5 ms·

At this level of accuracy, I wonder if there are effects even the researchers aren't aware of that could cause drift. Or maybe it's best to say they're that acc

by jquery 5y ago

At this level of accuracy, I wonder if there are effects even the researchers aren't aware of that could cause drift. Or maybe it's best to say they're that accurate under certain assumptions. I would expect a cosmic ray or a lightning strike or an earthquake to violate the umpteenth nines of accuracy they're claiming.

btilly 5y ago
Previous optical clocks were able to measure gravitational time dilation from under a meter of altitude. I'll bet that this one measures it to the order of a centimeter. And it isn't just height that is going to have an impact. Any major mass shift affects it. For example in Scandinavia, melting ice in Greenland and rising land will combine to make ultra-precise clocks there run measurably faster over time relative to where they started.
wbl 5y ago
So this accuracy claim is not saying that they engineered a clock that will only lose 1 second in several trillion years. For one thing that clock would have to survive the sun going nova. Rather it's a statement about the width of the frequency they are measuring and their ability to divide that down to a second. They are saying that they have two clocks measuring the same frequency and have analyzed their dispersion against each other over a period of time and gotten this result. Long-term aging effects aren't going to change the frequency of the atoms (except new physics, but we can rule that out via observations of the Lamb shift in distant hydrogen), but things like gas infiltration, lamp aging, changes in laser characteristics can all cause atomic clocks to drift. This is pretty significant for rubidium which is why the lamps need recalibration periodically.
- vosper 5y ago
  > For one thing that clock would have to survive the sun going nova. Off-topic, but our sun won’t go nova. https://www.space.com/14732-sun-burns-star-death.html https://www.space.com/14732-sun-burns-star-death.html
  - resist_futility 5y ago
    "NOVA: A white dwarf star pulls matter off of a companion red giant star until a powerful nuclear fusion explosion occurs on the dwarf’s surface" A supernova, no. But a nova to me, a layperson sounds possible but highly unlikely. sun-> white dwarf->random red giant intersecting our solar system https://www.space.com/31608-supernovas-star-explosions-infographic.html https://www.space.com/31608-supernovas-star-explosions-infog...

by jquery 5y ago

btilly 5y ago

Previous optical clocks were able to measure gravitational time dilation from under a meter of altitude. I'll bet that this one measures it to the order of a centimeter. And it isn't just height that is going to have an impact. Any major mass shift affects it. For example in Scandinavia, melting ice in Greenland and rising land will combine to make ultra-precise clocks there run measurably faster over time relative to where they started.

wbl 5y ago

So this accuracy claim is not saying that they engineered a clock that will only lose 1 second in several trillion years. For one thing that clock would have to survive the sun going nova. Rather it's a statement about the width of the frequency they are measuring and their ability to divide that down to a second. They are saying that they have two clocks measuring the same frequency and have analyzed their dispersion against each other over a period of time and gotten this result. Long-term aging effects aren't going to change the frequency of the atoms (except new physics, but we can rule that out via observations of the Lamb shift in distant hydrogen), but things like gas infiltration, lamp aging, changes in laser characteristics can all cause atomic clocks to drift. This is pretty significant for rubidium which is why the lamps need recalibration periodically.

vosper 5y ago
> For one thing that clock would have to survive the sun going nova. Off-topic, but our sun won’t go nova. https://www.space.com/14732-sun-burns-star-death.html https://www.space.com/14732-sun-burns-star-death.html
- resist_futility 5y ago
  "NOVA: A white dwarf star pulls matter off of a companion red giant star until a powerful nuclear fusion explosion occurs on the dwarf’s surface" A supernova, no. But a nova to me, a layperson sounds possible but highly unlikely. sun-> white dwarf->random red giant intersecting our solar system https://www.space.com/31608-supernovas-star-explosions-infographic.html https://www.space.com/31608-supernovas-star-explosions-infog...