Last week we looked at a number of the factors which combine to make our planet perfect for life. Now I want to widen the view and encourage you to consider our place in the universe, or more specifically our immediate solar system.
This gives you an idea of the size of the earth in comparison with our moon and the size of our sun.
We looked last week at the effect of the earth’s axial tilt and the gravitational pull of the moon which gives us the tides. The fact that our relative position to our moon is the proximity it is, an average of 384,403 kms) and our distance from the sun is 149,597,887 kms gives us the balanced conditions for life. We have already investigated the perfection of our distance from the sun. Now let’s consider our moon.
Be thankful for our great big beautiful satellite, the moon. Without the moon, we would not be here. Life on earth is made possible because of our nearest celestial neighbour. Our moon compared with the moons of other planets in our solar system is larger relative to the size of the earth. The moon stabilizes our planet's rotation, preventing drastic movements of the poles that could cause massive changes in temperature and would doom any chance for life on earth. The moon also helpfully pulls the ocean's tides which flush our planet regularly and replenishes the nutrients in the coastal waters. It also plays a part in the movement of the seas in a more general way combined with the rotational force of the earth to influence the ocean currents. The placement and size of the moon in relation to the earth is perfect. If the moon was any larger or closer the effect would be catastrophic. The gravitational pull on our tides would be more than the planet could sustain. The differences between tidal ebb and tidal peak would wash over the land with such force it would seem like a tidal wave. Given the fact that approximately 40% of the world’s population lives within 100 kms of the coast, the result would be devastating. If the moon were smaller or further away the movement of tides and the cleansing effect on the earth would be negligible.
The earth’s rotation, the axial tilt, the proximity and size of the moon, the orbital movement the moon around the earth and the earth and moon around the sun are all critical factors to ensure the the delicate balance of life on earth. If any one of those factors changed it could spell disaster. Consider for example a change in the speed of the earth’s rotation. The effect would be wide-ranging. The rotational winds on the planet would be severe. For instance, Jupiter has the shortest days in the solar system, just six hours. The wind velocities on Jupiter are estimated to be in the region of 500 kms per hour. Everything about life on earth is balanced to ensure our survival.
Let’s move out a little wider still to consider our more distant planetary neighbours. George Wetherall of the Carnegie Institute made an exciting discovery about our solar system. He conducted computer simulations of the orbital movement and rotation of the planets and planets and said “If it were not for Jupiter, we wouldn’t be around to study the origin of the solar system.” As I included in the Amazing Facts section of God’s Awesome Book, Jupiter is two and half times more massive than all the other planets combined. Because of its huge mass, thus huge gravity, and its location between earth and the clouds of comets surrounding the solar system, Jupiter either draws comets to collide with itself, or more commonly deflects comets right out of the solar system. In our position as the third rock from the sun, we are perfectly placed for our own protection. Wetherall says “without Jupiter, Earth would be struck about a thousand times more frequently than it is already by comets and comet debris.” Jupiter acts like a giant broom, sweeping the solar system of debris, rocks as small as cars and as huge as moons.
We didn't just happento show up in a place that's well-suited for life. Earth is perfectly placed in the Goldilocks position, within the sun's habitable zone. Mars and Venus lie outside it; if Earth's orbit had been just a bit further inside or outside of where it is, life would never have been possible and our planet would be a cold desert like Mars or a cloudy furnace like Venus. Earth remains the only known planet to host life, due to a unique combination of factors.
Alan Boss, a planet formation theorist at the Carnegie Institution of Washington in Washington, D.C. says, "Earth is the only planet we know of that has life."
Alex Wolszczan of Pennsylvania State University, who co-discovered the first planets beyond our solar system says Earth is still the only world known to support life. "So far, we haven't found it anywhere else." He says that life was Earth's single most impressive characteristic.
Don Brownlee, author of the book "Rare Earth" (Springer, 2003) says “So far, we haven't seen any planet outside the solar system that comes close to Earth [with the potential to sustain life]. Of the nearly 300 new worlds glimpsed elsewhere in the galaxy, most are "hot Jupiters", large planets that orbit close to their stars, on which life and liquid water are unlikely to exist. I doubt that in our galaxy typical stars have planets just like Earth around them, I'm sure there are lots of planets in the galaxy that are somewhat similar to Earth, but the idea that this is a typical planet is nonsensical.”