h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Historical Geology was my favorite subject in college. You've done a heroic job of putting your lizardlike subject in perspective.

You wrote, "But the snowball did thaw, we're not sure just how." Well, one theory is that breaking the feedback mechanism that kept the Earth so cold would have taken about 350 times as much atmospheric carbon dioxide as we have now. The question would be where that much CO2 would have come from. Well, it could have taken up to 30 million years for volcanoes to pump enough CO2 and methane into the atmosphere. Or maybe some organisms under the ice converted organic carbon into gas. Or the continents shifted enough to reduce sun reflectivity. Or the Sun went through one of it's cycles where it put out more energy. Or maybe the tilt of the planet changed in such a way as to focus more sunlight on portions of the earth that would absorb it rather than reflecting it back.

See how many factors go into climate? This just makes it more miraculous that lifeforms (including us) cope and even thrive.

Hello! I'm glad you enjoyed this ... I was a bit worried I'd crammed too much in. Anyways I wish I had time, I'd write an entire book about the history of Earth and its life!

Thanks for the suggested possibilities for how Earth might have broken from its snowball phase! For sure, climate depends on many variables. I am just hoping we haven't messed things up too badly. What I worry about a bit is that we might do something that might significantly change the atmospheric composition ... Very much lower or higher oxygen and/or carbon dioxide levels might make life virtually impossible for us. I'm still going to try to research more about what caused the Permian and other mass extinctions. Maybe we can learn something that might save us ...

I liked it too. Until Dr Who arrives in his tardis, I guess we'll never know what happened way back there. It is fascinating to think of the possibilities!

I tend to get philosophical about the ways in which human minds work -- not individually, but en masse. What were the two big defining human inventions? Fire and the wheel. We take them so much for granted nowadays that we automatically assume we can solve our problems with one or both of them. How to get around, for instance? Burn some gasoline in your car's engine, and go somewhere on wheels. The idea of getting your car to move without burning something goes against our assumptions. So what about electric cars? Well, generating electricity sometimes involves burning fossil fuels. Sometimes we let use photovoltaic devices, using the Sun's rays to generate power. Well, the Sun performs a form of burning, too. Or how about generating electricity by cranking something -- bicycle pedals hooked up to a generator, for instance. But even that involves the burning of glycogen by your leg muscles in order to perform the motions that run the pedals. You see, we can't seem to totally get away from those two big signature inventions.

Generating electricity from wind-driven or tide-driven rotors is also possible, but we don't warm up to this as much. Nothing had to burn in order to get electricity this way



Food for thought.

Hi Elektra! Well I'm hoping I might one day invent a tardis or some like time machine myself ... I just hafta know the details of what went down in the distant past.

Hi PaulH! Interesting musings there. I think fire outranks the wheel ... after all many cultures, even advanced ones, did quite well without wheels until very recently. Fire however is something primal. Humans have probably been making fire for more than a million years. Over here, in the Makapan's Caves, there is a cave called the Cave of Hearths, where ancient Homo erectus-folks lived and likely made fires. So for a million years or more on this continent, groups of people have huddles around the warmth and light of fires. I'm sure there's a genetic memory of that still inside us.

Excellent article, interesting and enjoyable, thankyou for your work writing this entry

Hi Bob, thanks for appreciating this article!

It deserved it