What were the first bifocals made of?

Why cant you see your shadows clearly at night? How do stratuscumulusand cumulonimbus clouds differ from each other? How large is the sun compared to other SUNS? Even thought earth has mass than they sun the moon orbits earth because its much nearer to it? What are all the 88 constellations? How can i contact scientists at NASA? When is Tennessee closest to the sun? Have any robots or satellites ever landed on the planet Pluto? Why shoud disc clean up be performed regulary? What is Bright star in sky late December? What was the first successful man-made satellite? What is the area of the moon? What accomplished by turning the coarse adjustment? When did garret a morgan invent the traffic light? Can tornadoes be seen? Where is NASA's Johnson Space Center located? Is there a full moon every night? What fuel was used in the Apollo 11 mission? What led to the discovery of three more planets than those that the ancient observers knew about? What planet do vulcans come from?