[MarianaM (OP)]

David is wondering...

If humans ever managed to travel into space at speeds close to the speed of light, what would replace clocks (since our conventional clocks would have no meaning in time)?

What do you think?

[Halc]

If humans ever managed to travel into space at speeds close to the speed of light, what would replace clocks (since our conventional clocks would have no meaning in time)?

Clocks work fine at those speeds, and you'd need them to tell when it's lunchtime.  The clocks would run at normal rate since they are stationary relative to those that are using them.

[alancalverd]

We are already travelling close to the speed of light. The clocks seem to work ok.

[Hayseed]

If one wants a stable clock, stay away from oscillation.  Oscillation can be influenced by all kinds of materials, external processes, and motion. It is so sensitive......that we use oscillation for sensitive detectors and sensors.  Especially motion.

There is no such thing as a stable oscillation.

The only stable dynamic is rotation.

Future clocks will be rotational.  Extremely accurate and stable.  Might vary slightly with acceleration, but always reset to same rotation rate at any velocity.

All one needs is the hardware.  Rotation-ally FFT an electron.
 

[evan_au]

since our conventional clocks would have no meaning in time

As Halc said, our conventional clocks would continue to have a meaning for us.
- Our clock would not have the same meaning to someone far away, travelling at a great speed relative to us.
- But we could do some calculations based on our clock, Einstein's equations, and the speed/distance/gravitational potential of a distant person to determine what their clock means to us (or vice-versa).
- But you can trust your local clock

We already do this to some extent, even on Earth.
- If I look at a clock in the USA, it tells me that it is the evening.
- But I look out the window, I see it is morning. And this agrees with my local clock.
- I can look at a map and do a calculation to determine what a clock in the USA means to me (or vice-versa).
- But you can trust your local clock

And we do this with GPS (which has satellites which are off the Earth):
- The designers did some calculations based on Einstein's equations, and the speed/distance/gravitational potential of the Earth's surface and the planned orbital altitude of the satellites.
- Then they pre-adjusted the clock on the satellite so it would have meaning to us, after it reached the planned orbital altitude.

If one wants a stable clock, stay away from oscillation.

An oscillation is a periodic function.
A conventional clock generates a periodic function (which we use to measure time).
This statement is (almost) a contradiction in terms.

A clock which does not use oscillation is not a repeatable clock.
- But it might be a 1-shot clock, like using radioactive decay to measure the age of rocks or wood samples.

[Hayseed]

A rotation is a one direction period.

[geordief]

We are already travelling close to the speed of light. The clocks seem to work ok.

Just as valid to say we are already moving at speeds exceeding the speed of light , account taken of expansion?

And at exactly the speed of light if measured against light itself....

[yor_on]

Hmm, isn't a rotation a acceleration?

[Hayseed]

rotation an acceleration?..........yes but only an acceleration of direction, not velocity, the velocity remains constant.....so the period remains constant.  A constant clock period.

[evan_au]

rotation an acceleration?..........yes but only an acceleration of direction, not velocity, the velocity remains constant

A bit of terminology confusion here. As I understand it:
- When we talk about speed and velocity, we normally mean Linear Speed and Linear Velocity.
- Linear Speed (eg 12 meters per second) is independent of direction.
- Linear Velocity (eg 12 meters per second, North) includes both speed and direction. So if you change the direction, you change the velocity.
- There is also a concept of Angular Velocity (eg 1 Revolution per second, clockwise). This is not the usual meaning of velocity, so it is distinguished by specifying Angular Velocity. If something is rotating at a steady 1 revolution per second, the angular velocity is constant. If the object has a fixed radius from the axis, then the Linear Speed will also be constant, even though the Linear Velocity is continually changing.

[yor_on]

:)