## Thursday, February 06, 2014

### Life 15 million years after Big Bang vs anthropic principle

Harvard/Israeli astrophysicist Abraham Loeb posted a rather creative, playful preprint one month ago that was discussed by Shalom Life (plus others) a few days ago:
The Habitable Epoch of the Early Universe
When we talk about life in the Cosmos, we usually think about habitable zones around the stars where the temperature is "just right" to allow for liquid water and other compounds that are useful for life as we know it.

But Loeb pointed out that the right temperature was once found in the whole Universe so stars were not needed.

Today, the temperature of the cosmic microwave background is about 2.7 kelvins. Because the Universe has been undergoing global cooling since its very birth, there has been a moment when the temperature of the cosmic microwave background was between 273 and 373 kelvins i.e. 0 °C and 100 °C. When was that?

Well, it was when the Universe was 10-17 million years old; the corresponding redshift is about $$z\sim 100$$. Assuming that there were any rocky planets – and I would argue that small rocks would be enough for microorganisms – some organisms may have had enough time to evolve over those millions of years (although we know that the Earth-bound journey of evolution ending with humans was substantially longer on Earth...).

He discusses the chances that the stars (producing heavier elements) form and explode in time and addresses the existence of "geological" thermal gradients that are needed for life. That "very early life" isn't necessarily connected with ours. The Universe probably had enough time to produce life from "scratch" in more modern eras. And it may have been hard to preserve the "hibernated" early life for our age.

But there's a possible implication for fundamental physics. If it were true that there were (intelligent?) life just 10-17 million years after the Big Bang, the cosmological constant at that time could have been 1 million times greater than it is in our Universe, without disrupting the life too much (by premature expansion). Such an alternative environment for life to emerge would pretty much destroy Weinberg's anthropic estimate of the cosmological constant.

Freeman Dyson and Juan Maldacena are among the folks who are thanked to in the paper.

Juan Maldacena talks about string theory and QCD for 2 minutes.

Off-topic: Czechoslovak hardcore communist dies

Today, in his rather fancy villa near the Bratislava Castle in the Slovak capital, Mr Vasil Biľak died at age of 96; ABC News. It's remarkable how long lives most of similar beasts have. The commenters at Czech servers generally celebrate the news.

A Czech "Kosmomol" group still worships such beasts as heroes.

He was born in Northeastern Slovakia but he was an ethnic Ruthenian (those folks mostly live on the Ukrainian territory today); nevertheless, he would learn the Slovak language rather well. Biľak was trained as a tailor; his final transcript famously said "don't allow him to touch tuxedos".

However, he would study some political schools and became a top commie. In 1968, he would be shocked by the liberalization of the society during the Prague spring. Along with 4 comrades, they would send a letter to Brezhnev: "Dear Leonid Iliyich..." in which they invited the occupation armies to come to Czechoslovakia.

And be sure, the sexy leader of our world (above) would listen and "help us" in August 1968. Biľak himself would be a top ideologue, the main author of the "Lessons from the Critical Development" after a 1968 conference of the Communist Party. His ideological 1971 speech is often quoted; it's full of Marxism, Leninism, opportunism, and he invented the story about the drunk farmer whose house is burning, so the sons have invited some firemen, but the dad then complained that the quilts got wet; it was a story that was later used by his comrade Al Gore. In the mid 1980s, he would try to fight against Gorbachev's perestroika.

After the fall of communism, there were attempts to arrest them for treason – something that they self-evidently have committed (even according to the laws valid in 1968) – but all such efforts were gradually stopped. So the reality is that none of the top commies has ever been punished in Czechoslovakia.

Milouš Jakeš, the last pre-revolutionary boss of the Czechoslovak Communist Party, is doing fine, older than 90 years, too. The only co-author of the "invitation letter" who had at least the decency to kill himself was Mr Antonín Kapek in 1990. After he found out he was a lousy shooter and survived, he would hang himself 20 miles from Pilsen.

Biľak prepared a book "Only After My Death" that will be published in March 2014 or so. I am slightly curious what it is about.

1. Firster than John Archer!

I screwed up my courage and actually read (or skimmed) through the paper. Luboš' characterization as "creative and playful" is accurate, I think. Now, keep in mind that I am math- and astrophysics-challenged. With those limitations in mind, I summarize the content as

(1) The first stars, whose collapse and explosion brought forth the heavier elements from which rocky planets could form, are generally thought to have lived and died during a time when the cosmic microwave background (CMB) temperature had fallen far below room temperature, below even the freezing point of water (at earth's sea level). However, there is a very small chance that such stars already formed and blew up within a few million years of the big bang, enabling rocky planets to form.

(2) If so, such planets would not necessarily have needed to orbit a star to enjoy life-friendly temperatures enabling water to stay in liquid form. The CMB was in the right temperature range then.

(3) However, that period (before the CMB temperature dropped below the freezing point of water) lasted only a few million years. As Luboš points out, a very short time for life to form, let alone higher lifeforms to arise. But if the planet had a warm core, heating from the core may have replaced external heating from the CMB, while planets "could have kept a blanket of molecular hydrogen that maintained their warmth". (Or maybe the microbes then living moved deep underground, miles below the surface, much like the microbes discovered miles below ground on Earth).

(4) The paper is speculative but not idly so: it is precise about what sort of conditions were needed to enable such a scenario and how likely (unlikely) they were, according to present knowledge. We may even discover evidence corroborating the scenario:

The feasibility of life in the early universe can be tested by searching for planets with atmospheric bio-signatures around low-metallicity stars in the Milky Way galaxy or its dwarf galaxy satellites. Such stars represent the closest analogs to the first generation of stars at early cosmic times.

The paper, however, is not content to discuss how life (of a form that we would recognize, i.e., most likely carbon-based lifeforms dwelling one or close to the surface of rocky planets) might have arisen. It is meant to challenge the "anthropic explanation for the value of the cosmological constant", namely, the hypothesis that the rate of expansion of the universe has to be what it is because otherwise there could not be intelligent observers (my recollection of the anthropic principle, hope it's not wrong).

Because the rate of expansion of the universe was orders of magnitude less in the early universe, the presence of life then would falsify this particular version of the anthropic hypothesis. The problem with that is that we will likely never have observational evidence of intelligent life during the earliest (~7 million years after the big bang) phase of the universe's life, whereas we do have unquestionable evidence of intelligent life during its present phase, namely ourselves.

2. one thing bugs me, because liquid water depends not only of temperature but also pressure. It seems that normal pressure is assumed, but at higher pressures liquid water may exist at higher temperatures. So habitable zones may be wider.

3. e.g., see this: http://files.abovetopsecret.com/images/member/f7d94d0b4523.png

4. So instead of shadow forming sunlight that we enjoy, the whole sky would be variously or smoothly bright, like on a fully overcast day.

5. Just to be sure, the wavelength corresponding to the hospitable temperature's black-body radiation is in the infrared, not visible! The visible light is close to (Sun-like) temperatures like 6,000 kelvins which are higher than hospitable. ;-)

6. kashyap vasavadaFeb 6, 2014, 3:22:00 PM

Hi Lubos: Was the CC really constant during most of the life of universe i.e after the first second
inflation, as the name ‘constant’ suggests or it varied by some factor? Is there lot of disagreement on that? Also personally (without any research on my part!)
I find it very hard to believe that the mechanism (e.g. inflaton etc.) which gives rise to enormous exponential expansion in the first second is
completely unrelated to the mechanism (CC) which gives rise to the current small acceleration. Of course it is possible.

7. Lumo, as Eugene S points out below, my first thought was that the first stars formed around 400 million years after the Big Bang and they went supernova several hundred thousand (or millions) years later. So heavy elements greater than hydrogen and helium needed to form rocky planets didn't exist yet at 10-17 million years after the Big Bang. Also not in existence at that time were carbon, nitrogen, oxygen, etc.; the building blocks of life. So Abraham Loeb is an astrophysicist who doesn't understand cosmology in the least. Even if current science is wrong about the first starts forming by several hundred million years (earlier), it STILL doesn't get us where we need to be with heavy elements in existence for life to start when the CMB was a balmy 273-373 Kelvin. If my logic is flawed, please correct me.

8. kashyap vasavadaFeb 6, 2014, 4:56:00 PM

I hope Lubos does not mind my jumping in before he replies to your comment. Most Asians belonging to eastern religions (excuse me for repeating this) and at least some Christians and Jews do not see that there is any conflict between religion and science.While doing science, of course, you do not bring in God. Even Newton, a devout Christian did not bring in God in his theories. Many people realize that both science and religion have limitations, talk about different issues and can coexist in the domains they overlap.

9. In the end, Communist policy became a mirror image of that of the most reactionary powers of Europe after the downfall of Napoleon, whose ringleader was Metternich. They signed the Troppau Protocol, providing that they would all unite in coming to the "aid" of any country affected by revolutionary disturbances. In the words of the protocol, "If, owing to such alterations, immediate danger threatens other states the powers bind themselves, by peaceful means, or if need be, by arms, to bring back the guilty state into the bosom of the Great Alliance." Brezhnev couldn't have written it better himself.

10. Is that a joke or are you serious? I honestly can't tell.

11. Well, he refers to lots of papers that talk about massive stars - 10-100 solar masses etc. - whose lifetime is comparable to 3 million years and presents calculations that many of those formed early enough.

400 million years is the moment of "reionization" which marks the start of stars as we know them today but you haven't convinced me that there couldn't have been stars well before that.

12. Better get out the history books, Lumo. Spain didn't have tanks back in the 15th Century, but a prominent (if dishonest) claim made was that the whole enterprise was made to "save the Indians souls." Not too different claims were made for the "white man's burden" to justify the conquest of India and Africa.

Conquest in the name of spreading imperial benefits actually goes back to ancient Mesopotamia. You can look it up.

13. Sorry, Pig, but this isn't in any way a counterexample to my assertion.

First, Spain was heavily feudal, not capitalist, in the 15th century. Second, as you observed, it didn't have tanks. Third, the Indians were not led by elected leaders.

14. So in order for this to work, we need:

1. Early star formation and supernovas creating and spreading heavy elements.
2. The formation from those heavy elements of planets/planetoids
3. Based on what Cesar Laia pointed out, we'd probably need those to be sufficiently massive to retain non negligible atmospheres so that the boiling point is not too low
4. We'd need them not to be around stars, since the near star environments are going to be too hot, I think? (I'm not sure about this one)
5. We'd really need, I think for this to be relevant to anthropic arguments, for life to evolve very rapidly into an intelligent form. Starting from scratch it took billions of years on Earth, so it needs to have evolved much more rapidly than that.

None of that is strictly *impossible*, the thing is that it is all *improbable*.

And also, we probably could never know even if it had happened, so it's not really useful for doing away with the anthropic argument in question. Much as we might like to be able to.

15. These days the science vs. bible debates seem to have a quaint 19th century obsolescent feel to them. The real fundamentalist action nowadays is in the toxic and regressive Islamic variety.

Its strange but true (although nothing is really strange any more in this multi-culti degenerate mess of an era) that in the old days the leftie elite shitheads would spend a lot of their time on the righteous struggle against Christian fundamentalism. Now of course this is completely forgotten in the rush to import as much as possible of the deadly Islamic version of the same thing. There's no question that your average Arab fundamentalist is a lot more
stupid and primitive than your average whitey bible basher. However both are rational beings compared with your average leftie wanker.

16. I agree that Bilak was a traitor, and that the invasion was an act of war. My point is that, in the end, the Soviet Union became the exact equivalent of the most reactionary regimes of the Holy Alliance, when it claimed to be their antithesis. In fact, at the behest of the Holy Alliance, France did the same thing to Spain in 1823 as the Soviets did to Czechoslovakia. They sent in a massive army to "help" Spain, deposing the government based on the constitution of 1812, and restoring Ferdinand VII to absolute power. The same policy was carried out in Hungary in 1849, when the Russians sent in a big army to "help" Austria by destroying a government that had the overwhelming support of the Hungarian people.

Apropos Hungary, it would be interesting to read your comments on Czech/Hungarian relations today. In particular, does any of the bitterness that prevailed between the two countries between the wars remain?

17. I don't know what you want to achieve by these bizarre comparisons. They sound weird and demagogic to me.

France's excursion to Spain in 1823 was mostly the action by one monarch who didn't want monarchies around him to disappear and be replaced by modern capitalism simply because it would weaken himself as well, so he started the same kind of ordinary "war for power" as hundreds of other wars in the history.

There was no "big ideology" behind it. It was just a normal innocent 19th-century-style (mini)war.

Hungary is viewed as mostly decoupled from Czechia and we don't have any major problems with Hungary these days - altough, Slovakia and Hungary have lots of problems and Czechs obviously prefer to side with the brothers Slovaks but they're not too vigorous about that preference. ;-)

18. Horthy didn't have too many compliments to spare for the Czechs in his memoirs. However, his rationalization of Hungary's acting as Germany's jackal at Munich, requesting that the powers not ignore "Hungary's claims" was a bit lame. It's been a long time, but I can imagine there are still a few people around, especially in Slovakia, who remember.

19. I had recently been thinking about another relevant fact in answer to the "where are all the aliens?" question. Earth successfully gained both lifeforms and advanced lifeforms. But we would have never gotten to radio and space travel without a massive asteroid situation killing off dinosaurs. They had millions of years and we haven't found any satellite dishes next to dinosaur bones that I'm aware of. So perhaps we should consider sufficiently rare mass extinctions as a necessary precursor to interstellar communication under the assumption that eventually a race will be able to control them. These events are likely necessary in case evolution takes a path that isn't conducive to interstellar communication. Of course, we still can't handle asteroids, but we are working on it and probably will be able to rather soon. Maybe planet hunters should add something like this to their list of goals (although I have no idea how to identify how many asteroids there are around another star since we have a tough enough time mapping those around our own).

20. kashyap vasavadaFeb 6, 2014, 7:06:00 PM

@Cesar Laia : Interesting point. We know that human beings cannot survive in deep oceans, under high pressure, without protection, because our tissues and blood vessels have small material strength. So to survive under
high pressure nature would have to design much tougher biological material!

21. kashyap vasavadaFeb 6, 2014, 7:18:00 PM

Thanks Lubos. I trust your answer. I asked a similar question on another blog. There the answer was that one could introduce a function (of space,time ?) instead of CC , without spoiling covariance of GR. That did surprise me.

22. Dear Luboš, let me, too, ask you about the constancy of the cosmological constant. On space dot com, our girl ;) Katya Lada Moskvitch equates the cosmological constant to "dark energy":

:Also known as dark energy, this constant can be interpreted as the energy density of the vacuum, one of the fundamental parameters of our universe.

According to Wikipedia:

In models where dark energy is a cosmological constant, the universe will expand exponentially with time from now on, coming closer and closer to a de Sitter spacetime. In this scenario the time it takes for the linear size scale of the universe to expand to double its size is approximately 11.4 billion years. (....)

In other models, the density of dark energy changes with time. In quintessence models it decreases, but more slowly than the energy density in ordinary matter and radiation. In phantom energy models it increases with time, leading to a big rip.

But when I look at this illustration on Wikipedia, the rate of expansion of the universe looks to be far from uniform, so how does that square with "dark energy = cosmological constant"? It's extremely rapid at the beginning, then slows down to a crawl, and recently (a couple billion years ago) starts to accelerate again.

Loeb specifically says that the "habitable cosmological epoch considered here allows for life to emerge in a Universe with a cosmological constant that is (1+z)^3∼10^6 times bigger than observed". Is that a conjecture that he is making, that the c.c, was a million times greater then, or is that generally accepted?

(Note that in the illustration, the "dark ages" (period before first stars form) lasts until 400 million years after the big bang, but apparently this picture is superseded by the recent papers Loeb cites, or in any case these papers make a plausible case that this much earlier star-formation could have happened, even if the odds are against it....)

23. Good summary, Werdna. It may be improbable with one particular arrangement of the assumptions but there may be many other very different contexts - arrangements of assumptions - where (intelligent) life could occur.

24. Well, the universe is a big place, so unlikely things can happen!

25. The mass of ordinary matter in the observable universe is equal to about 10^28 earth masses so very improbable things could have happened somewhere. At that early, 10 to17 Myear, epoch the (then) observable universe contained much more ordinary matter but the excess is not within our current light cone and you might dismiss early intelligent life in places that are now receding from us at more than the speed of light even if it did happen.
I think it is impossible to rule out the evolution of intelligent life in the early universe.

26. How do you know that dinosaurs would have never evolved to grow more intelligent? It's been 65 million years, and the Earth has much longer until it is no longer habitable.

27. kashyap vasavadaFeb 7, 2014, 1:29:00 PM

@ Peter Denton: You are assuming that any planet which has life must go through the same evolutionary history as the earth. This is a big assumption. If mutations are random, evolution on different planets can take
different paths. We have not found Feynman’s path integral method of generating
Human beings or superior beings yet!! As I mentioned in the discussion
following a previous blog, the superior aliens may be simply not interested in
contacting a primitive society like us!

28. Alberto's proof deals with the invariance of the Lagrangian, whereas I was hoping for a proof that was more general and dealt with the invariance of the action, as Susskind does here:

http://www.lecture-notes.co.uk/susskind/classical-mechanics/lecture-4/symmetry-and-conservation/

But I thought it might fall into what you would describe as contrived, and isn't rigorous enough.

29. Hey, Eugene, for a math and physics challenged guy you do pretty well! What did you major in if I may ask?

30. I loved his argument on the expansion of the universe. He uses an example of how in his lifetime the consensus of all the models and scientists were wrong, Yet he is oblivious to how that falsifies his appeals to consensus on global warming.

31. "we would have never gotten to radio and space travel without a massive asteroid situation killing off dinosaurs"
I would rather think that evolved reptilians would have walked on the Moon 60 million years earlier.

32. Universe is not a Blind Watchmaker,
Has a tendency towards development.
(Second Law Violation)