On the one hand, there's a huge universe - that could be teeming with life.
On the other hand, Earth is the only place where we know that there actually is life. So far.
Life, Not-As-We-Know-ItFred Hoyle, in his Black Cloud, described a vast creature that - or, rather, who - lived most of its life in deep space. It hadn't considered the possibility that anything could live on those little things orbiting stars, until folks on Earth started rather frantically trying to start a conversation. It's unlikely, in the Lemming's opinion, that Hoyle's cloud-creature is similar to anything we're likely to meet. Chiefly because it's really hard to see how a critter like that could develop.
Life As We Know It: Getting Down to Earth; or PlanetOf course, scientists aren't all that positive about how life got started here on Earth. Some 'explain' life here by saying that it was carried here from somewhere else, inside a meteor. That isn't, in the Lemming's opinion, much of an explanation since it still doesn't address the big question: wherever life got started, how did the process work?
And that's another topic.
It looks like living things need to have something to live on: a planet, moon, or whatever we're calling Ceres now. When the Lemming grew up, it was called an asteroid. Now: but that's yet another topic.
Until fairly recently, the only place we could be fairly sure there actually were planets or similar places was the Solar system.
The Solar NeighborhoodArmed with a little information, quite a bit of guesswork, truckloads of imagination, and a marvelously elastic capacity for willing suspension of disbelief, folks who made science fiction magazines in the early 20th century industriously populated the worlds from Mercury to Pluto with people. Colorful (literally) people.
Then we started learning more about the other planets circling our star. Mercury was simply too close to the sun, too hot, too small: interesting to study, but certainly not a home to disturbingly-friendly bat-eared crab people, like Chuckles over there.
Is it just the Lemming, or does that Mercurian with the 1,000-watt smile look like he's selling something?
Yet one more topic.
Venus might have been quite a bit like Earth: except it isn't. It's nearly the size and density as Earth. It even has (small) continents: that may be made partly of granite. No water, though. At least not for a very, very long time.
Mars looked promising: until about four decades back, when we learned just how thin Martian air is. For a while it looked like Mars was terribly dry, too: but that's changed recently.
The Lemming's written about the inner Solar system before:
- "New Look at the Lost Ocean of Barsoom"
(June 15, 2010)
- "Oceans on Venus; a Very Long Time Ago; Maybe"
(July 15, 2009)
- "Mercury: A Hot Little Planet"
(May 2, 2009)
- Compares Mercury to Mars
- "Climates in the Inner Solar System"
(February 28, 2008)
The outer Solar system just might harbor life: under the surface of Ceres or Europa; or on Titan. The Lemming thinks it's a long shot: but not at all impossible.
The Galactic NeighborhoodIt looks like our best bets for finding life elsewhere in the universe are circling other stars.
The count of planets beyond the Solar system passed 400 last year, and the rate at which new worlds are being discovered seems to be picking up.
Whatever else today's world is, boring it isn't. In the Lemming's opinion.
The first planets discovered outside the Solar system were huge, and orbiting very close to their stars. Astronomers have been developing more subtle techniques for finding extrasolar planets, and some of the recent finds have been not more than a few times as massive as Earth.
Nobody's discovered one with an atmosphere that's mostly nitrogen, with about 20 percent oxygen and oceans. But a few aren't all that unlike Earth. One of them, Gliese 581g, looks really promising in terms of size and how far it is from its star. (October 2, 2010)
What would life from another world be like? That's yet again another topic.
- "Life on Other Worlds: Limited Only by Imagination and Production Budgets"
(January 1, 2011)
- "GJ 1214b: Super-Earth, With an Interesting Atmosphere"
(December 2, 2010)
- "Gliese 581g: Then Again, Maybe So"
(October 14, 2010)
- Or, looking at all the data
- "Gliese 581g? Maybe Not"
(October 13, 2010)
- " 'More Than 100 Earth-Like Planets' Found? Well, No: Not Really"
(July 24, 2010)
- "Planets Found Circling Other Stars: 429 So Far"
(February 15, 2010)
- "Rocky Planets May be Common as Dirt"
(February 18, 2008)