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Tour: Einstein's Theory of Relativity, Critical for GPS, Seen in Distant Stars
What do Albert Einstein, the Global Positioning System (GPS), and a pair of stars 200,000 trillion miles from Earth have in common? (2020-10-22)

Video Podcasts: The Incredible Two-Inch Universe

Step 1: The Realm of the Earth and Moon

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If you shrink the earth to about 2 inches or 5 centimeters (cm) in diameter here's how other objects would compare in size and distance:

Note: distances in this activity are approximate in order to give you a rough feel for astronomical scale.
• Moon Size -1/2 inch (1.3 cm) - hold Earth and Moon images, one in each hand
• Earth-Moon Distance - 5 feet (150 cm) - spread your arms wide to hold images 5 feet apart
• Sun Size - 16 feet across (5 m) - imagine a yellow ball the size of a minivan
• Earth-Sun Distance - 1800 feet (550 m) - about 6 soccer fields apart
• Light Travel Time - Light travels through space at a constant speed of 186,000 miles per second (300,000 km/sec). At this scale, where the Earth is 2 inches across, we've shrunk 186,000 miles down to about 4 feet. It takes a beam of light a little more than one second to travel from the Moon to the Earth