving net. And ,as you have said the distance between every pair (or chain ends ) of events will be judged as identical no matter from what vantage point in the set of events one is judging?

I think one of the axioms of GR is that physical laws are the same everywhere,no matter what frame of reference. Is there any connection between that requirement and this invariance of the spacetime interval ,again under whatever frame of reference? Might it actually be possible to derive GR from using this latter requirement as an axiom in its own right? And what would it say if the opposite was the case? Would we be looking at a universe of chaos as opposed to a universe with "integrity"? ("Integrity" just intended to signify "wholeness" as opposed to disparity - no moral implications as applied.)

Plead ignorance at this stage in my life but how dods this process happen in the body? When I eat my meal there are both liquids and solids. Clearly they are separated somehow.Does this occur in the stomach? There can't be a Trump recommended centrifuge down there so how does the process get started (are there a few stages ,perhaps?)

Thanks for putting me right. Are there other things that those observers do agree on ? Can they agree i your scenario when they compensate for the difference in their gravitational potential? Is that kind of information always available to them in principle?

I struggle with the simple maths (and the implications thereof) of basic special relativity . So I can't with confidence say that it makes good sense or bad sense. (I will try to reread it a few times and it may become clearer) Edit: have dug up this very old old response from Markus to me where I asked him about the space time interval . http://www.thescienceforum.com/physics/41968-space-time-interval.html At the time I took it to mean that it was invariant in both inertial and non-inertial frames. As I said then ,I found that reassuring (because the physical world seemed to make a little(a lot) more "sense" to me as a result Hope I didn't misinterpret at the time.

My pipe is so long (the stretch I suspect is over 30 metres and others are longer) that I would not have confidence in a length of stiff kerosene piping going the distance since I am confident there is corrosion having repaired holes in the past. What it might do ,I suppose would be to actually locate the area that is holed. . Then I could dig down with confidence and maybe get some more years of life out of the system. I have used this stiff kerosene piping to unblock the sewage drains in the past .Again ,it can allow you to locate sections that are cracked so that you can repair them or ,with patience and flushing it allows the blockage of paper and excrement to make its way to the end. Those are much wider pipes ,of course . Since I repaired that cracked section there is much less maintenance and flushing works when necessary or ahead of time.

Sounds good to me.Yes ,I should have chosen a location removed from spacetime curvature,even though I still hope that the spacetime interval may be invariant under those conditions too. I wasn't aware it was easy to synchronize clocks like you said and that is why I assumed there would have to be signal capture at E and M.

I wondered where that post of mine went.I was going to delete it as that kerosene idea was a bit barmy but I couldn't find it for whatever reason. Sometimes the software on this site is a step ahead of me.... I had the kerosene idea since it leaves rainbow coloured stains in the soil. I just use this water for the garden really. It is a pretty ancient system ,one inch metal pipes now well corroded with ,I suspect one or two leaks along the line held together by compacted soil. I did once attempt to dig it up starting from one end but ran into lots of fuscia and ivy roots as well as a disappearing pipe...

We don't get many dry spells here. I have waited for them and searched then but the area is pretty overgrown and ,for all I know the pipe may go under a rocker/flower bed(I didn't put it in) It might be more obvious I'd have thought .... actually what would be obvious might be to put a a bit of kerosene in the pipe but I'd hesitate to do that as it would harm the insects and I might need a lot if the leak is a long way along the pipe (it goes about 100 metres at a guess)