October 20, 2017

Review: Rare Earth by Peter Ward & David Brownlee.

A controversial classic!

It is perhaps one of the greatest scientific questions of our time. How common are we? Is our existence here in time and space a widespread occurrence in the cosmos, or are we so unique that we are effectively alone? The topic of this week’s review represents a landmark paradigm shift and is an often quoted book that I’ve always wanted to get around to reading and reviewing. Rare Earth: Why Complex Life is Uncommon in the Universe by David Ward & Peter Brownlee posits that animal life in general and intelligence such as our own in particular is a rare, perhaps a singular event in our corner of the galaxy. Published in 2000, its interesting to see how the science of the day stacks up to current thinking. For example, in 2000 a handful of exoplanets were known; almost all were “hot Jupiters,” and the prospects for terrestrial planets looked slim. To date, 779 extra-solar planets have been discovered using a variety of methods, providing researchers with enough data to classify and characterize various types of planetary systems.

It should be noted that the authors do point out that while animal life may be a tough hurdle, simple bacterial life may be common in the cosmos. Our own story lends some credence to this supposition; once conditions in the early history of life on Earth stabilized about 3.5 billion years ago, simple life arose readily. For almost 90% of the span of life on Earth, however, life remained at the simple one-celled stage. It seems that at least in our own case, going to complex multi-celled life was the hard part; but yet in less than a billion years, the explosion of plant and animal life led to dogs, cats, humans, Ipads, etc. How common this tale is remains to be seen. Certainly, the discovery of bacterial life past or present within our own solar system may lend weight to the first half of the Rare Earth hypothesis.
Among the factors that the authors site as conducive to life as we know it;

-An orbit around a single relatively stable star that maintains a steady output for many billions of years, long enough for life to develop;

-A stable orbit within the habitable zone of said star, a place where water can exist in liquid state;

-Condensation from a proto-solar nebula with a high “metallicity” (remember, to an astronomer, the universe is hydrogen, helium, & metal!) full of lots of great but scarce raw materials such as carbon, silicon, nitrogen, etc.

-A single large Moon that acts to stabilize the tilt of the Earth;

-A large “goal tending” planet like Jupiter that deflects a good portion of the life extinguishing comets that come our way.

-A stable position in the galactic habitable zone, not too close to the radiation-riddled core and not in the outer metal poor ‘burbs. A good distance from any life extinguishing supernovae or gamma-ray bursters helps too, a sort of “may you live in mediocre times” curse/blessing.

-Active tectonic plates allowing for subduction and sequestration via a rock and carbon cycle.

To this end, the authors add some interesting twists to the famous Drake Equation, allowing for the events that brought us here in the mix. Certainly, if some of the scenarios such as the formation of our Moon are mandatory, chances for life are slim. One only has to look at the caveats offered by our neighboring worlds of Venus and Mars to see how different the Earth could be.

Still, a nagging hunch pulls at the back of our brain as we read Rare Earth… just how viable is a statistic of one? Are all of these happy accidents mandatory, or can life, once it’s started, make due even under drastically different conditions? One could also point out that these conditions aren’t exactly stable or permanent; the tilt of the Earth’s axis does vary, the output of the Sun is increasing and fluctuates with time, etc. It would be great to have a better understanding of the minimum and maximum criterion for life as it relates to these events. Carbon is probably crucial; no other element forms such long complex chains, although silicon is sometimes also cited as a possible alternative. Water also makes a great ‘universal solvent…” but might oxygen be poisonous to some forms of life? Would we recognize life drastically different from us if we saw it? I’m reminded of Arthur C. Clarke’s Report on Planet Three, where a Martian scientist gives a long and convincing discussion on why life on a hostile planet such as Earth couldn’t be possible.

Read Rare Earth as a very timely and still largely pertinent discussion on one of the biggest questions of our time. I would also recommend James Kasting’s How to Build a Habitable Planet as a great look at how the Earth came to be. Either conclusion has stunning implications; of course, most of us root for sentience and a cosmos teeming with diverse life with Klingons and Vulcans bickering about treaties in a Galactic Federation… but if we are truly  ”it” in our tiny niche of time and space, doesn’t that make us and the Earth all that much more precious and unique, a jewel worth safeguarding and preserving?

The Elusive Wow by Robert H. Gray.

On sale now!

Nothing fires the scientific imagination like the search for extraterrestrial intelligence. And likewise, no discovery would have further implications to our own existence and what it means to be human. Plus, it would just be darned interesting to get to know something about them. How unique are we?

[Read more...]

Review: Strange New Worlds by Ray Jayawardhana.


It’s weird to stop and think that we now live in a time that we know of the existence 573 new exoplanets, and by the time this cyber-ink goes to press, that rolling number will become obsolete. “In my day,” (my halcyon youth of the 70’s) Eight-tracks where still cool and astronomers guessed that exoplanets had to be common, but no one had as of yet found definitive evidence that this was indeed the case. [Read more...]

21.04.11: Of Alien Flora and Maunder Minimums.

Sol picking up in activity… (Photo by Author).

Some fairly thought provoking science has been coming out of the Royal Astronomical Society’s National Astronomy Meeting being held this week in Llandudno, Wales. One of the most interesting talks was by Dr. Robert Forsyth of Imperial College concerning a comparison of the current solar lull and the famous Maunder minimum of 1645-1715. [Read more...]

12.03.11: Attack (on the) Cyanobacteria?

Our x1023 Grandparents? (Credit: Richard B. Hoover, MSFC, Journal of Cosmology). 

This sunny weekend, we’d like to give some thought to the news story that erupted last weekend. Unless you’ve been off world, you’ve no doubt heard that researcher Richard B. Hoover of NASA’s/Marshall Space Flight Center released a paper via the Journal of Cosmology indicating the possible presence of fossilized cyanobacteria in certain types of carbonaceous meteorites. [Read more...]