Excerpts:
In the new story of the solar system, the future is a bit dicey, and it all began in chaos.
When most of us were growing up, the solar system seemed reliable and well behaved. “There were nine planets orbiting in well-determined orbits like clockwork, forever,” says Renu Malhotra of the University of Arizona. “Forever in the past, and forever in the future.” Planetarium displays and the lovely mechanical devices called orreries embodied this idea, which went back to Isaac Newton...
Soon clockmakers were building increasingly elaborate orreries, with brass planets that circled the sun on unchanging pathways...Newton himself knew that reality was messier. The planets, he recognized, must also interact with one another. Their gravitational tuggings are far weaker than those of the sun, but over time they affect the paths of neighbors...
But a far more dramatic view has arisen in the past decade or so. While the findings from Stardust indicate the solar system was turned inside out during infancy, many scientists now think it also went through a raucous adolescence: Hundreds of millions of years after they formed, the biggest planets swept into new orbits, casting large rocks and comets every which way. In this view the scarred surface of the moon is lingering testimony to a period of epic mayhem. [Electric universe theorists have a different explanation, see more below]
“Who would have thought the giant planets might move, that the entire layout of the solar system could change?”
By the early 2000s they had long since realized that the birth pangs of the solar system had been violent. The planets had not condensed gently from the solar nebula; instead they had grown to full size by absorbing planetesimals—rocky asteroids, icy comets, and larger objects—that smashed into them at high speed. According to one theory, the moon coalesced from the spray of molten rock that was blasted into orbit when a body the size of Mars collided with Earth...[depicted in National Geographic’s cover photo linked above]
The puzzle was that the extreme violence didn’t end then. Many hundreds of millions of years later, the moon suffered a series of major impacts that left it permanently scarred with huge craters. This so-called Late Heavy Bombardment would have pounded Earth even more viciously. Scientists had no good explanation for what sparked it, since by the time it happened, the planets had swept their orbits mostly clean of debris...
Clearly many planets had migrated, but smooth migrations didn’t seem to account for extreme orbits and late bombardments, at least not to Levison. He began to suspect that our solar system’s history had been anything but smooth—that it had somehow endured a “global gravitational instability,”...
A lot of comets were also hurled into the inner solar system, where they crashed into planets or fell apart in the heat of the sun. Meanwhile the giant-planet migrations also disrupted the rocky asteroid belt between Jupiter and Mars. Scattering asteroids joined comets from farther out to create the Late Heavy Bombardment...
A recent NASA mission called GRAIL documented how badly our moon suffered then and earlier in its history: Its entire crust was deeply fractured. Earth would have caught even more flak, but shifting tectonic plates have erased the craters. Any early life could only have survived deep underground.
[Electric universe theorists provide convincing arguments that the moon’s craters are the result of plasma discharges, not impacts, and that Earth actually caught less “flak” because, unlike the moon, it has an electromagnetic shield around it. However, thanks to GoogleEarth, many impact craters on Earth have been discovered—many of which occurred in relatively recent times.]
Forecasting the solar system is like forecasting the weather. There’s so much randomness in the system, says theorist Greg Laughlin of the University of California, Santa Cruz, that the forecast—as well as any historical reconstruction—has to be given in probabilities.
