Hacker News Reader

Comment by zoba | Hacker News Reader

I believe I remember him pointing out, of all the things that need energy on earth, most of them use the sun as their source either directly or indirectly. Plants are obvious, and animals rely on plants. While products of evolution aren't perfect, they can often be a useful guide.

View on HN

Wind is really an indirect result of solar energy as well -- solar energy creating different pressures in the atmosphere, which produce wind.

You are incorrect in stating that most things use the sun for energy. In fact, everything uses solar energy in one way or another.

Bacteria that live on nutrients emitted from deep sea hydrothermal vents do not use solar energy. Some theorize this is where life on Earth originated.

http://en.wikipedia.org/wiki/Hydrothermal_vent#Biological_co...

Doesn't that energy ultimately come from tidal forces in the Earth's interior that wouldn't exist if there weren't a Sun to orbit?

Earth's spin is due to asymmetry in the accretion of matter during planet formation. The dust and gas that would form the planet was orbiting the center of the nebula before either the sun or planets formed out of it; interstellar nebula begin rotating and flattening before they form a proto-star. If you could pop the sun out of existence, hydrothermal vents would continue feeding bacteria with absolutely no solar energy until the planet eventually shed too much its internal heat (from its initial formation, also not from the sun).

There is nuclear energy transformations inside planets that creates lots of energy:

http://physicsworld.com/cws/article/news/2011/jul/19/radioac...

Geothermal and nuclear are basically the only forms of energy that are not ultimately solar-derived.

Edit: I guess you could throw tidal in there as well.

Well, it depends on how far back you want to go. All elements come from nuclear reactions in suns/stars which occur partly due to gravity. Some elements are unstable making them radioactive, some of which we use for nuclear fission. Big chunks of stars form planets and the associated geothermal energy. So, solar reactions and gravity account for all energy either directly or indirectly. Gravity is also the cause of tidal energy.

Those don't count as we can't access them directly. The idea with solar is we can access it directly, but we are using indirect methods.

Nuclear.

Well, you could say the supernova that created our radioactive heavy elements billions of years ago were once "suns". But that power didn't come from our sun.

Reply on news.ycombinator.com