On Saturday 03 May 2008 20:06, Ben Crowell wrote:
>>> 1. imagined technology
>>> example: the FTL in Contact
>>>
>>> 2. imagined progress in scientific knowledge:
>>> example: bacteria are discovered on Mars
>>>
>>> 3. imagined scientific theories
>>> example: a working theory of quantum gravity
>>>
>>> 4. scientific mistakes
>>> example: the FTL in Star Wars
>>>
>>> What distinguishes category 4 from the others is that it violates the
>>> correspondence principle, which states that a new scientific theory
has
>>> to be consistent with older ones, within the realm of applicability of
>>> the older ones, because otherwise the new theory would be contradicted
>>> by the experiments that the older ones were based on.
>>
>> What's the difference between the two FTL technologies you mention?
>
> The FTL in Star Wars violates relativity in blatant and obvious ways,
> like getting the energy scales wrong.
We don't know that relativity applies for FTL speeds.
> Heck, even the STL in Star Wars
> violates classical mechanics, and violates it within the realm of
> applicability of classical mechanics. E.g., we have spaceships
> traveling across solar systems in a matter of hours, which means they're
> going at speeds of at least ~10^7 m/s. This is small enough compared to
> c that relativistic effects are small, and we're within the domain of
> applicability of classical mechanics (with an error of <~1%).
The same goes for Star Trek, but there's never been a story about
accumulated time differences. That's an obvious idea for a plot if the
writers are serious about SF.
> Classical
> mechanics says that at this speed, a spaceship with a mass of 10^7 kg
> has an energy of about 10^21 J, which is about the same as the total
> megatonnage of the world's nuclear arsenal. That means that every
> decent-sized spaceship in the movie is an awesome weapon of mass
> destruction, if you simply crash it into a planet. You don't
> need a Death Star. The reason the energy scales are totally wrong is
> that George Lucas planned the battle scenes of the movie by watching
> old WWII footage.
>
And that he wasn't trying to get things right.
> > It's often impossible to determine whether a certain technology is
> possible
> > or plausible, because we most ofter don't get any details at all.
> > Technobabble doesn't count in my book!
>
> I guess it depends on what you mean by "possible." My definition of
> hard SF would be that it has to be possible in the sense that it
> doesn't violate those laws of physics that have already been thoroughly
> verified within their realm of applicability.
Yes, that's just about what I meant.
> The FTL in Contact is
> "possible" in this sense. Of course just because a certain technology
> doesn't violate the laws of physics, that doesn't mean that it's
> practical, plausible, likely, ...
No, but it's not immediately offensive to out intellects.
//Niels
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