We Might Be Alone in the Universe

[malkie]

Given what we know about physical chemistry, do you believe there any reason to think it likely that complex organisms could evolve, based on anything other than C H O N P S compounds, on any of the exoplanets we have thus far detected?

That is, should we expect to find non-CHONPS "biologies" that could form in the physical conditions we know exist on any known planets?

https://en.wikipedia.org/wiki/Hypotheti ... ochemistry talks about a few possibilities, but, to me, they all seem very remote, compared to CHONPS. Of course, that is not to say that 1. these exhaust all of the possibilities, or, 2. one of them, or something not yet thought of, does not exist somewhere.

[Physics Guy]

I don't know nearly enough chemistry even to speculate about biochemistry based on a different suite of elements. I even wonder how different life with the same set of atoms could be from terrestrial life, through using different big molecules. Are there any potential competitors, in particular, to DNA or ATP?

I can maybe add the even weirder speculation that there could be life, and in fact stars and planets, made out of whole different kinds of elementary particles. We don't have any firm theory to constrain what kinds of elementary particles are possible; the Standard Model is just an empirically compiled list of the particles that we seem to find. We're pretty sure that all kinds of matter would have to interact with each other through gravity, but there could in principle be a whole zoo of alternative electrons and quarks and things that interact with each other through other kinds of forces, but that only interact with the matter we know gravitationally.

Since in particular this alternative kind of matter would not interact with the electromagnetic field that we know, it would be transparent to our kind of light, and not emit any of our kind of light. There could be alternative kinds of stars and planets not all that far away from us, and we might never have noticed them. If we somehow found such other planets, we could go into orbit around them, but not land on them, because their substance would not offer any resistance to us. If they were populated by intelligent life that sent out spacecraft to investigate us, they would be in the same situation with regard to our planet. We couldn't shake hands because our hands would pass through each other, and we couldn't see each other or send each other radio signals because our respective antennas would be blind to each other's transmissions.

On the other hand there's nothing that says the alternative set of particles would have to be at all analogous to the set we know. It might not include anything like our photons or have any counterpart to our electrons. It might be really different, so if it supported life, that life might be really different.

I don't think anyone considers that a likely scenario. That kind of alternative matter is in principle one candidate to constitute dark matter, which does seem to exist, but last I heard, at least, the gravitational implications of a lot of invisible alternative planets and stars flying around out there don't seem to fit well with observations. Still I think it's hard to rule this mind-boggling scenario out entirely. Perhaps someday we'll detect the gravitational waves emitted by a pair of alternative neutron stars colliding, or something, in a place where we know there was nothing visible.

[Doctor Steuss]

I haven't finished listening to it I'll have to listen to it a second time (after I am done listening to all of it) to give you a time stamp.

However, according to Universe Today,

"Overall, the Dark Forest Hypothesis has an internal logic and consistency that makes it an appealing (if somewhat somber) potential resolution to Fermi’s age-old question. Unfortunately, it also suffers from an inherent flaw that is capable of unraveling the whole thing. Like many other Fermi-related hypotheses, it only takes one exception to this rule to prove it wrong."
https://www.universetoday.com/149410/be ... ypothesis/

Fraser Cain is the owner and publisher of Universe Today.

What's Fraser Cain's relevant educational background, and publication history? Everything I can find has him self-described as a web developer and science journalist. Just curious what his expert background is, given that you felt it necessary to mention him by name as the founder/owner.

[Res Ipsa]

What I really enjoy about conversations about active areas of science research is using whatever information is available to understand the bigger context in which the research is taking place. Unlike the researchers who do the work in real time, I have the luxury of 20-20 hindsight and taking a view from 40,000 feet (in this case, maybe 40,000 light-years). The researchers in the trenches have to spend much of their time in a relatively narrow area of expertise.

Ever since I first read the Reinhold (2020) paper, I've puzzled over why the sample the authors used had such a high percentage of stars for which rotational periods could not be computed. A little more reading about Kepler and reading research done since the publication by that period (including papers by Reinhold) provides what I think is a pretty likely answer.

We were finding exoplanets before the Kepler mission, but they were mostly hot Jupiters. Because scientists recognized the instruments they had been working with to find exoplanets were limited, Kepler was specifically designed to find exoplanets in general. It looked at the same patch of the stars for a four-year period (although it malfunctioned prematurely, shortening the period over which data could have been gathered). What it measured was the brightness of the stars in its field of view. So, for every star, there is an enormous string of numbers from frequent observations, with each number being some sort of measure of brightness.

So, how do get from all those numbers to finding a planet? When a planet in the sun's orbit passes between Kepler and the sun, the brightness decreases and then increases as the planet "transits" across the sun. Easy peasy!

Except it's not, because there are other things that cause changes in the brightness of a star. One is the star's normal activity. All other things being equal, processes that are ongoing within the star that cause the brightness to vary over time. Stars with relatively small variations in this type of brightness are referred to as quiet. Those with relatively large variations are referred to as "quiet."

A second cause is the rotation of the star. The surface of stars is often not perfectly uniform. Features like sunspots create variation in the brightness of the star, depending on whether a given feature is in the field of view. The rotation of the star can create a periodic change in the star's brightness. Even more complicated is that the features that cause the variation in brightness come and go.

A third cause is binary stars that orbit each other.

A fourth cause is vibrations within the telescope or other sources of "noise" in instrument that create the appearance of changes in brightness, when there is a actually no noise.

So, you've got this enormous string of numbers with all these different factors that could cause the numbers to change from observation to observation. No human could ever sort through this mish mash of numbers and consistently spot which changes were transits and which weren't.

So, what scientists do is design a series of algorithms (described as a pipeline) that will sort the dimming and brightening due to transits from everything else (noise). They do that by using what they know about how a transit would appear in the data, how intrinsic stellar variation would appear in the data, etc. I think it would be fair to call it pattern recognition. There is no way to identify any single change in brightness as a genuine transit of an exoplanet. So, the algorithms need to recognize a pattern of transit appearing changes, representing multiple orbits of the planet around its star.

Even more complicated, the sensitivity of each element of the pattern recognition has an effect on the false positives (detecting a planet that isn't there) and false negatives (failing to detect a planet that is there). The more sensitive your test for whether a change is really intrinsic variation, the greater the risk of false negatives (i.e., you increase the rate of false negatives).

So, each pipeline is a series of judgment calls involving trade offs between accuracy (minimizing false positives) and sensitivity (minimizing false negatives).

As Kepler is designed to find exoplanets, the pipelines are created to find exoplanets. Run the data through your pipeline, and you get a catalog of stars of stars that have a high likelihood of having planets. Or even planets that might have planets but need more investigation (I think they call these Kepler Objects of Interest or KOIs.

The biggest such catalog was created in 2014 and is referred to as MMM after the initials of its authors.

Now, switch gears. Instead of being a scientist looking for exoplanets, be a scientist measuring the sun. It's lots easier to get data about the sun than about those pinpricks of light that are distant stars. I mean, it's right there (were there=93 million miles).

So, you study the crap out of the sun. You learn all kinds of detailed information it, including chemical composition, magnetic fields, cycles of activity (e.g., the sunspot cycle). But what does it all mean? You've got a warehouse full of facts, but you don't know which matter in terms of understanding how the sun works. You can develop hypotheses and theories, but you only have one experimental subject.

Or do you? You have a galaxy full of other stars. You can't study them in as much detail as you can the sun. But you can study some of their characteristics, look for patterns, and compare samenesses and differences to learn what the sun's different features mean.

So, there are instruments, including space missions, to gather information about stars. But, when you peek over at those damned exoplanet folks, they've got their own superstar space telescope that is a resounding success at finding exoplanets. And a metric buttload of data.

You think "Hmmm. That telescope measured brightness of stars. We can learn stuff from the brightness of stars. How about we borrow their data and use it to study stars, which are much more important. Stupid exoplanet scientists -- they did our research for us." In fact, I read a few references to Kepler as a "stealth solar mission."

Now we get to Reinhold (2020). Part of the beauty of the Reinhold study is that it started with the MMM catalog. The authors didn't have to reinvent the wheel by researching and developing a Kepler pipeline that was designed to look for rotation periods. Makes sense -- use the available data to see what happens. It also uses data from another project -- GAIA -- to refine some of the MMM data.

The downside of using the MMM catalog is that it the pipeline wasn't designed to find the rotational periods of stars -- it was designed to find transiting planets. For that pipeline, variation caused by the rotation of stars, when identified, is just one of many types of "noise" to be screened out. To me, that explains why the MMM catalog contains so many stars for which no rotational period could be determined. And the sheer size of the MMM catalog and effort saved by starting with it make using it a pretty reasonable decision.

What they found was unexpected and surprising -- a correlation between the sunlike stars for which periods of rotation had been determined and high levels of what I've described as intrinsic activity compared against the sun that they could not explain.

So, when faced with a puzzling result, what do good scientists do? They tried to figure it out. And a paper I've already referred to found the explanation: the MMM pipeline was very bad at recognizing rotation periods for quiet sunlike stars -- those most like our sun.


But the scientists didn't stop there. Maybe the MMM catalog could be made more useful for finding solar analogs or "twins" by combining it with data from a different project. Here's an example of a paper that tries just that:
https://iopscience.iop.org/article/10.3 ... jlab8795f1 Or maybe a pipeline could designed that could use the Kepler data to find the rotational period of quiet solar-like stars? That's what it looks like Reinhold himself is doing. https://iopscience.iop.org/article/10.3 ... c937a/meta Or maybe another mission that includes technological advancements is the best bet. Perhaps the Chinese proposed Earth 2.0 mission, designed to find an earth analog orbiting a sun analog will do the trick. Who knows?

To me, the ingenious efforts by solar or stellar scientists to turn the data from a mission that was designed to find exoplanets into data that helps us learn more about stars is interesting as hell. As is the process: trying things, seeing how they turn out, working at understanding why the results turned out the way they did, finding obstacles, designing ways around the obstacles, trying those things.... it shows how the scientific method works, warts and all. And it gives me some hope that there are enough humans dedicated to figuring things out and solving problems to get us through some of the problems humans are facing today.

[Res Ipsa]

I haven't finished listening to it I'll have to listen to it a second time (after I am done listening to all of it) to give you a time stamp.

However, according to Universe Today,

"Overall, the Dark Forest Hypothesis has an internal logic and consistency that makes it an appealing (if somewhat somber) potential resolution to Fermi’s age-old question. Unfortunately, it also suffers from an inherent flaw that is capable of unraveling the whole thing. Like many other Fermi-related hypotheses, it only takes one exception to this rule to prove it wrong."
https://www.universetoday.com/149410/be ... ypothesis/

Fraser Cain is the owner and publisher of Universe Today.

What's Fraser Cain's relevant educational background, and publication history? Everything I can find has him self-described as a web developer and science journalist. Just curious what his expert background is, given that you felt it necessary to mention him by name as the founder/owner.

I listened to his podcast for several years during time it was co-hosted by Pamela Gay, who I believe is an astronomer. He's self taught but a good communicator. Here's his story of how and why he founded the web sight. https://www.universetoday.com/27694/uni ... -turns-10/

I think he's a good science communicator, taking news stories about space stuff and turning them into stories understandable to non-experts. I always thought he "stayed within his lane" -- at least during the period I listened to the podcast.

I don't know that anyone is an expert on the Dark Forest Hypothesis. At the level he seems to be discussing it (logic, consistency, robustness), I'm not sure how much expertise should be required. If he is still adhering to past practice, any sources he cites will be linked to on the Universe Today website.

[doubtingthomas]

If the Sun is only slightly unusual, such as in belonging to a 1/3 minority of stars or so, then it makes no sense to even mention this issue in a discussion of the abundance of intelligent life. There are decisively important factors in that question about which we are uncertain by factors of trillions. A mere 1/3 versus 2/3 issue probably won't deserve attention, in this context, until the galactic conference of 24523.

Yes, it would be 1/3 of five percent, only about 5% of stars are sun-like. Kipping argues that most Sun-like stars have solar flares thousands of times more powerful than super solar flare events of the Sun.

And here is a small transcript of the video "Is the Sun Unusual?"

aging stars is notoriously difficult but recently Timo Reinhold and colleagues found a way around this. Remember that since the spin of stars slows down with age, they decided to take a group of stars with similar masses and sizes to the Sun just like Gilliland but further constrain the sample to only those stars with similar rotation periods to the Sun 25 days. In their new paper published just recently in science, they yet again find that the Sun is quieter than average ... they showed that the sun's typical activity places it in the lowest third of quiet sun-like stars[see Figure 3]......there is an emerging picture that the Sun, at least we see it today, appears to be unusually quiet compared to stars of similar type and using indirect evidence that behavior of the Sun in the last century and a half, doesn't seem to be any different than that of the preceding 9 thousand years, we really do seem to have a quiet home star

https://www.youtube.com/watch?v=TAQKJ41eDTs

Do you believe Kipping has misrepresented Reinhold's paper? and why would the researchers call the paper "The Sun is less active than other solar-like stars" if that's not the case? https://arxiv.org/abs/2005.01401

[doubtingthomas]

?

I think Res Ipsa is full of BS. He accused me of misrepresenting Reinhold's paper. However, I was only sharing Kipping's interpretation of the paper, not mine. His issue should be with Kipping! not with me.

It's like getting diagnosed with diabetes by a medical doctor, but some anonymous idiot telling you that you've misunderstood the symptoms.

Res Ipsa doesn't have to balls to accuse Kipping of misrepresenting Reinhold's paper. Res Ipsa has no background in astronomy or astrophysics, but miraculously knows more than an exoplanet researcher who went to one of the best universities in the world. Res Ipsa could get very famous by calling out Kipping.

I am very disappointed in Res Ipsa, he's blaming me for something I shouldn't be blamed for.

Here's a small transcript of the Kipping video.

aging stars is notoriously difficult but recently Timo Reinhold and colleagues found a way around this. Remember that since the spin of stars slows down with age, they decided to take a group of stars with similar masses and sizes to the Sun just like Gilliland but further constrain the sample to only those stars with similar rotation periods to the Sun 25 days. In their new paper published just recently in science, they yet again find that the Sun is quieter than average ... they showed that the sun's typical activity places it in the lowest third of quiet sun-like stars[see Figure 3]......there is an emerging picture that the Sun, at least we see it today, appears to be unusually quiet compared to stars of similar type and using indirect evidence that behavior of the Sun in the last century and a half, doesn't seem to be any different than that of the preceding 9 thousand years, we really do seem to have a quiet home star

https://www.youtube.com/watch?v=TAQKJ41eDTs

[doubtingthomas]

I am honestly very disappointed, I thought Res Ipsa was an intelligent person.

[Doctor CamNC4Me]

Cain addressed this.
https://open.spotify.com/episode/7K3HHdxIt8dRYesXmpQ2kV

The Dark Forest doesn't explain why we happen to live in an unusual star system.

At what timestamp does he address the Dark Forest theory?

[doubtingthomas]

At what timestamp does he address the Dark Forest theory?

I think around the 15-minute he addresses a version of the Dark Forest.

The Dark Forest theory is fully addressed and debunked here on his website.
https://www.universetoday.com/149410/be ... ypothesis/

Overall, the Dark Forest Hypothesis has an internal logic and consistency that makes it an appealing (if somewhat somber) potential resolution to Fermi’s age-old question. Unfortunately, it also suffers from an inherent flaw that is capable of unraveling the whole thing. Like many other Fermi-related hypotheses, it only takes one exception to this rule to prove it wrong.

As David Brin explained in his famous 1983 essay, “The Great Silence – the Controversy Concerning Extraterrestrial Intelligent Life,” it would only take a single malevolent race willing to break its self-imposed silence to explain the “Great Silence.” He raised this point when addressing the Deadly Probes Scenario” (a.k.a.. “Berserker Hypothesis“), which postulates how an advanced civilization could invent probes to do their dirty work.