Rare Earth: our protective magnetic field (Introduction)

by David Turell , Sunday, April 17, 2016, 23:38 (3142 days ago) @ David Turell

This paper takes the position that until the magnetic field grew strong enough to protect us from gamma rays and other nastiness, multicellularity did not appear. I think that is a side issue. The magnetic field is protective but it also holds our atmosphere here:-https://www.washingtonpost.com/news/speaking-of-science/wp/2016/04/14/you-might-still-be-a-simple-bacterium-if-not-for-magnetism/-"Earth is a giant magnet, and the atmosphere stays in place because of this magnetism. But the atmosphere wasn't always as thick as it is today, nor was the magnetic field as strong. Scientists think that about 500 million years ago, Earth's core solidified, turbocharging our magnetic field. This would have allowed the atmosphere to hold more gas, in part shielding early life from powerful solar rays - and allowing multicellular life to evolve.-***-"For 3 billion years, life on Earth was only home to water-dwelling, single-celled organisms like bacteria. But suddenly, multicellular life ballooned, knocking over the first domino in an evolutionary cascade that would one day allow you — yes, you — to exist and think and even read stuff on the Internet.-"Scientists think that until 500 million years ago, life on Earth fell victim to high-energy blasts from the sun, which at the time contained a lot more of the cell-killing gamma, ultraviolet and x-rays than it does today. The atmosphere then was too thin to fully protect our single-celled ancestors, whose DNA would have been damaged by such powerful rays. That kept them from becoming more complex.-***
"As Earth got older, heavier metals like iron and nickel sunk to the center and solidified under the pressure of the rest of the planet. Once the inner core was solid, it started spinning separately from the outer core. That would have made Earth into a more powerful magnet, which could have boosted its magnetic field.-***-"Scientists think the stronger magnetic field would have kept more gasses in the atmosphere, just as a stronger magnet can hold more paper clips. That means more oxygen was around to help cells grow, and a thicker atmosphere could protect those budding organisms from solar blasts. Simultaneously, the aging sun's radiation started weakening, which means its flares contained fewer dangerous, DNA-altering rays.-"That perfect confluence allowed the number of species to skyrocket, the authors say.-"Others also emphasize the importance of Earth's magnetic field as crucial to life on the planet. Recent work even suggests Mars's lack of strong magnetic field was what allowed the sun to strip away its atmosphere, leaving the planet barren."-Comment; their theory makes little sense. Bacteria existed in the ocean, protected from the rays. So did the Cambrians, who were multicellular. But as part of 'rarity' of Earth is the magnetic field, absolutely vital.