New Atomic Clock 1000 Times More Accurate

stevelinton writes "The UK National Physical Laboratory has a new atomic clock potentially 1000 times more accurate than current cesium clocks: to within 1 second in about 30 billion years! This could lead quite soon to a new definition of the second, and in a while to improved resolution in GPS successor systems. More interestingly, there are theories that some of the universe's fundamental dimensionless constants may have changed by a parts in a million over the last 10 billion years or so. These clocks are so accurate that they should be able to detect these changes over a year or two."

Re:Accurate distance too?

[MasterC]

The length of the meter is defined by time

http://physics.nist.gov/cuu/Units/meter.html

"The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."

So if you can measure time more accuractly then you can measure a meter more accurately.

Re:Accurate distance too?

[Mister Attack]

The trouble with measuring a meter this way is that it's tricky, to say the least, to know the frequency of a laser beam to high enough precision for this to be a useful measurement. You'd basically have to do exactly what these guys are doing -- cool some ions to within a few microkelvins of zero, use them as a frequency reference and lock a laser to them. Then you'd have to do it again with a different frequency. Then you'd have to actually measure the intensity of the standing wave to high enough resolution that you could get a reasonable measurement. So basically, don't hold your breath.

Much more reasonable is to keep the current definition of the meter, which is the distance that light travels in 1/299,792,458 second in a vacuum. Then your better clock gives you a more accurate length standard without all the fuss.

Re:Why go any further

[gtkuhn]

But this won't help them find deviations in physical constants even if they "find them". Unless we build dozens or hundreds of these clocks, we'll never know if the universe is changing or if there is a manufacturing defect in the clock.

Precisely?

[starglider29a]

I'm relativistically certain that when these articles and replies use the word "accurate", they really want to be saying "precise." Right?

I mean, 'what time is it?' to the Universe? What time WAS it 'when time began'? Was there a 'countdown to the beginning of time?' And in which Universal Time Zone are we? Are we on "Universal Light Matter Savings Time?" Was Heinlein correct? IS THERE Time Enough for Love?

Re:damn whippersnappers

[mangu]

When Galileo started timing things he used his heartbeat as a standard. No, he didn't like it. He tried to improve it, in some experients he used the rhythm of music as a time standard.

Re:Bad reporting

[brian0918]

Can I get +4 Insightful for catching all those errors as well? :D

Re:Why go any further

[arminw]

...we'll never know if the universe is changing....

If the universe IS changing, we'll never know from these clocks since they would also be subject to change. The atomic forces that control the vibrations of the atoms that govern these clocks also could change, and if they do, all the clocks they are based on would change and we would never detect any differences.

If the basic parameters of space-time change, the properties of the atoms within the space-time would also have to change. All equations governing atoms have a time units associated with them, whereas the equations of gravity do not. Therefore, in order to detect any variation in these atom based clocks, their timing would have to be compared to clocks that use the force of gravity, rather than atomic behavior. The orbital motions of heavenly bodies are based on gravity and therefore the atomic clocks would have to be compared to this motion. Unfortunately, measuring gravitational clock ticks to this kind of accuracy over the short time periods that are available to us humans is exceedingly difficult.

There is some astrophysical evidence that atomic properties have changed dramatically since the universe began. There are NO laws of physics that mandate that these fundamental time-based "constants" must be invariant.

Re:Accurate distance too?

[SnowZero]

Since at least the 1970s, the US system has been defined off of the metric system. A foot is exactly 0.3048 meters [nist.gov]. Everyone wins, as normal people keep the values they are used to (to at least an accuracy they would never care about), and scientists get the exact values that they need.

Re:Why go any further

[Council]

If the universe IS changing, we'll never know from these clocks since they would also be subject to change.

Understandable first reaction but not at all true.

For one, that's saying that we can't measure changes in fundamental constants AT ALL, which isn't true. We could find that our value for G has changed over time in the fifth decimal place.

All these researchers are syaing is that we can now look for changes three decimal places further than we used to.

(Regarding the idea of measuring the change of something fundamental -- there's no reason that the effect you're measuring has to be an effect relevant to the workings of your clocks -- I can measure the fundamental constant, say, G (strength of gravity, by timing how long things take to fall), using, say, a spring-based clock (or a light clock) that is in no way dependent on G. If G changes, I'll see the change. Just because a constant is fundamental doesn't mean it has an effect on the relevant operation of my measuring device.)