[pdonis]

> life could have evolved in interstellar space

This is not a "fringe" idea; it's been a fairly common speculation for decades. What's different about the paper you cite, AFAIK, is the idea that the CMBR during the epoch he describes was the heat source. But there's nothing "fringe" about the CMBR temperature he gives for that epoch; that's standard mainstream cosmology.

> he is so clearly using his tenure as a defense against the weakness, and untestability, of his ideas

That's actually what tenure is for--to give people the security to be able to explore all kinds of ideas, many of which appear weak and untestable, and most of which will never pan out, but a few of which will end up creating enormous value. Loeb's ideas may never pan out, but that doesn't make it wrong for him to explore them or publish them or use his tenured position as a secure base from which to do those things.

What I find off-putting about the article is the fact that he appears to think that resistance to unconventional ideas is somehow wrong. It's not. It's a part of the same dynamic of scientific progress as his proposing of unconventional ideas. Even ideas that end up proving correct still get resisted at first, and that's the way it has to be; it's not some defect that we could somehow avoid if we were just smart or open-minded enough. If he wants to play the role of "explorer of unconventional ideas", he should be willing to take what comes with that territory.

[zozbot234]

> What's different about the paper you cite, AFAIK, is the idea that the CMBR during the epoch he describes was the heat source.

If the CMBR was the heat source, what was the heat sink? You need a temperature difference to produce negentropy and allow for life. Did life evolve in the shadow of primordial black holes, or what?

[est31]

Life doesn't need a temperature difference. It only needs some material in one energy state whose transition to a lower energy state it can catalyze. Say converting visible light to infrared radiation using photosynthesis, or rusting iron [1], etc. The CMBR with 0-100 C provides for the environment that allows for the molecules to be stable without life needing to take any precautions.

[1]: https://en.wikipedia.org/wiki/Iron-oxidizing_bacteria

[antognini]

No, the temperature differential is necessary. If life is consuming some food in a high energy state, converting it to a low energy state, and then using the difference for itself, it needs to put that waste energy somewhere once it's done with it. It can do this if the bath is at a lower temperature. But if the bath is at the higher temperature (i.e., if there's no differential) then the organism will be unable to convert the food into the lower energy state.

Strictly speaking, the important thing is to have a differential in entropy. The processes of life produce entropy, and that entropy has to go somewhere else if the organism is to live. But a differential in entropy implies a differential in temperature (though you may have to be careful about how you define temperature since there are different kinds of temperature).

[est31]

Consider everything in the universe being 40 deg C, including all matter, the CMB, etc. Consider now an organism that eats some food and releases the energy inside that food. It converts this energy into heat and i now 42 deg C. Suddenly there is a differential again. Sure, it can get rid of the heat easier if the differential were larger, but it can get rid of it at all, due to the existence of a differential.

[pdonis]

> If the CMBR was the heat source, what was the heat sink?

Good question. I haven't read through the paper yet, so I don't know if the author addresses it.

[pdonis]

It looks like he talks about "thermal gradients" in section 3 of the paper.

[chunky1994]

Precisely this, he is perfectly within his right to explore these ideas, that can and in fact should be done. His reaction to the reaction of the wider community is rather odd, and has probably caused him more harm than good in the long run.