Re: How to Cool a Planet (far fetched ideas)

Paul F. Dietz wrote:

You can get by with *far* less mass if the orbital element
just scatters the light through a small angle. A diffractive
element at the earth-sun L1 point would need to scatter the
light by ~ .01 radians. This would require roughly 100x
less mass than a reflective element. Moreover, it would
have close to 100% duty cycle, unlike LEO mirrors, and it
could be designed to scatter non-visible IR, so it would
not alter the night sky.

Metal mirrors can be as thin as 1 micrometer and they
are easy to fabricate. Anything that scatters light and
is more lightweight than 1-micrometer thick metal mirror
would require expensive technology, for example a ***
that has grooves spaced at 1 micrometer interval. If the
grooves are much farther apart than 1 micrometer it would
scatter mostly infrared light.

Another problem is chemical etch by the solar wind.
It may destroy very lightweight sheets.

My favorite idea is a thin mirror placed close to the sun
that is reflective on the sunny side and black on the
dark side. The mirror would be cool because it would
radiate infrared from its dark side. It would be small
because it would be close to the sun. Its surface
would be slanted so that it propels itself like a solar
sail and thus always keeps itself between the sun and
the earth.

A mirror placed in a low earth orbit would not be
efficient cooling contraption, but a slanted mirror
could scatter some space junk back to the earth.

All these albedo modification schemes fail to solve the
ocean acidification problem, though, and they cause
the stratosphere (which is cooled by increasing CO2)
to get even colder. At some point the CO2 has to be
kept out of the atmosphere. Burning all the seafloor
methane, for example, is going to put an enormous amount
of carbon into the air, more than even from burning
all the coal.

Nearly all the clouds are below the stratosphere, so
the stratosphere's temperature does not effect the
weather.

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