The “sensible anthropic principle” says that certain apparently unusual features of our environment might be explained by selection effects governing the viability of life within a plethora of diverse possibilities, rather than being derived uniquely from simple dynamical principles. Here are some examples of that principle at work.
- Most of the planetary mass in the Solar System is in the form of gas giants. And yet, we live on a rocky planet.
- Most of the total mass in the Solar System is in the Sun. And yet, we live on a planet.
- Most of the volume in the Solar System is in interplanetary space. And yet, we live in an atmosphere.
- Most of the volume in the universe is in intergalactic space. And yet, we live in a galaxy.
- Most of the ordinary matter in the universe (by mass) consists of hydrogen and helium. And yet, we are made mostly of heavier elements.
- Most of the particles of ordinary matter in the universe are photons. And yet, we are made of baryons and electrons.
- Most of the matter in the universe (by mass) is dark matter. And yet, we are made of ordinary matter.
- Most of the energy in the universe is dark energy. And yet, we are made of matter.
- The post-Big-Bang lifespan of the universe is very plausibly infinite. And yet, we find ourselves living within the first few tens of billions of years (a finite interval) after the Bang.
That last one deserves more attention, I think.
Re #22, #25:
“Ring” is a 1994 science fiction novel by author Stephen Baxter.
“… Lieserl is abandoned for five million years, leaving her to observe the sun’s interior. She discovers dark matter -based life, which she names photino birds. These birds gradually drain the energy from the core of a star, ending fusion and causing premature aging into a stable red giant—the birds’ preferred habitat, as it has no risk of going supernova and destroying them….”
http://en.wikipedia.org/wiki/Ring_(Baxter_novel)
Moshe, one of the few things we know empirically about dark matter is that it’s mostly dissipationless; it doesn’t collide and stick together. (Otherwise it wouldn’t make big puffy halos with ordinary matter accumulated in the center, at the bottom of the potential well.) It doesn’t follow that you can’t make life out of dark matter, but if nothing else indicates that the corresponding timescales for the dark metabolism would be enormously longer.
Dr Who, I am thinking of the Hawking radiation in the vicinity of an horizon. Which is not anisotropic, which (as you say) makes it much easier to make life. In fact, my guess is that there’s absolutely no way to support life from de Sitter radiation, but with black holes you at least have a shot.
And now I have to catch a plane to China. Have fun.
My query posted belatedly at the end of the July 29 item on the Reykjavik conference may be relevant to this item (here I’m taking as given that our Big Bang was a bubble nucleation in a larger multiverse, and that “the universe” in Sean’s last point refers to our bubble):
What was said in Reykjavik about the measure problem in multiverse cosmology?
In particular, (a) does it make a big difference whether the measure is defined on individual bubbles (e.g., on points in the “Landscape discretuum”) or takes volumes of bubbles into account? In the latter case, (b) is it compelling to regard the measures of individual bubbles as finite, even for bubbles that have infinite spacetime extent?
The possible relevance is that a “yes” answer to (b) might say that the finite measure rather than the infinite future lifespan is the important factor, thus removing the “anthropic surprise” of the latter.
(Or am I talking thru my CS-only hat? At least I found this recent talk by Maloney(-Shenker-Susskind) asking my question (a). My possible research angle is actually on the former case of (a), asking whether some Landscape points are “simpler” than others, and whether those points would be favored.)
The fact that a Caltech physicist (albeit a non-tenured one) is parading this nonsense would have Feynman rolling in his grave.
Who knew Feynman was such a fan of appeals to authority?
So Brian, would that be life as we know it, which requires oxygen and/or water had to wait for mud to form, to crawl out of the mud, and is finite – whereas life in other forms (tinkerbell-like) could have existed since the dawn of Time? or soon after the big bang. After all if the elusive higgs field gives particles mass, there could always be something even more elusive – which cannot be fathomed or measured – yet.
is there any species external to our solar system, and what effect would this have upon locally gathered data, would the discovery of other data gatherer’s, strengthen or weaken OUR anthropic notions, how credible would the any-anthropic principle be if the Universe were teaming with varying species.. life?
Then we’d have to answer the question of why we are us and not them. This is conceptually the same as the childhood question “why am I me” (and not someone or something else), or in many-worlds QM, the question of why I find myself in one universe and not another. I don’t know if anthropic reasoning can be extended to answer these questions. Analyzing the why-am-i-me question can lead you down a rabbit hole so deep you may never return.
Moshe—Sean is correct that life can’t be made out of dark matter. It can, however, be made of dark energy. Proof: Richard Cheney
For the last point, the current instance of life on Earth is viable only for a very narrow range of temperatures. It would be neat to determine the likelihood of finding a planet with that stable temp range as a function of distance from the Big Bang.
OK, another counterfactual question:
Helium is actually rather complicated stuff. Why couldn’t life be made of vortices in blobs of liquid helium?
And another: why couldn’t life be made of black holes? It has at least been shown that one can make a Turing machine out of them.
… The question of the possible future infinity of the Universe is a funny one. But unless there is some highly energetic matter-creating event in the future, heat death surely wins in the end. That is, very slowly through fusion or fission everything turns to iron – and if protons decay, not even iron survives. So there is a finite interval of time within which chemistry is possible.
The problem is that we seem to live very early in this interval – unless there are additional conditions on astrophysical evolution which prevent anything from living much later.
“The fact that a Caltech physicist (albeit a non-tenured one) is parading this nonsense would have Feynman rolling in his grave.”
You mean Archie Feynman, who used to be the janitor in your building? Certainly not that other Feynman who used to sit around in hot tubs discoursing on nanotechnology.
Let me explain to you how it works. Questions about the origin of the arrow of time are real science — only a few crackpots think otherwise. Playing with questions about the possible forms that life might take is just an attempt to find new ways of thinking about that real problem. Of course it is not important whether life might evolve around an evaporating black hole. But understanding *exactly* what the sun does for *us*, in terms of the second law of thermodynamics, is of course a genuine question. Again, the fate of the arrow of time in the remote future is a question worthy of anyone at Caltech. Or even at a good university [sorry, sorry 🙂 ]
Hi Sean,
Why do you think the last one does deserves more attention?
Also, I have recently been thinking about the talk you gave at PI some while ago. The entropy/arrow of time stuff – I’m still chewing on that. A somewhat odd question: how much of your argumentation relies on QM being non-deterministic?
Best,
B.
But, Thomas D, did you see my earlier post about the views of Andy Albrecht? I don’t think he is right, for various reasons, but the possibility is there that an arrow of a *new* kind might be getting started now that acceleration has taken over…..
B, since Sean is in China, maybe I can make a stab at that: quantum indeterminacy has nothing to do with it. Again, see Andy Albrecht’s wonderful paper. I agree with him on this matter.
As for oddball life (which I find fascinating): The late Dr. Robert L. Forward, who also championed offbeat (but physically plausible) new propulsion schemes, wrote some books (articles/excerpts first, in Analog first I remember) about life on a neutron star. Dragon’s Egg was first in the series. The Cheela were essentially spiced-up nuclear matter. They were the size of sesame seeds, and their activity rate was millions of times faster than ours. It’s fascinating. There were also some writings by Poul Anderson about the Kyrie, “energy” beings. In one touching story (IIRC), one of them sacrifices itself to save some humans, IIRC, and falls into a black hole. Because of time dilation approaching the event horizon, a telepath partner of the Kyrie can experience its thoughts for the rest of her life. (If it’s still working, you can listen to a reading of it at Link)
BTW, there’s some recent rethinking of what happens around black holes, but it doesn’t look like fundamental theory (like evaporation) but the nuts and bolts of what actually happens when matter falls in:
Link
For life to arise in or around black holes would be very weird and interesting indeed.
One of the cutest notions wasn’t about alternate life in our own universe, but the saga of the 2-dimensional Ardeans that had a rough time coping with their planar world. (This was a true 2-D analog, with the planet being a circle and movement going around that, instead of the floor-like world of Flatland.) It was The Planiverse: Computer Contact with a Two-Dimensional World by A.K. Dewdney, who later got some notoriety challenging official reports of 9-11 events. The Ardeans had to walk over each other when the met on the planet’s surface! The attempt to adapt to 2-D was ingenious, and made me almost think it could work somewhere. (Note there were real Ardeans who revolted against Rome long ago.)
Supposedly consistent physics was developed for the Planiverse, with “obvious” features like 1/r force attraction between masses and charges. However, that would make the potential energy between any two masses or charges infinite. If energy has mass, that’s a real problem (and not at the quantum level here.) I also can’t see how EM radiation would work out consistently. That reminds me, where can I find a good rundown of extrapolations of classical EM etc. to other dimensionalities, not high-brown string theory etc? Thanks.
B, the last statement deserves more attention because it doesn’t start with: ” Most of the…” 🙂
Hi Dr. Who:
Thanks. I will have a look at the paper. Maybe I should clarify my question. On Sean’s earlier post (against bounces) he wrote you have one of two choices: either the entropy continues to decrease as we travel backwards in time through the Bang, or it changes direction and begins to increase. Sadly, neither makes any sense. I remarked that to me the obvious conclusion (besides throwing away the model) would be that entropy remains constant.
I still don’t understand that point. What is entropy? It is the number of possible microscopic configurations for a given macrostate. If I start with a universe that has entropy soandso, the second law of thermodynamics tells me it doesn’t decrease. This is based on a stochastic reasoning. The probability that the macroscopic state remains ‘ordered’ is just very small. Fine, I understand that. But think about what ‘ordered’ means if the evolution is deterministic. The present state would be a one-to-one map of the initial state. It might not appear to be ordered, but it’s in no way more or less random than the initial state was. This argumentation relies on a determinism though, in which case there is no ‘true’ stochastic evolution. It’s only with QM that outcomes of interactions/scattering are truly random and disable the possibility to trace the state back in time.
Best,
B.
Hi Count:
😉 Well, yes ‘deserves attention’ can be interpreted in many ways. I just meant to point out one has to be careful with probability distributions over time, as we know there are evolution laws (causal connections) that have to be obeyed, so one can’t just ‘distribute’ without correlations according to a given density (as one could do over space-like surfaces). See my post on the Doomsday argument and comments there. Best,
B.
B, thanks! That was an interesting posting on your blog that I missed. My opinion on this matter is essentially what Ken Olum has pointed out.
The Doomsday paradox is, i.m.o., an artifact of, on the one hand saying that we could have been any person in the history of the human race (that can be disputed e.g. using your arguments, but let’s accept it for argument’s sake), and on the other hand not taking into account that then we must also take the a priori probability for finding ourselves alive at all to be proportional to the total number of people that will ever live.
This is explained in detail in the article by Olum.
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Re #29, 30, 37:
Technically, there have been at least 5 Feynmans on the Caltech campus several times each.
Richard Feynman (my mentor and coauthor); his (2nd) wife (now widow); his sister (who lives in Pasadena and does NOT have her brother’s thick Brooklyn accent); his son; his daughter (most recently on campus when the Postal Service released the Feynman postage stamp). His daughter apologizes for the Permissions Editor screwing up and leaving a poem I coauthored with Richard Feynman out of the Selected Letters.
“Footnote to Feynman”, Jonathan V. Post and Richard Feynman, [Engineering & Science, Caltech, Pasadena, CA, Vol.XLVI, No.5, p.28,
ISSN: 0013-7812, May 1983; reprinted in Songs from Unsung Worlds, ed. Bonnie Bilyeu Gordon, intro by Alan Lightman (award winning author of Einstein’s Dreams), Birkhauser Boston/AAAS, hardcover ISBN: 0-8176-3296-4, paperback ISBN: 3-7643-3296-4, 1985
“Starscapes” for Chamber Choir, Three Woodwinds, Piano and Magnetic Tape;
Composer: Van Decker; texts by Jonathan V. Post & Richard Feynman, “Footnote to Feynman”, University Music Center, California State University, Long Beach, CA, 18 May 1990]
I am lucky indeed to have coauthored with Feynman, Forward, and so many other collaborators. Indeed, I am collaborating now on a paper which discusses in depth two of Sean Carroll’s arXiv papers.
As to the far future, my article on this, which cited Freeman Dyson and others, which first published the idea that we are most likely simulations by a far future dilute electron positron plasma civilization, and which served as the extensively quoted basis (quotation marks accidently omitted) of some Greg Benford novels, is:
“Human Destiny and the End of Time” [Quantum, No.39, Winter 1991/1992, Thrust Publications, 8217 Langport Terrace, Gaithersburg, MD 20877]
ISSN 0198-6686
We find ourselves in a young Universe, but we may indeed find ourselves in an old Universe, at some time in the future. It’s a great experiment. It may take billions of years, but, i’m willing to wait.
Time flies like an arrow. Fruit flies like a banana.
What is this obsession about infinity? As far as we are concerned, in practical terms infinity does not exist for us. How can you tell when you have found one? It would take forever to measure it. How can you tell when one has elapsed? It would take forever to wait that long.
Finite but unbounded is the best we can do.
To: all
From: CEO
Subject: Devilish vendor causes major anthropic screw-up
It was the Corporate Committee on Systematic World Ordering which initiated an RFP, cost-plus basis. Failure to recognize that Hellaburton was an unreliable contractor, certain problems with shoddy workmanship and substandard materials quickly emerged.
These however were plastered over for at least 4 billion years until the first multicellular creatures appeared in planet’s Precambrian oceans. By then it was too late to adjust any nucleotides. After all, it is a double blind test.
The last 550 million years, however, have proved one unforeseen disaster after another, culminating in Nature’s Greatest Mistake, humanity. Currently, almost 7 billion cases of hypertrophy of the prefrontal cortex!
Looks like heads must roll. The Corporate Committee on Oort Cloud Exploitation hopes to find a suitably large comet in the next 65 million years, give or take 5 million years.
However, let there be light. The standing Corporate Committee on Bio-organics has estimated that the average species lasts only about 2 million years.
Personally, I find myself inordinately fond of beetles. Call it the arthropodic principle.
eye-of-horus
copyright asserted 2007