Man-Made Atomic Clocks the Best In the Universe

An anonymous reader writes "The widespread belief by astrophysicists that pulsars and white dwarfs are the best clocks in the universe is wrong, say two Australian physicists. John Hartnett and Andre Luiten from the University of Western Australia have recently shown that man-made terrestrial atomic clocks take the crown, contrary to numerous claims in astrophysical literature that the natural timing provided by pulsars and white dwarfs is the most precise. The preprint of their paper, available on the arXiv, shows that terrestrial clocks exceed the accuracy and stability of the astrophysical 'clocks' by all sensible measures, in some cases by several orders of magnitude."

Comments

I hate to be condecending...

[epiphani]

But .. duh? I mean, there is a lot of stuff between these pulsars and us. Any change in the local matter density, nearby gravitational disturbances, and there is no reliable time out of a pulsar. We can't honestly think that there is no undetectable gravitational effects between us and every pulsar in the universe, do we?

Then again, I'm nowhere near being an astrophysicist.

Re:I hate to be condecending...

[qoncept]

I'm nowhere near being an astrophysicist.

I'm not either, so ... honest question. How does gravity affect light? How much matter is in space? Or, more specifically, in the space between Earth and pulsars visible on Earth?

Re:Too much noise in pulsars

[Locke2005]

I would assume because the dust cloud around the pulsar that remains from the supernova that created it is slowly spiraling back into it... changes in mass effect angular momentum.

How do they know?

[BitterOak]

How do you determine which is the best clock in the universe? Don't you need a better one to run a comparison against?

Re:How do they know?

[maxwell demon]

You compare two clocks built the same way. Since they are basically identical, it's a fair assumption that they also have the same precision.

If you have a clock with known precision (measured the way described above), you can measure a different clock with it. If the measured precision is worse than the known precision of the known clock, you know the other clock is worse. If the measured precision is equal to the precision of the known clock, the other clock is at least as precise. In order to learn more about its precision, you have to compare it either to a clock known to be more precise, or to (a copy of) itself.

General Relativity Simplified

[Roger W Moore]

How does gravity affect light?

Strictly speaking it does not - it bends space-time and light travels on a straight line which looks bent. Think of it this way - you took off and flew in a straight line from Edmonton, Alberta to London, UK someone in orbit would see that you had actually flown a curved path on the surface of the Earth. Light is the same - it thinks it is following a straight line but when looked at from a different frame it appears as a curve.

This is news?

[Angst Badger]

The irregularity of pulsars has been known for decades now. Most of them are better than your watch, but I've got a textbook on pulsars that's twenty years old and mentions the drifts in their frequency in the first few pages.

It's one in 10^15

[Chris Burke]

Most of them are better than your watch, but I've got a textbook on pulsars that's twenty years old and mentions the drifts in their frequency in the first few pages.

Uh yes it's been known that pulsars do in fact have period drift for many years. However for quite some time after their discovery, their drift was vastly smaller than any man-made clock. This is what lead to the common belief that pulsars are the best (known) clocks in the universe, because for at least several decades they were. Man-made clocks have made tremendous improvements however, and now are better than pulsars. Those super-awesome clocks still experience frequency instability, though. It's just on the order of 1 in 10^17 instead of 10^15 like the best pulsars.

Which based on the statement that our clocks have improved "more than an order of magnitude, on average, in each decade", while we have not found pulsars significantly better than those previously known, means that it's possible that when your textbook was written man-made clocks were only just surpassing pulsars or possibly even still behind.

So yeah this probably is not NEW news, but it's probably going to be news to a lot of people who had the (previously correct) idea that pulsars were better than the best man-made clocks. And no you shouldn't have assumed man-made clocks were better based simply on the existence of frequency instability in pulsars.