TerraForming Mars

All you need to do to bring Mars nearer to Earth is reduce Mars angular momentum somewhat. It is a simple matter to calculate and maybe not too hard to model. But, why would you want Mars nearer anyway? Or Venus? which would need a little more angular momentum added to bring it nearer.

JIM wrote: ". . . But, why would you want Mars nearer anyway? Or Venus? . . . "

So that we can get to them easier, even see them in the sky as bright circles like the Moon. At 1-2 million miles away, they'd be the most interesting thing in the sky after the Moon. We'd want to get to them easily for experiencing their landscapes in the usual ways that we are used to: as settlers, prospectors, miners, trekkers, environmental tourists and so on. There's a huge amount of land between the two of them, much more than on Earth. Mars and the Moon have each about the same as the Earth, Venus much more. Their landscapes are similar enough to ours to make them comfortable, but new and different enough to make them extremely attractive.

Well ok I agree it would be easier to get there if they were nearer but what is there thats not on Earth? And what about changing the angular momentum of either body to make them come nearer?

New and different landscapes, landforms, more living room and so on. And if Venus and Mars were brought up close to the Earth, not only would distance not be the big problem it is now. Climate would also be much less a problem, with Venus being extremely hot where it is, Mars extremely cold where it is. As for the technology of bringing them as close as 1-2 million miles, well yes, that is a dream at the moment . . . There's plenty of room for dreaming; there's so much we don't know about gravity . . .

Climate is a most important consideration when it comes to human habitation of the planets, just as it has been on Earth (as Vostok ice core data shows), and the main driver of climate is solar insolation. Distance and economics are also important.

In their present positions, Mars gets too little solar radiation, Venus too much. The other planets we are most interested in exploring, Europa and Titan, are climatically even more extreme. Only the Moon is very habitable. It is also nearby and economic, and big and interesting enough to keep us occupied for a very long time. The Moon's extremely thin atmosphere is a relatively small problem.

We are lucky that our Science allows us to experience those other planets through robots (ultimately cyborgs/androids and their machines), probably our best way of going beyond the Moon for a very long time. Mars Rovers and other probes have been a great start.

Correction: "Vostok ice core data shows" that "the main driver of climate is solar insolation".