3 ms·

Alien Worlds Might Be Covered in Enormous Mountains

10 points by Thevet 10y ago

methodover 10y ago
It's hard to express how sad it makes me that I'll never see photos of the surface of another inhabited world.
- manachar 10y ago
  Probabilistically, this is true, but think how amazing it is we have photos take from the surface of such far away places like Mars, Titan, comets, etc. Heck, the latest photos of Pluto are some of the most amazing things I've ever seen. It's conceivable that we will be able to send a probe to Europa that can drill through the ice to sample an alien ocean and maybe even find life! You can talk to people today who remember life before flight was really around, and for whom the universe was mostly just a background to evening activities. Every time we look out with more modern equipment we find the universe is more and more vibrant. Alien worlds inhabited by other intelligences than ours would be amazing though.
  - paavokoya 10y ago
    One could consider our Mars rovers as life on other planets.. They don't have "organic" (as in water based) cells but they are self-sustaining and active to this day.. They communicate back to Earth and do what we tell them, which is what most isolated lifeforms do in regards to their parents.
pavel_lishin 10y ago
Would it be plausible for a mountain on an alien world to reach high enough to aid in space exploration? High enough to make launches cheaper from its peak?
antognini 10y ago
A classic question in Order of Magnitude Physics classes is to calculate the maximum height of a mountain that a planet can support. There are a couple of solutions to this around the internet [1--2], but the main result is that the maximum height is inversely proportional to the surface gravity. At constant density, the surface gravity, in turn, is proportional to radius. So the maximum height of a mountain is inversely proportional to radius and you would expect that smaller planets have taller mountains. You can take this to one extreme and ask how large an asteroid can be before it becomes spherical under its own gravity. This essentially means that the tallest mountain must be much less than the radius of the asteroid. If you work out the math it turns out that the largest non-spherical asteroid should be around a few hundred km in size, which agrees well with observations. At another extreme you can perform this calculation for a neutron star. Although the radius is very small (which would seem to imply that it can support tall mountains), the density is much different from ordinary matter. As a result, the tallest mountains a neutron star can support is on the order of a few millimeters! Neutron stars are extremely spherical. (More correctly, due to spin, neutron stars are extremely spheroidal.) [1]: http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/mount_high_e.html http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/moun... [2]: https://talkingphysics.wordpress.com/2011/09/08/how-high-can-mountains-be/ https://talkingphysics.wordpress.com/2011/09/08/how-high-can...

10 points by Thevet 10y ago

methodover 10y ago

It's hard to express how sad it makes me that I'll never see photos of the surface of another inhabited world.

manachar 10y ago
Probabilistically, this is true, but think how amazing it is we have photos take from the surface of such far away places like Mars, Titan, comets, etc. Heck, the latest photos of Pluto are some of the most amazing things I've ever seen. It's conceivable that we will be able to send a probe to Europa that can drill through the ice to sample an alien ocean and maybe even find life! You can talk to people today who remember life before flight was really around, and for whom the universe was mostly just a background to evening activities. Every time we look out with more modern equipment we find the universe is more and more vibrant. Alien worlds inhabited by other intelligences than ours would be amazing though.
- paavokoya 10y ago
  One could consider our Mars rovers as life on other planets.. They don't have "organic" (as in water based) cells but they are self-sustaining and active to this day.. They communicate back to Earth and do what we tell them, which is what most isolated lifeforms do in regards to their parents.

pavel_lishin 10y ago

Would it be plausible for a mountain on an alien world to reach high enough to aid in space exploration? High enough to make launches cheaper from its peak?

antognini 10y ago

A classic question in Order of Magnitude Physics classes is to calculate the maximum height of a mountain that a planet can support. There are a couple of solutions to this around the internet [1--2], but the main result is that the maximum height is inversely proportional to the surface gravity. At constant density, the surface gravity, in turn, is proportional to radius. So the maximum height of a mountain is inversely proportional to radius and you would expect that smaller planets have taller mountains. You can take this to one extreme and ask how large an asteroid can be before it becomes spherical under its own gravity. This essentially means that the tallest mountain must be much less than the radius of the asteroid. If you work out the math it turns out that the largest non-spherical asteroid should be around a few hundred km in size, which agrees well with observations. At another extreme you can perform this calculation for a neutron star. Although the radius is very small (which would seem to imply that it can support tall mountains), the density is much different from ordinary matter. As a result, the tallest mountains a neutron star can support is on the order of a few millimeters! Neutron stars are extremely spherical. (More correctly, due to spin, neutron stars are extremely spheroidal.) [1]: http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/mount_high_e.html http://www.phy.cuhk.edu.hk/phyworld/articles/mount_high/moun... [2]: https://talkingphysics.wordpress.com/2011/09/08/how-high-can-mountains-be/ https://talkingphysics.wordpress.com/2011/09/08/how-high-can...