That is incorrect. The fact that time is relative is a very real part of the universe we live in, which means that it IS possible to travel away close to the speed of light and come back having aged only two years while everyone might have aged seven years. There is evidence that the rate at which actual time ticks varies due to relative motion, and it is actively accounted for in our GPS satellites. Also, there are several issues with your analysis. Before I tackle those let's start with the fundamental postulates of (special) relativity:
1) The laws of physics are invariant for all observers in uniform motion.
2) The speed of light "c" (where c ~= 300,000 km/sec) in a vaccume is invariant for all observers in uniform motion. Think of that number as the universal speed limit. Nothing can go faster and it's always the same speed for all observers.
For the above "uniform motion" implies a constant velocity (speed and direction of motion) and is also called an "inertial frame of reference".
Based off of the above several conclusions can be derived:
- If the speed of light is the same for all observers, regardless of their velocity, you cannot simply use additive velocities for relevistic speeds as we normally do for everyday speeds. For example, if someone watches me chase after a beam of light at a rate of .99c (297,000 km/sec) they can conclude I am travelling at that speed, 297,000 km/sec, and the light is travelling at 300,000 km/sec. This yields a diference of 300,000 - 297,000 = 3000 km/sec between my speed and the light's speed. However if I do the same measurement myself while chasing the light I could not possibly get the same result, because if I did I would only see the light moving at 3000 km/sec, violating postulate no. 2 described above! I NEED to see the light moving at a speed of 300,000 km/sec, just like the person watching me from the ground. Since Distance = Rate * Time, and the rate (which is the speed of light) cannot change, then either distance or time must change. In reality both change. Distances shrink in the direction of motion (length contraction) and time slows down (time dialation). This change can be calculated via the Lorentz Transformation.
- Events along the direction of motion are not simultaneous. Rear facing events happen first. This means that if two distant events are simultaneous in my frame, they will NOT occur simultaneously in the other person's frame. Neither of us in wrong, and each observation is equally valid and true. I won't go into why this is true for the sake of brevity, it can be easily looked up.
- Relavistic mass increases, which means that mass increases with relative speed. As a result this coupled with length contraction implies that if you were to travel at the speed of light you would have an infinate mass and no volume. Infinate mass at light speed also means that infinite energy is required to get you there. This is why no particle with mass can ever achieve light speed with things like rockets and other propulsion devices. As an example, if I were watching you drive by at 60 mph I would observe you as being slightly more massive than I would if you were standing next to me at rest.
- There are no absolute, universal, or privileged frames of reference, and no absolute times. Every frame is relative to another, and each observer has the right to view himself as at rest relative to another. This means that if I see myself as at rest and you as moving relative to me, you are equally entitled to see me as moving relative to you (in the opposite direction) and yourself as at rest.
Now onto the issues:
1) You assume faster than light travel is possible
2) You assume additive velocities between the person and the light travelling from the clock by saying "Conversely, if I now flew FTL back towards the sun, time would appear to speed up rapidly, such as if I was travelling at 60xLS then one minute of the sun's clock would appear to pass in each second of my flight.". Because you assume that, you are assuming that the speed of light is not the same for all observers, which violate's the second rule.
3) You assume that time is constant. It's not. The speed of light is constant, which means that time and distance cannot be.
4) And the fundametal problem is you are assuming that everything described by relativity is merely because of visual artifacts, which was shown above to not be the case.
Some good info on the subject:
- Relativity, written by the man himself, Einstein: http://www.amazon.com/Relativity-Special-Theory-Explanation-Understand/dp/0517029618/ref=sr_1_1?ie=UTF8&qid=1259380847&sr=8-1
- Time dialiation: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970701a2.html
- There is also the twin "paradox" (not really a paradox once you understand the physics behind it). It's an awesome thought experiment and demonstrates special relativity really well: http://www.phys.unsw.edu.au/einsteinlight/jw/module4_twin_paradox.htm
Again, time dialation is real and has been measured. In fact, our satelites are calibrated to account for it. If they didn't account for the difference in the rate at which time "ticks" they would not be functioning properly:
- http://en.wikipedia.org/wiki/Effects_of_relativity_on_GPS
- Astronauts age slightly less in orbit around earth:
http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter13.html
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meedeegee
15 years ago
Old post revival...
The satellite GPS clocks vary to earth clocks because of micro-gravity, NOT because of their orbital speed. Look up how atomic, mechanical and digital clocks work, and read up on GPS clocks.
Their orbital speed, or that of astronauts on the shuttle, are significantly too slow with regards to lightspeed to have any difference on "time". Any pages that state that GPS clocks and shuttle astronauts age differently then "earthlings" due to faster orbital speeds are incorrect.
I realize that my previous post makes some presuppositions because it requires FTL and other issues to be resolved. It is a simple method of visual explanation of reference frames for relative visual time events. In reality it couldn't occur because spacetime contains too many factors that will change the example.
My one example assumes time within its limited context is constant to explain reference frames. Not all "types" of time are constant, spacetime has numerous factors that cause variance between reference frames, for example changes in gravity can affect mechanical time. Also, the speed of light is NOT a constant. The common value is determined as light in a vacuum. SpaceTime and our universe is not a perfect vacuum everywhere. Physicists have "stopped" light. The speed of light can only be used when referencing visual time comparisons, for example it has nothing to do with mechanical time.
We must always be careful to not confuse mechanical time, constant time, visual time, etc. SpaceTime is a 3D multi-variable value when influenced by specific factors within a spacetime region. btw, constant time is a theoretical, but is valid.
To get back to the original issue, if I flew away from and back to earth, regardless of my travel speed (even though I could never get anywhere near light speed), the only way that I could age differently than another person on earth would be if I encountered a non-symmetrical spacetime anomaly. And like "wormholes" and other "theoreticals", they do not exist, they have never been actually found by any astronomers or physicists, and imho never will be. I don't believe that a non-symmetrical spacetime anomaly could even exist for any duration without collapsing or destroying itself.
Good conversation though... :-)
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Firewalker2396
15 years ago
I have not studied physics outside of a few semesters at the college level, two years of astrophysics and standard physics at the high school level, and reading and learning on my own time. I am hardly a definitive source on the subject, but I love learning new things about it. With that being said I still cannot reconcile what I was taught with what you are stating in your post. What you are stating here is in direct contradiction with not only what I have learned by own research, but also with what I was taught by my professors.
1) With regards to GPS clocks ticking at different rates, the clocks on the satellites (or shuttle astronauts) in orbit ~20,000 km off the ground (with a velocity of ~14,000 km/hour or an orbital period of 12 hours) tick faster by 45
micro-seconds/day due to more gravitational potential (gravitational time dilation due to general relativity). They also tick 7 micro-seconds/day slower because of their relative velocity/orbital speed (special relativity and kinematic time dilation). This means that relative to us on the ground they are a net of +38 microseconds/day faster than our clocks. While weaker gravitational force is the more dominant of the two, the relative motion is the difference between +38 micro-seconds and +45 micro-seconds. That 7 micro-seconds is ~15% of the total time difference which is hardly negligible. This is also consistent with what I have learned through course-room material. See the following three links below explaining and calculating these effects, written independently by three physics professors:
Calculations of (special/general) relativistic effects on satellites:
http://www.usna.edu/Users/physics/mungan/Publications/TPT11.pdf
http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html
http://www.phys.lsu.edu/mog/mog9/node9.html
...to simply claim "any sources that state that the motion of the satellites causes them to age differently than 'Earthlings' are incorrect" is not good enough. I consider NASA (http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter13.html) to be a credible source, so if you have sources proving that this is not the case that's great, I would love to see them if you post them...
2) With regards to the speed of light not being constant, see my previous post in which I stated that it is the speed of light in a vacuum that is constant.
3) I have never heard of anyone distinguish between different "types" of time (mechanical, visual, etc). Could you provide links to any credible sources from which you derived this information? A search yields nothing on these terms.
4) There was an experiment done to show that clocks tick at different rates due to relative velocity. See the link to the "Hafele and Keating Experiment" which was conducted to put the theories to the test, and concluded that time does indeed vary depending on a couple factors, one of them being relative motion:
Hafele and Keating Experiment
http://hyperphysics.phy-astr.gsu.edu/HBASE/relativ/airtim.html#c1
...also...
See the twin paradox, a thought experiment which came about as a direct result of special relativity's implications about time and relative motion, and shows the rate at which clocks tick is dependent on the observer's relative motion:
Twin paradox
http://hyperphysics.phy-astr.gsu.edu/HBASE/relativ/twin.html
The Hafele and Keating Experiment and Twin Paradox both show that if you flew away at .5c, turned around and came back at .5c you would be younger than the people you left behind. This is due to your changing your frame of reference by accelerating, which means that you are in three different frames while those on Earth would have been in the same frame at all times. By accelerating you are leaving your initial (Earth's) inertial frame. When you decelerate, turn around, and head back home you are again changing your frame to another, which is why it is you who is the one that is younger. See General Relativity for a better explanation of these effects due to acceleration.
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