So You Want To Write A Hard Science Fiction Story With Space Travel Discussion

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11:52:43 PM Jan 11th 2014
The habitable planet restrictions seemed far too pessimistic. I've taken the liberty to rewrite it and add info about non-Earth like possibilities.
09:42:23 AM Dec 12th 2013

I believe there is an error in the FTL section that assumes that someone traveling at light-speed or higher will be able to "time travel", the correct term should be "time dilation" and that traveler will not be able to sent information to the stationary person in the past.

The issue happened with this two paragraphs:

"When the space ship passes by Earth, both Oberver A and Observer B synchronize their clocks at 5:00 PM. In Observer A's frame of reference, when his clock reads 7:00 PM, Observer B's clock will read 6:00 PM. However, in Observer B's frame of reference, when his clock reads 7:00 PM, Observer A's clock will read 6:00 PM."

Since both syncronized at 5 pm what will happen is:

Observer A time = 7:00 pm, then Observer B time 6:00 pm Observer A time = 9:00 pm, then Observer B time 7:00 pm.

Observer A clock is going faster relative to Observer B, not backwards as the sentence implies.

"Observer A could send the winning lottery numbers to Observer B's space ship at 6:20 PM on Oberver A's clock. With instantaneous communication, the numbers would arrive on board the space ship at 5:40 PM on Observer B's clock. If Observer B then sent the same numbers back to Observer A over the same subspace ansible, they'd arrive on Earth at 5:20 PM on Observer A's clock. Observer A would have the winning lottery numbers an hour before they were announced."

This actually will not happened because then B receives the information and send it back to A it will always be after the lottery, even if they use instantaneous communication.

The reason why is that each traveler is traveling is own timeline, the only difference is how fast they travel. For B the lottery event happened at 5:40 pm not 6:20 pm, and for A the event happened a 6:20 pm when they sent the information to B, which replies with the winning numbers after 6:20 pm.

In one sentence: there is no way that Observer A clock goes backwards.

They both moving forward at different speeds, and they will experience normally their own timelines, for every interaction between then, even using instantaneous communication, you must considered the difference in speed and the fact that both are independent.

09:10:37 AM Dec 13th 2013
edited by
Answer by Anthony Yeh to Why does time slow down as you approach the speed of light?
07:41:13 AM Feb 11th 2013
I think only issues affecting physics are really issues, of course Earth like planets without terraforming and green skined space babes/rubber forehead aliens are anthropocentric but they are less of an issue. Obviously one would avoid aliens all together alá Gundam or Planetes, but I don't see how non-anthopocentric views of alien beings and worlds are as unrealistic as faster than light travel. Also why are space pirates frowned upon, they don't generally mean pirates in space just looters, smugglers and bounty hunters like in star Wars or Cowboy Bebop which are admittedly not realistic but my point still stands. The Space Pirates page even lists examples were space is not an ocean which moves on to my next argument, although space is vastly different, being 3 dimensional and all, surely there are different levels of space is an ocean, what if a massive space cruiser does take into account the 3rd dimension yet still remain a maritime-esque space craft? What if it's a realistic spacecraft utilising naval uniforms and designations but not necessarily fight as they would on the ocean?
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