NPR: New Clock May End Time As We Know It

[bystander]

New Clock May End Time As We Know It
National Public Radio | 2014 Nov 03

Scientist working to create the perfect atomic clock have a fundamental problem:
right now, on the ceiling, time is passing just a little bit faster than it is on the floor.

Strontium atoms floating in the center of this photo are the heart of the world's most precise clock. The clock is so exact that it can detect tiny shifts in the flow of time itself. [b][i]Courtesy of the Ye group and Brad Baxley/JILA [/i][/b]

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[orin stepanek]

No more tick; no more tock; coming from grandfather's clock!

[MargaritaMc]

New Clock May End Time As We Know It
National Public Radio | 2014 Nov 03

Scientist working to create the perfect atomic clock have a fundamental problem:
right now, on the ceiling, time is passing just a little bit faster than it is on the floor.

I'm usually pretty boggle-proof, but that has boggled me...

M

[Nitpicker]

New Clock May End Time As We Know It
National Public Radio | 2014 Nov 03

Scientist working to create the perfect atomic clock have a fundamental problem:
right now, on the ceiling, time is passing just a little bit faster than it is on the floor.

I'm usually pretty boggle-proof, but that has boggled me...

M

The ceiling is slightly further from the centre of the Earth, than the floor. So, as the Earth spins on its axis, the ceiling moves slightly faster than the floor (except at the poles). According to Einstein, this would cause a slight time dilation between ceiling and floor. Solution: only make one clock.

[geckzilla]

Haha, Nit. The solution the article suggests is to use the clock not as a clock but as a measuring device. Apparently the clock is too accurate for practical use.

[rstevenson]

This clock has taught me the secret to a long life -- just lie on the floor, so I age more slowly.

Rob

[Beyond]

Decrease your aging by twice the amount. Lay on the basement floor.

[Chris Peterson]

The ceiling is slightly further from the centre of the Earth, than the floor. So, as the Earth spins on its axis, the ceiling moves slightly faster than the floor (except at the poles). According to Einstein, this would cause a slight time dilation between ceiling and floor. Solution: only make one clock.

I think this effect is small compared with the fact that the clock on the floor is deeper in Earth's gravity well than the one on the wall.

[Nitpicker]

The ceiling is slightly further from the centre of the Earth, than the floor. So, as the Earth spins on its axis, the ceiling moves slightly faster than the floor (except at the poles). According to Einstein, this would cause a slight time dilation between ceiling and floor. Solution: only make one clock.

I think this effect is small compared with the fact that the clock on the floor is deeper in Earth's gravity well than the one on the wall.

Gah! I never did get general relativity that well. (And only a tenuous grasp on special relativity.) Imagining gravity equal for a moment and with a clock on the floor and on the ceiling, a floor-dweller would think the ceiling clock was moving slower and a ceiling dweller would think the floor clock was moving slower. (I think.)

[alter-ego]

The ceiling is slightly further from the centre of the Earth, than the floor. So, as the Earth spins on its axis, the ceiling moves slightly faster than the floor (except at the poles). According to Einstein, this would cause a slight time dilation between ceiling and floor. Solution: only make one clock.

I think this effect is small compared with the fact that the clock on the floor is deeper in Earth's gravity well than the one on the wall.

Yes. In fact the special-relativistic analogy using velocities doesn't apply here because the clocks are not moving with respect to each other. Interestingly, when considering relative motion, clocks in orbit run slower that clocks on the ground whereas when considering a gravity well, clocks in obit run faster in orbit. A clock located at an orbit of ~1.5 R_Earth will not loose nor gain time (time dilation = 0) wrt a clock on the ground.

http://en.wikipedia.org/wiki/Time_dilat ... n_together

Clocks on the floor and wall do share a non-inertial (accelerated) reference frame but the correct analysis is not as simple as time dilation due to differential velocities.
Viewed another way, if we put a clock at Earth's center and compare that clock to the floor and ceiling clocks on the surface, time dilation due to motion is the same for the floor and ceiling clock, so their times don't drift due to motion. In this view, the only dilation component between the surface clocks is due to their radial positions in the gravity well, i.e. the height difference between the floor and ceiling.

[Nitpicker]

I'm definitely only having one clock now!

[alter-ego]

Regarding the topic of clocks and their sensitivity height changes, the eye-opening experiment for me was the measurement if the gravitational time dilation (gravitational redshift) to a precision of <10^-8 over a free fall distance of 100 microns This was done my measuring the interference between two vibrating ceasium atoms, i.e. matter-wave interference (quantum physics baby!) at a "native" (de Broglie) frequency ~10²⁵Hz. The time dilation between the two atoms amounted to ~10^-20 seconds! Lasers were used to set up the atoms this experiment and measure the interference between the atoms.
http://physicsworld.com/cws/article/new ... -confirmed

[Ann]

Good to see you here, alter-ego! Long time no see.

You made a mindboggling point, too!

Ann

[alter-ego]

Good to see you here, alter-ego! Long time no see.

You made a mindboggling point, too!

Ann

Thank you, Ann; that was kind of you
Yup, I come and go though I try to keep track of forum pulse.

[BMAONE23]

Decrease your aging by twice the amount. Lay on the basement floor.

So by the end of the day our feet are younger than pur heads...must be the reason for lying down to sleep with elevated feet so that the aging process can balance out overnight

[alter-ego]

Viewed another way, if we put a clock at Earth's center and compare that clock to the floor and ceiling clocks on the surface, time dilation due to motion is the same for the floor and ceiling clock, so their times don't drift due to motion. In this view, the only dilation component between the surface clocks is due to their radial positions in the gravity well, i.e. the height difference between the floor and ceiling.

"Viewed another way" ...mmmm, I failed to follow through here. Wrt Earth's center, the two clocks do have different velocities, even though wrt each other they don't. The delta velocity, Δv, = ω_e x Δh (angular velocity x height above surface). I think we can use special relativity for this case to get a reasonable estimate for the general relativity component of time dilation.

- In the weak, constant gravitational field regime (Earth's surface) the magnitude of (differential) time dilation≈ 1 sec x g/c² x Δh, c = speed of light, g = 10m/s²
- Due to velocity, the magnitude of time dilation = (γ-1) x 1 sec. (This is for each clock, not the delta between them)

Differentiating the Gamma equation wrt velocity and expressing it in terms of Δh (2nd clock elevation), now gets both gravitational and SR time dilation in terms of Δh and differential form. Long story short, in a constant, weak g-field the ratio of SR time dilation to gravitational time dilation is constant. At least so this approximation goes.

This ratio simplifies to ≈ R_e·ω_e²/g ≈ 1/3%      where R_e = Earth's radius.

Sensibly, this is the ratio of Earth's angular centripetal acceleration to its gravitational acceleration. In this parameter regime, I can believe that.

So, ignoring the sign difference, the time dilation due to gravity is about 300 times larger.

[Speculator]

I believe the mass and spin of each galaxy may create time unique to that galaxy but that there is a universal "now" which could be used to transmit information and physical objects from one side of the universe to the other instantaneously.
Mega Non Locality.