Why does time slow time when matter approahes spped of light?

[MobiusPizza]

The experiment they did putting an atomic clock on a spacestation confirms that the time passed by a little more slowly on the spacestation which is travelling at higher speed than on the ground.

Initially I do not believe the result, I simply do not know why such preculliar thing happened. However I've think of an explanation to convince myself as follows:

As matter speeds up, their mass also increases. The cause of time dilation is that the objects with higher speed have more inertia due to the more mass and therefore affect the time to perform physical activity. It takes more time for matter to slow down or speed up in microscopic scale, even electrons orbit slower.

The caesium atom in atomic clock in the space station, by the same anology, has increased mass. The vibration of itself had slowed down a tiny fraction due to the tiny increase in mass, and therefore the clock runs slower.

I am no expert in this, with my high school knowledge of physics. But this seems a promising explanation to convince myself. If anyone has knowledge in this please disapprove me if I am wrong or credit me if I am correct. Thanks.

 

[imported_jb]

this is discussed a bit in the "edge of the universe" thread i beleive. one of the 3 space threads anyway.
one fact worth mentioning was there is a type of photon maybe that's half-life is like only 2 seconds, but its origin is like lightyears away.
i never thought about inertia being the factor. so maybe for a high-speed traveller, thoughts/other human-processes would take a lot longer than without a velocity?

 

[itachi]

Originally posted by: jb
this is discussed a bit in the "edge of the universe" thread i beleive. one of the 3 space threads anyway.
one fact worth mentioning was there is a type of photon maybe that's half-life is like only 2 seconds, but its origin is like lightyears away.
i never thought about inertia being the factor. so maybe for a high-speed traveller, thoughts/other human-processes would take a lot longer than without a velocity?

a photon with a half-life of ~2 seconds.. with origins lightyears away.. quite the paradox you got there. 1 light year = distance light covers in 1 year.. roughly 9.5 femto-meters (10^15).

 

[Smilin]

You can find the formula on the 'net pretty easy. The relationship will make sense.

The super short answer:
Remember speed is distance over time. Also remember that the speed of light is constant no matter what speed you are traveling at (relative to the observer). Something's gotta give

 

[imported_jb]

Originally posted by: itachi
a photon with a half-life of ~2 seconds.. with origins lightyears away.. quite the paradox you got there.

it probably wasn't a photon.. but the idea is the same. couple second half-life and a > 2 second journey.

 

[Subhuman25]

The perception of time is relative to ones physical velocity?

 

[Geniere]

Originally posted by: AnnihilatorX
The experiment they did putting an atomic clock on a spacestation confirms that the time passed by a little more slowly on the spacestation which is travelling at higher speed than on the ground.

Initially I do not believe the result, I simply do not know why such preculliar thing happened. However I've think of an explanation to convince myself as follows:

As matter speeds up, their mass also increases. The cause of time dilation is that the objects with higher speed have more inertia due to the more mass and therefore affect the time to perform physical activity. It takes more time for matter to slow down or speed up in microscopic scale, even electrons orbit slower.

The caesium atom in atomic clock in the space station, by the same anology, has increased mass. The vibration of itself had slowed down a tiny fraction due to the tiny increase in mass, and therefore the clock runs slower.

I am no expert in this, with my high school knowledge of physics. But this seems a promising explanation to convince myself. If anyone has knowledge in this please disapprove me if I am wrong or credit me if I am correct. Thanks.

Good thinking but based on insufficient knowledge. In our universe there is no point of reference to determine an objects speed. The best we can do is say that with respect to the Earth, the satellite is moving in its orbit at a high velocity. To someone on the satellite, a point on the Earth is moving by very rapidly. Which is really moving? The Earth revolves around the Sun at high velocity; the Sun revolves around the center of mass of the Milky Way Galaxy. The Milky Way Galaxy revolves the center of mass of our local galactic cluster. Our local galactic cluster revolves around the center of mass of the local super cluster. Space is expanding at a high velocity?

All physical reactions, in all moving objects, proceed at the same rate as perceived by the object when it is in orbit or after it returns to the Earth. After landing the object will think something weird happened on Earth. We on Earth will think something weird happened to the object. We occupy no special region in space nor do we have a special velocity, nor do physical reactions occur differently out there than they do here. We only perceive them to differ based on the objects velocity with respect to the Earth.. The only thing we can say is that relative to the Earth? Oh shoot I think what?s-his-name already constructed a Relativity Theory.

 

[jhu]

there're two parts to the answer

1) we can calculate the time dilation as velocity approaches c. and such calculations confirm physical findings.

2) that's just the way the rules of the universe work. you might as well ask why 'pi' = 3.1415926...

 

[Smilin]

Originally posted by: Subhuman25
The perception of time is relative to ones physical velocity?

No, the perception of time will always be the same to the observer. So will the speed of light. The perception of time will change in another frame of reference based on it's velocity relative to you. If you are moving, time will be slowed but it will appear normal to you. After all, the chemical reactions in your brain (the way you think and sense time) have been moving slower as well so in your perception time will be unchanged.

Take a satellite with an atomic clock and whip it around the earth at high speed a few times. In it's frame of reference time will be advancing just as always (heck it KNOWS this because it has an atomic clock on board.). Time has also advanced normally for you staying on the ground - you have an atomic clock too. Yet relative to each other, the orbiting clock has been moving so it will be slowed.

The kicker here is which one has been moving? To the satellite it could appear as if it were stationary and the Earth whipping around it. It would expect the Earth clock to be slower. It's the classic "twins paradox". The way you can tell which one was moving is that it has to return to the starting point to be measured (or the signals from it must at least).

 

[imported_jb]

my 'favorite' part of this issue is what if i run in a circle in my backyard or something really fast? if i run @ near light speed for a year, will you all die watching me? ha... funny, but i guess it's true.

 

[Smilin]

Originally posted by: jb
my 'favorite' part of this issue is what if i run in a circle in my backyard or something really fast? if i run @ near light speed for a year, will you all die watching me? ha... funny, but i guess it's true.

More true than you can imagine.

If you really, truly ran in a circle in your backyard for a year I certainly would die watching you. Even if you only did it at regular speed and not at C, I would die watching you. Depending on how small the circle and what kind of look you had on your face it might happen in a matter of weeks.

 

[DrPizza]

Originally posted by: itachi

Originally posted by: jb
this is discussed a bit in the "edge of the universe" thread i beleive. one of the 3 space threads anyway.
one fact worth mentioning was there is a type of photon maybe that's half-life is like only 2 seconds, but its origin is like lightyears away.
i never thought about inertia being the factor. so maybe for a high-speed traveller, thoughts/other human-processes would take a lot longer than without a velocity?

a photon with a half-life of ~2 seconds.. with origins lightyears away.. quite the paradox you got there. 1 light year = distance light covers in 1 year.. roughly 9.5 femto-meters (10^15).

It's not a paradox. The "light years" are measured in our frame of reference. If the photon is travelling at the speed of light, relative to the photon, time isn't passing. What jb is referring to is the half life of a mu-meson (muon for short). Muons are produced when cosmic radiation enters the earth's atmosphere at relativistic speeds.

In some experiment performed in the 1940's, the number of muons per second were measured at a couple kilometers in altitude. Then, the number of muons per second were measured at ground level. Since their half life is known, by estimating that they are traveling at the speed of light, the time to reach the surface can be simply calculated. Using their short half life, there should have been only a small fraction of the muons remaining when they get to the surface. This wasn't the case - there were far more muons than expected. By measuring the number of muons per second reaching the surface, and knowing the half life, they were able to work backwards to calculate how much time actually passed for the muons. (ie if there are 16 in the atmosphere, and 2 at ground level, you would estimate that it went from 16 to 8 to 4 to 2 - - 3 half lifes. If a half life is 7 seconds, then 21 seconds have passed. In reality though, there were far more muons and the half life is measured in microseconds) The experimental data matched what time dilation predicts.

Or, using fake numbers (the concept is here though) instead of the actual numbers. Muons at rest on earth have a half life of 1 second. If you have 8000 of them, you should expect them to decay to around 4000, then 2000 then 1000 then 500 then 250 then 125 then 62 then 31 then 16 then 8 then 4 then 2 then 1.... 13 seconds and you're down to 1. BUT, if these suckers are travelling at the speed of light, they can manage to travel for light years before they decay.

 

[DrPizza]

Here's a site with actual numbers: http://hyperphysics.phy-astr.g...se/relativ/muonex.html

Wow, I think I'm going to use that site for my high school physics class. Pretty good stuff!

 

[MobiusPizza]

The concept I thought of is that time is slower when object is near speed of light because they gain mass. To us as the observer, they looked as if time is slowed in their point of sense. and the object itself do not quite know their time is slowed in our frame of reference. To us the object's frame of reference time is slowed since they is not as agile as use just because they have more mass. Electrons are slowed, radiation is slowed, etc. Any atomic reactions are slowed. As if they 'think' and 'act' slower. But they do not notice themself as slower. Therefore when we see them it is as if they are slower according to our reference.

E.g., if you travel at speed of light, you do not know time is slowed in your sense. If I am watching you and I am stationary, if I say Hi to you, you would be slower responding to me just because the atomic interactions in you is slower because your mass has gained. So I get your response late therefore I think your time is slowed.

 

[beansbaxter]

Time did not slow down, the device that was used to measure time slowed down. Time as I know it is the measurement of the rotation of the earth in relationship to the sun and this event did not change because someone took a clock into space. The function of the clock and the matter it consists of slowed down, but "time" marched on at the same speed as always.

Though I'm not sure why this phenomenon happens (not sure that i buy the theory of mass increasing with speed, first time i heard of it anyway), I think saying that "time slows down" is something of a misnomer. in my mind, time is constant, it's just that the subject's reaction to time has slowed down. I tend to assume that physicists mean it in the same way as i take it, and that the idea of time actaully slowing down around the object in question is just a coloquialism brought on by the misnomer itself.

 

[beansbaxter]

Originally posted by: jb
this is discussed a bit in the "edge of the universe" thread i beleive. one of the 3 space threads anyway.
one fact worth mentioning was there is a type of photon maybe that's half-life is like only 2 seconds, but its origin is like lightyears away.
i never thought about inertia being the factor. so maybe for a high-speed traveller, thoughts/other human-processes would take a lot longer than without a velocity?

well...ok,here goes some stuff to think about. (keep in mind - all this stuff is relative). As the velocity of an object speeds up, its mass increases. It is ever so slight at our normal "newtonian" speeds, but as you approach the speed of light, the mass gets larger at an increasing rate (think of an x/y axis curve as the curve approaches but never quite intersects an axis). As the mass of the object increases... a few "interesting" things happen. First, its "attraction" or gravitational pull increases. This in itself has an interesting effect. Side note - space "warps" around gravity. This "warping" contributes to the "slowing" of time relative to an observer who is moving at a slower rate. Keep in mind - time to the person traveling at such a fast velocity seems to be constant.

One interesting "similar" effect occurs in theory around the event horizion of a black hole. an object that is "falling" into a black hole gets faster and faster and actually slows down to the point that an outside observer that is not falling into the black hole will see the object slow slow slow and eventually appear to stop, never crossing into the black hole. . There is some crap to think about!

 

[byosys]

The way I understand it:

Objects (atoms and all their parts) pass through space-time at a constant rate ie space-time, where k is a constant. As you increase speed, time must slow down. Another way to look at is this: think of speed + time passage always equaling 186,000 units. The units can be speed (mph in this case (c)) or time. There is not common standard for the speed at which time progresses because we live in a world where the change in physical speed is small enough not to have a noticalbe effect on the passage of time. There is a conversion factor to change physical speed into the passage of time, but I don't know what it is. As physical speed goes to c, then time passage must go to 0. I don't fully understand space-time, but this was the explanation given in the string theory book that I'm reading.

 

[stephenbrooks]

The above is almost correct except the way space and time interact has an opposing sign, so the effect is that you move more rapidly through a certain reference frame of space and time as you approach c. That is, going at 99%c relative to Earth you travel into Earth's future at 7.089 of their seconds per your second.

Your "4-velocity" is (c,0,0,0) when at rest (this is a "4-vector" where the first [actually "zeroth"] entry is in the time axis and the next 3 are X,Y,Z) in a certain reference frame. If you start going at a speed v in the X direction, it becomes (gamma*c,gamma*v,0,0), where gamma=(1-beta^2)^-0.5 where beta=v/c. The 4-velocity (c*g,k,l,m) always obeys (c*g)^2-k^2-l^2-m^2 = c^2, which is the relation between space and time alluded to above.

Now, this thing determines your rate of progress through spacetime in a certain reference frame. Specifically, if you have 4-velocity (c*g,k,l,m), then in 1 of your seconds, you will travel k metres in the X direction, l in the Y direction, m in the Z direction and g seconds forward in the reference frame's time. Note that g actually equals the 'gamma' above (this is the relativistic time dilation factor).

These effects have nothing significant to do with gravity, FYI. This is 'special relativity' whereas the one including gravity is 'general relativity', which builds in this 4D space time formulation, but does not really have effects backwards into special relativity.

 

[beansbaxter]

What about the effect of gravity on the speed control of the clock (the hydrogen atom)
They do use hydrogen don't they?
When they are launching the clock into space, those atoms experience lots of G-forces, would that have any possible affect on the "vibration" of the atoms? (temporaily throwing the clock out of whack)
Does zero G have any effect on the speed of atoms compared to earth gravity?
I would think that if we had actual "gravity machines" you might be able to slightly affect the orbit of the electrons by exposing them to extreme gravity.
Then again, maybe not.

A neutron walked into a bar and
asked how much for a drink.
The bartender replied,
"For you, no charge."

 

[DrPizza]

Originally posted by: beansbaxter
What about the effect of gravity on the speed control of the clock (the hydrogen atom)
They do use hydrogen don't they?
When they are launching the clock into space, those atoms experience lots of G-forces, would that have any possible affect on the "vibration" of the atoms? (temporaily throwing the clock out of whack)
Does zero G have any effect on the speed of atoms compared to earth gravity?
I would think that if we had actual "gravity machines" you might be able to slightly affect the orbit of the electrons by exposing them to extreme gravity.
Then again, maybe not.

A neutron walked into a bar and
asked how much for a drink.
The bartender replied,
"For you, no charge."

Even if there was an effect by gravity, electromagnetic and nuclear forces are many many orders of magnitude stronger than gravity. 10^thirty something for the electromagnetic. And, since the radioactive decay (cesium is used, isn't it?) is dependent on the nuclear forces, it's even greater than this.

 

[flawlssdistortn]

Basically - Time is not universal!! Time depends on your frame of reference. Simultanaety depends on your frame of reference. Why? Because the one thing that common sense says should not be constant (the speed of light), actually is.

 

[silverpig]

Originally posted by: DrPizza

Originally posted by: beansbaxter
What about the effect of gravity on the speed control of the clock (the hydrogen atom)
They do use hydrogen don't they?
When they are launching the clock into space, those atoms experience lots of G-forces, would that have any possible affect on the "vibration" of the atoms? (temporaily throwing the clock out of whack)
Does zero G have any effect on the speed of atoms compared to earth gravity?
I would think that if we had actual "gravity machines" you might be able to slightly affect the orbit of the electrons by exposing them to extreme gravity.
Then again, maybe not.

A neutron walked into a bar and
asked how much for a drink.
The bartender replied,
"For you, no charge."

Even if there was an effect by gravity, electromagnetic and nuclear forces are many many orders of magnitude stronger than gravity. 10^thirty something for the electromagnetic. And, since the radioactive decay (cesium is used, isn't it?) is dependent on the nuclear forces, it's even greater than this.

There is an effect of gravity on the rate of passage of time and it is very measurable. The GPS sattelites must correct for this. The clocks aboard the sattelites actually go FASTER than the clocks here on earth do because we are deeper in the earth's gravitational potential. In fact, if you had a clock accurate enough (we're slowly getting there too), you could measure your altitude with it quite easily.

You can use hydrogen maser clocks as they are much more accurate than cesium clocks, but they are also very unstable.