why is the sun hot?

Answer 1

Sometimes you can't do better than quote the now immortal poet Hy Zaret:

The sun is a mass of incandescent gas
A gigantic nuclear furnace
Where hydrogen is built into helium
At a temperature of millions of degrees
Yo ho it's hot! The Sun is not
A place where we could live
But here on Earth there'ld be no life without the light it gives

More at:

http://tinyurl.com/2pcht5

The music will set you free.

Answer 2

At the core of the sun the pressure due to gravity is so great that hydrogen atoms are squeezed together, 4 at a time to form one helium atom. Since 4 hydrogen atoms have slightly more mass than one helium atom and since mother nature says you can't leave pieces of atoms just laying all over the place this little bit of matter turns to energy. Over a million years or so this energy seeps up to the surface and escapes into space as heat and light. This process is called nuclear fusion because the nuclei of hydrogen atoms are fusing together. Our sun is called a main-sequence yellow dwarf, meaning it's middle-aged. As it starts to run out of hydrogen in about 5 billion years the outward force of the fusion will overcome the lessened gravity and the sun will expand into what's called a red giant, engulfing the earth. It will then collapse into a white dwarf, a super-dense small star that will then start fusing the helium.

Answer 3

It's a gravitationally bound hot FUSION reactor ..

Answer 4

Due to the thermonuclear reactions taken plae in its core

Answer 5

SUN, SUN, what sun?