Forgot the bit about how the Sun becomes a Red Giant.

What will happen eventually (after ~ 5 billion yrs. ) is that the Sun's store of hydrogen (protons) will be exhausted so that it will be impossible to sustain proton-proton fusion.

This means a less efficient fusion process will commence in its core.

Note the next effect of proton-proton fusion is to accumulate helium 4:

H1 + H1 + H1 + H1 -> He 4

So now He4 must be fused for the star to be sustained. This is done via the "triple alpha (for alpha-particle) process":

He4 + He4 + He4 - > C12

This fusion process is not as efficient as the proton-proton cycle so hydrostatic equilibrium (pressure-gravity balance) cannot be sustained.

This means the core heats up much more causing the outer layers of the star to EXPAND.

As the layers expand - larger surface area - they cool, so one ends up with a Red Giant.

Of course, this isn't the ultimate end. That will come when the Red Giant "collapses" and becomes a white dwarf.

Hopefully, now this is completely clear!

pragma: "I either learned wrong or the science has changed since I checked last. I was under the impression the sun would cool down until it became a red giant. In fact it's heating up

1) The Sun won't "cool down until it becomes a Red Giant". The Sun is currently on the Main Sequence (of the HR diagram) meaning it is hydrostatically stable (outward radiation pressure balanced by gravity) - so long as it undergoes proton-proton cycle nuclear fusion. Thus it maintains an even temperature at its surface (~ 11,000 F) within +/- 0.1%.

2) The Sun is not now "heating up". For the same reason. True, it will exhibit variations within that +/- 0.1 % tolerance, but just because we may be on the slight upside cycle doesn't mean it is "heating up".

SO long as it is in hydrostatic equilibrium and its inward directed gravitational force balances outward directed radiation-gas pressure this will be so.

So, I guess you were taught wrong.

Your school wasn't in Texas, was it?

Let 'em go! I always wanted to get rid of this loathsome state since their right wing crazies (at the behest of oilman H.L. Hunt) offed JFK and blamed it on the little New Orleans loser Lee Harvey Oswald.

Barton is as dense and ignorant as that Gooper from OK, who chaired numerous energy meetings during Shrub's reign. Can't even recall his name now. But he didn't impress any more than mental flyweight Barton does.

I do believe Chu was trying his best not to embarrass the moron.