Science and Inquiry discussion

What do people think? Is there extra-terrestrial life? Is there extra-terrestrial intelligence?

Perhaps more importantly, will we discover extra-terrestrial life in the near future?

Unmanned missions to Mercury, the Moon and Mars have so far not definitively found life. There may be hope for finding life in the ocean of Europa (one of Jupiter's moons). Why should we search for life on other planets? For the sake of pure intellectual curiosity, or for better understanding of biology on Earth? Will finding extra-terrestrial life have any meaningful impact on religion or philosophy or our worldview?

What do you think?

The prospect of extraterrestrial life is fascinating. I find it hard to believe Earth is unique in our vast universe. Plus, I am a Trekkie, and I adore the fantasy of seeking new life and new civilizations. What Sci-Fi books are recommended for feeding that fantasy?

I think the chances of finding life are pretty good, although we don't have a good definition so there may well be arguments. My guess is that it will be something less complex than bacteria in the solar system.

Don't forget Titan as another spot for possible life & I seem to recall another moon of Saturn's has been mentioned, too. That's just for life somewhat similar to ours.

Our definition of intelligence is even worse than that for 'life'. Most seem to mean it to resemble ours. That I doubt. While I believe other intelligent life exists, has existed, &/or will exist in the universe, it's a big universe covering a lot of time. Even if some organisms had an intelligence that we would recognize, I think the window for us to detect & recognize it is too small. We'd have to detect it fairly close both in time & space which cuts the chances to extremely low levels. I'd love to see it, though.

A lot of people think finding alien life will create dramatic changes in our religions, philosophies, & worldview. I doubt it. Any philosophy or worldview that doesn't already include the possibility probably hasn't managed to survive the technological changes of the past couple of centuries.

Religions are so irrational that evidence doesn't matter. We seem to be predisposed to religious belief. All my neighbors use cell phones & yet half of them believe the Earth is only 5000 years old & that evolution is "only a theory". I'm sure religions will manage to survive even the revelation of extra terrestrial life just as I'm sure the reasoning will be laughable.

Andrea wrote: "The prospect of extraterrestrial life is fascinating. I find it hard to believe Earth is unique in our vast universe. Plus, I am a Trekkie, and I adore the fantasy of seeking new life and new civil..."

Andrea, there are too many sci-fi books to list on the subject of extraterrestrial life.

Instead, here are a few non-fiction books that I enjoyed very much, and should be even stronger fuel to feed your fantasy!

The Intelligent Universe: A New View of Creation and Evolution
This is an old book, really a classic but controversial, by the famous astronomer Fred Hoyle.

Avi Loeb - Extraterrestrial: The First Sign of Intelligent Life Beyond Earth - Hardcover
I greatly enjoyed this book by theoretical physicist Avi Loeb. He details a strange, brief visitor to our solar system that exhibited behavior that is not common to comets. Here is my review of the book.

The Fifth Miracle: The Search for the Origin and Meaning of Life by Paul Davies

Jim wrote: "... Religions are so irrational that evidence doesn't matter. ..."

This is so true! Many people don't believe in evolution, but use antibiotic drugs anyway. Some people don't believe in relativity, but ignore that accurate GPS locations rely on the equations of general relativity. Many people are adamantly against vaccines, but ignore the fact that measles can cause irreparable brain damage.

So many people don't understand what a scientific theory is (vs. a hypothesis), and they don't even know what they don't know.

David, I could not agree more with your opinions on the subjects you have discussed above.

David, thanks for the recommendations and reviews. I will explore them (pun intended).

This general topic has been written quite explicitly by Drake (see Drake Equation). It is a comprehensive assessment based on probabilities.

N = R* • fp • ne • fl • fi • fc • L
"where

N = the number of civilizations in the Milky Way galaxy with which communication might be possible (i.e. which are on the current past light cone);
and

R∗ = the average rate of star formation in our Galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space" (Wikipedia; Drake Equation)

I will focus on one element of this equation (and, as the product of its features, if one or more components is zero or near zero, the product is zero or near zero).

I will focus on fl (the fraction of planets that could support life that develop life at some point}.

All known life is DNA-based, composed of four bases encoding amino acids, among other functions.

There is ZERO evidence of any form of life having an independent origin from those DNA-based functions. Life has only popped into existence a single time.

The most likely value for fl is, therefore, near zero.

Any argument that does not address this merely discusses angels on the head of a pin.

Bob wrote: "...There is ZERO evidence of any form of life having an independent origin from those DNA-based functions. Life has only popped into existence a single time.

The most likely value for fl is, therefore, near zero.

Any argument that does not address this merely discusses angels on the head of a pin."

I'm sure we're all familiar with the Drake Equation. It's a good one even if it is over 60 years old. It allows for the huge time & distance gaps as well as our ever increasing knowledge of what might be life, but we don't know enough to assign proper numbers to too many variables.

I disagree with your last point on 2 points. First, we don't know that life only 'popped' into existence once even on this planet. We only know that we've only discovered one sort that we recognize so far. They're finding bacteria deep down in the ground now, something thought to be impossible just a few years ago, so who knows?

Second, 'angels dancing on the head of a pin' puts the possibilities into the realm of the fantastic & unknowable rather than the unknown. Back when Drake wrote his equation, I don't think we knew extremophiles existed & the idea of silicon-based life forms was pure science fiction, but we're making them today. Who knows what tomorrow will bring?

I suspect you are correct if you mean "DNA like" or "analogous to DNA" rather than actual DNA. 'Reproduceable' & 'evolvable' are the only two constraints I can think of offhand. After all, aren't there RNA viruses? Last I read, we weren't sure if viruses were dead or alive because we haven't been able to define 'life' properly yet. They're also experimenting with a variety of different chemicals in man-made 'DNA'. I think I read that some had more than 2 strands too & we're still very early in our investigations.

We don't know that complex organic molecules are the only way to create an evolvable recipe for 'life' (whatever that is) it's just the only way we're currently familiar with. Remember that we can't even see 95% of the universe. In the late 19th century, wasn't some famous scientist (Bohr? Planck?) told by one of his teachers not to go into physics since almost everything was known? I don't think you're allowing us enough ignorance.

How do we know DNA is the only basis from which consciousness can evolve? It's a big universe. We don't know much about most of it. I would say that entities with consciousness, even if based on something other than DNA, could be be considered "life."

Thanks for your comments. You are correct that there are RNA-based viruses (many of which have a DNA-based intermediate). All of these use identical triplet-based protein-encoding (with some dialects). Your correction is noted. A more robust definition of all known life forms is the four-base "alphabet" and three-base amino acid encoding. Needless to say, all known life forms fit the evolutionary model originating in an early life form with similar features.

Even the Archaea, however, use a triplet-based nucleic acid code for the direction of protein synthesis.

As you note, viruses are not free-living organisms. They do presume the existence of a living agent for their existence, which, as I have already stated, are exclusively nucleic acid-based and trilet encoding.

Even prion proteins have a cellular nucleic acid precursor. Like viruses, they are not free living.

Your comments about the definition of life, but can you name a single living thing that does not use a nucleic acid-based triplet code?

As you note, the Drake equation has stood the test of time.

Manufactured nucleic acid-based (non-free living) "life forms" have existed since the 1970s, and our experience with them is robust, as the development of mRNA-based vaccines attests.

Your comment, "Who knows what tomorrow will bring?" is consistent with my assertion that all known life forms are consistent with an evolutionary model. Anything more is speculation. Speculation is good, but it does not address the time-tested fl element of the Drake equation.

To date, there is no known life form that is not evolutionarily related to a four-base, triplet codon precursor.

Nancy wrote: "How do we know DNA is the only basis from which consciousness can evolve? It's a big universe. We don't know much about most of it. I would say that entities with consciousness, even if based on so..."

You are correct: we don't know that only DNA leads to consciousness. But that is not the question. It is nearly the opposite of that.

Let me explain. Drake encapsulated a broad analysis from first principles. He considered what would be needed for intelligent life to exist, and he considered the problem in great depth. His great leap was to remove all extraneous information. For example, he asserted that life would require planets, and those planets would form around stars. Thus, he stated that the star formation rate in our galaxy would determine how many potentially new places for life to form over time.

Okay - that's a mouthful. He went further and reduced the question to a single mathematical equation that considered a broad range of independent factors needed for intelligent life (his definition of life was described precisely, and the thing called "life" could be made of anything or nothing).

The equation can be found under "Drake Equation" on Wikipedia. The importance of the equation is on a level similar to "F=ma" or "e=mc**2".

He didn't say (nor did I) that only DNA-based life counted.

So why did I speak about DNA, you might ask? I was speaking in the sense that Drake was speaking. Another part of his famous equation asked: How often does life arise? Well, that number seems to be extremely low.

How low or how unlikely is that life will ever arise? All of the elements of Drake's equation describe planets like Earth, and it looks like life only occurred once on Earth. That is, ALL life that we know of comes from a nucleic acid (like DNA) with 4 "letters" in its alphabet and three letters in a row specifying how to select a specific amino acid (the basis of protein). Indeed, I challenge everyone to find an example of life that does not have those properties,

Thus, your comment is spot on: we don't know that life must be DNA-based. But if there is another way to create life, and is it made frequently, where on Earth is it?

My assertion then is quite simple: I assert that the frequency that life originates is very low. Since the frequencies of the other factors are pretty large, mathematically, the conclusion of the Drake equation depends greatly on only the frequency that life forms. The best evidence? That only happened once here.
--
A brief aside: Drake's equation only considers the Milky Way galaxy. It does not specify a DNA based life; the equation is written in a way that it does not matter what the life form is made from.

Bob wrote: "My assertion then is quite simple: I assert that the frequency that life originates is very low. Since the frequencies of the other factors are pretty large, mathematically, the conclusion of the Drake equation depends greatly on only the frequency that life forms. The best evidence? That only happened once here."

Bob, I have a question: How do we know that life originated only once on Earth? Could it not have happened, that a few million years after life first originated on Earth, that an entirely independent event originated life again? Since the first life had time to evolve and adapt better to the environment, the second life might not have had a chance to survive against a stronger competitor.

By the way, Fred Hoyle (see my reference above) speculated that life originated perhaps only once--but not on Earth! Instead, through panspermia life propagated over interstellar space aboard meteors, comets and the like. Today, Hoyle's ideas are not well respected, but who knows?

"Cosmopsychism is a theory that the universe itself is conscious. It's a variation of panpsychism, which is the idea that consciousness is a fundamental feature of reality and is not unique to complex organisms." Maybe Drake was unable to see the forest through the trees.

Bob wrote: "Thanks for your comments. You are correct that there are RNA-based viruses (many of which have a DNA-based intermediate)..."

You seem to have missed the point I was making entirely. I never disagreed about life as we know it. I was just pointing out that our knowledge is extremely limited & our definition of what life is sucks. That leaves a lot of room for discovery & we need to keep open minds.

You're not proving your point to me with basic science lectures. You don't seem to be particularly open to other possibilities, so we'll need to disagree on that point.

As for the likelihood of other life, I have absolutely no idea. There just isn't enough data. IMO, there could have been & might still be a number of types of life on Earth that are simply outcompeted by DNA based life. I'd be surprised if it left any trace before it lost. That doesn't mean it might not exist elsewhere, though.

Historically we have assumed that the way life evolved on earth is the only way life can evolve. For example, we always thought oxygen was necessary for cellular respiration. However, now we know that some organisms use hydrogen sulfide, not oxygen. For an interesting discussion about the weird biochemical possibilities for life different than our own, I recommend "Weird Life: The Search for Life That Is Very, Very, Different from Our Own" by David Toomey, ISBN: 978-0-393-34826-2

As I understand it, the law of infinite probability states that if something has even the slightest chance of happening, if you wait long enough, it will happen. 

The quantity of planet systems in the Universe is very large. Elapsed time for all planet systems in the Universe is very large.

In our everyday life, events whose occurrences are improbable move into the likely to occur set when taking into account the very large elapsed time and very large number of planet systems in the Universe.

I'm unsure if Drake considered the law of infinite probability.

Michael wrote: "As I understand it, the law of infinite probability states that if something has even the slightest chance of happening, if you wait long enough, it will happen. ..."

If I understand you correctly, I think there's a problem with the way that is framed. The Drake Equation gives the odds for a particular civilization, ours in this case, finding another. What you're proposing is any civilization finding any other which is a lot different. The odds that I'll win the Powerball are about 1 in 300 million, but the odds that someone will win it are much lower.

Jim, Your understanding agrees with mine. To use a simile for brief clarification: If a tree falls in the woods and no one sees or hears the crash, did it happen? I have never been comfortable with the 'no' answer.

I can understand why you'd compare the Drake Equation to a koan, but I don't care for the idea. A koan is basically unknowable, an opinion. The Drake Equation has so many variables that we don't know that it is arguably the same at this time, but there are mathematically precise answers. We just don't know what they are at this time. Still, it shows us where we need to improve our knowledge & that's a huge difference. It's unknown, not unknowable, a point I am touchy about since I'm surrounded by people who think their version of a bible is the ultimate answer to everything.

Next month our book-of-the-month will be The End of Everything by Katie Mack. (It is an easy read, very informative about cosmology and humorous, to boot!) Towards the end of the book, Katie Mack has this to say about the Drake Equation:

Of course, many of these input numbers are, at least with current data, completely impossible to determine, which means that the final answer isn't meaningful. The thing that's useful about the Drake Equation is that it makes us think about our assumptions about extraterrestrial life, and to figure out what we do and don't know about this whole question.

This quote is in complete agreement with Jim--the equation does not give us any quantitative answers, but it helps us to pinpoint what we do and what we don't know, in the search for life.

i recall, not too long ago, when people or groups of people, opposed to evolution pointed to a lack of fossils showing evolutionary evidence. Other people knew the fossils to support evolution of humans existed, but had not, yet, been found. Now, decades later, abundant fossils showing the evolutionary descent of man have, indeed, been found. And I would say, evolution as a mainstream understanding has gained traction, but the bump in our collective understanding is not massive.

The finding of human evolutionary fossil evidence is a practice run ahead of finding evidence of sentient life forms in our galaxy. Drake may have made progress with quantification goals, though if a similar quantification theory had emerged for the finding of human evolutionary fossil evidence, it would have looked like rubbish nonsense, in hindsight.

That comparison really hit the spot this morning, Michael! I just finished reading an article in Nature about a new find of wooden construction about 1/2 million years old. https://www.nature.com/articles/d4158...
I also watched "Dinosaurs-The Final Day with David Attenborough" (2022) recently.

Fossils are pretty unlikely. Has anyone has ever made a 'Drake Equation' for fossilization? If they did, I imagine it would be almost as full of holes & think of how much more we know about the subject. Your idea of a practice run really struck a chord.

Jim, I like your observation: "Fossils are pretty unlikely". Additionally, your two outside references spark my interest.

The BBC wrote an interesting article on this.
https://www.bbc.com/news/science-envi...