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Author | Topic: The Twins Paradox and the speed of light | |||||||||||||||||||||||
MasFina Junior Member (Idle past 5146 days) Posts: 1 From: East Coast Joined: |
After lurking for too long I wanted to thank all the participents in this thread for convincing me to sign up. This discussion has been informative and useful. Thanks again.
And just to make sure I'm on topic: Good point!
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cavediver Member (Idle past 3644 days) Posts: 4129 From: UK Joined: |
Cool Welcome aboard!
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boysherpa Junior Member (Idle past 5372 days) Posts: 19 From: Lomita, CA Joined: |
Thanks for the reply,
Read that post, nothing of the sort there. You may be confusing algebra with explanation. I have quite a firm grip on these calculations. I am, actually, quite familiar with most things scientific. That is not my point. Let me list my observations, so that some of you could help. 1. Consider 3-space (x,y,z). A change in 3-space has two characteristics we will agree upon. The first is innocuous - a function f(x,y,z) describing a change in coordinates in 3-space is continuous. In other words, no magic teleportation. Second, and this is important, the function f(x,y,z), describing change in coordinates, instantiates time or necessitates the creation of time.2. Examples of allowed changes in 3-space include: motion resulting in change in coordinate in a positive or negative direction relative starting point, a return to any previous coordinate desired, a wide range of velocities and accelarations decribing changes in coordinates. 4 (no, 3 sir). Consider the dimension of time. A change in this dimension is in no way similar to a change in 3-space. There is no instantiation of time with a change of time, if you follow my meaning. One may not move arbitrarily amongst time coordinates. There is no concept of time velocity or acceleration. In fact, there seems to be only one time coordinate, that being "present". 4. Finally, time has only one direction, an effect which we call causality, and this is firmly rooted in the space-time diagrams folks have interspersed among the posts in this thread. (It is therefore an inherent assumption in the calculations as well.) There is no corresponding restriction in 3-space. So, I am confused about how time is considered on equal footing with 3-space. I fully understand the equations. Heck, I work with such mathematics more than most of you do. But I understand that models do not equal reality, and often do not explain reality. It could be that if we accept all these caveats, that we may model space-time as including a psuedo-dimension called time. In this case, time as a dimension would merely be a convenient mathematical model. Is that what SR is saying?
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cavediver Member (Idle past 3644 days) Posts: 4129 From: UK Joined: |
I fully understand the equations. Heck, I work with such mathematics more than most of you do. Really? What do you do? It's always great to find direct applications of complex equations in the workplace, rather than just in academia. I used to work in derivatives - actually, I do feeel a bit guilty at the moment, as one of my main areas of expertise is calculating a bank's exposure to complex credit backed securities... Perhaps if I hadn't left the sector all those years ago
Consider 3-space (x,y,z) Ok, is this simple Euclidean space, with the basic Pythagorean metric?
a function f(x,y,z) describing a change in coordinates in 3-space is continuous. I'm unsure as to how f() represents a change in coordinates - is f a vector, a more general tensor, or is it just a scalar as you have written? Let's say we go from the triple (x,y,z) to (x+dx, y+dy, z+dz) - how do we encode this change in f? And I'm not sure what you mean by f(x,y,z) necessiating time - do you mean we should really write f(x,y,z,t)?
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mogplayer101 Junior Member (Idle past 5420 days) Posts: 4 From: Canada Joined: |
Ok, here is the straight goods of an easy to understand explanation of how time dilation due to velocity works. Ok, now picture if you would (as in this picture) a spaceship that has two mirrors on either side of the cargo bay, and for arguments sake the mirrors are one meter apart, so the photon of light has to move two meters to get there and back. Now if the shuttle is traveling at half the speed of light, the shuttle will move one meter sideways as the photon is moving between mirrors, now the light is no longer traveling in a straight line to an observer off of the ship, but in a triangular shaped line, therefore the photon is now traveling a longer distance, and will take a longer time outside of the ship to complete its journey. Check out this page.
http://musr.physics.ubc.ca/~jess/p200/str/str9.html -Help at all?
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Kev The Thiest Evolutioni Junior Member (Idle past 5410 days) Posts: 4 From: Ipswich, Suffolk, England Joined: |
I presume tthe reason is that velocity equals distance devided by time. Therefore time equals velocity times distance.
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Percy Member Posts: 22392 From: New Hampshire Joined: Member Rating: 5.3 |
Hi Key,
Below each message are a row of buttons. One of those buttons is labeled "Reply" and is for replying to that specific message. When replying to a specific message it is better to use that button, because then links to and from the messages are also created. About this:
I presume tthe reason is that velocity equals distance devided by time. Therefore time equals velocity times distance. That's an interesting universe you live in, but here in the real world we find that t=d/v. --Percy
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lyx2no Member (Idle past 4716 days) Posts: 1277 From: A vast, undifferentiated plane. Joined: |
velocity times distance. The E=mc2 of lawn mowing theory. Ridicule is the only weapon which can be used against unintelligible propositions. Ideas must be distinct before reason can act upon them. Thomas Jefferson
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WaveDancer Member (Idle past 5404 days) Posts: 37 From: NSW Australia Joined: |
"Scientists have found that, when twins are orbiting a massive object, time dilation can cause the accelerated twin to be older if that twin is moving slower than the other twin; in this case, velocity is the deciding factor of age, and the twin with the greater velocity is younger."
http://www.physorg.com/news163738003.html I guess this just goes to prove how difficult facts in cosmology are to pin down and how ambiguous the whole concept is.
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onifre Member (Idle past 2951 days) Posts: 4854 From: Dark Side of the Moon Joined: |
I guess this just goes to prove how difficult facts in cosmology are to pin down and how ambiguous the whole concept is.
There is one minor problem with this statement, the "twin paradox" wasn't actually a fact.
Sourcequote: The key point is "acceleration". Further in the link you'll find the Twin Paradox without acceleration as well. - Oni Petition to Bailout Comedy The Laugh Factory is imploring Congress to immediately fund what owner Jamie Masada calls an "Economic Cheer-Up." If Congress fails to act quickly, the Laugh Factory comedians are planning to march to Washington and plea to President Obama.
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WaveDancer Member (Idle past 5404 days) Posts: 37 From: NSW Australia Joined: |
Hmmmm I always thought it was a fact. One twin gets on a spaceship which goes at the speed of light the other one stays home. When the spaceship returns the twin that stayed at home is older. FACT! At least I thought it was. Owell I still have alot to learn then.
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Percy Member Posts: 22392 From: New Hampshire Joined: Member Rating: 5.3 |
I'm not sure what Onifre is getting at, but the twin paradox is a fact. It not only has a very strong theoretical foundation, it's been verified experimentally with atomic clocks sent up in airplanes and into space.
--Percy
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cavediver Member (Idle past 3644 days) Posts: 4129 From: UK Joined: |
but the twin paradox is a fact. Perhaps the confusion is that there is no paradox. The effect is real but there is nothing paradoxial about it...
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onifre Member (Idle past 2951 days) Posts: 4854 From: Dark Side of the Moon Joined: |
Perhaps the confusion is that there is no paradox. The effect is real but there is nothing paradoxial about it...
Thanks, cavediver. That's what I meant. I guess I should have expressed that better. - Oni Petition to Bailout Comedy The Laugh Factory is imploring Congress to immediately fund what owner Jamie Masada calls an "Economic Cheer-Up." If Congress fails to act quickly, the Laugh Factory comedians are planning to march to Washington and plea to President Obama.
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Trae Member (Idle past 4307 days) Posts: 442 From: Fremont, CA, USA Joined: |
Twin Paradox Revisited Sans Rocket-ships.
SciFi's Assumption: Mystical magical aliens have some sort of FTL or FTL-like travel. Specifically some means from getting from interstellar point A to B 'instantaneously'. In SciFi this 'solves the problem' for SciFi authors and audiences, but would it actually work? Acceleration isn't limited to spaceships and visitation takes time, so wouldn't the twins paradox still be in play since those objects (earth and the alien home-world) are under the influence of different bodies in different gravitational fields? While I presume this comes into play within our own galaxy, I think it might be easier to use an example of aliens from a different galaxies. If aliens from galaxy A (a galaxy not in our local group) somehow managed to arrive on Earth instantaneously, and if galaxy A and galaxy B are hurdling away from each other, it seems to me that time would pass at a different rate on the alien planet than on Earth.
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