The Five Ages

The current state of the distant future

Archive for May 2009

Seven subjects

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Picture 8

Over the past decade, I’ve resided on the swampy verge of being a public intellectual.  This generates an intermittent stream of inquiries from producers of television documentaries dealing with futuristic global catastrophes. Of late, the frequency of these inquiries has increased. A trailing (and leading) indicator, perhaps, of the zeitgeist. Last Thursday, I got an email which read in part:

“We are in early development of a big one-off special for Discovery Channel. The narrative is simple – seven great scientific miracles of the Earth, how they’ve gone wrong in the past, and what would happen if they went wrong again now. Our subjects are:

1. The spinning Earth suddenly stopping

2. The Earth’s core becoming unstable

3. The collapse of the Earth’s magnetic core

4. How gravity might go wrong

5. When is the next ice age?

6. Does life come from outer space?

7. Are humans indestructable?”

Point one is clearly of no concern. There’s no viable mechanism of any consequence whatever that could induce  gross worldwide violation of angular momentum conservation. The Dow will go to zero. Earth will continue to spin. In the growing clamor of anxieties, we have confidence that the Sun will continue to rise.

Maybe point two alludes to concern over a near-term episode of trap volcanism? Catastrophically large eruptions associated with mantle plumes, which with a significant stretch of colloquial license might be described as “the Earth’s core going unstable”, have wreaked havoc in the past. Last September, queued seven-deep on the hot asphalt at a traffic light, I heard an NPR segment that linked the formation of the Siberian traps at the Permian-Triassic boundary to the Great Dying, the Permian extinction. The parallels — catastrophic global warming, ozone depletion, massive buring of coal, anoxic oceans, paving 7 million square kilometers of land area — all seemed to have a certain currency.

Point three must be referring to a reversal of Earth’s magnetic field. No big deal. A declining global dipole field prior to a reversal would wreak havoc on satellite electronics, and there is a possibility of environmental consequences (see here), but field reversals have occurred thousands of times in Earth’s history, and we’re here.

Point four. There’s no immediate problem with gravity (that I know of). It would be very weird if it “went wrong”. Perhaps decay of the false vacuum would change G? Orbital instability mediated by gravity, however, is an entirely different and much more clear-cut matter: one percent chance in the next 5 billion years. Laskar’s upcoming Nature paper will be the definitive reference on this issue.

Point five. Possibly later rather than sooner, but as of this writing, I’m currently out of my depth. Here’s a peer-reviewed article (Berger & Loutre, Science 2002) arguing that the present pulse of greenhouse gasses will act to delay the onset of the next ice age. It’ll be interesting to return to this question.

Point six seems a little out of place. Does he refer to an Andromedae Strain-style extraterrestrial virus? To the space refugium hypothesis? It seems clear that there’s very little transfer of material between mature solar systems in our galaxy, making it a real stretch that extrasolar microorganisms seeded Earth via an impact vector. Aliens arriving in space ships likely pose a higher risk.

A recent paper in the Astrophysical Journal argues that it’s possible that Earth has seeded several extrasolar planets with microbes. That would indeed be quite an accomplishment.

Point seven: no.


Written by Greg Laughlin

May 25, 2009 at 7:23 pm

The Doomsday Argument

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Graham Giller sent me an e-mail the other day.

Greg, are you familiar with the Doomsday Argument? Since you’ve done work on long term evolution of systems, I was wondering what you thought of it. My feeling is that it fails because of the assumption that there exists a final human with absolute certainty. That is Pr(Exists M s.t. M > N for all N)>0, where N is the ordinal number of the last human, which seems to be unjustifiable.

Any thoughts?

A number of lines of evidence make it quite clear that we live in a universe with a non-zero cosmological constant. The rate of expansion of non-gravitationally bound regions of the universe is accelerating, and if the cosmological constant is truly fixed, this acceleration will proceed indefinitely. Kraus and Starkman have done an extensive back-of-the-envelope treatment of the survival of life (or more specifically computation) in an accelerating universe. They conclude that computation cannot proceed indefinitely — the cosmological constant implies a minimum temperature for space, which will eventually make it impossible to store and retrieve information.

I think N is finite. Any guesses as to its value?

Written by Greg Laughlin

May 25, 2009 at 12:09 am

Fast forward

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Picture 102

The long-term fates of Civilization, Life, the Earth, the Solar System, the Galaxy, and the Universe are areas that can be meaningfully explored using our current fund of information. Our view of the future can yield insights into the present — the goal of this web log.

Written by Greg Laughlin

May 24, 2009 at 9:30 pm

Posted in Uncategorized