For the light from the star Spica, it’s been a long journey. It began about 250 years ago — around the year 1771. By then, the American colonists were getting angry at their rulers in England, and were only a few years away from declaring independence. A few skirmishes even broke out that year in some of the colonies.

Since then, the light from Spica has traveled about one-and-a-half million billion miles. To put it another way, if you were flying in a jet airliner, it would take you more than 300 million years to cover that distance.

Spica’s light doesn’t take nearly that long to cross the interstellar gulf because it moves at, well, the speed of light — 670 million miles per hour. According to Albert Einstein’s theories of relativity, nothing can move faster than that.

As the light races toward Earth, some of it gets absorbed by gas and dust between the stars. There’s not a lot between here and Spica, though, so most of the light is uninterrupted — it just keeps on cruising.

Spica stands well to the lower left of the Moon at first light tomorrow, and closer to the Moon on Wednesday morning. And if you happen to look in that direction, some of the star’s light will end its journey across the galaxy by striking your eye — a journey that began on the surface of a brilliant star, and ended on a winter’s night on a planet 250 light-years away.

Tomorrow: seeing the future in a shadow.

Script by Damond Benningfield

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