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Forum » SpaceEngine » Science and Astronomy Discussions » Science and Astronomy Questions
Science and Astronomy Questions
apenpaapDate: Tuesday, 25.09.2012, 18:22 | Message # 61
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I think the formula goes something like the square root of (your speed's square divided by light speed squared), and then I think you have to divide that by something. You can calculate the speed you seem to be travelling from your own perspective like that at a certain speed when seen from Earth. (From Earth, instead of you going 17 times light speed, you would be going near-light speed and instead getting much more massive, on which the energy you spent is wasted)




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neutronium76Date: Tuesday, 25.09.2012, 18:26 | Message # 62
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Quote (Aerospacefag)
The one that is not from the Hollywood. You can't fly faster then speed of light when you're slower then a speed of light


Aerospacefag read my post again. I didn't suggest suggest that they were travelling faster than light. If you check at the middle of the post ''relative'' suggests that they were travelling at close to light speed and that is why they experienced time as 2 years, 4 months, 18 days, 36 (ship) hours. (=2.38 years) which is because of time dilation/compression. People on earth would still percieve that they travelled for about 35 Ly for the outbound journey (actually more if you take into account the acceleratioon phase).

Quote (Aerospacefag)
The reason is, that this is their observable speed (from the point of destination), which is 34,5 LY away. They might seem to be traveling faster than speed of light, but this isn't true for all observers. From the Earth it most likely would be about 69 years, and for the ship itself it's 34,5 years


I don't understand what you are trying to say.





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AerospacefagDate: Tuesday, 25.09.2012, 18:50 | Message # 63
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I repeat again then: you can't cover 35 LY in 2,5 years of inertial flight if you're traveling slower then a speed of light. By the way, according to Eisenstein, you can't travel faster then light.

Quote (neutronium76)
time dilation/compression

Quote (neutronium76)
I don't understand what you are trying to say.

Here is your problem. The nature of "compression of time" seems to be completely different from what you're imagining.

apenpaap, it's called Lorentz transformation.

 
HarbingerDawnDate: Tuesday, 25.09.2012, 19:07 | Message # 64
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Aerospacefag, the 2.38 years was the time experienced by the crew due to time dilation, not the actual time that an external observer would record the ship to travel in. The actual time the ship took to travel the distance as seen by an external observer would have been around 35 years.

I think you are misunderstanding what neutronium76 has said.





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neutronium76Date: Tuesday, 25.09.2012, 19:08 | Message # 65
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Quote (Aerospacefag)
I repeat again then: you can't cover 35 LY in 2,5 years of inertial flight if you're traveling slower then a speed of light. By the way, according to Eisenstein, you can't travel faster then light


And I repeat again: you can cover 35LY in 2.5 years of internal flight time if you are travelling slower than speed of light I am refering to the time the crue experienced and not the time an external observer experienced. You just have to travel 0,0023743933697326 slower than 1c ccording to this guy: http://www.prometheus-movie.com/community/forums/topic/7753 and scroll to the midle of the post. All I was asking was the math behind this result. dry





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Edited by neutronium76 - Tuesday, 25.09.2012, 19:13
 
AerospacefagDate: Tuesday, 25.09.2012, 19:13 | Message # 66
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The actual time the ship took to travel the distance as seen by an external observer would have been around 35 years.

But how can you measure that? I think that the duration depends on position of observer. If the light from starting location arrives to you in 35 years, and the ship arrives in 37 years, then the duration of flight for this observation point is 2 years, right?
 
HarbingerDawnDate: Tuesday, 25.09.2012, 19:42 | Message # 67
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Quote (Aerospacefag)
If the light from starting location arrives to you in 35 years, and the ship arrives in 37 years, then the duration of flight for this observation point is 2 years, right?

Yes, it would appear that way, that is the cause of real observed apparent superluminal motion in the universe. But if they knew the distance to the object's point of origin, then they could easily add the light travel time into their observations, so 2 years + 35 ly/c = 37 years. So they would observe it to be 37 years, even if the appearance of the observation looks like 2 years at first.





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AerospacefagDate: Tuesday, 25.09.2012, 19:50 | Message # 68
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Quote (HarbingerDawn)
So they would observe it to be 37 years

However, they would also observe that clocks in the ship counted 37 years of flight time - as more direct approach.
That's what I was talking about before. happy


Edited by Aerospacefag - Tuesday, 25.09.2012, 19:51
 
HarbingerDawnDate: Tuesday, 25.09.2012, 20:05 | Message # 69
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Quote (Aerospacefag)
However, they would also observe that clocks in the ship counted 37 years of flight time - as more direct approach.

No, the clocks in the ship would not count 37 years of flight time, because the clocks would tick more slowly close to the speed of light. Here are some formulae: http://en.wikipedia.org/wiki/Time_dilation#Overview_of_formulae

Time dilation really does affect clocks moving at greater speeds, we have actually measured this, it must be taken into account in order for navigation satellites, like GPS and GLONASS (which also have to account for time dilation due to a different gravitational field).





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apenpaapDate: Tuesday, 25.09.2012, 20:10 | Message # 70
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From the point of view of the ship and everything in it, including the clocks, the journey really would only take two years. In that sense, from their own point of view it would be like going 17 times the speed of light. Of course, they wouldn't go faster than light seen from outside observers, and they're arrive 37 years later.




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AerospacefagDate: Tuesday, 25.09.2012, 20:20 | Message # 71
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Quote (HarbingerDawn)
No, the clocks in the ship would not count 37 years of flight time, because the clocks would tick more slowly close to the speed of light.

Does that also mean that Universe will move with superluminal speed in relation to the spaceship...
....
...
......
Well..
On second thought, I forgot about http://en.wikipedia.org/wiki/Length_contraction phenomena.
....
.......
...
So, basically, original poster forgot that too. I.e., Lorentz transformation again.



Edited by Aerospacefag - Tuesday, 25.09.2012, 20:23
 
WatsisnameDate: Wednesday, 26.09.2012, 05:06 | Message # 72
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Quote (Aerospacefag)
Does that also mean that Universe will move with superluminal speed in relation to the spaceship...


In a way, yes, though the view will look very strange. Everything will appear compressed in the direction of travel, with objects in front of you being brightened and blueshifted, while objects behind are dimmed and redshifted. Some visualizations of these relativistic effects can be seen here and here.

Apenpaap and HarbingerDawn are correct on the matter of time dilation, and it's all a result of Special Relativity and what is called the Lorentz Transformation. If you consider an object in motion relative to some frame of reference, like the space ship as seen from Earth, then relationship of time intervals measured between the two is given by

where t is the time interval measured on the ship, t0 is the interval measured in the rest frame, v is the ship's velocity relative to the rest frame, and c is the speed of light.

For "everyday" velocities like walking, driving, and flying in airplanes, the term v2/c2 is extremely small and the time dilation effect is not apparent without incredibly accurate measurements. (It can be measured with atomic clocks, and actually becomes very important for things like the Global Positioning System, as Harbinger noted. If relativistic effects were ignored then the GPS system would incur an accumulated error and be rendered useless in a matter of weeks!)

But as the velocity approaches the speed of light, the relativistic effects become exponentially more noticeable.







Edited by Watsisname - Wednesday, 26.09.2012, 05:07
 
neutronium76Date: Wednesday, 10.10.2012, 10:31 | Message # 73
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For dummies like me, I found this series of documentaries on youtube veery informative and well explained :
http://www.youtube.com/watch?v....ynext=1 smile





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smjjamesDate: Wednesday, 10.10.2012, 20:08 | Message # 74
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Is it true that the word 'Black Hole' means something in Russian that is not said in polite society? I read in a book that mentioned about that, however it was a science fiction book though, so I have no idea if that is actually true or not.

Personally, I think it was a made up thing (or maybe exaggerated), but yeah, it's just something that I'm wondering is even true







Edited by smjjames - Wednesday, 10.10.2012, 20:12
 
SpaceEngineerDate: Wednesday, 10.10.2012, 20:34 | Message # 75
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No, in Russian "black hole" means the same as in English, not more than black colored hole. I believe the term is coming from English via direct translation. Some persons may call anus "black hole", but I guess in English it is possible too smile




 
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