Philip Rosedale, who actually started out studying Physics in college, has a fun post that throws water on the popular notion (at least among technophiles) that we'll soon be traveling to the stars. Philip says the math doesn't add up:
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.
I thought solar sails might solve the energy problem, but that's way above my pay grade. [SEE UPDATE BELOW FROM PHILIP]*
He goes on to suggest this is the answer to Fermi's Paradox, i.e. if there's thousands of aliens civilizations out there, where the fuck are they? With his math, their absence is actually common sense:
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.
One surprising conclusion is something he's mentioned to me before for the first book, but he says it again here — virtual worlds could supplant our yearning to visit the stars, if they were made on massive scale:
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?
* UPDATE, 10:22PM: Just got this from Philip about solar sails as a possible solution: "They remove the weight of propellant, but the power of the laser gets lower as you get father from earth, so you need more and more power to get something there. But yeah I should analyze that case too. But I think the laser power to launch a good sized ship with a solar sail would be many gigawatts. Probably would ignite the atmosphere, etc." And no, you can't just sail from the solar rays themselves: "That works too but at the lumosity of the sun, only incredibly small things could be sent." So… send an armada of sail-powered nano-bots?