We all know that one could not travel at speed c (186,000 miles per second), but the closer you travel to c, the slower your time goes around you. Example: if you traveled in a spaceship at a super high speed for 10 years, earth would have aged 100 years (you age 10 years, earth ages 100). Therefore, people on earth view your time as "slowing down". If it were possible, and you travel at a great rate of speed, and made a phone call to earth; would the phone call seem "normal" to you, but sound slower to people on earth (the speed of your voice seem slower and longer to speak)?
Space-Time, Relitivity, and Phone Calls
| dgrowe wrote: |
| If it were possible, and you travel at a great rate of speed, and made a phone call to earth; would the phone call seem "normal" to you, but sound slower to people on earth (the speed of your voice seem slower and longer to speak)? |
Any relativistic effect (though present) would be drowned out by the effects of Doppler shift.
In this pictured example, we'll need to change a few things to make it more applicable.
The car is your spaceship.
The sound from the car is the radio (or light or whatever) waves from your 'phone'.
The observers are the Earth, depending on where your ship is relative to it.
So, you can see, that if you're going towards the Earth, it'll be much faster, and if you're headed away, it'll be much slower.
But the Doppler effect doesn't include the variable of time, which in this case is the problem. Since you're aging much slower due to your speed in the spacecraft, would you be speaking slower to someone on earth.
If you're using a cell phone, the sound in front and behind the observer is not changed due to there is no "compression" from to air molecules. This works great for objects traveling on earth; but doesn't work for space situations that are near vacuum. The variable in this case, is time. Would you sound slower because of your high rate of speed (and thus, time travel)?
If you're using a cell phone, the sound in front and behind the observer is not changed due to there is no "compression" from to air molecules. This works great for objects traveling on earth; but doesn't work for space situations that are near vacuum. The variable in this case, is time. Would you sound slower because of your high rate of speed (and thus, time travel)?
| dgrowe wrote: |
| But the Doppler effect doesn't include the variable of time |
f0=[(v+vr)/(v+vs)]*f1
(where v is the velocity of waves in the medium, vs is the velocity of the source relative to the medium
and vr is the velocity of the receiver relative to the medium).
Since velocity is the rate of change of position, time is implicit.
But the Doppler shift isn't the question here; time is. When speaking to astronauts in the space station (via phone), the Doppler effect isn't noticed here on earth to people on that call. As the astronauts orbit the earth, the phone call doesn't go slower (as they pass the earth person), than faster (as they orbit earth and come back around the other side) due to their speed relative to those on earth, right?
The original question was if time effects a phone call. Therefore, if the International Space Station station where to speed up 1,000 times faster in orbit than it is now (and it were to stay in orbit by propulsion), would the time-relativity theory make the conversation for someone on the space station to someone on earth go much faster?
The original question was if time effects a phone call. Therefore, if the International Space Station station where to speed up 1,000 times faster in orbit than it is now (and it were to stay in orbit by propulsion), would the time-relativity theory make the conversation for someone on the space station to someone on earth go much faster?
| Quote: |
| As the astronauts orbit the earth, the phone call doesn't go slower (as they pass the earth person), than faster (as they orbit earth and come back around the other side) due to their speed relative to those on earth, right? |
The thing is, that time is not constant - each experiences time differently according to their relative motion.
| Bikerman wrote: | ||
The thing is, that time is not constant - each experiences time differently according to their relative motion. |
i don't think you need air for the Doppler effect. >_< i think that in the case of EM radiation propagating without a medium (self-propagating), the Doppler effect is due only to relative velocity of the source and receiver.
So, in this case, the Dopper effect will mean observer 1 will hear the message coming in very slowly (redshifted, like the batteries running down on an old-fashioned tape player), while observer 2 will hear the message coming in very quickly (blueshifted, like chipmunks talking).
You also have to consider the time dilation to consider how much slower the people on the ship making the phone call are moving relative to the receiver on either end.
So it's a really complicated situation that i can't just figure out off the top of my head without crunching numbers. But... i suspect you'd get a situation like this:
Ship calling observer 1: Observer 1 will hear people on the ship talking very slowly, and vice-versa.
Ship calling observer 2: Observer 2 will hear people on the ship talking very quickly, and vice-versa.
And in either case, the time delay between sending and receiving will be huge.
Yes, OK, mea culpa. Of course the Doppler effect occurs regardless of the medium.
It is indeed complex and I'm going to have to think about it before saying much more (if I get the time and can be bothered
)
It is indeed complex and I'm going to have to think about it before saying much more (if I get the time and can be bothered
)| ocalhoun wrote: |
| Any relativistic effect (though present) would be drowned out by the effects of Doppler shift. |
Doppler effect appears if the ship moving towards or away from the observer.
What if the ship circles the observer. Then the distance is constant and there's no doppler effect, right?
| TomS wrote: | ||
Doppler effect appears if the ship moving towards or away from the observer. What if the ship circles the observer. Then the distance is constant and there's no doppler effect, right? |
Correct, but there's still time dilation.
It's too bad i can't do equations here, or it would be easy to show what happens, and you could experiment by playing with the values.
| Indi wrote: |
| Correct, but there's still time dilation. |
And that was the original question of this thread. Until the doppler effect was brought into play.
| Indi wrote: |
| It's too bad i can't do equations here, or it would be easy to show what happens, and you could experiment by playing with the values. |
Try http://math.at.gg/
It's only available in german, but eventually you figure out how to use it. Mathematics is a universal language.
For example:
| Bikerman wrote: |
| Of course it does.
f0=[(v+vr)/(v+vs)]*f1 |
*f_1.png)
| TomS wrote: | ||
And that was the original question of this thread. Until the doppler effect was brought into play. |
The Doppler effect does matter, and - depending on a lot of factors - may even dominate.
| TomS wrote: | ||
Try http://math.at.gg/ It's only available in german, but eventually you figure out how to use it. Mathematics is a universal language. |
ich werde hineindenken. ^_^
Ok, here's the relationship:
f(s): the frequency of the source signal.
f(o): the frequency you observe.
v: speed of the ship.
θ: the angle the ship is travelling at with respect to the observer (0° is flying away, 180° is towards).
c: speed of light.
The first term is the time dilation factor, and it is always (0, 1] so it always slows down the frequency (makes f(o) less than f(s)) unless you're standing still. It is dominant at higher speeds.
The second term is the Doppler shift factor, and it ranges from (0.5, ∞), so it can slow down the frequency a bit (but not as much as time dilation), but it can speed it up infinitely. It is dominant at low speed, or when the ship is coming right at you at high speed (but is somewhat cancelled out by the time dilation).
When both time dilation and Doppler are combined, the frequency shift is (0, ∞)... basically the final frequency can be anything - higher or lower than the original signal - so you could hear ultra fast messages or ultra slow ones. If the ship is moving away or perpendicular to you, then you will always hear slow messages. If the ship is moving towards you... that's where it gets complicated. Depending on the exact angle and speed, you could hear the message as faster, slower, or... even normal speed. (In fact, if you have time on your hands, you could use the quadratic formula to calculate what angle you would have to fly at (θ) to get normal message speed for any v.)
i did not get a ting you all are talking about! What is this phone call doing with the topic?
| Chinmoy wrote: |
| i did not get a ting you all are talking about! What is this phone call doing with the topic? |
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