Have A Very Merry Christmas, Earth

NASA’s MESSENGER space probe photographed Earth and moon on May 6, 2010 from a distance of 114 million miles (183 million km). NASA

We celebrate Christmas today on a ball of rock 7,917 miles wide. Depending on your latitude, or how far north or south of the equator you live, you’re spinning with the planet anywhere from a mile an hour near the poles to 1,041 mph at the equator. Earth in turn orbits the sun. Its average speed is 66,616 mph, but because the planet is closer to the sun in winter, today we’re zipping along at 67,732 miles an hour.

The sun moves across the sky, rising in the east and setting in the west, but we know that’s only an illusion caused by Earth’s spin. That doesn’t mean the sun stands still. With respect to the other stars in its neighborhood the solar system is speeding approximately in the direction of the bright star Vega in the constellation Lyra the Harp at 43,000 mph.

The Milky Way is a spiral galaxy with a dense bar of stars through its core. The sun and planets are located within a spiral arm some 27,000 light years from the galaxy’s center. NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

All the stars you see in the night sky belong to a pinwheel-shaped, flattened disk of suns called the Milky Way Galaxy. As the galaxy spins, the stars whirl about its massive core at an average speed of 470,000 mph or more than 7 times faster than the Earth orbits the sun. Even at this speed it still takes the sun some 225 million years to make one circuit of the galaxy. In its lifetime our sunny star has celebrated just 21 birthdays.

The Milky Way is moving through space, too. Its speed depends on which reference point you choose since everything else is also moving. With regard to the Virgo Supercluster, a massive cluster of galaxies of which our local group of galaxies is a member, we’re pulled in its direction at 540,000 mph. But relative to the cosmic background radiation — the ever-expanding , steadily cooling energy left over from the Big Bang that permeates all of space — we’re moving at the unholy velocity of 1.3 million miles per hour in the direction of the constellation Hydra.

As we fly through the void on this Christmas Day, enjoy the intimacy and warmth of the present moment with loved ones on this speck of a planet. There’s no place like home.