Einstein Pedometer App Measures Relative Time Gain 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."
I used the extra 300 femtoseconds (Score:5, Funny)
To beat you guys to first post. Bah!
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You gained none... (Score:3)
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... (Score:4, Funny)
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!
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At which height? (Score:2)
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.
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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...
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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.
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This app seems more and more inaccurate, let me know when they fix it.
This way I can use any time I save, looking at this app.
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Considering that at speeds far far far below 1% of light speed, the speed itself is completely irrelevant and only 'acceleration' matters .....
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Considering that at speeds far far far below 1% of light speed, the speed itself is completely irrelevant and only 'acceleration' matters .....
No, this is incorrect. Both the kinematic time dilation and the gravitational time dilation are extremely small, but they are roughly on the same order of magnitude in many situations in ordinary life. E.g., if you're flying on a passenger jet, the size of the two effects differs by less than a factor of 10. Also, it's not acceleration that determines your gravitational time dilation, it's gravitational potential.
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You are mistaken, I did not talk about gravitation, I talked about acceleration. (Gravitation however is also a factor, but was not my topic)
Speed is completely irrelevant as long as it is not close to light speed. It is the acceleration that brought you to that speed, that matters.
angel'o'sphere
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You are mistaken, I did not talk about gravitation, I talked about acceleration. (Gravitation however is also a factor, but was not my topic)
The equivalence principle says they're the same thing.
Speed is completely irrelevant as long as it is not close to light speed. It is the acceleration that brought you to that speed, that matters.
No, this is completely incorrect. There is a small effect when your speed is far below the speed of light. All of the effects we're talking about are small.
You may want to take a look at the classic papers by Hafele and Keating and Alley from the 1970's. A good summary of Alley's work is available here:
In NASA. Goddard Space Flight Center Proc. of the 13th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting, p. 687-724, 1981 (SEE N82-20
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Then we both have a problem to agree on the word "irrelevant". Irrelevant is the oposite of relevant, it does not mean not existing.
The time delation effects are calculated with a very simple formula: t0 = T * sqrt(1-(v*v/c*c)).
If you enter small speeds like a car moving you see the effect is very very very low.
I never neglected that effect. I only said: it is not really relevant as ACCELERATION is what matters. My grandparant mixed up acceleration with speed.
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If you want to learn some relativity, the first book I always suggest to people is Gardner, Relativity Simply Explained. You could also try Geroch, Relativity from A to B. At a somewhat higher mathematical level, there is Exploring Black Holes by Taylor and Wheeler, or various upper-division undergrad books like Hartle.
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No, this is incorrect. Both the kinematic time dilation and the gravitational time dilation are extremely small, but they are roughly on the same order of magnitude in many situations in ordinary life. E.g., if you're flying on a passenger jet, the size of the two effects differs by less than a factor of 10. Also, it's not acceleration that determines your gravitational time dilation, it's gravitational potential
FWIW the contribution of gravity is the same as the escape velocity .. on the surface of earth it is about ~7miles/sec.
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22 more nanoseconds (Score:5, Informative)
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 (Score:5, Informative)
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.
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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.
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"The time one lives on this planet is relative to measurements made by other people and by other devices."
Not at all. It's the same for everybody and it's as absolute as C: exactly one life.
(unless you belong to one of the religions that allow you to reincarnate, of course).
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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.
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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.
Can someone explain to me how if I walk around and you stay "still" we aren't moving at the exact same speed relative to one another?
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Lateral thinking; what if I would sit on the read end of someone else?
You get AIDS
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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.
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soo.... you'd have to have two pedometers for it to work -- one to take with you and one to leave behind?
Is a pedometer only a pedometer when you take it for a walk? What is the one left behind, a sitometer?
relative to what? (Score:3)
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?
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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
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You should rest easy! It's been confirmed directly using planes and atomic clocks:
I'm glad those experiments were conducted back in the 70's. If someone thought that up now, well, just imagine what the TSA goons would do if you said the mysterious electronic device in your carry on was an atomic clock.
Re:relative to what? (Score:5, Interesting)
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!
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I haven't run the math on this example in many years, but you've hit on the nut of the answer. Due to foreshortening the hanger dudes see an 80m rocket inside for the (extremely brief) period that the doors are simultaneously closed. Due to time dilation the rocket pilot sees first one, then the other door close and open as the rocket moves through. They are never both closed at the same time from his reference frame. Extra cool points for the fact that the two ends of the hangar are connected by a bu
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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
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hopes for links explaining exactly what gravity is
That's a vain hope, nobody knows what gravity is [youtube.com], same goes for the other fundemental forces. Like time and space they can't be defined without self-reference.
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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. A
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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.
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Ah, sorry my fault ;D
But 50 years is not a *noticeable* fraction of the speed of light, it is a 1/10th at best, there is no real time delation effect. (Ofc you can measure it with good clocks but I doubt it is in the range of an hour even)
angel'o'sphere
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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
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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 gen
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You don't need to factor in acceleration to have the clocks get out of sync, just remember that changing directions means you won't be at rest the whole time in any reference frame:
Inertial frame of your friend: First you move away with say 1 m/s. Halfway through yo
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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.
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Wouldn't this "gain" depend on which direction you're walking - along with the rotation of the earth, or against it?
Assuming both people are on earth it would NOT matter which direction realitive to the other or rotation of the earth they were moving. If they were going 100 mph twoard you or 100 mph away from you the effect is exactly the same.
However there is a problem in that the person who gets in their cars or starts walking their realitive velocity is the one in the accelerated frame realitive to the person standing still. So references only work against fixed features like Micro$ft HQ unless both people run the a
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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
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> 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 ca
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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
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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.
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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: y
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An object at rest will remain at rest and an object in motion will remain in motion in a straight line and at a constant speed, unless acted upon by an outside force. F=m*a, but also a=F/m. Applying a force to a mass produces acceleration; acceleration cannot exist without a force being applied. Any force will do: pushing, pulling, magnetic attraction/repulsion or gravity. If there are no forces upon the mass, there is no acceleration. If there is acceleration, there is a force acting upon the mass. Remove
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It was part of the question and the answer that we're talking about the same magnitude of acceleration. And since F=ma means the force depends on both the 'a' and the 'm', to get the same a with a ludicrously higher m means a ludicrously higher force.
It would also of course take ludicrously more energy, yes. But if you were to apply the same force for the same amount of time, then you would actually expend the same energy accelerating the universe, though the amount of acceleration would be ludicrously lo
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"It does not need force to move something around, but acceleration. Force is the product fo acceleration times the mass of the moved thing."
Not exactly. You *measure* force by observing how much a mass is accelerated.
It is acceleration the result of applying a force to a mass so, in some sense, it would be better to describe Newton's second law as F/m=a instead of F=m*a.
In other words, you can't change the moving status of a mass without applying a force to it (first Newton's law).
"A force like F = m * a b
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I don't think so, perhaps you should scroll up a bit and see my parents post ;D
Sorry that I simplified my answer to him so much that you felt the need to answer as well.
angel'o'sphere
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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.
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"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 [wikipedia.org]"
No, general relativity is not required in order to describe objects that accelerate. Here's a FAQ I wrote on this topic.
FAQ: Does special relativity apply when things are accelerating?
Yes. There are three things you might want to do using relativity: (1) describe an object that's accele
Badly named (Score:5, Funny)
It's actually a pedantometer.
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Dammit, I pointed my pedantometer at your post and it exploded.
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It should really be called a pedometric pedantochronograph.
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bad english (Score:2)
Speaking of "badly named," pedometer sounds like something made up on 4chan to rate the age of children in image posts.
Thats because of 4chan's poor grasp of English.
I laugh every time some one calls me a pedo, I tell them my foot fetish has nothing to do with the discussion.
pedophile - foot fetish
paedophile - kid fetish
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so a silent 'a' changes the meaning of a word?
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sorry, wrong link earlier, but you're still wrong.
You LOSE time not gain it. (Score:5, Informative)
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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.
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The treadmill companies aren't going to like the sounds of this.
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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.
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At best it's getting an estimated speed from the gps, and applying a
Just downloaded it... (Score:2)
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 assumi
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(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?
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...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 a
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Thank you very much!
Saving silicon (Score:2)
Does this mean that the faster I run my CPU, the longer it will last?
Something I've never understood (Score:2)
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.
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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.
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My confusion, of course, comes from wha
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There are time dilation effects from acceleration alone, independent of speed. This can be proved by a thought experiment: imagine you are at the rear end of an accelerating car. At the front end a light flashes exactly once per second. According to your measurements, the flashes occur at shorter intervals than one second, because between each pair of pulses you are moving faster than between the former pair.
Note that this has nothing to do with Lorenz time dilation, since you and the clock are always movin
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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.
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Calculates, not measures. (Score:3)
Measuring would just a tad more difficult...
Oh great (Score:2)
How fast are we going? (Score:2)
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Considering movement is relative, the momentum and vector of motion of the Earth does not matter. You want to compare your time dilation to the Earth's, you don't need more than those two frames of reference.
Obviously, there's the problem that the Earth is not an inertial frame of reference (since it is accelerated), and that likewise you are not an inertial frame of reference even when assuming that the Earth is (since you are on its surface, which is spinning), so you'd need to do some fairly complex gene
The Flash! (Score:2)
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 (Score:2)
what a lot of BS (Score:2)
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?
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The explanation is that the Speed Force (an extradimensional force that these characters somehow tap into) causes an aura to appear around them as they are running, protecting them from friction and minor harm.
Earth moving (Score:2)
Am i the first to question whether this includes the earth rotation?
Besides, when talking about general relativity and moving, can't we determine the exact a centre of our universe by finding the spot (mass points excluded) that (relatively speaking) has the greatest time-dialation potential for any trip in the vacuum of space?
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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. :-)
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How many plane trips would I have to take to go backwards in time all the way to the 70's?