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Repeated tests have shown that the theory of relativity affects satellites orbiting Earth as well as galaxy clusters billions of light-years away ... but does it affect you when you're going up the stairs? Experiments reported in this week's issue of the journal Science say yes.
According to general relativity, someone who lives on the second floor of an apartment building should age ever so slightly faster than the neighbor downstairs — because Earth's gravitational force is ever so slightly weaker. Wristwatches should run faster as well. The experiments conducted by physicists at the National Institute of Standards and Technology in Boulder, Colo., show that it really, really works that way.
But don't move to the basement just to extend your life: Over the course of 80 years, that slight difference would add up to far less than a millionth of a second. The NIST researchers found that a height difference of about one foot (33 centimeters) resulted in a time variance of roughly a billionth of a second per year. That time difference is too small for humans or even most clocks to measure directly — however, even trillionths of a second could make a difference in future scientific applications.
After all, readings from the Global Positioning System's satellites have to be adjusted to compensate for relativity's effects. Twice. Because of general relativity, the satellites' nanosecond-accurate clocks would speed up relative to the ground by 45 microseconds per day. But because of special relativity, which applies to objects moving in different frames of reference, there would be a slowdown effect for the clocks in motion aboard the satellites, to the effect of 7 microseconds per day.
The bottom line, as explained by Ohio State University astronomer Richard Pogge on this Web page, is that there would be a net speedup of 38 microseconds a day. Because the GPS satellites determine location by making highly precise measurements of radio transmission times, they'd quickly become totally useless if they couldn't compensate for the speedup. That's why the atomic clocks and the onboard computers have been tweaked to take relativity into account.
You can learn more about relativity and its applications to the real world by clicking through our interactive graphic, "Putting Einstein to the Test," which also explains Albert Einstein's famous "twin paradox." That's the story about one brother who gets on a rocket ship and travels through space for decades at a velocity close to the speed of light. When he returns to Earth, he has aged markedly less than his doddering twin brother. The time difference is due to special relativity — that is, the fact that the jetsetting brother was in relativistic motion as seen from Earth's reference frame.
This old-school calculator from PBS' "Nova" program lets you turn the dials and see how relativity would affect the twins' ages (Shockwave plug-in required).
The NIST researchers used their aluminum-ion clocks to check on the truth of the twin paradox as well. Here's how they did it: Usually, the ions in the atomic clocks are motionless during measurements. But the researchers fiddled with the ion in one clock so that it gyrated back and forth at speeds equivalent to going several meters (yards) per second. The clock with the moving ion ticked more slowly than the clock with the stationary ion, just like the heart of the traveling twin.
It's nice to know that Einstein was right again, but the clock research could have practical as well as theoretical applications: NIST is planning to improve the precision of its aluminum-ion clocks so that they can detect how time flows differently on the scale of a centimeter (half an inch) in height difference. That could open the way for the use of atomic-clock networks as "inland tidal gauges." NIST says such networks could record the ups and downs in Earth's gravity field created by geological shifts. And that information, in turn, could provide a better understanding of how seismic events arise.
"If you have plate movement that's a redistribution of mass contributing to Earth's gravity field, we should be able to see that with a network of clocks connected by optical fibers," NIST's James Chin-Wen Chou, the principal author of the Science paper, told me today.
Beyond relativity, more precise clocks could lead to more accurate GPS systems — for example, systems that could tell a robot-driven automobile not to veer so close to the highway lane divider. "With higher accuracy, we might be able to get higher resolution in our receiver," Chou said.
More about relativity and clocks:
- Einstein's revolution enters second century
- Black hole puts a dent in space-time continuum
- Stephen Hawking says time travel may be possible
- Clarifying Einstein's rules of the road for relativity
- Satellite maps our planet's gravity field
- Ultra-precise atomic clocks will redefine time
- NIST: Aluminum-ion device is world's most precise clock
- Inside Science: Time moves faster upstairs
The authors of the Science paper, "Optical Clocks and Relativity," include Chou as well as D.B. Hume, T. Rosenband and D.J. Wineland of NIST's Time and Frequency Division. The research was supported in part by the Office of Naval Research. This report was last updated at 6:30 p.m. ET, give or take a few nanoseconds.
Check out my other postings on Cosmic Log, and connect with me via Twitter (@b0yle) or Facebook.
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Time is a concept there is no past and there is no future . There is only right now .. If every thing on the face of the earth that could comprehend the concept of time was to die would time in essence stop ??
No.
There may be no yesterday, but my socks are right where I left them last night.
Thats right its a concept . You remember .Try to go back and put them in the washing machine see how far you get . There is only right now .Things ether are or they are not You are alive or you are dead .If the earth was covered with water it wouldn't make any difference how many times the earth went around the sun if nothing could understand the concept of time ..
I am not currently in Boston, but Boston still exists.
Its only there right now tho . There is only right now time is a concept only animals that can learn or play pretend can in any way understand the CONCEPT of time ..
Only animals that can learn can understand the concept of anything. :)
If the earth were entirely covered in water and nothing understood time it would still exist. Microbes don't understand time but the more time passes the more they multiply. No microbes? The more time passes the cooler the earth's core gets.
sounds like Zeno's paradoxes to me. As I recall they were solipsistic, no?
This is true . Stress and anxiety will age you , if not kill you . Everything effects us ! Live modernly on the first floor . Save your money for a rainy day . The only flight of stairs that we need are to HEAVEN . Treadmills are not as healthy as they say they are either !
What does that have to do with this topic?
we're fine its reality that's a mess.
Check out the famous October 1971 Joe Hafele and Richard Keating Twin Clock Experiment
for understanding the special relativity mathematics of Twin Clock Paradox
at Relativity Calculator ( do a Bing search ), then look for Twin Clock Paradox under General Relativity drop - down menu . Good luck!
Better yet: Check out the famous October 1971 Joe Hafele and Richard Keating Twin Clock Experiment
at
http://www.relativitycalculator.com/twin_clock_paradox.shtml
And this, my friends, is why I live in a deep deep cave. Three millionths of a second is still time, you know!
Find me a basement apartment!! A whole billionth of a second of added life....
There is a time to everything! a time to plant a time to reap. if you are driving a car and you are moving closer to an object the time to put the brakes on would be be foryou hit it; unless the object moves out of your path time is also relevant.
I'm confused, I must admit. As you go upstairs, you are farther from the center of the earth and theirfore don't you go faster? as in the twins paradox where the one goes close to the speed of light and returns long after his brother is dead, won't you age slow on the second floor not slower?
sigh.. won't you age slower on the second floor not faster?
Mmm, I don't think so. Sure, you're in a spinning reference frame (that is, going around the earth) ... but your second-floor neighbor still has a relative velocity of zero in that reference frame (unless he's running out to the balcony to yell at you).
You are correct, however, in the sense that if someone keeps running back and forth on the second floor, that motion ("moving clocks appear to run slower") will counteract the gravity effect ("clocks in a stronger gravitational field appear to run slower").
Devin Powell's story for Inside Science News Service makes particular note of that:
http://www.insidescience.org/research/time_moves_faster_upstairs
Yes, what it all comes down to is that relativity applies to both MOVEMENT and the PULL OF GRAVITY. In the situation with the twins, the one twin is moving at such high speeds that the elastic nature of time becomes apparent due to his movements.
But if two people are moving at our normal everyday speeds and thus not altering time through movement, than the only thing really affecting the passage of time is the pull of gravity on each individual. And the closer an object is to the center of the Earth, the stronger the pull is, which means the person on the first floor would be feeling the effects more than the person on the second floor :)
The arrow of time is not likely to reverse itself. When was the last time the ball jumped out the pocket, then collided sending the cue ball right stright back till it hit your stick. Put that in your pipe and smoke it.
I realize that sometime in the future this new knowledge will have some importance on the understanding of the universe; but please, until those connections are made, let's keep such pieces of esoterica confined to the scientific community. One billionth of a second added to my life expectancy is not going to have me moving to the basement any time soon.
RBT: You hit on a point that I meant to mention in the article. Perhaps the biggest real-world effect of this kind of research is that you begin to realize that time and space truly are not absolute. The "clocks" in the atoms of our bodies are constantly moving out of sync with each other and the rest of the universe, although by amounts that don't make much difference at our human scale. The amounts do make a big difference, however, when we're talking about great speeds (such as those achieved in a particle accelerator) or great distances (such as the nearest star beyond the sun). The idea of time constantly shifting and shimmering boggles my mind if I dwell on it for too long.
There was a young lady called Bright
who could travel much faster than light.
She departed one day
in a relative way
and returned on the previous night
One twin moving fast relative to the other causes him to age slower. But from the one twin's perspective, the other twin is moving fast. What determines which twin is older when they meet?
It's literally determined by the speed at which the two twins are moving. This scenario assumes that the twin in the shuttle is moving at velocities nearing the speed of light. The twin back on Earth is not. It's like if you pushed your friend out of the car and drove away. They would appear to be moving away from you quickly in your rear view mirror, but you are the one actually moving. So you are the one feeling the stronger effects of time dilation.
Here is a pertinent fragment from "Intuitive Concepts in Quantum Mechanics" at:
http://scripturalphysics.org/qm/qmconcpt.htm#EffectsOfSpin
*****
Finally, this is probably a good place to remind readers that our concepts of space and time come from motion. Motion is what we actually observe and measure. Our concepts of space and time are derived from the type of motion we observe. Motion is the primary concept (the basic "substrate"), whereas space and time are secondary concepts (or abstractions). Think of a box. The box has an "inside" and an "outside", but these are secondary concepts. They are not needed to construct a box; but if the box already exists, the concept of an "inside" and "outside" can then be defined in terms of the box. Without the box, the concepts cannot be defined.
See also:
See also "An Overview of the Nature of Time" http://fqxi.org/data/essay-contest-files/Fraser_NatureOfTime.pdf
Gravity effects the parts of the clock, at different lvls of gravity, the clocks react differently.
I don't think that's what they are saying. Gravity is causing time itself to flow at different rates at different heights. This is observed on a clock but it is not because the clock is malfunctioning due to gravity's pull.
You are right Paul it is error ..
That is not really true, couptaker. Time is the progression of the universe from one state to the next, as well as a measure of the general flow of entropy from low to high. Even if no one was around to comprehend this, the universe would still progress like that in accordance with the second law of thermodynamics.
After all, How did the universe get to this point before we were around to comprehend that it was changing?
Yo Lobster-
I agree with you- I think it has become "fashionable" to say that there is no such thing as tiime - I hear a lot of that on these types of discussions. But it sounds more like the "maybe our solar system is just an atom in a giant's fingernail" type of doobage-inspired ponderings.
Time may be a unidirectional b*tch, but it exists.
RonC:
OT, but I gotta say---
"unidirectional b*tch" = BAND NAME!
True for some there is a tomorrow we understand that concept .. You cant go forward any faster than than what the [universe] takes you no matter how you [bend space] or speed away from the earth ..
We understand there is a tomorrow and that there was yesterday six weeks from now and a thousand years ago ... But the only thing that is real is right this second.
Again, not quite true. Here is a fine conceptual example. Imagine it being spoken with the voice of the Old Spice guy.
Put a pen down. Look away from it.
Look back at it. The pen is still there.
It is there because the past affected it so that it would be right there, rather than say, in your hand.
Toss a coin in the air. Look left. Look back. The coin is now in a new position.
The coin is in a new position because over the past few fractions of a second, a force that doesn't necessarily require someone to comprehend it has been acting on it. In this case, gravity.
The Past is very real. It's the reason the present is the state it is in, rather than another state. The present is constantly flowing, and leaving the past behind it.
Confused? Don't worry. It's because your puny human brain is ill equipped to comprehend such abstract concepts, whereas my mighty lobster brain is more than able to wrap around them.
Crustacean power.
Awesome explanation Lobster. The real question is what is the present, and when does it become the past. Does the present even exist or is it simply a barrier between the past and the future. You can't remember the present, so what is it? I am not necessarily saying it doesn't exist, but it is fun to think about.
Crap, Lobster, now my head hurts! Do I exist? Am I a figment of my own imagination? What's going on?
Gravity is a manifestation of the curvature of spacetime, NOT a foreign and physical force transmitted through space and time. This is why I guess if you want to live a long life, you run in the mountains instead of lounging on the beach.
Space and time are not related You know that's why no one really understands it ..Time is a concept .There is only right now ...
Well, making an assertion would require some evidence to support it. And repeating the assertion doesn't count. :)
I second RonC on this one.
Let's see your math.
If time travel was possible then it would be happening all the time .. The future is a part of time as is the past .If it was going to happen it would be happening as we speak . Wouldn't you go back and change [the second world war ?] All of a sudden there was no WW2 All those killed weren't and had children What if you were to travel to a time when the earth was uninhabitable by man .would you die there but be alive at another time ? If it doesn't make sense its not true ..
What you say may be true, but this article is not suggesting that time travel into the past is a possible phenomenon through the use of relative time dilation. It would theoretically be possible to experience "the future", by jumping in a light-speed-space-ship and riding it for awhile to slow down your aging process. If you stayed in the ship for 5 years, you might step out of it and see that 50 years have passed on Earth, which could arguably be considered time travel into the future. But there's no evidence that this could be used to go BACK in time.
something not making sense just means you can't comprehend it, the universe's rate of expansion is increasing, does it make sense? Not to me, but that doesn't mean that it isn't true. The idea of cameras didn't make sense at one point, but cameras exist. Just because you are unable to grasp a concept does not mean that it is not right, that is possibly the most arrogant view possible.
If time travel was possible all our lives would have to be predestined . Could you really hold someone accountable for something they have no choice but to do ??
If time travel was possible all our lives would have to be predestined . Could you really hold someone accountable for something they have no choice but to do ??
Woops wish i could go back in time and fix that one
The danger of using a recent example (WW2) as something that a visitor from the future would want to change is that it is very, um, current-centric. No one ever picks WWI. Or the Peloponesian war. Why? Because things that are tragic to us are merely history to those in the future. So if we invent time travel 1,000 years from now, do you really think that the deaths of those in WW2 are going to be meaningful? No, I'm afraid not, and people so far in the future would not want to monkey around with something so distant due to the butterfly effect. Have we learned nothing from Ashton Kutcher? :)
Aside from that, would we even notice if someone did change history. Maybe someone did travel back in time and stop WWII but that created an even worse war that we now call WWII. We wouldn't even notice if someone changed history, its possible that all of their efforts only made the world worse so they simply stopped.
Yes if the US had minded their own business and stayed out of WW1 there would of been no WW2 ..Hitler would of just been a paper hanger no dead Jews no nation of Israel no pissed off Arabs..
uh..severely off topic.
It happens ..