It is often cited that as a fundamental of relativity absolute time as a concept is no longer valid. I understand that absolute time was once accepted as a reality but Einstien found that this was not the case. a quote from JamesR in discussion with MacM (twins paradox thread) What is it that relativity has put aside? But I ask, what are we talking about when we refer to this concept "Absolute time"? What does it mean? Care to discuss?
there is absolute time,the time it takes for an electromagnetic wave to travel into space is absolute,or is it not then physics is false time zones around the world i guess to be relative time at the end of the day,it is "just time"
Absolute time is the idea that all clocks anywhere in the universe, whatever their state of motion, tick at exactly the same rate at all times. If separated clocks are set to the same time at one point, then regardless of what happens to them afterwards, they will continue to read the same time (provided they are accurate, not damaged etc.).
Philo, Yep that sounds like invariants 'c' JamesR, Is that it, just clock rate.......is there no mention of anything else about time that relativity sets aside.
just a thought, if we had a photonic clock a clock set by lights velocity wouldn't that be absolute time?
ha...what an idea.......a clock that ticks everytime a beam of light travels 29792 kms would produce an invariant tick rate of one light second and according to relativity it would be invariant.......ha....absolute time ....
funnilly enough I can't see any problem with a photonic clock.....a light cell that takes the velocity of light over any distance within it and computing a second by that velocity. Any one else agree? JamesR?
I think the history is a little more complicated then that. The nature of time has been in dispute since the classical Greek philosphers. I think that the notion of absolute time and space didn't really get good formal "approval" until Newton's model of time and space (Laws of motion and gravity). There were disagreements at that time as well, most notably (I think) by Leibniz, the codiscoverer of calculus. "absolute time" implies that the temporal relationship between any two event is fixed and unambiguous. If the Universe works with absolute time then it is possible to pick any two events and unambiguously state "The time between event A and event B is x seconds". Special relativity suggests that temporal relationships are dependant of reference frame; that the time between two events will be different in different frames.
Thanks again Pete unfortunately I have a problem with my browser. I've taken note of the link and will have a look later. Again, though yo uhave clearly stated that the term "Absolute Time referrs directly and only to the passage of time "the Tick Rate" and as quite rightly so relativity has determined that the "tick " rate is in fact variant, or variable. So to state that the "Now" is absolute does not go against relativity. Possibly the absolute Invariance of the "now" is assumed to be a given by Einstien as this appreas to have never been in dispute prior to Einstiens inspirations. Because dilation events have been proved to occur then relative time is essential to fit in with with reality. This I agree with. There are two forms of time, tick rate and the moment betweeen past and future. Tick rate could be considered the x axis ( variable) and the centre of time as the Y axis. But as the Y axis is static and absolute time just passes with it at it's centre (NOW) But I am pleased that relativity does allow an absolute NOW.
Not so. My statement: "Special relativity suggests that temporal relationships are dependant of reference frame; that the time between two events will be different in different frames." Does not imply what you said. The time between two specified events may be positive, negative, or zero in different reference frames. The difference is not just a multiplier.
