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.