21.   For aligning points on distant objects, like fence posts, you can use a water level.

22.   Gravitational lensing, which can greatly magnify images from very distant objects, occurs when light from the object passes near very massive clusters of galaxies.

23.   If these tests, known as refractions, detect myopia -- the ability to see close objects clearer than distant objects -- the child is immediately provided with eyeglasses.

24.   In interviews the day after their LASIK procedures, both said they could see distant objects clearly with the treated eye.

25.   Its most powerful telescope can see quasars, the most distant known objects in the universe.

26.   Long-baseline interferometry, which astronomers use to make highly accurate observations of distant objects, needs extremely accurate atomic reference clocks.

27.   Now alternately close your left and right eyes, and see if your thumb appears to jump to the right or left with respect to the distant object.

28.   One of the rules of perspective, which nearly everyone understands intuitively, is that distant objects only appear to be smaller than nearby objects.

29.   One theory attributes the moon illusion to how the brain deals with the apparent size of distant objects.

30.   Rest the eyes by looking away from the screen and refocusing on a distant object.