Einstein's Theory of Relativity Tested at Tokyo Skytree

Originally published at: https://boingboing.net/2018/10/22/einsteins-theory-of-relativi.html

  1. The whole idea that gravity effects time is freaky.

  2. I have heard of measuring it by clocks placed in orbit.

  3. It is freaky we have clocks so accurate we can measure it in a single tall building.


optimal lattice clocks

Optical. Optical lattice clocks.


Hasn’t this already been done like a gazillion times already? What is different about this experiment?


This isn’t testing Einstein’s theory – that’s long been settled. The classic example is that GPS wouldn’t work at all without the time adjustments taken to account for the drift.

What this is testing is the ability to accurately measure heights using just time. The clocks would need to be extremely precise for that to work, hence this test.


“A lot of people don’t realize what’s really going on. They view life as a bunch of unconnected incidents and things. They don’t realize that there’s this, like, lattice of coincidence that lays on top of everything. Give you an example, show you what I mean: suppose you’re thinkin’ about a plate of shrimp. Suddenly someone’ll say, like, “plate,” or “shrimp,” or “plate of shrimp” out of the blue, no explanation. No point in lookin’ for one, either. It’s all part of a cosmic unconsciousness.”

– Miller


O snail
Climb Mount Fuji,
But slowly, slowly!

Kobayashi Issa
(as translated by R.H. Blyth)


Sounds technically possible, but maybe not the simplest method?


I am sad that I have only one like to give for your excellent “Repo Man” reference.

  1. Build two optical lattice clocks.
  2. Bring one of them to the roof of the building.
  3. Push the clock off the roof of the building and use the other clock to measure how long it takes for the first clock to hit the ground.
  4. Calculate the height as 0.5•9.8•t².

Or use a barometer.


@granroth @Boundegar
I think it’s rather about measuring time than height.
It’s pretty cool. Someone can correct me but I think it is because the higher the clock is the longer the path it has to take during the earth rotation - hence its higher speed and consequently the time dilation.

Normally to measure the time dilation you had to accelerate the clock to high speeds, and here you just put the clocks in an attic and a basement and wait few years :slight_smile:


if they want faster results they should put one clock on top of Trumps boundless ego, and one below his moral depravity.


Or a piece of string tied to a stone.

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The article said "According to Einstein’s theory of relativity, time should move faster on the observation deck than at the bottom floor. " but do we agree that the top deck clock should be slower then?

But gravity is also a bit less. How does that work out?

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the speed difference contributes but i think it’s a 2nd order effect. the main effect is that the earth’s gravity (i.e. the distortion of spacetime caused by the earth’s mass) causes clocks to run slower closer to the center of the earth.

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People do this now and then. A guy I know left three of his cesium clocks at home, then the other three to the top of Mt. Ranier for a couple days. http://leapsecond.com/great2005/


Do we know the drag coefficient of the falling clock?

According to the linked article (article is in English; only the video is in Japanese):

If the time difference caused by slightly differing gravity levels at different altitudes can be measured precisely, that could lead to the development of technology to accurately estimate the difference in height based on the time lag.

“I want to take the first step toward a paradigm change to measure the height based on the theory of relativity,” said Hidetoshi Katori, 54, an engineering professor at the university.

Optional lettuce clicks? Sounds like some suspicious botnet activity.


0.13 microseconds

Ummmm … 130 nanoseconds is not all that short a time. My so-so processor in this computer runs over 500 computational cycles in that time period. I confess to being old enough to be impressed by that speed (and I was in the business of making that happen!)

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