How Earth Avoided a Fiery Premature Death 114
Hugh Pickens writes "Space.com has a piece about changing theories of planet migration. The classic picture suggests that planets like Earth should have plummeted into the sun while they were still planetesimals, asteroid-sized building blocks that eventually collide to form full-fledged planets. 'Well, this contradicts basic observational evidence, like We. Are. Here,' says astronomer Moredecai-Mark Mac Low. Researchers investigating this discrepancy came up with a new model that explains how planets can migrate as they're forming and still avoid a fiery premature death. One problem with the classic view of planet formation and migration is that it assumes that the temperature of the protoplanetary disk around a star is constant across its whole span. It turns out that portions of the disk are opaque and so cannot cool quickly by radiating heat out to space. So in the new model, temperature differences in the space around the sun, 4.6 billion years ago, caused Earth to migrate outward as much as gravity was trying to pull it inward, and so the fledgling world found equilibrium in its current, habitable, orbit. 'We are trying to understand how planets interact with the gas disks from which they form as the disk evolves over its lifetime,' adds Mac Low. 'We show that the planetoids from which the Earth formed can survive their immersion in the gas disk without falling into the Sun.'"
Re:If it didn't happen, it wouldn't have happened. (Score:4, Insightful)
I suppose so but this article is about why it didn't happen.
Who knows (Score:2, Insightful)
Re:Who knows (Score:3, Insightful)
Or maybe we ARE plummeting into sun, but at a rate that is too slow to be observable.
Except for the fact that if something is falling slowly, it ain't a plummet. From the Oxford American Dictionary:
Worst. Semantic. Structure. Ever. (Score:2, Insightful)
The incorrect use of periods to indicate emphasis is not linguistic evolution. It is just semantic stupidity. I wish it didn't catch on.
Re:not this shit again (Score:2, Insightful)
Re:If it didn't happen, it wouldn't have happened. (Score:5, Insightful)
I just want to point out 1 more important factor in contacting, or meeting other civilizations in the universe: Time.
The age of our sun is a blink of an eye in the cosmological time scale. It's like tiny little lightbulbs going on and off and on and off. We might not reach an "on" one before ours turns "off", the destination is simply not turned on yet. It's a very lonely picture, but highly probable.