In another thread (http://www.sciforums.com/showthread.php?threadid=24869&goto=newpost) there was the topic of extra-terrestril life, arisen oh high gravity planets, and their attributes in relation to terrestrial life.

Well their conclusion sounded like somthing out of deep space nine. Yeah guys.

What I was wondering was...

What would be the maximum size of a planet, before it became impossible for a species to excape it, given energy constrants as we know them today?

Before you say "They would have to develope on a black whole for it to be impossible". You may be right in a technical sense, but think deeper. How much energy does it take us, in what form? How much would we potentially use given our world today in a non-evacuate the globe today kind of society. .01% of the fuel developed? Probably less. We wouldn't go to even 25% if we needed to. Well, that was just to clarify what I meant, post away my "colleagues"

I am not sure planet size has anything to do with it. You could have a huge planet that is not very dense. This may actually be benefitial to the ability to leave the planet, because of the distance from the planets center of gravity. On the other hand you may have a very small planet composed entirely of lead and have a VERY difficult time standing.

You know, I knew what you meant and I apologize for the non-serious response. I guess I am just ridiculing your question in a feable attempt to sound smart without having to a decent answer.

Honestly, I do not think we are utilizing a very efficient method of leaving our planet. I think in the future we will find many more efficient methods, unfortunately (much to my dismay) I do not know what these methods will be or how efficient they will be, so I cannot answer your question. One method I can think of - a space elevator. A space elevator does not necessarily have to be an elevator in the classical sense. It could be a super highway twisting around the interior of a 5 mile wide building, a building that is so tall it leaves our atmosphere. Or, instead of a highway, you could have bullet train that runs on superconducting coils (I would still spiral it around the interior instead of going straight up). In both scenarios you are using simple machines (a ramp) to overcome a gravity. I do not see why this elevator would not work on any planet that it would be able to stand on (no matter how dense or large).

- KitNyx