We measure the extremely long distances between things in space by light years. A light year is the distance that light travels in one Earth year. Light travels at about 300,000 kilometres per second.

"One explanation is that Theia lost its rocky mantle in earlier collisions and then slammed into the early Earth like a metallic cannonball ... The team ruled out meteor impact as a source of origin ...

Tucson is the epicenter of a meteorite hunt after a shower of space rocks landed north of the city Tuesday night.

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