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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."
You need to trust something as the "absolute truth" before you can start saying that something is off-the-standard, because its off THAT standard that you chose already.
Aside from there being no privileged reference frame to say has the "absolute true time", this has nothing to do really with saying that it's exactly 4:20pm exactly when it should be 4:20pm.
The measure they're talking about is how much variance there is in the frequency of the pulses over time, and you can measure that without any 'standard' to compare to -- you're actually comparing the signal to itself.
As long as GPS, Cell phone networks, and TV channels are within a split second of each other, I'm fine.
They could all claim exactly the same time as each other, but if the method they use to track time is "x many events in a second", then if the event in question does not have a stable period then you'll eventually have to add/subtract a second from the GPS, cell phone, etc time.
But yeah, for the majority of practical purposes you don't need timing precision equal to that of a pulsar, much less better.
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Not really. What we're looking at here is the suitability of something for BEING the measuring stick. You can say that 300 pulsar pulses is a second, or you can say that the time it takes for 2000 cesium atoms to decay is a second if you like (both numbers pulled completely out of thin air, as for the purposes of this discussion actual measurements are irrelevant), and that technically can define a second, but the suitability of that measuring stick is in how consistent those events are. If the cesium atoms are decaying at a far more consistently measurable rate than the pulsar is pulsing, then that is a better measuring stick.
It'd be like saying that a mile is officially defined as how far a certain runner can run in 10 minutes. The fact that it's the official definition doesn't change that it's a poor measurement method, because of the inherent variability involved.
"People who think they know everything are very annoying to those of us who do."-Mark Twain
Man > Nature... Take that religion!
LOL... I think religion would answer, "when you've created something from nothing, rather than simply measure something accurately, give us a call."
To which man replies: "We created you, Religion, out of absolutely nothing!"
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It is more accurate to say that mass affects space by bending it. Light though it is traveling in a straight line follows the curves in space. A good starter example would be taking a thin rubber surface, like a baloon and drawing graphing paper like lines on it. If you stretch it out and place a heavy metal ball in the middle it will sag and the once straight lines will now appear to curve around the ball.
Though incomplete this example explains gravity pretty well.