So it's the year 3000. An asteroid or some other cosmic disaster has destroyed planet earth and now you're riding one of many deep space vessels on a trip to other star systems to to escape the destruction. But oh noes! The ship's power fails for a little while and all the clocks on the ship are reset.

So, how should the crew keep track of time now that they have nothing like the orbit of their planet to measure it by?

Seeing as humanity has moved beyond our original solar system, I'd say they should use something that's relevant across the entire universe to measure time. http://en.wikipedia.org/wiki/Hubble%27s_law

Atomic clicks of argon fountains spaying cesium

I'll admit that I had a hard time reading the Wikipedia article provided, but I was under the impression that the universe's expansion was actually accelerating. I'm not sure how fast it is accelerating, but it would seem difficult to use this non-constant as the basis for keeping time.

Keep a watch?

Like in Star Trek, they'd use the engine as a guide line. It would have a regular vent/power cycle and it would last a while, the power cycle would determine how much time had passed as it should remain fixed.

What about using gravity (artificial or otherwise) to devise a way to make up a unit of time? Like using the time it takes an object to fall 100 meters in a vacuum?

EDIT: Or use the length of the ship and the constant speed of light. How long does it take a photon to travel the length of the ship? That could be a small unit of time.

I believe you mean atomic clocks?

Anyway, the trouble with that is that without a point of reference, atomic clocks don't actually measure anything besides the number of ticks that have occurred after the point when the clock was set in motion. Oh, and we just had another power failure.

Just because it's not a constant doesn't mean it's not measurable.

Aren't you eventually doomed to find yourself entering some distortion of spacetime during your deep space travels? Unless of course you're just thinking about keeping track of time relative to you and the Earth refugees. I imagine it would be difficult to keep track of time if it keeps bending.

Then the decay rate of aluminum space hulls

Subject to what form of radiation under what circumstances?

Time? Who needs, time?!

Seeing how in 1000 years http://www.youtube.com/watch?v=kffacxfA7G4 will be the worldwide anthem, we could create new units of time measurement based on its tempo.

the yelling of the crew protesting nuclear power from a battery... silenced when no air or cut out tongues

Wait. So lemme understand this. My planet was destroyed so I boarded a ship to go to some unknown location in a system on a new planet I've never been to. But, to make the matter of no longer having a home where I grew up worse the intergalactic ship I've just boarded has lost power and is now just floating around willy nilly in space. With emergency power keeping the life support system online for a short time. Eventually the emergency power system will run out of power and then we'll be floating around a tin can awaiting for our long nap in the void of space.

And you're worried about how anyone should be keeping time? Seriously, they'd better get their asses below deck and into the engine bay to figure out why the [censored] power out in the first place and never mind how anyone is supposed to keep time. FIX THE SHIP!!! I don't want to have left my dying planet only to die floating around in space. I would've much rather burned on Earth.

Use a Newton's Cradle?

If the Earth is gone, use the planet we are traveling to as the new way to measure days/years. That's simple enough, and the best solution.

I think we'd mostly be concerned with keeping track of time relative to the other earthlings, as I'm pretty sure we'd never have a reason to measure the lifespan of a bug living on the rim of a black hole.

Half of the earthlings decided to trip over to http://en.wikipedia.org/wiki/Sirius and they want Christmas cards too.

The protests will last till the end of the universe! We're saved!

The ship was fixed, but that won't get the time back.

If only they replaced the 9v battery in the alarm clock...

alas they the replacements were left on Earth

DOH!

Seriously I don't see the universal expansion as a reliable timekeeping source,

if a section of the ship is designed to use Centrifugal artificial gravity to simulate 1G would that work for clocks as well?

My favorite idea so far. What are the variables for this anyway? Is the RPM needed to achieve 1G the same for any wheel of the same diameter? But this depends on having a control item for mass, I believe. Each ship would need a calibrated weight of some kind, so they can adjust the RPM until the 1 kg of mass equals 1 kg of weight.

I think the best bet would be the use of a fixed distance and the speed of light somehow.

How constant is Hawking radiation coming out of black holes?

It's not stable enough for practical purposes. If the amount of "gravity" and general interference there changes too often, it really wouldn't make a good clock, especially since there's no reference for the clock to count by beyond its own tick count.

they are called stars, you track their movement and judge time... like in startrek, also you use them for navigation like we did while roaming the seas....

see you up there..... some day... soon

I believe stars also rotate. So there's that.

http://en.wikipedia.org/wiki/Pulsar

Just because universal expansion is accelerating doesn't mean it wouldn't make a good time keeper. We use constants to calculate it, and it already allows us to pinpoint the observable age of the universe via extrapolation.

I admire the precision of the universe, and the mind that created it.