What is found in the highest concentration in the atmosphere?

Do coloured objects form coloured shadows? How do you hear sound? How do you get the tianna key in command mission? How much money did NASA spend on making a pen that writes in space? How does the moon pull on the Earth and what effects does this gravitational force have on our planet? Is another name for observations? What clock came after the sundial? An astronaut inside a small space ship orbiting around the earth cannot detect gravity.If the space station orbiting around the earth has a large size can he hope to detect gravity? Is every night an adverb? Can you use the hubble telescope? What are the names of the elements used to create the light in a star? Do you have day and night at the same time on your planet? What is Jetseam? In New York in what season is the earth actually closest in distance to the sun? Who was the yongest person to go into space? Do space bags work? Apart from the sun which is the brightest star seen on earth? What principle of light does the periscope use to work? Which planet in the solar system has the longest revolution period? What constellation looks like a pot?