Mark Freed, age 12, of Los Angeles, California; for his question:

How far can you see on ‑a clear day?

This, of course, depends upon the direction in which you are looking. It also depends upon how high you are standing and whether any object is blocking the view. If you are about four feet tall and look out to the ocean, you can see about two miles. A six‑foot man can see about three miles. In other words # you can see about half a mile for every foot in height.

Looking towards the mountains you can see much farther because their peaks may poke above the horizon. Sometimes you can see the Rockies from 60 or 70 miles away.

At dawn or sunset you may dare to look at the sun: And this bright star is about 93 million miles away. There seems no limit to how far our eyes can see ‑‑ if the object is big and bright enough. Some of the bright stars we see are hundreds of light years away and a light year is about six million million miles.