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Interstellar travel isn't possible
We need to make Earth work for us, not plan on leaving
Although difficult, traveling to other planets in our solar system is possible. For example, the energy required to transport a single person to Mars on the SpaceX Starship is (very roughly) 10x the amount of electricity that person might use in a year of a typical western living. That’s a lot if everyone were to start commuting there, but doable for a small number of crazy astronauts. There are interesting unsolved problems, like how to shield us from radiation if we were on one of Saturn’s moons, or how to keep people from going crazy after months or years in a small spacecraft, but it is doable. It’s mostly about energy - if you make a big enough rocket, you can do it.
But going to other stars is a whole different matter, because the distances involved are tremendously greater, meaning that we need to accelerate a spaceship to relativistic speeds - close to the speed of light - to shorten the trip to take only a few years. The good news is that because of relativity, a trip of a tremendous distance (even across the galaxy) can be shortened to a few years - if you have enough energy and don’t mind that you can never return (because due to time dilation your friends and family back on earth will be long since dead when you return to share your findings). But the bad news is that the amount of energy we are talking about is unfathomably large, even for a very small spaceship.
Consider the very closest star to earth - Proxima Centauri. It is 4.4 light years away, which is about 100,000 times farther away than Mars. To send a spaceship of the size of the SpaceX Starship there in two years would require… wait for it… around 200 years of our current global energy production. In different units, it would require around 1,700 times the energy contained in all the nuclear weapons in existence. And that’s to make one trip to the closest star. Going farther - lets say across our galaxy - would require 8.5 Million years of energy production to fill up the gas tanks.
And if that wasn’t bad enough, the rocket engine needed would be made with technology we presently have no idea how to make. The best idea is a matter-antimatter drive (which to reach Proxima Centauri would require an amount of propellant antimatter close to the mass of the existing chemical engines for the Starship), but we have absolutely no idea how to use energy to efficiently change regular matter into antimatter.
The chances of finding interesting forms of life on any one particular exoplanet are very small. With each trip taking a couple years and no alien signals yet arriving to tell us which direction to search, what sort of astronaut explorers would sign up? Even with some exotic suspended animation ability (which we also presently have no idea how to build) that might reduce the travel/wakeup/explore/try again time to a few months, being an interstellar explorer would be a losing bet. One human in one lifetime could visit maybe 100 other stars, and almost certainly find nothing.
And… the sci-fi idea of having our AIs make the trip for us with frozen embryos and expand civilization to all over the galaxy… that’s not going to happen either. Even if the AIs weighed nearly nothing, the mass of the antimatter propellant would still be huge and the energy requirements similar. The only power source capable of propelling us for interstellar travel would be the sun itself, in some way we cannot imagine. Perhaps the AIs themselves can help us think up a way to make wormholes or something, but the laws of physics are what they are. I wouldn’t bet on it.
It seems possible that the answer to the Fermi Paradox may be that too much energy is required to go exploring, even for technologically advanced beings. It may make more sense to make the moon into computronium and use it to simulate new worlds where new forms of life can evolve that we can then visit with. If inner space is enormously more accessible and interesting than outer space, why leave home?
And if we can spread to other planets but not out of our own solar system, is that really much better than us just being on earth? When the sun eventually burns out we’d all still be screwed. Plus, has anyone stopped to consider (or watched Expanse) the sort of fighting that might happen between humans on other planets from each other? Reducing the risk of extinction from a meteor strike might not be worth the risk of a Terran-Mars war. Let’s focus on getting along here on Earth, instead. Or, as Robert Frost put it - “Earth’s the right place for love: I don’t know where it's likely to go better.”
P.S. Yes of course I used GPT to help me check the numbers. And the header picture is the cover of a wonderful book I read and re-read as a stars-longing kid.