Tens of billions of potentially habitable, Earth-size planets in our galaxy

Re:Tens of billions of potentially habitable, Earth-size pla... by thangalin on Wednesday November 06, 2013 @01:54PM (#6684598)

I was assuming conventional propulsion at 95% c. An Alcubierre warp field would be ideal, assuming the problems can be overcome:

http://en.wikipedia.org/wiki/Alcubierre_drive#Difficulties

http://arxiv.org/abs/1001.4960

http://arxiv.org/abs/1202.5708

I'd enjoy seeing your calculation of the number of years that would have passed on Earth for a round-trip of 100 light-years out.

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Re:Tens of billions of potentially habitable, Earth-size pla... by gliese1337 on Wednesday November 06, 2013 @02:05PM (#6684683)

You've seen it. 210.52 years. The passengers on the ship should only experience 65.7 years- (210.52)sqrt(1-.95^2). Hence the famous twin paradox- the twin who goes on a relativistic trip comes back younger than the one who stayed behind. What you calculated was how much time would pass on Earth for a trip that took 100 years and 100 light-years from the perspective of the people on the ship, which is not generally what people mean when they say that a star is 100ly away.

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Re:Tens of billions of potentially habitable, Earth-size pla... by thangalin on Wednesday November 06, 2013 @03:50PM (#6685417)

I found the source of my confusion.

The post I replied to stated, "I don't know how much time would have passed on Earth though." You stated I calculated "how much time would pass on Earth."

The OP was wondering, "if a person on a ship visited a star 100ly away, how much time would have passed on Earth when they returned?"

However, the OP was wondering about time frames in terms of a warp drive, rather than a conventional almost-light-speed drive. Take my upvotes. :-)

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