# If there was air between the Sun and Earth, how warm would we get?

Based on this question: How loud would the Sun be?

If instead of a vacuum we had air between the sun and earth (let's say of the same composition we have here on earth) how warm would our planet get?

• About a billion degrees. (I'm not kidding). – userLTK Jan 27 '17 at 13:03

Your only way of answering this question is to look at the current atmosphere of the Sun and try to extrapolate. Take a look at the figure below. This represents both the temperature (solid line) and density (dashed line) of the Sun vs height from the surface (what the "surface" of the Sun means is a whole other question). The temperature at the surface of the Sun is a measly $5800\:\mathrm{Kelvin}$. As you increase in height, this temperature (i.e., the temperature of the plasma atmosphere above the "surface" of the Sun) doesn't change much. This region of the atmosphere is known as the chromosphere. But then, at a particular height known as the transition region, there's a drastic increase in the temperature. It goes from a few thousand degrees to a couple million degrees. This area of the atmosphere is the Corona. This graph cuts off at $10,000\:km$ but the Sun's atmosphere extends far out beyond Pluto.
Hopefully you can fully appreciate the point I'm getting at which is that Earth actually is inside the atmosphere of the Sun and that atmosphere is really hot! The reason we of course aren't boiled to death is that the atmosphere is incredibly sparse. Only a handful of particles per cubic centimeter. So what you're really proposing is to increase the density of this atmosphere by an insane amount. You want to make it approximately $10^{20}$ times more dense! If we just extrapolate properties, that's going to turn the already hot atmosphere of the Sun (around the Earth) into something incredibly hot. And the huge density means we'll really feel the effects. The Earth will likely be vaporized in a flash, before the cataclysmic explosion which I alluded to above can even happen.