Where is the sun?

It's daylight and you are standing outside: Where is the sun?
-- How do you know?

It's daylight and you are standing inside a four-walled room with no windows: Where is the sun?
-- How do you know?

It's the middle of the night, you are outside standing in the forest: Where is the sun?
-- How do you know?

It's 5:00 AM, just before dawn, your home is in a valley surrounded by mountains: Where is the sun?
-- How do you know?

It's midnight on the night of the new moon: Where is the sun?
-- How do you know?

What informs your knowledge about the sun?

For me, it is the bath of golden light in the daytime, the moon's reflective surface, the lightbulbs that are recycled sunlight, the green trees which though darkened in the night air promise me there was a sun that passed by recently, and the pattern of the sun's 24 hour cycle (a.k.a earth's 24 hour cycle) which I've been conditioned to believe will continue tomorrow.

Make sure you keep a friend like the moon around in your orbit so you can always be reminded that there's light on it's way to your place in the world, no matter how dark it may look now.

All these things witness there is a sun that was here, and will soon come again.