Sun temperature

There is no 'air' around the sun. Your question needs to be clarified. As it stands, it makes no sense.

Re: Sun temperature

If there were air, the distance would have to be about 93 million miles.

When standing on the Moon the sunny side can reach 180 degress whereas in the shade it's 100 below freezing.

Methinks the asker of this question doesn't understand how heat travels (conduction, convextion and radiation) and how bodies in space are continually absorbing and emitting energy as heat in the radiation spectrum until they reach equilibrium.

MG - it would depend on:

1. Your surface material, design / shape of body in question, colour or shade, rotational speed if the shape is asymeterical, which then begs is the body firm, gaseous and or liquid - or some hybrid which could cause complex equilibrium systems to occur
2. How well this material absorbs and emits solar radiation - particularily at the infra red and near infra red spectrum
3. What other matter if any surrounds this body to bring it into equilibrium and each bodies relative mass and surface area

An a few more factors too! Consider Venus which is way hotter at its surface then Mecury - which is far closer to the Sun, because Venus has a runaway Greenhouse effect, trapping heat because of the composition of its atomsphere being largely CO2.

Also consider Earth has been Ice bound in an ice age lasting 10,000 years - at a time when it was closer to the Sun - so average temperatures where 20 - 30 degrees colder than today - because Ice and airborne dust reflected alot of solar radiation away form the Earth's surface.

g__day everyone knows that stuff! But we must ask ourselves -- how di Venus get that greenhouse effect? What caused all that CO2? Could there have once been an advanced civilization that destroyed itself much the same as we are now???

Are then you are getting into a field of planetary ecosystems dynamics, which I have posted on in detail more than once to show how models would predict advanced intelligent life existing in the Universe is an extremely remote chance. Read my post about "Why is the Universe so big ? - faith vs science" about 18 pages in to get the 30 or so factors which must all align for advanced life to have an environment in which to blossom.

These conditions aren't all present on Venus - e.g. there are no plate tectonics or silica balance and of course atomspheric pressure is too high and water is only present as water vapour and carbon dioxide is mainly present in the atomsphere, whereas on Earth a major of CO2 is trapped in the soil and rocks (surface temperature is too low to sublimate the gas out of the soil).

Now you factors have to deal with the initial form of the planets atomsphere and where its surface conditions (temperature) would allow water to form in a liquid present in the oceans (that act to stabilise global temperatures) rather than in the form of water vapour (which like CO2 traps Infra Red radiation) and can cause run away green house effects! Venus had too high surface temperatures so the oceans would boil, then CO2 would sublimate out of the rocks.

see

http://www.astronomynotes.com/solarsys/s9.htm

or

http://csep10.phys.utk.edu/astr161/lect/venus/greenhouse.html

For a basic overview. Then you have to understand cloud dynamics and turbulence to uderstand how Venus's atomsphere actually pumps the heat to the surface, given only 10% of the Sun's energy makes it to the surface - yet its hot enough to melt copper!

http://www.esa.int/SPECIALS/Venus_Express/SEMFPY808BE_0.html

For what happened to the water once it became vapour (ultraviolet radiation breaking the Hydrogen apart - and Venus being too light to gravitational trap atomic Hydrogen), and how temperature equations actually interact with molecular CO2 to produce a runaway heat sink, I invite you to peruse http://ircamera.as.arizona.edu/NatSci102/lectures/venus.htm

esp the section on The Greenhouse Effect - why the surface is so hot



No life on Venus sorry!

Certainly no life "as we know it". But I have read that in Venus upper atmosphere there are indications that there are reactions taking place which would require organic compounds and possibly microbial life! And let's not forget the mysterious "red rain" that fell over India in 2001 which contained some sort of life that reproduced wildly at temps over 600F without the benefit of DNA! http://arxiv.org/ftp/astro-ph/papers/0312/0312639.pdf

Since when does an extremely basic microbe count as an advanced civilization that destroyed the planet with a runaway greenhouse effect?

More plausibly, the suggestion has been made that the red raindust was the result of incomplete incineration of chemical waste at the Eloor industrial zone, the particles being formed from microparticles of fly-ash or clay which coalesced around an aerosol of partly burnt organics as the incinerator plume cooled. The chemical composition of the raindust matches that of burnt organics plus clay; the fallout pattern matches with the prevailing winds; and various organic chemicals will form cellular structures which replicate in the prescence of clay.

The inner planets all started with an atmosphere rich in CO2. The question is not how did Venus get CO2, but how did Earth lose it, and why didn't Venus lose it? The answer, as you have already eluded to, is the runaway greenhouse effect.

On Earth, high energy ultraviolet light from the sun caused photodissociation of CO2 in the atmosphere, which could recombine with new compounds on the surface and be dissolved by water. In order for amino acids to form for life the atmosphere the atmosphere had to be suboxidized by this process first. This also resulted in the freeing and escape of the light hydrogen atoms, though.

We are lucky that on Earth, the process of photosynthesis evolved during the relatively short window after the free oxygen started to run out, because the suboxidized conditions that are necessary for life to begin never come back.

Venus is closer to the sun, and therefore hotter, and liquid water could not exist there. Any form of water would be in the form of vapor in the atmosphere, which is a greenhouse gas like CO2. The photodissociation of water would release the hydrogen into free space. We do know that Venus experienced a runaway greenhouse effect by observiing the ratio of deuterium (heavy hydrogen) to hydrogen. Deuterium is always created in the same proportion to hydrogen but there is much more of it on Venus because it is heavier and had a lower probability of reaching escape velocity than regular light hydrogen.

Without water Venus could not have developed the conditions for life, CO2 could not be removed from the atmosphere, the planet is kept cooking in an oven by it's own atmosphere for eternity.

The CO2 that started in Earth's atmosphere has been stored in carbonate limestone sediment from early shelled marine organisms. If you total the amount of CO2 in these stores and put it back into the atmosphere, you get at least 70 times the pressure of the current atmosphere...very close to the 90 bars of pressure that we measure on Venus.

Therefore, even though the surface of Venus was erased from geological processes merely 500 million years ago, we can still deduce that there was never an advanced form of life, and in fact we can tell that the conditions for life probably never existed.