Astronomy Picture of the Day

Explanation: Want to build a scale model Solar System? A blue marble 1.4 centimetres (about half an inch) across would be a good choice for a scale model Earth. Since the Sun is 109 times the diameter of Earth, a 1.5 metre diameter balloon could represent the Sun. But the distance between the Earth and Sun, 150 million kilometres, would translate to just under 180 metres (590 feet) at the same scale. That would mean the completed project, including the orbits of the outer planets, is probably not going to fit in your backyard. Still, you might find enough room on a dry lakebed. Check out this video for an inspirational road trip through the Solar System to scale.