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Xall
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Now it's been some time since I've watched this series, but I remember Carl Sagan saying something that if you travel close to the speed of light for about 47 years (in your frame of reference) it would be enough that when you decelerate, you will have come to the end of time (as understood as the "ultimate fate of the universe, cooldown); however, don't hold me on that, I might be mistaken as to the details (it was in episode 8, I think, when he was in Italy filming). I'm just curious how factual (supported by some serious calculations) that is, or was it just pulled out of the hat, for hyperbole's sake.

Otherwise, what thoughts have you of Cosmos in general and Carl Sagan in particular?

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Actually, it was my memory playing tricks on me; around the 33rd-34th minutes he says that such travels close to the speed of light "would permit us to circumnavigate the known universe in 56 years, ship-time; we would return tens of billions of years in the far future, with the earth a charred (?) and the sun dead".

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Obviously dated - since the current light barrier is approximately 13 billion light years off. 56 light years wouldn't get us out of our own galaxy. Or across it.

What do you mean? It could. He is talking about the time that passes on the ship. If you could travel significantly close to the speed of light, time on the ship would slow down enough so that only 56 years would pass for the travelers. We can use the relativity equation to calculate exactly how fast we would have to go in order to cover 13 billion light years in 56 years, ship time. Obviously for everyone else not traveling at close to speed of light 13 billion years would pass. It doesn't even have to be 56 years. The closer you get to the speed of light the slower time goes for you. Theoretically if you get close enough to the speed of light you can cover that distance in a second. For the traveler. And at the speed of light it wouldn't take any time at all.

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Sagan is a really good communicator ( at least during Cosmos anyway) of ideas, and his really enthusiastic which obviously helps the audience become enthusiastic as well. It is hard not to watch the series and become interested in whatever he is talking about.

Also the series strikes a good balance between subject matter which is important, without getting too far into technical details which would confuse the layman. It is a really good overview of the field of astronomy.

As for the time about time dilation and general relativity, well I really think it would have been better without that stuff. I am a firm believer that modern physics needs to purge those sorts of bad interpretations as soon as possible.

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As for the time about time dilation and general relativity, well I really think it would have been better without that stuff. I am a firm believer that modern physics needs to purge those sorts of bad interpretations as soon as possible.

Thats highly improbable. Time dilation has been tested and observed in hundreds of thousands of expirements. They even have obsevational evidence in experiments done at normal speeds such as on an airplane. Measured with a atomic clock the time dilation was insignificant, however it was still there. Time for a moving object moved slower then for stationary object. What exactly is bad about them that needs to be purdged? Why do you feel that they are bad theories?

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Thats highly improbable. Time dilation has been tested and observed in hundreds of thousands of expirements. They even have obsevational evidence in experiments done at normal speeds such as on an airplane. Measured with a atomic clock the time dilation was insignificant, however it was still there. Time for a moving object moved slower then for stationary object. What exactly is bad about them that needs to be purdged? Why do you feel that they are bad theories?

Incorrect. What has been tested and observed is that there is something taking place which which is taken to be time dilation (for whatever various reasons). But I have seen nothing that proves definitely that A) time exists in the sense claimed and that B) It must dilate for the events described in said experiments to be possible. Though I am aware that is commonly believed that both must be true according to the results of these experiments.

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Incorrect. What has been tested and observed is that there is something taking place which which is taken to be time dilation (for whatever various reasons). But I have seen nothing that proves definitely that A) time exists in the sense claimed and that B) It must dilate for the events described in said experiments to be possible. Though I am aware that is commonly believed that both must be true according to the results of these experiments.

Denying that experimental evidence is not evidence is not an valid argument, it can be done for anything.

Electromegantisim does not exist. What has been observed is that there is some attraction taking place which is taken to be electromagnetism(for whatever various reasons). But I have seen nothing that proves definitely that A) electromegantism exists in the sense claimed and that It must attract for the events described in said experiments to be possible.

Or Dogs do not exist. What has been observed is that there is some animal that is taken to be a dog(for whatever various reasons). But I have seen nothing that proves definitely that A) Dogs exist in the sense claimed and that it must bark for the events described in the said experiments to be possible.

I am assuming you are not familiar with the experiments of special relativity, and all the practical applications we have of it in todays technology.

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Okay Prometheus. "Time" is a measurement. It is, ultimately, a measurement of distance via the use of light (so the time it takes light to bounce between two mirrors may be deemed to be one picosecond (that'd be about .01 inches or so as the distance between mirrors). If I travel at a velocity that is non-zero in another frame of reference, the light travels at the same speed in my frame of reference and the frame of reference outside in which I am moving. This means that the light travels at the same speed between the mirrors, but is now having to take what is essentially a diagonal path instead of a perpendicular path between the two mirrors in my friends frame of reference. This means that my watch is going slower in his frame of reference than it was when I was stationary.

Problem is, everything is about light. After all, photons are the bearer of the EM force, and the EM force holds together all atoms, and interacts with all the quarks in the nucleus of atoms, etc. And so ALL time (i.e. ticks of the clock between events) on the moving object is just a teensy bit slower than it is as the measured by the stationary observer.

The reason is because time isn't a thing, it is measurement, and the objective facts of reality make that measurement depend on your velocity with respect to everyone else, and indeed on your acceleration. This is the same way "space" can bend; space is a generalized measurement between all pairs of points at a specific moment in time. But of course time already varies with velocity, and as it turns out for similar reasons (again, a result of light moving at the same speed no matter what), so does length. Really, a "straight" line in space is the shortest distance you can move between two points, but since you can't go faster than light, and light is effected by gravity, you ultimately have space be curved. It doesn't mean anything is actually curved. It means that your measurements of distances are going to make your "space" defined by all the distances between all the points, will have the shortest distance between two points be a curve when viewed from a higher-dimensional cartesian space.

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