Earth’s Perfect “Address”
OUR address often includes our country, city, and street. By way of comparison, let’s call the Milky Way galaxy earth’s “country,” the solar system—that is, the sun and its planets—earth’s “city,” and earth’s orbit within the solar system earth’s “street.” Thanks to advances in astronomy and physics, scientists have gained deep insights into the merits of our tiny spot in the universe.
To begin with, our “city,” our solar system, is in a part of the Milky Way that many scientists call the galactic habitable zone. This zone is about 28,000 light years from the center of the galaxy and contains just the right concentrations of the chemical elements needed to support life. Farther out, those elements are too scarce; farther in, the neighborhood is too dangerous because of the greater abundance of potentially lethal radiation and other factors. “We live in prime real estate,” says Scientific American magazine.
The Ideal “Street”
No less “prime” is earth’s “street,” or orbit within our solar system “city.” About 93 million miles from the sun, this orbit is in what scientists call the circumstellar habitable zone, where life neither freezes nor fries. Moreover, earth’s path is almost circular, keeping us roughly the same distance from the sun year-round.
The sun, meanwhile, is the perfect “powerhouse.” It is stable, it is the ideal size, and it emits just the right amount of energy. For good reason, it has been called “a very special star.”
The Perfect Neighbor
If you had to choose a “next-door neighbor” for the earth, you could not improve on the moon. Its diameter measures just over a quarter of the earth’s. Thus, when compared with other moons in our solar system, our moon is unusually large in relation to its host planet. This, however, is no coincidence.
For one thing, the moon is the principal cause of ocean tides, which play a vital role in the planet’s ecology. The moon also contributes to earth’s stable spin axis. Without its tailor-made moon, our planet would wobble like a spinning top, perhaps even tipping right over and turning on its side, as it were! The resulting climatic, tidal, and other changes would be catastrophic.
Earth’s Perfect Tilt and Spin
Earth’s tilt of 23.5 degrees causes the annual cycle of seasons, moderates temperatures, and enables a wide range of climate zones. “Our planet’s tilt axis seems to be ‘just right,’” says the book Rare Earth—Why Complex Life Is Uncommon in the Universe.
Also just right is the length of day and night, a result of earth’s spin. If the rotation period were substantially longer, the side of the earth facing the sun would bake while the other froze. Conversely, if days were shorter, perhaps just a few hours long, earth’s rapid spin would cause relentless gale-force winds and other harmful effects.
Yes, everything about our planet—from its “address” to its rate of spin to its lunar neighbor—gives evidence of thoughtful design by a wise Creator. * Says physicist and evolutionist Paul Davies: “Even atheistic scientists will wax lyrical about the scale, the majesty, the harmony, the elegance, the sheer ingenuity of the universe.”
Could such ingenuity be a product of chance, or does it reflect purposeful design? Think about that question as you read the next short article, which discusses two amazing shields that protect life on earth from threats originating in space.
^ par. 13 Essential to the existence of the universe as a whole are the four fundamental forces that govern matter: gravity, electromagnetism, and the strong and weak nuclear forces. All are marvelously fine-tuned.—See chapter 2 of the book Is There a Creator Who Cares About You? published by Jehovah’s Witnesses.
[Box on page 5]
ARE YOU GOING FASTER THAN A BULLET?
By the time you finish reading this box, you will have traveled thousands of miles—and without any bumps! Consider the following.
The earth is 25,000 miles [40,000 km] in circumference and rotates once every 24 hours. Thus, points at or near the equator move at about 1,000 miles [1,600 km] an hour. (The poles, of course, just spin on the spot.)
The earth itself orbits the sun at 18.5 miles [30 km] a second, while the solar system as a whole travels around the hub of the Milky Way at an astonishing 155 miles [249 km] a second. Bullets, by comparison, travel at less than a mile a second.
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Milky Way: NASA/JPL/Caltech
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Earth: Based on NASA/Visible Earth imagery