4 ms·
That's not really a big deal. Most GPS satellites have two in them and they're not all that huge.
by astrodust 9y ago
That's not really a big deal. Most GPS satellites have two in them and they're not all that huge.
- ceejayoz 9y agoGPS uses cesium (deviation, per Wikipedia: 10^−13), rather than strontium (deviation: 10^-17). Cesium clocks were already pretty small back in the 1970s (https://en.wikipedia.org/wiki/File:President_Pi%C3%B1era_receives_ESO%27s_first_atomic_clock.jpg https://en.wikipedia.org/wiki/File:President_Pi%C3%B1era_rec...), but if you're going to measure relativity-caused differences between the top and bottom of a mountain, I suspect the extra accuracy is important.
- astrodust 9y agoI'm not sure how this experiment works as the strength of gravity is variable across the planet anyway. Accounting for this could be tricky. https://news.nationalgeographic.com/news/2011/04/110406-new-map-earth-gravity-geoid-goce-esa-nasa-science/ https://news.nationalgeographic.com/news/2011/04/110406-new-...
- lttlrck 9y agoThat’s across the entire surface of the plant. It isn’t going to vary much at all across the distance relative to the base and peak where they made their measurements would it?
- astrodust 9y agoIt'd require careful calculation between the base of the mountain and the top, plus some other location for calibration purposes.
- madengr 9y agoI thought they used rubidium, with cesium standards on the ground to broadcast corrections.
- ceejayoz 9y agoInteresting - looks like they have two rubidium, two cesium. Rubidium's an order of magnitude more variable than cesium - 10^−12 - strontium will be a big improvement either way.