Einstein's Relativity Affects Aging on Earth (Slightly)

nationalgeographic ^ | September 23, 2010 | Ker Than

[JoeProBono]

Like a vignette from The Twilight Zone, new research shows that you'll age slightly faster standing on a staircase than you do on the floor below.

The finding is linked to the strange, time-bending effects of Albert Einstein's theories of relativity, which for the first time have been shown to affect earthbound distances and time frames.

(Related: "Einstein's Gravity Confirmed on a Cosmic Scale.")

Specifically, Einstein's special theory of relativity predicts that time does not flow at a steady rate, and it can be affected by acceleration. As a result, a clock speeding away from an observer will appear to tick slower than a stationary clock.

This theory is the basis of a famous thought experiment known as the twin paradox, in which a twin sibling who travels on a fast-moving rocket ship would return home younger than the other twin.

The equations of relativity also predict that gravity similarly slows down, or dilates, time.

"So if you are experiencing stronger gravitational pull, then your time is going to go slower," said study co-author James Chin-Wen Chou of the National Institute of Standards and Technology (NIST). Atomic Clocks Show Gravity Slowing Time

The time-slowing effects of acceleration and gravity have been demonstrated in experiments that compare real clocks on Earth's surface with timepieces in high-flying spacecraft and satellites, such as ones used for global positioning systems.

(Related: "Every Black Hole Contains Another Universe?")

But the new study, appearing in this week's issue of the journal Science, shows that these effects are also measurable here on Earth's surface.

The pull of gravity on an object increases closer to the center of mass, so an object on Earth's surface actually experiences a slightly stronger pull than one floating in the atmosphere.

Using two ultraprecise atomic clocks, Chou and colleagues showed that lifting one clock by only about a foot (33 centimeters) above the other creates enough of a gravitational difference that the higher clock ticks slightly faster.

In a second experiment, the team measured the effects of relativity on the time-keeping aluminum atoms inside the clocks.

Atomic clocks work based on the number of vibrations an electrically charged atom experiences as it moves between two energy levels. For the clocks used in the experiments, one second is equal to more than a million billion vibrations.

In one of the clocks, the team nudged the normally stationary aluminum atom so that it gyrated back and forth as it vibrated. As Einstein predicted, the clock with the moving atom ticked at a slightly slower rate than the second clock.

Before anyone rushes to lower elevations, though, the NIST scientists note that these effects are much too small for humans to perceive directly—adding up to approximately 90 billionths of a second over a 79-year lifetime.

"It's not a road to youth," said Daniel Kleppner, a physicist at the Massachusetts Institute of Technology who was not involved in the study.

[SunkenCiv]

Thanks JoeProBono.

---

· String Theory Ping List ·

---

---

· Join · Bookmark · Topics · Google ·
· View or Post in 'blog · post a topic · subscribe ·

---

[JoeProBono]

[drtom]

Thought experiments are not a rational basis for physics.

That is not correct. Most theories-turned-laws in physics originated in an observation that could not be explained at the time. Hypotheses about the physical explanation emerge which then evolve into theories which are meant do be refuted, often in the span of decades. If a theory cannot be disproven it evolves into a lemma or construct. Special relativity has been proven hundreds of times over. General relativity is generally accepted (at least the concept that gravity influences time has been accepted). QED is another example of a framework that started as a hypothesis which is now generally accepted.

[Texas Songwriter]

Is that a photograph of Tommy Lee Jones and Stalin?

[JoeProBono]

[dr_lew]

...General relativity is generally accepted (at least the concept that gravity influences time has been accepted).

Einstein, in his book, RELATIVITY, written for the layman, shows the necessity of this using a THOUGHT EXPERIMENT based on the Principle of Equivalence. It's very interesting, especially because you actually get a quantitative result from it.

I note Galileo also proposed a THOUGHT EXPERIMENT to show that objects must fall ( or accelerate ) at the same rate in a gravitiational field. He supposed an iron ball, say, to be cut in half and the two halves to be regarded as separate objects falling side by side. Then repeat the experiment with them touching. "In what way is this pair different than the original ball?" he asks.

MYTHBUSTERS did an experiment, which was purely kinematical. That is, the necessary result could be seen by conducting the experiment in thought. The "myth" being tested was that a ball shot backward from a moving vehicle with a muzzle velocity equal and opposite to the vehicle would fall straight to the ground.

Of course, there could be questions of air turbulence and such in the execution, but they did get a confirming result, and Adam was rather excited about, too.

[wendy1946]

There are at least two or three elephant-in-livingroom type problems with what Einstein said about gravity. One, Einstein claimed information could not be passed around faster than C while gravity is known to propagate instantaneously to within our ability to measure. Two Einstein tried to describe gravity as a four dimensional differential geometry thing and there is no way to start with that and believe that it could ever have changed much on our own planet recently; nonetheless it is an easy demonstration that it has. The heavier kinds of dinosaurs could not function in our present world due to the familiar square/cube problem, and there is also a problem with carved stones in several parts of the world, Puma-Punku for instance, which could not be moved with any technology ancient or modern, in present gravity.

Einsteins thought experiments involving light assume that the Michelson/Morley experiment actually did fail and the failure was not simply a case of not having good enough equipment; nonetheless the experiments were run continuously in the 1920s and 30s at higher elevations and with significantly better equipment, and they did not fail. Try google searches on "Dayton Miller" for that one.

[LomanBill]

>>Relativity was based entirely on thought experiments

But relativistic time differentials have been observed - and are thus compensated for in various technologies.

In the GPS System for example.

http://www.google.com/#sclient=psy&hl=en&q=gps+relativity+correction

That does not confirm science fictions like time travel or multiverses, however.

Begin with the assumption that time is a derivative function of state change - the rate of which is relevant to the inertial frame(s) in which it is being observed... and Special Relativity returns to reality.

[allmendream]

“Always being the one to have to disillusion the feeble-minded is a dirty and thankless job, but somebody’s gotta do it.”

Hate to break it to you, and disillusion the feeble-minded; but calling theoretical physicists the feeble-minded, in preference to creationists sources(the less you know, the more likely you are to be a creationist) really takes the cake!

Relativity was based upon “thought experiments”, because there were no machines yet built that could test the effect. The machines were built and the theory of relativity came out ACES!

Creationism is based upon “stupidity experiments” and that is not a rational basis for understanding the physical world.

[LomanBill]

[If time is a measurable property of the universe, and that universe is a creation of God, then time itself is part of the creation. In other words, before the universe, there was no time. ]

;-}

Time is a derivative function of state change whose rate is relative to the inertial frame(s) in which it is being observed.

That’s what’s self-evident to me.