[ExI] The Universe is big - really, really BIG.

[BillK]

On Tue, 11 Jul 2023 at 18:36, Adrian Tymes via extropy-chat
<extropy-chat at lists.extropy.org> wrote:
>
> Most interstellar ambitions are flat-out impossible without some form of faster than light drive.
> What few theoretically possible ways we know of to achieve this, can not be developed without the sort of mature outer space industry that seems highly unlikely to happen without associated human colonization of non-Earth bodies in our solar system.
>
> Therefore, to reach across the stars we must first seriously begin to colonize the solar system.
> _______________________________________________


I asked the new Claude 2 LLM (that was just released today) about FTL travel.
It was not very hopeful.
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What are the problems facing travel at near light speed?

There are a few key challenges faced by travel at near light speed:

Energy requirements: As mentioned before, it takes an enormous amount
of energy to accelerate to a significant fraction of light speed due
to relativistic mass increase. Just getting a spacecraft to 90% the
speed of light would require energy outputs rivaling a star.
Conventional rockets won't cut it. New propulsion technology would be
needed.

Time dilation: A traveler moving at 90% the speed of light would
experience time dilated by a factor of about 2.3 compared to a
stationary observer. This means that a 10 year journey for the
traveler would mean over 20 years passed on Earth. Long journeys would
find the traveler returning to an aged earth.

Communication delays: Signals sent between a near-lightspeed traveler
and Earth would experience huge delays. A message sent from a ship
traveling at 99% light speed would take over 5 years to reach those on
Earth. Normal communication would be impossible.

Navigation hazards: Even small particles like dust grains would carry
enormous kinetic energy from a near-lightspeed ship's perspective.
Impacts with these particles would be seriously damaging. Detection
and avoidance of hazards would be critical.

Deadly radiation: Collisions with particles would also bathe the ship
in radiation. Shielding requirements would be extreme, adding more
mass and energy needs. The hazard increases as speed increases.

Required precision: Near light speed travel would require extremely
precise trajectory control and navigation. Even tiny errors in course
or speed could result in missing the destination completely.
Autonomous systems or AI may be needed.

While these challenges are daunting, some physicists think that
technology could one day make near-lightspeed travel possible. But it
would require major innovations in propulsion, materials, navigation
and more. Significant obstacles remain before we're zipping around at
99% the cosmic speed limit.
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What are the problems facing travel exceeding light speed?

Exceeding the speed of light poses both practical and fundamental
physics problems:

Infinite energy: As mentioned before, accelerating an object with mass
to speeds faster than light would require infinite energy due to
relativistic mass increasing to infinity at lightspeed. So some new
physics or loophole would be needed.

Violating causality: Faster than light travel would violate cause and
effect and allow time travel to the past according to relativity. Most
physicists think causality should remain inviolate. So the
implications of FTL travel for timelines would need to be resolved.

Time travel complexes: If FTL allows time travel, it also introduces
logical problems like the grandfather paradox where someone goes back
to change their own timeline. The implications and paradoxes of time
travel are complex.

Exotic matter: Many hypothetical FTL concepts like wormholes or warp
drives require large amounts of "exotic" matter with negative
mass/energy. But this exotic matter has not been shown to exist. It
may not be possible to obtain or produce.

Unknown side effects: The full effects of FTL travel are hard to
predict. But it's likely that traveling faster than causality would
have profound and possibly dangerous side effects. Think unstable
wormholes, time loops, quantum disruption, etc.

Lack of evidence: So far, there is no solid experimental evidence that
FTL travel is even possible. Many concepts are entirely theoretical.
So viable mechanisms for exceeding light speed remain speculative.

While FTL could offer tantalizing possibilities, it comes with
practical barriers and would require overturning much of known
physics. Most experts think exceeding light speed is highly improbable
given our current scientific knowledge. The problems and paradoxes may
simply be insurmountable. But the quest continues.
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BillK