There are five things that make interstellar space travel nearly impossible.
- Earth-like planets are very rare. We are unlikely to encounter worlds that would be worth traveling to.
- Space is full of deadly radiation that is difficult to shield against. This becomes exponentially worse at high fractions of the speed of light. At those speeds, even simple interstellar dust particles become explosive missiles that could destroy a spacecraft.
- The distances are so vast that interstellar travel becomes extremely difficult.
- The energy requirements are enormous. We simply don't have the resources to accelerate a spaceship to anything approaching relativistic speeds.
- The cost is enormous. It could take the resources of an entire planet to create an interstellar ship.
If we wanted to send a probe to a nearby star, we would have to send a computer AI with heavy shielding at a modest speed and be willing to wait 50,000 years for the ship to arrive. However, if we did this in the near future, it could be self-defeating because future generations will likely be able to create faster ships that could arrive in a fraction of the time. Being able to create a ship twice as fast a thousand years from now would make the first ship we send pointless.
I feel the same way about sending humans to Mars. It is such a perilous and expensive journey, just to go to a big, dead rock with about a third of Earth's gravity. We will never have a viable colony on Mars because the planet is simply too hostile. It is far too cold, has significant radiation hazards, and its chemical makeup is not conducive to human life.
It seems possible, if not likely, that life could have existed on Mars billions of years ago. Finding that out might be interesting, but we don't have to send people to Mars to study the planet. We can send unmanned probes much more cost-effectively.
The future of humanity does not involve expanding out to the stars, at least not in the next few thousand years. Although we could create orbital habitats, these will never be cost-effective. The real future of humanity involves making the best use of the resources on planet Earth. We need to manage the planet well while slowing population growth, which creates more competition and conflict over natural resources. The vast fortunes that we spend on space exploration could be better spent managing our existence on Earth.
We live on Spaceship Earth, which is traveling around the galaxy at 140 miles per second. Not all the stars in the Milky Way travel at the same speed, so in 1.29 million years, another star will come within 0.14 light-years of our star. That is close enough to send a space probe. We just have to be patient. 😀
