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Einstein Pedometer App Measures Relative Time Gain

samzenpus posted about 3 years ago | from the walking-your-way-to-a-younger-you dept.

Idle 148

cylonlover writes "Among other things, Einstein's theory of special relativity says that as an object's velocity increases, time as experienced by the object will slow down when compared to another object traveling at a lower velocity. This means that a 'relatively' short round trip on a space ship traveling at close to the speed of light would see you arrive home having aged less than those back on Earth. While the greater the velocities involved, the greater the effect, the theory applies to all relative movement. Now there's an iPhone app that will let you know just how many extra nanoseconds you've gained by getting moving as opposed to sitting on your rear end."

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148 comments

I used the extra 300 femtoseconds (5, Funny)

Anonymous Coward | about 3 years ago | (#35782050)

To beat you guys to first post. Bah!

Re:I used the extra 300 femtoseconds (0)

Anonymous Coward | about 3 years ago | (#35784292)

Yeah? I'll show you. I'll walk backwards and get LAST post!

Scarface (-1)

Anonymous Coward | about 3 years ago | (#35782058)

That tongue she look like a lizard.

You gained none... (2)

sznupi (719324) | about 3 years ago | (#35782098)

It doesn't matter much how the time in your frame of reference relates to times of "stationary" observers; it's still the same amount of time for you.

Of course, the gain (and much larger than nanoseconds) might be there vs. just sitting on your rear end. But it depends greatly on the type of movement, for example whether it involves regular exercise.

Re:You gained none... (3, Funny)

Chris Burke (6130) | about 3 years ago | (#35782186)

It doesn't matter much how the time in your frame of reference relates to times of "stationary" observers; it's still the same amount of time for you.

True! But it does bring the future to you that much quicker. And let me tell you, from my perspective of a person from a few nanoseconds ago, the present-ne-future is an amazing place!

Re:You gained none... (1)

bberens (965711) | about 3 years ago | (#35783352)

As a person who is from a few nanoseconds into your future let me just say: wait until you see what happens next!

Re:You gained none... (1)

laejoh (648921) | about 3 years ago | (#35782196)

Lateral thinking; what if I would sit on the read end of someone else?

Re:You gained none... (1)

c0lo (1497653) | about 3 years ago | (#35782898)

Lateral thinking; what if I would sit on the read end of someone else?

Sitting on your top end changes something in the equation?
Anyhow, I'm relatively better if I'm sitting on my rear end in a car travelling at least 10 times faster than I'm walking.

Re:You gained none... (-1)

Anonymous Coward | about 3 years ago | (#35782224)

You neglect the relativistic speeds of electrons (at approx 2.5V and greater) that warp space in their immediate vicinity - the faster you're thinking the faster these fire, and the slower the matter moves. Free your mind, attain Zen or the death of the self as Crowley would state it - and you allow for these effects to materialize. It really doesn't surprise me though, that in spite of all Steve Jobs' drug use and spiritualism he's able to turn it into something that will hinder those brainwashed crApple lusers in all facets of life - black is white, red is cyan, and you're mother is a man, right Steve?

At which height? (1)

mangu (126918) | about 3 years ago | (#35782330)

If you climb up a mountain you'll be higher up in the gravity well and time will run faster than for people down below. The app should be integrated with GPS readings to take that into account.

Re:At which height? (1)

Cytotoxic (245301) | about 3 years ago | (#35782434)

and what about latitude? You'd have to factor in the relativistic differences between sitting near the earth's axis of rotation and whizzing about at the equator. Surely that speed differential is bigger than your walking speed...

Re:At which height? (1)

srjh (1316705) | about 3 years ago | (#35783322)

Not once you take general relativity into account.

The equator is whizzing about faster, but it experiences a weaker gravitational field, and a subsequent decrease in gravitational time dilation.

At sea level, the weaker gravitational time dilation and stronger kinematic time dilation cancel. Although GP is correct in pointing out that altitude must be taken into account.

Re:At which height? (1)

angel'o'sphere (80593) | about 3 years ago | (#35783988)

Considering that at speeds far far far below 1% of light speed, the speed itself is completely irrelevant and only 'acceleration' matters .....

Re:At which height? (1)

sznupi (719324) | about 3 years ago | (#35782644)

Of course, then it would be only decent to also calculate & show different risks of cancer from cosmic radiation (hence expected average differences of available time), or unhealthy effects of low oxygen levels ;P (but yeah, IIRC the differences from going up&down the gravity well are quite on par with those from human-scale speeds of movement)

22 more nanoseconds (4, Informative)

mangu (126918) | about 3 years ago | (#35782790)

There is at least one hobbyist [wired.com] that has measured it by taking a surplus rubidium oscillator up mt. Rainier. "It was the best extra 22 nanoseconds I've ever spent with the kids,"

Philosophical Exercise (4, Informative)

hellfire (86129) | about 3 years ago | (#35782474)

The time one lives on this planet is relative to measurements made by other people and by other devices. Your watch on your own wrist is probably the most accurate personal time you can get, but you have to adjust it based on other clocks around you to remain in sync with the rest of the world. Even more so, computers and phones now regularly ping a clock server to get an updated time automatically, and that server is somewhere else, being stationary. Time on the Earth is measured in terms of the velocity of the planet's orbit and rotation, but not in terms of your personal velocity relative to the sun or earth itself. The earth rotates and orbits at a specific velocity. If you move, your velocity relative the sun is different than the planet itself.

However, by moving, based on the theory of relativity, you are gaining a fraction of a fraction of a second by moving faster than the world around you. The clock is a philosophical exercise exploring relativity, and it's not like you'll gain 200 relative years by constantly walking or running anywhere, but it's fun to observe relativity in action. The "gain vs loss" here is that 1 second for you is still 1 second, but if you were say running, 1 second for you is, for example, 1.000000000000000000000000000000000000000000000000000000000000001 seconds for everyone you pass that are standing still. So you gain that fraction of a second relative to the world around you, and thus travel into the future a little faster than others.

Re:Philosophical Exercise (3, Insightful)

wood_dude (1548377) | about 3 years ago | (#35783084)

No, I'm at rest. Everything else is revolving around me. It's a chaotic dance to be sure, but I'm at the center of it ! :)

Re:Philosophical Exercise (1)

camperdave (969942) | about 3 years ago | (#35783358)

I think that this is the true heart of the twins paradox. Motion induces time dilation, that's easy to understand. Nothing paradoxical about it. However, from the point of view of the "moving" twin, the "stationary" twin is the one that moves, thus each twin sees the other as stationary. Each twin will see time passing more slowly for the other than for themselves. In other words (A<B) AND (B<A) is true.

Re:Philosophical Exercise (-1)

Anonymous Coward | about 3 years ago | (#35783524)

wow. relativity is so revolutionary, it suspends basic math.

either that or you're misinterpreting it, but you read this book about it once, and that's as good as if you'd derived the equations by hand

fuck off and die

Re:Philosophical Exercise (2)

lxs (131946) | about 3 years ago | (#35784592)

No the twin paradox is resolved by noticing that one twin has to accelerate at least twice on his round trip (and thus his frame of reference isn't in an inertial frame of reference and therefore not valid for calculations in special relativity) while the stationary twin doesn't accelerate at all.

Re:Philosophical Exercise (1)

TheTrueScotsman (1191887) | about 3 years ago | (#35784100)

You're generally correct, but your example of differences of 10^-70 seconds is way off (yea, I know, you just pressed the zero key for 'some time'). These relativistic effects are at about 10^-14 seconds and anything below plank time (10^-44s) is meaningless in current physics.

Re:You gained none... (1)

digitig (1056110) | about 3 years ago | (#35782488)

It doesn't matter much how the time in your frame of reference relates to times of "stationary" observers; it's still the same amount of time for you

True, but you'll look younger to your peer group. Of course, the effect is negligible -- so the cosmetics and pharmaceutical industries will be marketing this PDQ.

relative to what? (2)

ron_ivi (607351) | about 3 years ago | (#35782120)

Wouldn't this "gain" depend on which direction you're walking - along with the rotation of the earth, or against it?

Or if you're comparing to non-earthly reference points - along with the revolution around the sun & galaxy or against them?

Re:relative to what? (1)

Anonymous Coward | about 3 years ago | (#35782152)

Not only that, the moment you accelerate you switch inertial frames, thus special relavitity no longer applies, the clocks converge and you gained nothing. Refer to the twin paradox.
http://en.wikipedia.org/wiki/Twin_paradox

Re:relative to what? (1)

Richard_J_N (631241) | about 3 years ago | (#35782724)

Not quite sure you've got this right. Switching inertial frames doesn't "make the clocks converge". What happens is that, because the twin who moves away and then returns is doing an intertial-frame swap (he has to accelerate when he turns round to come back), we can break the symmetry and define him as the one who "moves". this symmetry breaking is why it isn't just "all relative". So the one who moves is the younger. (But time passes more slowly for him; he doesn't get to have "any more fun"). BTW, SR is actually quite straightforward - you just have to understand it as a way of doing co-ordinate transformation between two frames.

Re:relative to what? (1)

camperdave (969942) | about 3 years ago | (#35783396)

But how do we know it was the "moving" twin that stopped and returned? From the point of view of that twin the "stationary" twin is the one who moved away and came back.

Re:relative to what? (1)

Richard_J_N (631241) | about 3 years ago | (#35783542)

> But how do we know it was the "moving" twin that stopped and returned?
> From the point of view of that twin the "stationary" twin is the one who moved away and came back.

The symmetry is broken, so we can tell. The stationary twin feels no acceleration (and remains in one inertial frame of reference throughout).
The moving twin must accelerate away, turn around (decelerate + accelerate) and then brake on arrival. So he switches frame at least 3 times.

In SR, there is no special "rest" frame, and you can't tell what your own absolute speed is (it's not even defined). However, you *can* tell that you are accelerating, because of F = m.a . If you experience a force, you must be accelerating. The 2nd twin can feel himself being pushed back in his spacecraft's seat.
  [in SR there is no gravity; once gravitation enters the fray, we have the equivalence principle (briefly, inertia === gravity) and then we must resort to GR]

Re:relative to what? (1)

camperdave (969942) | about 3 years ago | (#35783788)

Okay, Forget about the coming back part, and the stopping and starting part. Just imagine two people who are moving in inertial reference frames (say coasting in space ships on parallel courses. Each will think they are stationary. Each will think the other is moving. Each will measure a time dilation in the other.

Re:relative to what? (1)

Richard_J_N (631241) | about 3 years ago | (#35784242)

That only has one event in it, rather than 2.

An event is a point in space-time: some marker that has coordinates (ct, x,y, z) in a particular frame of reference, S.
In a different frame, S', the coordinates of that same event will be (ct', x', y', z').
Relativity lets us do the maths: if we know (ct,x,y,z) and the relative velocity of S' and S, then we can calculate (ct',x',y',z') (and vice versa).

In the standard twin-paradox, event A would be the twins saying goodbye, and B would be them saying hello again later. The time for the stationary twin is then
  t_B - t_A, whereas the time for the moving twin has to be calculated in two frames, S' and S''.

However, to measure elapsed time, (B-A), both twins have to agree on the co-ordinates of the events. You can synchronise one event as the twins pass each other, but if they remain in intertial frames, you cannot define a second event to the satisfaction of both twins.

Re:relative to what? (1)

HTH NE1 (675604) | about 3 years ago | (#35783706)

For one, because it takes far more force to move an entire universe around one individual than it does to move one individual around in a universe at any speed, let alone relativistic speeds. Such an exertion of force upon the whole universe will be hard to ignore, and the energy requirements to do so could not be solely attributable to the propulsion device your moving twin is using.

Re:relative to what? (1)

angel'o'sphere (80593) | about 3 years ago | (#35784208)

For one, because it takes far more force to move an entire universe around one individual than it does to move one individual around in a universe at any speed, ....

Well, this sentence is flawed from the beginning. It does not need force to move something around, but acceleration. Force is the product fo acceleration times the mass of the moved thing.

A force like F = m * a bottom line only depends on 'a'. It does not matter if m is the mass of the universe or your body mass.

What you likely mean is energy: yes, to accelerate a small mass you need less energy than to accelerate a huge mass.

angel'o'sphere

Re:relative to what? (1)

donscarletti (569232) | about 3 years ago | (#35782832)

Methinks you did not read that article so well. The twin paradox is not a paradox precisely because it is the swapping of inertial frames which is causing the apparent time dilation to begin with.

Re:relative to what? (1)

Ironhandx (1762146) | about 3 years ago | (#35782302)

Relative to the speed of light. Meaning walking saves you a nearly infinitesimal amount of time.

Theoretically, as you get closer to the speed of light, time should slow down for you. Hence all the mumbo jumbo about a flight to Alpha Centauri taking maybe 50 years, but at that speed it would only be 20 years to the people doing the traveling. Those numbers are no where near accurate, but hopefully you get the idea.

While not an expert in the field, obviously, I myself harbor serious doubts as to the accuracy of this particular portion of relativity. Given its nature it will be quite a while before it can be fully proven/disproven as well.

Yes, yes. I know the maths line up but the maths have lined up for other things that turned out to be wrong.

Re:relative to what? (1)

sznupi (719324) | about 3 years ago | (#35782454)

Time dilation is proven to you every time you use a friggin' GPS; a system which wouldn't work without taking the effect into account (also... [xkcd.com] )

Re:relative to what? (1)

wanerious (712877) | about 3 years ago | (#35782546)

You should rest easy! It's been confirmed directly using planes and atomic clocks: http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment [wikipedia.org] as well as in observed ratios in muon detections from cosmic rays and in the operation of particle colliders like the LHC and at Fermilab. Also, interestingly, it is what is ultimately responsible for magnetic fields. The fact that you can stick these things to your fridge is a consequence of time slowing down and space shortening for charges in motion. It's fascinating.

Re:relative to what? (4, Interesting)

Cytotoxic (245301) | about 3 years ago | (#35782588)

It isn't just about math. These effects have been proven experimentally - just not by sending a human off to Alpha Centauri. Follow the references for more relativity fun. [wikipedia.org] I personally find length dilation to be the most interesting and difficult to get my head wrapped around.

Fun thought experiment:

A 100m rocket speeds toward a 90m hangar building at .99C. As the rocket passes through the open doors of the hangar the operators of the building close both sets of doors while the rocket is entirely inside the building. This is possible because of the length dilation happening at the high relativistic speeds (the rocket is compressed to less than 90m from the view of the hangar).

But from the point of view of the ship, it is the hangar that is approaching at .99c. Therefore the hangar is foreshortened - even shorter than 90m - leaving more than 10m too much rocket hanging out. What do each of the door operators and the pilot of the rocket see happening?

This is a fun use for all that math you learned to figure out relativity. Even though both frames of reference see things in entirely incompatible ways, both versions of the truth are entirely consistent via relativity.. Fun!

Re:relative to what? (1)

Em Adespoton (792954) | about 3 years ago | (#35783366)

The answer is simple; due to the speed of the rocket (or hangar), the neurons in the brain are unable to process the results before the explosion where all observers go up in a large fireball.

A more interesting one would be to place telemetric laser gates 10m on either side of the building and see if a remote observer is able to witness either being broken while the rocket is within the closed hangar ;)

Re:relative to what? (1)

Em Adespoton (792954) | about 3 years ago | (#35783434)

One other thought... when the relative motion between you and the objects around you approaches the speed of light, isn't it true that the objects approaching you shorten while the ones moving away from you lengthen? And by objects, we're talking quantum objects, not physical objects?
This means that the front of the rocket from an internal observer will appear to be closer to the front hangar door, where all space is shrunk... but it will appear farther from the rear hangar door.

Looking at it from a different perspective, this means that the rocket will appear to be in a different location at the same time from inside the rocket than from inside the hangar... which is exactly what we'd expect from time dilation.

Re:relative to what? (0)

Anonymous Coward | about 3 years ago | (#35783922)

Why is there a pilot on the rocket? Wouldn't you want the rocket self guided, especially if it is speeding towards a hangar?

Re:relative to what? (0)

Anonymous Coward | about 3 years ago | (#35783950)

Length dilation is easy to understand once you realize that it's a direct consequence of time dilation, and not really a separate effect. When you look at the front of a moving object, you're looking into its past, and when you look at the rear, you're looking into its future. (Rule: "leading clocks lag"). Therefore, when you look at where its front edge would be if it were standing still, you're effectively looking backwards in time from the object's point of view, and at that time, the object hasn't yet arrived at the point you're looking at. Similarly, when you look at the back edge, you are looking forwards in time, and the object has already left.

It's not really that the object becomes "shorter" so much as that you are looking at it in a skewed timescale such that you are looking at the object's past on the leading edge and at its future on the trailing edge. That, plus the fact that it is moving, creates the illusion that it has become shorter, but it really hasn't.

Re:relative to what? (1)

Ironhandx (1762146) | about 3 years ago | (#35782980)

Well then, thanks for all the responses showing how wrong I am >_.

Its something that has never stuck well with me however. I believe that with the evidence its probably(99.9e10^20 %) right, but won't be terribly surprised if they discover some other weird QM effect or something that causes the evidence to appear like what we think should confirm the theory. Basically I'm cynical about it. So sue me.

All the rest of that stuff is really cool though. Never knew the thing about the magnetic effect. Wouldn't that stuff also go a long ways towards figuring out exactly what gravity is?

*hopes for links explaining exactly what gravity is*

Re:relative to what? (1)

angel'o'sphere (80593) | about 3 years ago | (#35784074)

Considering that Alpha Centauri is only 4 light years away, from an outside observer you would accelerate 100 days, and decelerate 100 days and fly like 3 years and 10 monthes + 200 days (acceleration + deceleration) but from your point of view it would be only 200 days (acceleration + deceleration) + a few weeks at close of speed of light.

Well, you don't need to know anything about relativity, no one really expects that.

But that alpha centauri is the closest star to our sun, THAT you perhaps should know. And that it is just 4 Light years!! That you also should know.

As a small hint regarding relativity: it is not a 50 years versus 20 years ratio but depending on final speed a dozens of years versus a few weeks ration. In other words, if we would put you into a rocket flying close to light speed you would be (from your perspective) at alpha centauri in less than 3 months.

angel'o'sphere

Re:relative to what? (1)

Ironhandx (1762146) | about 3 years ago | (#35784424)

That would be traveling AT the speed of light.

I'm aware of the 4 light year distance, but currently with top end projected attainable speeds from what I understand the trip will still be better measured in decades than years.

Even 50 years means traveling at an appreciable fraction of the speed of light.

Re:relative to what? (1)

sznupi (719324) | about 3 years ago | (#35782528)

The effect stems from relative differences in speed of object in question vs. chosen frame of reference, it essentially (*) doesn't matter "in which direction you spin" or other scifi mumbo-jumbo ( * it sort of might when you take into account how the space itself is being dragged by rotating object, particularly a massive and compact one)

Re:relative to what? (1)

Charliemopps (1157495) | about 3 years ago | (#35782612)

no.
The article very poorly described the way relative velocity works.

While moving relative to another object/person, time slows for you relative to that object/person, not relative to all of space/time. When you return, you are in their future. Time dilation relating to the Sun/Earth/Galactic center are all different depending on your velocity in relation to those objects.
So, for example, if there are 3 people, 1 remains at rest on earth, the 2nd travels away at 25% the speed of light, and a 3rd travels in the same direction at 50% of the speed of light, if both the travels turn around and come back, all 3 people, the person at rest and the 2 travelers will all have aged at different rates. Even the 2 travelers have aged differently from each other.

At that point you start asking questions that will take a lot more space than Slashdot allows for a post to answer.

Re:relative to what? (2)

Lanczos (1786578) | about 3 years ago | (#35783156)

The problem is that the article is a little bit wrong. In special relativity lets say I'm sitting next to someone and then I go for a walk and come back. When we compare clocks they will be the same since otherwise there would be symmetry breaking and we could establish a preferred inertial frame. Now in general relativity the symmetry is broken by the bending of time caused by my acceleration and when I return to my desk I will be younger than my stationary friend. i.e. this is all a consequence of general relativity not special.

Re:relative to what? (1)

ceoyoyo (59147) | about 3 years ago | (#35783806)

No. It depends on whether you accelerate or not. If you fly around the planet at a particular speed you'll experience less time than someone left behind. It doesn't matter which direction you go. Since the planet, solar system, galaxy etc. are all in inertial reference frames, their relative rate of time is not affected by their relative velocities.

Fine example... (0)

Anonymous Coward | about 3 years ago | (#35782182)

A fine example of a completely useless application.

Badly named (5, Funny)

Anonymous Coward | about 3 years ago | (#35782184)

It's actually a pedantometer.

Re:Badly named (1)

Maestro485 (1166937) | about 3 years ago | (#35784418)

Speaking of "badly named," pedometer sounds like something made up on 4chan to rate the age of children in image posts.

This is wrong. (0)

Anonymous Coward | about 3 years ago | (#35782188)

Traveling at a speed close to the speed of light does not make you age more slowly because in your frame of reference time is traveling at the normal speed. To you, time in the outside world has slowed down because in your frame a reference you are stationary and universe is moving past you. So in this case it's symmetric and neither will age faster or slower.

What breaks the symmetry in the twin paradox is that the one twin had to accelerate up to speed, decelerate, turn around, accelerate back up to speed and then finally decelerate again. It's the acceleration that causes it not the velocity. One twin spends time in a non inertial reference frame.

You LOSE time not gain it. (5, Informative)

digiplant (581943) | about 3 years ago | (#35782194)

Think of it this way: Two guys have a deadline in an hour. Guy #1 sits at his desk and does nothing. Guy #2 zips around at a high velocity and returns to meet guy #1. Both guys check their watch, guy #1 notes an hour has past, while guy #2 notes that half an hour has past. Although guy #2 has aged less, he actually had less time to work to meet the deadline. In the spirit of the original post, guy #2 has lost time instead of gained it.

Re:You LOSE time not gain it. (0)

Anonymous Coward | about 3 years ago | (#35782360)

Also I'm pretty sure the times shown on the app are wrong. As you took the clock with you the normal amount of time progressed (unless it re-synced with the cell tower) should be the "elapsed time after relativity effects", while adding relativity effects could lead you to "elapsed time had you not been walking around".

Re:You LOSE time not gain it. (1)

meerling (1487879) | about 3 years ago | (#35784548)

I agree. When it takes Nasa using a paired set of atomic clocks and a spaceship that travels way faster than your feet or any car you can own to find and measure the temporal discrepancy thus proving the time dilation predictions. I really doubt any ijunk would have the accuracy necessary to measure that, and that's not even taking into account the localized gravitational variations of our world which also effect such minuscule variations.

At best it's getting an estimated speed from the gps, and applying a generic formula to calculate the discrepancy without regard to localized variations, and without coordinating with atomic clocks. The same way I can estimate how much fuel you've burned in your car by looking at your odometer and referencing the sales materials stated mpg for your car. By the way, if you've changed tire size either through low air or pimping your ride, your odometer is wrong, you need to get it recalibrated, or your tires restored to the correct pressure/diameter.

It's amazing what weak ijunk they keep trying to sell in Apples app store.

Re:You LOSE time not gain it. (1)

MartinSchou (1360093) | about 3 years ago | (#35782634)

Maybe that's why exercise extends life. They don't really live longer, it's just that their 60 year old body has only experienced 59 or whatever.

Re:You LOSE time not gain it. (0)

Anonymous Coward | about 3 years ago | (#35783148)

Maybe that's why exercise extends life. They don't really live longer, it's just that their 60 year old body has only experienced 59 or whatever.

What about people that drive all the time or pilots, do they live longer?

Re:You LOSE time not gain it. (1)

meerling (1487879) | about 3 years ago | (#35784254)

Exactly, you are behind the times due to time dilation, it only lets you watch the world zoom past.

Re:You LOSE time not gain it. (1)

Draek (916851) | about 3 years ago | (#35784470)

That's because you're doing it wrong: if you have a deadline in an hour, what you should do is to put your boss in a spaceship travelling at near light speed, not go in it yourself.

Just downloaded it... (1)

wisebabo (638845) | about 3 years ago | (#35782282)

Ok, the App is very minimal, just tells you how much time you've gained(?) compared to a "stationary" observer.

The info panel allows you to put in your birth date. Presumably this is to show you how much time you've added to your life? (It also allows you to turn on multi-tasking for the app so I guess it can constantly determine how much time you've saved).

I wish it would give a little more info (ideally a running graph showing time slowing down as you're speeding up). It says it uses GPS but I'm assuming it isn't calculating how much time is speeding up if you climb up some stairs (out of the gravity well). For that matter I assume it isn't taking into account acceleration (note to physicists: does non-gravity acceleration cause time dilation?).

Still it is free, and makes me feel very very very slightly younger!

Re:Just downloaded it... (1)

Cytotoxic (245301) | about 3 years ago | (#35782626)

(It also allows you to turn on multi-tasking for the app so I guess it can constantly determine how much time you've saved) ... It says it uses GPS but I'm assuming it isn't calculating how much time is speeding up if you climb up some stairs

Does it explain how much the advertisers gain by getting continual updates on your position using your GPS?

Re:Just downloaded it... (1)

MultiModeRb87 (804979) | about 3 years ago | (#35783612)

...For that matter I assume it isn't taking into account acceleration (note to physicists: does non-gravity acceleration cause time dilation?).

Still it is free, and makes me feel very very very slightly younger!

IAAP (I am a physicist), so I can confirm that non-gravitational acceleration causes time dilation, under some circumstances. Since I'm waiting for some calculations to finish running through Mathematica, I'll also try to explain. :-)

Non-gravitational acceleration does cause time dilation, at least when viewed in the frame of the accelerated observer. When analyzed in the frame of an inertial observer (read: if someone who isn't accelerating calculates how much time has passed for you based on how you are moving), these effects appear to be the result of your velocity, and *not* your acceleration.

A fun example of this is the Langevin twin paradox problem. Two twins, floating in space, synchronize their watches. Then twin A uses a rocket to travel out a certain distance d at a more or less constant velocity v, turn around, and return, also with velocity v. He only uses his rocket for a very brief period upon leaving, during turnaround, and finally to return to rest relative to his twin. Twin B just sits there. They then compare their clocks.

Twin B sees that twin A spent essentially all of his time moving with velocity v, and figures that time-dilation has caused twin A's clock to record less time than twin B's. This is correct.

From twin A's perspective, it was twin B who moved with velocity v, and so he figures that time-dilation has caused B's clock to record less time than A's. This seems paradoxical until twin A accounts for the fact that he was accelerated at the far end of his trip. During that acceleration, everything not attached to his rocket (including twin B) seemed to accelerate in the direction his engine was pointed. There's a bunch of math one can do to justify it, (see chapter 13 of Misner, Thorne, and Wheeler's "Gravitation", if you want the full scoop) but the short version is that acceleration acts just like gravity (and vice versa). So twin A figures that twin B's clock must be gravitationally blueshifted relative to twin A's clock (twin B is 'higher' in the apparent gravitational potential produced by the acceleration). It turns out that over the amount of time twin A must accelerate to return to his twin, twin B's clock seems to gain exactly twice as much time as he seems to lose while twin A is coasting, which is just enough to bring each of the twins' calculations into full agreement upon their reunion.

Relativity is fun. :-)

Great ad on the oven... (1)

elsurexiste (1758620) | about 3 years ago | (#35782312)

That would be a cool idea for an Adidas or Nike ad.

Einstein relativity theory: when you are moving, the time of the world around you goes faster and your time is slower. The faster you go, the longer you think, the longer you live. The world turns into a blaze of events, unimportant things are even more insignificant... and everyone else sees you resilient and stoic.

Or some crap like that...

Re:Great ad on the oven... (1)

Mindcontrolled (1388007) | about 3 years ago | (#35782772)

Someone just sold his soul to the PR department. You are lost, mate, eternally. One does not joke with matters like that, matter that were never meant to be dealt with by humans.

Exercise Related? (0)

Anonymous Coward | about 3 years ago | (#35782402)

Maybe this is why people who exercise live longer?

Something I've never understood (1)

John Jorsett (171560) | about 3 years ago | (#35782486)

If motion is relative, how does the universe know which of us is moving in the near-light-speed vehicle so that person's clock runs slower than the stay-at-home's? We're both moving relative to each other.

Re:Something I've never understood (0)

Anonymous Coward | about 3 years ago | (#35782586)

Which of you accelerated more from you initial state?

Re:Something I've never understood (1)

mangu (126918) | about 3 years ago | (#35782638)

how does the universe know which of us is moving in the near-light-speed vehicle so that person's clock runs slower than the stay-at-home's?

The person who traveled accelerated to change his relative speed.

If you travel to a distant planet and get back, you will have accelerated to near light speed, braked down, accelerated back again, and braked down to get back to your twin's side, while he was at rest all the time.

However, if you travel to a distant planet, and then your twin follows you there, you will both have the same age in the end, because you suffered the same accelerations.

Re:Something I've never understood (0)

Anonymous Coward | about 3 years ago | (#35782784)

No. If I travel to a distant planet, the universe accelerates around me to near light speed, then slows down. I don't move at all.

Re:Something I've never understood (0)

Anonymous Coward | about 3 years ago | (#35783834)

Which would only appear to the be case if you've invented some sort of inertialess drive, allowing you to accelerate without feeling any acceleration. Otherwise, the force you felt would clue you in to why the two situations aren't equivalent.

Re:Something I've never understood (0)

Anonymous Coward | about 3 years ago | (#35783318)

How is that different from the planet accelerating towards you, and then accelerated away from you?

Re:Something I've never understood (1)

quickgold192 (1014925) | about 3 years ago | (#35783858)

a=f/m

So in order to be accelerated, you need to have a force applied to you. I don't think there's a force moving the entire universe around you at your whim.

Re:Something I've never understood (0)

Anonymous Coward | about 3 years ago | (#35784200)

Right on! The Elegant Universe by Brian Greene, excellent read.

Re:Something I've never understood (1)

cforciea (1926392) | about 3 years ago | (#35784378)

Actually, acceleration has nothing at all to do with the twin paradox, insofar as it is explained by special relativity, which does not address acceleration. It would work the same way if, for instance, an object passed by earth at relativistic speeds, moved out a distance x, passed its clock measurement on to a second moving objecting moving in the exact opposite direction, which then compares its clock to one sitting on Earth and finds that less time has gone by.

My confusion, of course, comes from what happens when you assume that the object moving towards earth is the rest frame instead of earth itself.

Re:Something I've never understood (1)

camperdave (969942) | about 3 years ago | (#35783588)

Doppler shift of the cosmic background radiation. If you're stationary, the background radiation is the same "color" in every direction. If you're moving, it is blue shifted in the forward direction, and red shifted in the backward direction.

Re:Something I've never understood (1)

cforciea (1926392) | about 3 years ago | (#35784534)

Using uniform background radiation as a privileged inertial frame is cheating. Who is to say that the source of that radiation wasn't just moving fast enough to cause a blue shift equal to what I see while I am walking to keep pace with the rest frame, and the uniform color you see isn't the result of matching your velocity to that of the cosmic background radiation's moving inertial frame?

Exercise is good for you (2)

Hultis (1969080) | about 3 years ago | (#35782530)

Anything that gives anyone motivation to perform some kind of exercise is good. This is one idea, achievements is another. Geocaching provides a good system for achievements for physical activity, and nerds often find themselves enjoying it (in my experience anyway. I was introduced by a nerd, have introduced several nerds and met a whole lot of nerds doing it.). A third is AR-based games. The "time gain" that general relativity supposedly gives is just as good a carrot as anything else - the real gain is health.

You can STILL be lazy!!! (0)

Anonymous Coward | about 3 years ago | (#35782616)

You can STILL just sit on your rear end all the time and gain nanoseconds (age slightly less than everyone else). Just sit your ass down on a plane, taking flight after flight all over the place.... or ride Cedar Point's Top Thrill Dragster over and over. By you moving fast relative to the Earth and its inhabitants, you gain those extra nanoseconds (A LOT OF 'EM) without having to burn any calories off your fat ass!

Re:You can STILL be lazy!!! (1)

$0.02 (618911) | about 3 years ago | (#35782816)

Sure. You can just sit on your lazy ass and fly very fast to get some extra time. But do not forget you also gain some extra MASS. :-)

Interesting, but (0)

Anonymous Coward | about 3 years ago | (#35782630)

Does it factor in the time you just wasted installing the app?

blah,blah,blah (0)

Anonymous Coward | about 3 years ago | (#35782792)

Only shows that most people still don't understand the basics. The article's description, of course, doesn't address the fact that if object A is moving directly away from object B, then object B is moving directly away from object A. So B's time should be slowed down relative to A as much as A's relative to B. Which would be a paradox, if it were so. But it isn't. The relative velocity can only refer to the component of the velocity tangential to circular motion. So if someone were to move in a CIRCLE around you and near-light speed, then their time would be passing slower than yours. This is why passing close to an object at near-light speed would make time slow down relative to the time experienced ON the star -- because as you get closer to the star, your trajectory is tangent to a smaller circle. So the tangential component is larger.

Cancellation (1)

stealth_finger (1809752) | about 3 years ago | (#35782878)

So if I walk to the shop, which for the sake of argument is with the direction of spin of the earth, ie I am moving faster than it, does it then follow that on the walk home where I would be going in the opposite direction of the spin and thusly slower that the rest of the world would 'catch up' to me?

How fast are we going? (1)

NicknamesAreStupid (1040118) | about 3 years ago | (#35783008)

If everything is relative, wouldn't we need to know what is relevant? The earth rotates and revolves around the sun while the sun revolves around the galaxy while the galaxy moves through the universe. That is a lot of movement. Relative to the center of the universe, the one who moves fastest might be the one who sits still. More importantly, the relative difference in momentum between any two of us might be infinitesimal when compared to the whole. Nanoseconds might seem like millennia by comparison. But I know, it is all relatively unimportant when selling an iPhone app. What's really important is what's cool. This app will definitely get someone laid. Too bad all that movement will probably make it seem too short.

The Flash! (1)

DarthVain (724186) | about 3 years ago | (#35783558)

So in reality the Flash should be relatively (pun intentional) immortal compared to the rest of us.

To really bend you bonnet out of shape, so while he is vibrating so fast as to go back in time, that would be relativistically speaking the rest of the world would be moving forward in time at a faster rate.

Also

The Flash would kick Superman's ass in a race... :)

I need the related "red shift" app (1)

Rob the Bold (788862) | about 3 years ago | (#35784170)

That would help warn me when an apparently green traffic signal was actually red to a stationary observer. Talk about savings. This beats extra nanoseconds by a . . . uh . . . it beats them!

what a lot of BS (1)

rossdee (243626) | about 3 years ago | (#35784294)

If you could walk fast enough to make a difference, your body would wear out real fast.

Sure they have measured time differences in atomic clocks that have traveled on jet planes, but imagine the stress on your joints and bones if you could walk at 600mph, not to mention the likelyhood of having an accident (most people can barely cope with car driving speed in terms of reaction abilty..

Somebody mentioned (DC comics) The Flash. How come he doesn't burn up from the heat of air resistance?

Relative velocity and Home repair (0)

Anonymous Coward | about 3 years ago | (#35784324)

This explains why, whenever I return from a bike ride, my house always seems to have something that needs to be done to it. Of course, it could just be my wife.

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