AST101: The Sun and its Neighbours
November 1, 2012
- 2nd midterm review: Tuesday 4-6 PM, MS 2158
- Why is Venus so different from Earth?
▯ - biggest difference is that Venus's surface is much hotter than Earth's
▯ - this is because Venus is a lot closer to the sun than Earth
▯ - more intense sunlight would raise surface temperature by about thirty degrees
▯ - this would lead to a lot more water evaporation on the planet
▯ - water is a strong greenhouse gas, but it doesn't have a negative feedback cycle
▯ ▯ the way that CO2 has.
▯ - water in the atmosphere would raise the temperature even more, until the
▯ ▯ planet was above the boiling point of water, and everything in the oceans
would ▯ ▯ be in the atmosphere
▯ - this would lead to a runaway greenhouse effect
▯ - if Earth was where Venus is, it would wind up a lot like Venus
- why does temperature in the "troposphere" decease with altitude?
▯ - the atmosphere's pressure comes from the weight of what's above, so pressure
decreases with height
▯ - the "troposphere" is the convective part of the atmosphere...it carries heat up
▯ - a gas expands and cools off when its pressure goes down
- in the regions above the troposphere, it gets HOTTER as you go up. This happens
because something is heating these layers (ultraviolet radiation)
- where does the magnetic ﬁeld come from?
▯ - magnetic ﬁelds "thread" metallic (or electrically conducting) mater and can be
wound up and strengthened by motions of the matter.
- three ingredients lead to strong magnetic ﬁelds:
▯ 1. Metallic (or conducting)