The Earth’s Safety Zone

When I observe Your heavens, the work of Your fingers, the moon and the stars, which You set in place, what is man that You remember him, the son of man that You look after him? - Psalms 8:3-4 HCSB

When reading this psalm, I usually focus on the humility that comes from observing the vastness of space but what struck me today was the association of the placement of the heavenly bodies with Yahweh’s protection. The Lord our God provided the heavenly bodies for the benefit of all people everywhere.[1]

The earth is vulnerable to asteroids and comet heads. These arrive as meteoroids and those that make it to the surface are called meteorites. We can see evidence of their existence in the craters on the moon.

The Earth is the only planet located in the Habitable Zone of the solar system. The prime location of the planet allows temperatures and pressures to be such that liquid water is stable at the planetary surface.[2] This further allows an atmosphere that forms a protective barrier, burning the vast majority of the meteors that actually make it this far.

However, the Earth is also protected because a lot of the interplanetary debris has been swept up, reducing the rate of large impacts on our planet.[3] But what swept up the debris? For one, the Earth is somewhat protected by the moon from collisions.

However, Earth's distant big brothers, Jupiter and Saturn are continuously sucking meteorites and asteroids from traveling inwards towards the earth.[4] Jupiter, in particular, has been responsible for attracting many such bodies including most recently and spectacularly, the comet Shoemaker-Levy 9.

Years ago, astronomers predicted a spectacular meteor storm in 1899 that failed to show on schedule. It was later determined that the Leonids did not make it at the same rate as was predicted due to close encounters with both Jupiter in 1898 and Saturn in 1870.[5]

In 1967, one of the first mathematical surveys of the perturbations suffered by the Leonid meteor streams determined that Jupiter and Saturn were primarily responsible for altering the courses of potential meteorites but that Earth itself could also shorten their revolution period by several years, strongly altering their eccentricity and even their inclination!

The only conclusion I can draw is that the combined effects of the Earth’s constant motion around the sun, the sun’s overpowering attraction as asteroids approach the center of the solar system, the constant shielding presence of a large rock circling us, and the two planets farther out that each come in and out of the range of incoming debris, places Earth at a precise sweet spot within the solar system.

Add to that a protective atmosphere capable of burning up most of the debris that makes it through that gauntlet and which is only available at this precise distance from the sun and I’d say that God is doing a pretty awesome job of looking after us.


[1] Deuteronomy 4:19
[2] http://www.nhm.ac.uk/index.html
[3] http://library.thinkquest.org/12857/earth/earth.html
[4] http://naca.central.cranfield.ac.uk/dcsss/2004/C21_vedern1c.pdf; also, Wetherill, Science News February 18, 1995; also, Liou and Mlhotra, Science, January 17, 1997 p. 375 “Depletion of the Outer Asteroid Belt”
[5] http://meteorshowersonline.com/showers/leonidhis.html