The sun's spectrum is very complex, and indeed there are a lot of lines—both light and dark (emission and absorption)—amidst a sea of what looks to be continuous frequencies. How long until the sun gets burned down to the point where it cannot sustain life on earth anymore? Similarly, how would you prove to them.
How would you prove to them that earth orbits the sun? Those are completely different things. What are the main factors which determine the.
You say that sun rises in the east (with a certain degree of oscillations due to the tilt of the axis) just because the earth. The sun will last, at its current brightness for 9 billion more years. Assume you're talking to someone ignorant of the basic facts of astronomy. As i asked before, separate.
It's consensus that the very similar apparent sizes of the moon and the sun as seen from earth is a coincidence (as already answered in this site). The sun does not rise, it is the horizon that goes down. The core temperature of the sun is on the order of 15 million degrees kelvin while its surface temperature is around 6000k. On the other hand, if the water were completely still, with a smooth and horizontal surface, then the sun glitter ribbon would be gone, and you would just see a direct mirror.