unfortunately, i think the earth would burn up, due to compression and friction

Hence he wrote:

> (laws of physics would be have to be different obviously)

On the other hand, it might be a cold, lifeless rock, since the sun can already barely penetrate a tiny sliver of atmosphere, as sunsets demonstrate.

In that case, we would perhaps still be a millennia from the technology required to get there. Imagine the fuel required to get to Mars with air resistance! The materials that would be required to keep the plane from being destroyed by the heat and vibrations from the speed for such a duration!

The heat dissipation required would presumably be immense with that constant acceleration due to air resistance.

I think we can be glad that space is a hostile vacuum.

Can’t we just fly a U-2 all the way up and out of Earth SOI, then drift towards Mars in that situation? Do we still need to establish an orbit?

If the air had no currents, the steady state would be motionlessness except gravity effects. If it had currents, the steady state would be to follow them.

Of course those gravity effects would also apply to the air, which makes the scenario inconsistent. I'd be interested to see a formulation of the laws of physics that actually makes a substantial interplanetary atmosphere possible.

OTOH, sailing might be possible. Odds are against the atmosphere being perfectly still, certainly.

It would just take too long. Modern space capsules travel at kilometers per second, and it would still take months to reach Mars. If were to travel there a 30km/h it would take centuries to get there.

... This is all ignoring the fact that orbital mechanics just wouldn't work if there was air resistance. The planets would quickly slow down and crash into the sun.

Right, of course the real answer is that none of this is possible, at least not just replacing the interplanetary atmosphere without adjusting anything else for consistency.

But imagine this: a breathable nitrox atmosphere co-orbiting with the planets. Each planet is roughly at rest with respect to the local atmosphere, so no drag. Just lots and lots of wind shear. Probably planetary scale vortices. That'll sap orbital energy into heat, so probably not stable, but pilots can probably exploit it to acheive velocities comparable to orbital velocities over time. I think you'd probably have to have two sails connected by a tether, sufficiently far that their air streams are at significantly different speed, with one of them acting like a keel.

That Mark Twain story about the flying boat comes to mind.

You’d have to have different physics.

If the earth were revolving in an atmosphere and air resistance was a thing, we’d have spiraled into the sun by the Cretaceous.

It's quite amusing what this is the second time this week when I recommend 'Exhalation' by Ted Chiang.

[0] https://archive.org/details/ExhalationByTedChiang

[0] https://www.lightspeedmagazine.com/fiction/exhalation/

It's not exactly air, but there is still some "stuff" filling the solar system.

https://en.m.wikipedia.org/wiki/Interplanetary_medium

I think you air-quoted the wrong word in that sentence. I think it would be more appropriate to say: there is still some stuff "filling" the solar system.

:-)

Bob Shaw's SF novel "The Ragged Astronauts" plays with this idea. A major plot point is a journey to a neighbouring planet - by balloon. The novel indicates that the laws of physics are different, e.g. a scientist character indicates that π = 3 (IIRC).

[0] https://en.wikipedia.org/wiki/The_Ragged_Astronauts

We would live suspended in a great universal "ocean" and would navigate the heavens via submarine. Of course, it would be easier for other creatures to swim between planets as well...

I wonder if advanced conscious life would be possible in this universe given that the number of isolated "buckets" is so much smaller. A lot of anthropic arguments would break down in such a universe.