If you have got your
astronomical education from watching science fiction movies, you
probably think that travel between stars is a pretty fast experience.
You just jump into your interstellar spaceship like Han Solo's
Millennium Falcon, turn on the warp drive, and whoosh,
you jump through hyperspace arriving at a distant planet. Even more
recent movies (like the movie Interstellar) depict the same
type of rapid interstellar travel.
But this is fiction, not
science fact. There is no known evidence for anything like hyperspace
that can be used to enable rapid interstellar travel. Nor is there
solid evidence that you can instantaneously transport anything by
using a space warp. Scientists have not been able to transport even a
grain of sand from one place to another using a space warp.
It seems, regrettably,
that interstellar travel will be a very slow affair. According to
Einstein's special theory of relativity, the speed of light is the
fastest speed that can ever be reached. If you could somehow build a
spaceship capable of traveling at the speed of light, it would take
you about five years to get to the nearest star. But there are
engineering reasons for thinking that a spaceship will never be able
to accelerate to more than a small fraction of the speed of light.
This means that it would take many years to get from one star to
another.
I wonder: what if
Hollywood were to make a realistic movie about interstellar travel –
a movie that was as realistic as possible about the difficulties of
interstellar travel, and also the low chance of finding life in some
particular target of an interstellar mission? Let's imagine what such
a movie might be like.
You might think that such
a movie might involve a plot in which the starship crew was put into
suspended animation, so that astronauts slept through the
interstellar voyage of many years. But that wouldn't be particularly
realistic, since the prospects of people being put into artificial
hibernation for many years are pretty dim.
One realistic plot for an
interstellar voyage would involve astronauts who left Earth on an
interstellar voyage while they were young men in their twenties. By
the time the starship got to the distant star, the astronauts would
be so old that they would not have energy to do much exploring. That
might work as a comedy.
Another realistic
possibility would be to depict a multi-generation starship. This is
the most plausible scenario for interstellar travel. The ship would
be large enough for someone to live his entire life on the ship. The
original astronauts would have children while the ship was traveling
between the stars. By the time the ship finally arrived, the starship
would be manned not by the original astronauts, but by the children
of such astronauts – or perhaps the grandchildren or the
great-grandchildren of the original astronauts.
Clearly this movie would
need an ensemble cast, and it would need to be one of those movies
that spans many years. But what would happen when the spaceship
reached the distant planet revolving around another star? Would the
astronauts find a lush world teeming with life?
The current thought
exercise is to imagine a movie about interstellar travel that is as
“realistic as possible.” It seems that such a movie should
therefore not find the astronauts discovering life on the distant
planet the ship finally reached. The origin of life on our planet
still seems like quite the little miracle. We have no idea of how
self-replicating molecules could have formed from mere chemicals
billions of years ago. We have no idea of how the genetic code that
life depends on could have arisen through mere chance. The genetic
code is what programmers call a lookup table, and we have no known
cases of any lookup tables in nature that ever arose through chance
processes.
It seems, therefore, that
if we are making our interstellar travel movie as realistic as
possible, our astronauts should arrive at the planet revolving around
a distant star, and find nothing but a dead rock planet. This might
make a nice tragic ending, but it wouldn't have the dramatic oomph
that makes a good tragic ending. Perhaps our astronauts could perish
on the lifeless planet in a kind of “die in the desolate
wilderness” ending resembling the ending of the opera Manon
Lescaut.
A more hopeful ending
might involve terraforming, an engineering effort to make a rocky,
lifeless planet more like Earth. The astronauts on the starship
could launch an engineering effort to bring earthly life to the
lifeless planet. They might have to stay on their multi-generation
starship for many years, orbiting the planet, while lifeforms slowly
spread around the planet. Finally landing craft from the starship
could land on a planet that had grassy fields. This event might
occur hundreds of years after the multi-generation starship had
arrived in orbit around the distant planet.
So the movie might depict
a scenario like this:
Generation 1:
Leaves Earth in the multi-generation starship, and dies aboard the
starship.
Generations 2, 3, 4,
and 5: Lives their entire lives in interstellar space, never
seeing a planet.
Generation 6:
Lives to see the starship orbit the lifeless planet revolving around
another star.
Generations 6, 7, and
8: Lives aboard the starship, in orbit around the planet, waiting
for the terraforming process to finish.
Generation 9:
Finally gets to land on the planet, which by now has life and grassy
fields.
Although highly realistic,
such a movie would probably make much less money than absurdly
unrealistic sci-fi epics in which traveling to another star is as
easy as riding from one subway stop to another.
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