[mrep]

I was mostly making a point that grandiose statements can be rebutted by similar (in this case, changing 3 words) grandiose statements.

To answer your question though, the main problem with space travel isn't physics (assuming you are ok with long travel times), it's economics. We have sent astronauts to the moon and probes all across the solar system. The main reason we don't do more though is because of how expensive it is. However, a thousand years of 2% growth (not a given but again, grandiose) means we would have 400 million times more money to possibly spend on space travel. A NASA budget 400 million times larger could certainly build and send a spaceship 4 light years to alpha centauri.

Now how long will we sustain exponential growth? Well that's anyones guess but I don't see us becoming resource constrained for a long long time. The sun produces 10^13 more energy than the world used in 2013 according to [0] and we have plenty of resources in the solar system to build with (and we can recycle more).

[0]: https://www.quora.com/How-much-energy-does-the-sun-produce-p...

[jcranmer]

> To answer your question though, the main problem with space travel isn't physics (assuming you are ok with long travel times), it's economics.

I'd argue it's biology, not physics. Sending a rock to another star is easy. Sending a rock that can send back data is probably possible with our technology, but it's unlikely it would retain data transmission capabilities long enough to actually report back from another star. Sending a bunch of humans and keeping them alive the entire journey? It's not clear we can do that for a round trip to Mars, let alone an interstellar journey.

[mrep]

The 2 biggest health problems that I am aware of with spaceflight are due to weightlessness and radiation. However, both can be probably be solved with enough money (make the spaceship a rotating one with artificial gravity and add more shielding). There might be others but I am pretty confident you could engineer your way past each and every one given a large enough budget.

[jcranmer]

You're sort of missing the biggest health problem of all: how do you make a self-sustaining closed ecosystem?

[mrep]

True, I was thinking more in the context of the mars trip you mentioned where you can generally take the resources you need for the trip. For intersteller travel, you would need to make it self sustaining since the travel times are so long and that would be extremely expensive.

[maxerickson]

The article suggests moving stars.