Known physics defeated by simple puzzle?
in [Relativity]
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From: Inertial on 9 Apr 2010 21:29 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:39d118a7-ca01-462a-8232-e8db9b1c5116(a)u34g2000yqu.googlegroups.com... > On Apr 9, 9:10 pm, "Inertial" <relativ...(a)rest.com> wrote: >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message >> >> news:6a682982-c761-41e1-b146-64cdaaca44c1(a)v20g2000yqv.googlegroups.com... >> >> >> >> > On Apr 9, 8:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> On 10 Apr, 00:46, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >news:b55913f6-a3d0-401c-878b-4d0ec3677fa3(a)11g2000yqr.googlegroups.com... >> >> >> > > On 9 Apr, 22:24, PD <thedraperfam...(a)gmail.com> wrote: >> >> > >> On Apr 9, 3:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> >> > >> > > But that is not what happens. >> >> > >> > > For example, if I see a car traveling west at 10 kmh, and a >> >> > >> > > car >> >> > >> > > traveling east at 35 kmh, then you have the expectation that, >> >> > >> > > to >> >> > >> > > a >> >> > >> > > passenger riding in the car traveling east, the other car is >> >> > >> > > traveling >> >> > >> > > 45 kmh west. >> >> > >> > > But in fact, it is not traveling at 45 kmh west to a >> >> > >> > > passenger >> >> > >> > > in >> >> > >> > > that >> >> > >> > > car. >> >> > >> > > It is traveling at something close to that, but only >> >> > >> > > approximately. >> >> >> > >> > > The bottom line is, the basic sum rule you've been taught for >> >> > >> > > relative >> >> > >> > > velocities is a LIE. >> >> >> > >> > i would expect the combined speed to be a real 45kmh, yes, >> >> > >> > although >> >> > >> > it's quite possible that none of them will any longer agree on >> >> > >> > the >> >> > >> > definition of "hour" or "kilometer". >> >> >> > >> Oh, no, they agree on the definition of hour and kilometer, >> >> > >> alright. >> >> > >> Something that is measured locally to be a km will still be >> >> > >> measured >> >> > >> locally to be a km. And a standard process that locally takes an >> >> > >> hr >> >> > >> will still locally take an hour. >> >> >> > > Indeed, the question is whether their respective measures of "an >> >> > > hour" >> >> > > are truly identical. >> >> >> > What do you mean by 'truly identical' >> >> >> In other words, whether they are measuring the same periods of time - >> >> whether the interval of each tick of each clock would be the same as >> >> each other. >> >> > The coordinate time of SR is derived >> > from light signal exchange. E-sync. >> >> That describes how synchrnoized clocks should behave (ie that they give >> the >> same reading for what must be identical times, and show identical time >> durations as identical). > > ============== >> >> > Real clock mechanisms don't "measure" time >> > they mark it. >> >> A not terribly relevant semantic difference > > <<Elements of a Clock > > Before we continue describing the evolution of > ways to mark the passage of time, perhaps we > should broadly define what constitutes a clock. > All clocks must have two basic components: > > * a regular, constant or repetitive process > or action to mark off equal increments of time. ...>> > http://physics.nist.gov/GenInt/Time/early.html Yes .. we know that. we know how clocks work. They mark the time, and you can use that to measure elapsed time. Its all just pedantic and semantic nonsense whether we say clocks measure time or mark it. The difference doesn't change our meaning and intent.
From: Sue... on 9 Apr 2010 22:09 On Apr 9, 9:29 pm, "Inertial" <relativ...(a)rest.com> wrote: > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > news:39d118a7-ca01-462a-8232-e8db9b1c5116(a)u34g2000yqu.googlegroups.com... > > > > > On Apr 9, 9:10 pm, "Inertial" <relativ...(a)rest.com> wrote: > >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > >>news:6a682982-c761-41e1-b146-64cdaaca44c1(a)v20g2000yqv.googlegroups.com.... > > >> > On Apr 9, 8:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: > >> >> On 10 Apr, 00:46, "Inertial" <relativ...(a)rest.com> wrote: > > >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >> >news:b55913f6-a3d0-401c-878b-4d0ec3677fa3(a)11g2000yqr.googlegroups.com... > > >> >> > > On 9 Apr, 22:24, PD <thedraperfam...(a)gmail.com> wrote: > >> >> > >> On Apr 9, 3:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > >> >> > >> > > But that is not what happens. > >> >> > >> > > For example, if I see a car traveling west at 10 kmh, and a > >> >> > >> > > car > >> >> > >> > > traveling east at 35 kmh, then you have the expectation that, > >> >> > >> > > to > >> >> > >> > > a > >> >> > >> > > passenger riding in the car traveling east, the other car is > >> >> > >> > > traveling > >> >> > >> > > 45 kmh west. > >> >> > >> > > But in fact, it is not traveling at 45 kmh west to a > >> >> > >> > > passenger > >> >> > >> > > in > >> >> > >> > > that > >> >> > >> > > car. > >> >> > >> > > It is traveling at something close to that, but only > >> >> > >> > > approximately. > > >> >> > >> > > The bottom line is, the basic sum rule you've been taught for > >> >> > >> > > relative > >> >> > >> > > velocities is a LIE. > > >> >> > >> > i would expect the combined speed to be a real 45kmh, yes, > >> >> > >> > although > >> >> > >> > it's quite possible that none of them will any longer agree on > >> >> > >> > the > >> >> > >> > definition of "hour" or "kilometer". > > >> >> > >> Oh, no, they agree on the definition of hour and kilometer, > >> >> > >> alright. > >> >> > >> Something that is measured locally to be a km will still be > >> >> > >> measured > >> >> > >> locally to be a km. And a standard process that locally takes an > >> >> > >> hr > >> >> > >> will still locally take an hour. > > >> >> > > Indeed, the question is whether their respective measures of "an > >> >> > > hour" > >> >> > > are truly identical. > > >> >> > What do you mean by 'truly identical' > > >> >> In other words, whether they are measuring the same periods of time - > >> >> whether the interval of each tick of each clock would be the same as > >> >> each other. > > >> > The coordinate time of SR is derived > >> > from light signal exchange. E-sync. > > >> That describes how synchrnoized clocks should behave (ie that they give > >> the > >> same reading for what must be identical times, and show identical time > >> durations as identical). > > > ============== > > >> > Real clock mechanisms don't "measure" time > >> > they mark it. > > >> A not terribly relevant semantic difference > > > <<Elements of a Clock > > > Before we continue describing the evolution of > > ways to mark the passage of time, perhaps we > > should broadly define what constitutes a clock. > > All clocks must have two basic components: > > > * a regular, constant or repetitive process > > or action to mark off equal increments of time. ...>> > > http://physics.nist.gov/GenInt/Time/early.html > > Yes .. we know that. we know how clocks work. They mark the time, and you > can use that to measure elapsed time. Its all just pedantic and semantic > nonsense whether we say clocks measure time or mark it. The difference > doesn't change our meaning and intent. If we can put your intentions aside for just a bit we won't have to explain the difference in a Seiko and a Rolex. A clock marks time with a process. In helping with Einsetin's General theory (a few years after 1905) Noether and Hilbert discovered that "just any process" won't do. So I have described a process easily compared between inertial frames. http://en.wikipedia.org/wiki/Noether%27s_theorem#Applications The energy of a spring and the mass of a balance wheel is just a good but the maths is a bit easier with a bullet and metre stick. This little detail may cause some problems for LET and 1905. It is better to make the full specification and use the 1920 paper and fully satisfy the OP that there is no monkey business in SR. Sue...
From: Inertial on 9 Apr 2010 22:50 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:3e683cff-694a-4c23-9116-17446bdd3ac2(a)g30g2000yqc.googlegroups.com... > On Apr 9, 9:29 pm, "Inertial" <relativ...(a)rest.com> wrote: >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message >> >> news:39d118a7-ca01-462a-8232-e8db9b1c5116(a)u34g2000yqu.googlegroups.com... >> >> >> >> > On Apr 9, 9:10 pm, "Inertial" <relativ...(a)rest.com> wrote: >> >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message >> >> >>news:6a682982-c761-41e1-b146-64cdaaca44c1(a)v20g2000yqv.googlegroups.com... >> >> >> > On Apr 9, 8:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> >> On 10 Apr, 00:46, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >> >news:b55913f6-a3d0-401c-878b-4d0ec3677fa3(a)11g2000yqr.googlegroups.com... >> >> >> >> > > On 9 Apr, 22:24, PD <thedraperfam...(a)gmail.com> wrote: >> >> >> > >> On Apr 9, 3:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> >> >> > >> > > But that is not what happens. >> >> >> > >> > > For example, if I see a car traveling west at 10 kmh, and >> >> >> > >> > > a >> >> >> > >> > > car >> >> >> > >> > > traveling east at 35 kmh, then you have the expectation >> >> >> > >> > > that, >> >> >> > >> > > to >> >> >> > >> > > a >> >> >> > >> > > passenger riding in the car traveling east, the other car >> >> >> > >> > > is >> >> >> > >> > > traveling >> >> >> > >> > > 45 kmh west. >> >> >> > >> > > But in fact, it is not traveling at 45 kmh west to a >> >> >> > >> > > passenger >> >> >> > >> > > in >> >> >> > >> > > that >> >> >> > >> > > car. >> >> >> > >> > > It is traveling at something close to that, but only >> >> >> > >> > > approximately. >> >> >> >> > >> > > The bottom line is, the basic sum rule you've been taught >> >> >> > >> > > for >> >> >> > >> > > relative >> >> >> > >> > > velocities is a LIE. >> >> >> >> > >> > i would expect the combined speed to be a real 45kmh, yes, >> >> >> > >> > although >> >> >> > >> > it's quite possible that none of them will any longer agree >> >> >> > >> > on >> >> >> > >> > the >> >> >> > >> > definition of "hour" or "kilometer". >> >> >> >> > >> Oh, no, they agree on the definition of hour and kilometer, >> >> >> > >> alright. >> >> >> > >> Something that is measured locally to be a km will still be >> >> >> > >> measured >> >> >> > >> locally to be a km. And a standard process that locally takes >> >> >> > >> an >> >> >> > >> hr >> >> >> > >> will still locally take an hour. >> >> >> >> > > Indeed, the question is whether their respective measures of >> >> >> > > "an >> >> >> > > hour" >> >> >> > > are truly identical. >> >> >> >> > What do you mean by 'truly identical' >> >> >> >> In other words, whether they are measuring the same periods of >> >> >> time - >> >> >> whether the interval of each tick of each clock would be the same >> >> >> as >> >> >> each other. >> >> >> > The coordinate time of SR is derived >> >> > from light signal exchange. E-sync. >> >> >> That describes how synchrnoized clocks should behave (ie that they >> >> give >> >> the >> >> same reading for what must be identical times, and show identical time >> >> durations as identical). >> >> > ============== >> >> >> > Real clock mechanisms don't "measure" time >> >> > they mark it. >> >> >> A not terribly relevant semantic difference >> >> > <<Elements of a Clock >> >> > Before we continue describing the evolution of >> > ways to mark the passage of time, perhaps we >> > should broadly define what constitutes a clock. >> > All clocks must have two basic components: >> >> > * a regular, constant or repetitive process >> > or action to mark off equal increments of time. ...>> >> > > > http://physics.nist.gov/GenInt/Time/early.html >> >> Yes .. we know that. we know how clocks work. They mark the time, and >> you >> can use that to measure elapsed time. Its all just pedantic and semantic >> nonsense whether we say clocks measure time or mark it. The difference >> doesn't change our meaning and intent. > > If we can put your intentions aside for just a > bit we won't have to explain the difference > in a Seiko and a Rolex. > > A clock marks time with a process. Yes it does .. I didn't argue with that. And the differences between those marks let you measure elapsed time
From: Sue... on 10 Apr 2010 00:00 On Apr 9, 10:50 pm, "Inertial" <relativ...(a)rest.com> wrote: > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > news:3e683cff-694a-4c23-9116-17446bdd3ac2(a)g30g2000yqc.googlegroups.com... > > > > > On Apr 9, 9:29 pm, "Inertial" <relativ...(a)rest.com> wrote: > >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > >>news:39d118a7-ca01-462a-8232-e8db9b1c5116(a)u34g2000yqu.googlegroups.com.... > > >> > On Apr 9, 9:10 pm, "Inertial" <relativ...(a)rest.com> wrote: > >> >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > >> >>news:6a682982-c761-41e1-b146-64cdaaca44c1(a)v20g2000yqv.googlegroups.com... > > >> >> > On Apr 9, 8:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: > >> >> >> On 10 Apr, 00:46, "Inertial" <relativ...(a)rest.com> wrote: > > >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >> >> >news:b55913f6-a3d0-401c-878b-4d0ec3677fa3(a)11g2000yqr.googlegroups.com... > > >> >> >> > > On 9 Apr, 22:24, PD <thedraperfam...(a)gmail.com> wrote: > >> >> >> > >> On Apr 9, 3:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > >> >> >> > >> > > But that is not what happens. > >> >> >> > >> > > For example, if I see a car traveling west at 10 kmh, and > >> >> >> > >> > > a > >> >> >> > >> > > car > >> >> >> > >> > > traveling east at 35 kmh, then you have the expectation > >> >> >> > >> > > that, > >> >> >> > >> > > to > >> >> >> > >> > > a > >> >> >> > >> > > passenger riding in the car traveling east, the other car > >> >> >> > >> > > is > >> >> >> > >> > > traveling > >> >> >> > >> > > 45 kmh west. > >> >> >> > >> > > But in fact, it is not traveling at 45 kmh west to a > >> >> >> > >> > > passenger > >> >> >> > >> > > in > >> >> >> > >> > > that > >> >> >> > >> > > car. > >> >> >> > >> > > It is traveling at something close to that, but only > >> >> >> > >> > > approximately. > > >> >> >> > >> > > The bottom line is, the basic sum rule you've been taught > >> >> >> > >> > > for > >> >> >> > >> > > relative > >> >> >> > >> > > velocities is a LIE. > > >> >> >> > >> > i would expect the combined speed to be a real 45kmh, yes, > >> >> >> > >> > although > >> >> >> > >> > it's quite possible that none of them will any longer agree > >> >> >> > >> > on > >> >> >> > >> > the > >> >> >> > >> > definition of "hour" or "kilometer". > > >> >> >> > >> Oh, no, they agree on the definition of hour and kilometer, > >> >> >> > >> alright. > >> >> >> > >> Something that is measured locally to be a km will still be > >> >> >> > >> measured > >> >> >> > >> locally to be a km. And a standard process that locally takes > >> >> >> > >> an > >> >> >> > >> hr > >> >> >> > >> will still locally take an hour. > > >> >> >> > > Indeed, the question is whether their respective measures of > >> >> >> > > "an > >> >> >> > > hour" > >> >> >> > > are truly identical. > > >> >> >> > What do you mean by 'truly identical' > > >> >> >> In other words, whether they are measuring the same periods of > >> >> >> time - > >> >> >> whether the interval of each tick of each clock would be the same > >> >> >> as > >> >> >> each other. > > >> >> > The coordinate time of SR is derived > >> >> > from light signal exchange. E-sync. > > >> >> That describes how synchrnoized clocks should behave (ie that they > >> >> give > >> >> the > >> >> same reading for what must be identical times, and show identical time > >> >> durations as identical). > > >> > ============== > > >> >> > Real clock mechanisms don't "measure" time > >> >> > they mark it. > > >> >> A not terribly relevant semantic difference > > >> > <<Elements of a Clock > > >> > Before we continue describing the evolution of > >> > ways to mark the passage of time, perhaps we > >> > should broadly define what constitutes a clock. > >> > All clocks must have two basic components: > > >> > * a regular, constant or repetitive process > >> > or action to mark off equal increments of time. ...>> > http://physics.nist.gov/GenInt/Time/early.html > > >> Yes .. we know that. we know how clocks work. They mark the time, and > >> you > >> can use that to measure elapsed time. Its all just pedantic and semantic > >> nonsense whether we say clocks measure time or mark it. The difference > >> doesn't change our meaning and intent. > > > If we can put your intentions aside for just a > > bit we won't have to explain the difference > > in a Seiko and a Rolex. > > > A clock marks time with a process. > > Yes it does .. I didn't argue with that. > > And the differences between those marks let you measure elapsed time Also note that the bullet fired from the top of Harvard Tower follows a flatter trajectory and arrives at the end of the metre stick sooner than a bullet fired at the bottom of Harvard Tower. Consistent with a well known experiment: http://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment So if someone says a clock runs slower or the time is different at the bottom of Harvard Tower we have an experiment and an example of what it means. It is likely inconsistent with a lot of philosophical notions that might have seemed plausible prior to Hilbert and Noether's work with GR. Historical and long but shorter than the described maths: http://arxiv.org/abs/physics/9807044 Sue...
From: Ste on 10 Apr 2010 00:35
On 10 Apr, 02:26, "Inertial" <relativ...(a)rest.com> wrote: > > > Incidentally, if you have two clocks a certain distance apart, > > synchronised (obviously, accounting for propagation delays), > > Yes .. that is always assumed. > > > and > > stationary relative to each other, > > Yes > > > what happens when you accelerate > > them towards each other. Does the distant clock appear to slow down, > > or speed up? > > Acceleration complicates things uncesssarily .. so lets assume no > acceleration for simplicity. Well, I asked the question precisely because I wanted an answer to *that* scenario. If the clocks are already moving (and don't stop before passing each other), then that really tells me nothing about what I wanted to know. The purpose of having the clocks stopped at the beginning and end is that it allows a 'simple' correction for any propagation delay when testing for synchronisation. > An equivalent set up is this, with no acceleration invovled, where A, B, A' > and B' are all clocks. > > A'->v B'<-v > A o B > > Let A and B be our mutually-at-rest, synchronized clocks (as you mentioned) > > Let A' and B' be moving at the same speed (but opposite directions) relative > to A and B. > > As A' passes A and B' passes B (at the same time according to A and B), we > copy the reading from A clock to A' clock, and copy the reading from B clock > to B' clock. A' and B' keep moving and arrive together at o, where there > times are compared. As I say, I'd also like to discuss the specific scenario that I raised. Because at least in my scenario, we can agree that they are both synchronised at the start, and at the end, and that we have accounted for propagation delays when testing for synchronisation. So the question is how to interpret what happens in the middle, but obviously I need you to describe what happens. > After the pass A and B and have their clock readings adjusted, the an A' > observer would measure B' as ticking slowly (as I described above), and a B' > observer would measure A' as ticking slowly. They will both also see the > other as showing the 'wrong' time (in particular, from what I think (not > done the calculations), each frame will measure the other clock as being > ahead of their own). Each frame will measure the other clock as being *ahead*? By any chance, does the other clock always appear slow when they are sailing into the distance away from each other, and always appear fast when approaching each other? > > And do their times match when they meet up and are > > brought back to stationary again? > > Yes. Ok. |