Ultimate Clock

[noz92]

According to general reletivity, there can be no absolute time, thererefor, there is no way to build a clock that can be the same time for everyone.

 

Yet special theory says that light is the same speed to all observers, no matter what there speed.

 

Why not build a clock that measures the speed of light. For example, say when light reaches point A to point B, we count that as one second, or something [of course that would be a sort of artificial time, but it would deffinitly help people never be late (of course, the time difference of moving at 2km/s and 0km/s would be so small we don't even count it)].

 

Every second, or what have you, a radio signal would be sent out (but then again, that would kind of mess up your wach), and waches would pick them up, kind of like how we have the atomic clocks today.

[swansont]

According to general reletivity' date=' there can be no absolute time, thererefor, there is no way to build a clock that can be the same time for everyone.

 

Yet special theory says that light is the same speed to all observers, no matter what there speed.

 

Why not build a clock that measures the speed of light. For example, say when light reaches point [i']A[/i] to point B, we count that as one second, or something [of course that would be a sort of artificial time, but it would deffinitly help people never be late (of course, the time difference of moving at 2km/s and 0km/s would be so small we don't even count it)].

 

Every second, or what have you, a radio signal would be sent out (but then again, that would kind of mess up your wach), and waches would pick them up, kind of like how we have the atomic clocks today.

 

While c is constant, the distance it travels is frame-dependent (length contraction) and that makes the time also frame-dependent.

 

What you end up doing is just picking a reference frame artificially, and let everyone do the conversion. AFAIK we choose the ECI frame (Earth-center inertial) and arbitrarily set all GR corrections to zero on the geoid.

[noz92]

I'm not ecxactly understanding what you're saying.

[Stumblebum]

I'll try this analogy. These #'s are just arbitrary. Three guys are watching a football game. One from the sidelines, one from the end zone, and one from a blimp above the field. Punter kicks ball 30 yds above field at its highest point, from his 30 to the opponents 30 or 40 yds downfield, the ball is in the air(or in motion) for 6 secs(3 secs up/3 secs down). The guy on the sidelines sees ball travel in an arc for say a total of 50 yds, the guy directly in front of the punter in the end zone sees ball go up 30 yds then down 30 yds for a distance of 60 yds, the guy directly above sees a straight line of travel for 40 yds. Each of them agree it took 6 secs. but each will say the ball travelled a different distance.

 

Let's say we had asked each of them how long it took the ball to travel 30 yds. In this case they will agree on the distance ... that being 30 yds. But the guy on the sidelines will say it took 3.6 secs approx, the guy in the endzone will say 30 yds in 3 secs, the guy in the blimp will say exactly 4.5 secs. Although they agree on the distance they do not agree on the time.

 

Different observers will agree on the time but not the distance, or when they agree on the distance but not the time.

[RICHARDBATTY]

It wouldn't realy be that usefull I don't think. If our time is constantly varying due to the rotation of the galaxly orbit etc then our clocks wouldn't make sense. All we realy need is acurate time in our frame. If interstellar travel takes off then it might be good. The only problem I can see is that the components of the clock would be subject to dilation which might make it tricky to build it. But thats only my op.

[noz92]

oh

[RICHARDBATTY]

oh

Don't let me put you off. My brain is like a swiss cheese version of dog food. I am only an authority on the inside of my eye lids. Please Please continue it is a good point.

[swansont]

I'm not ecxactly understanding what you're saying.

 

Which part?

 

The problem with measuring c, is that if I am in a different frame of reference (i.e. moving with respect to you), we won't agree on the distance you are using. Thus our time measurements won't agree.

 

The way around that is to just pick a reference frame to use. So that's what we do.

[mEarly1102]

i have a quick questino on time dilation.....

 

doesnt one have to incorporate the speed of the earth going through the universe/orbiting the sun? if people were to be launched into space and perhaps land on anohter planet, they would be traveling at an entirely differnt speed than that of those on earth, and though it may not be c, it should cause some sort of descrepincy in the passage time of the space traveler versus the passage of time of someone on earth.

[swansont]

Yes, you have to account for all of the effects - the gravitational potential of the earth and the sun, and the various speeds with respect to some coordinate system.