# What did Carl Sagan get wrong? **URL:** \ **Category:** Great Debates\ **Created:** [April 10, 2023, 11:27pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476 "2023-04-10T23:27:07Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [April 10, 2023, 11:27pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/1 "2023-04-10T23:27:07Z")
First let me say that I love Carl Sagan and owe him a great debt of gratitude for giving me my interest in science. And I don’t have a bad thing to say about him. I was reading an article in IAI News titled “Carl Sagan was wrong: [ordinary evidence is enough](https://iai.tv/articles/carl-sagan-was-wrong-ordinary-evidence-is-enough-auid-2348)”, in which astrobiologist, Sean McMahon apparently makes the case that Sagan overstates his assertion that extraordinary claims require extraordinary proof. I wouldn’t necessarily say he’s wrong, maybe just passionate? And it’s certainly catchier than Hume’s version! Anyway, I’ve read that his Nuclear Winter predictions have been recalculated and shown to be overly dire. And that Greek history buff Spencer McDaniel takes issue with his facts in the Library of Alexandria segment of Cosmos, Episode 13, etc. So that got me thinking, it’s been a while since Sagan promoted his ideas (and, hey, even Einstein miffed a couple) so what, if anything did Sagan get wrong? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 11, 2023, 12:06am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/2 "2023-04-11T00:06:33Z")
There are a number of detail items that Sagan was in error about in _Cosmos_ (one thing that comes particularly to mind was his explanation for the samurai-like face on the shell of the _Heikegani_ crab) but I think you’d be hard pressed to find any general popular science program that doesn’t wiff a few things that someone with specific experience won’t take issue with, but _Cosmos_ holds up surprisingly well, certainly vastly better than Bill Bryson’s celebrated but more-wrong-than-right _A Short History of Nearly Everything_. The TTAPS report certainly overstated the potential for “nuclear winter” in duration but that came from the relatively primitive ability to model global climate circulation and the assumptions that went into the model at the time; his essential conclusion that a strategic nuclear exchange would have dire consequences for billions of people and civilization as a whole is still valid, and he was exactly on point in warning about [the dangers of anthropogenic carbon dioxide on climate change](https://youtu.be/Wp-WiNXH6hI). As for what has come to be known as Sagan’s Principle (or sometimes ‘Dictim’): “Extraordinary claims required extraordinary evidence”, the link to Sean McMahon’s essay engages in a bit of semantic sparring without really quibbling with the essential point that Sagan was trying to make, that not all claims should be weighed with equal weight just because someone can express them. McMahon writes: > _Now we can see why some extraordinary claims require extraordinary evidence and some don’t. Those that do are either highly improbable (requiring highly unambiguous evidence) or counter to a weight of evidence that seems to rule them out (which the new evidence must somehow be reconciled with); those that don’t are simply out of the ordinary or counterintuitive, like the claim about Caesar’s last breath. Now, let us imagine a scenario in which scientists in Sagan’s own field, astrobiology, make a stupendous announcement: they have found a signal of extraterrestrial life. What happens next? I expect there will be a mass outbreak of Sagan’s dictum and wall-to-wall demands for extraordinary evidence (including from scientists themselves). But these demands may be unreasonable. We don’t know if life is rare or common in the universe, probable or improbable. There is very little evidence either way, so the claim isn’t really “extraordinary” in the sense required for Sagan’s dictum to apply. We might suspect that the scientists are wrong for technical reasons, or we might think they have neglected alternative explanations of their data because they are too excited by the prospect of a great discovery, but these worries should only motivate us to check that the normal burden of evidence has been met and to proportion our beliefs accordingly, not to impose a double standard by asking for something extra._ Well, okay, we shouldn’t “…impose a double standard by asking for something extra.” But what does that mean? In the context of, say, looking at spectrographic chemical signatures, that should mean that we examine all possible sources of organic chemistry that could possibly be an indication of life-like promises. If you recall from a few years ago, [the compound phosphene was discovered in spectra from Venus](https://www.nationalgeographic.co.uk/space/2020/09/possible-sign-of-life-on-venus-stirs-up-heated-debate) and no sooner were unreviewed pre-prints released on the subject than enthusiastic advocates were proclaiming that this was almost assuredly evidence of some kind of life in the atmosphere of Venus despite how implausible that would be. As it happened, later critical analysis indicated that this was very likely [a measurement and interpretation error](https://www.washington.edu/news/2021/01/27/phosphine-venus-so2/), and that no evidence of life-like processes were to be found. Avi Loeb—an otherwise accomplished and well-educated astrobiologist, made an utter fool of himself by virtually insisting that the comet _Oumuamua_ had to be an alien spacecraft or probe based upon some anomalous trajectory measurements even though [a far more mundane and explicable explanation](https://news.uchicago.edu/story/surprisingly-simple-explanation-interstellar-visitor-oumuamuas-weird-orbit) has been proposed and demonstrated by model. Sagan was warning that we shouldn’t just accept far-out claims that would seem to defy our expectations based upon science as we currently know it as being the same as those grounded in our understanding of physics, chemistry, and biology, and more generally, that we should be skeptical investigators of our world and the phenomena in it, driven by criticism grounded in scientifically-validated evidence rather than what we would prefer to believe. Given today where politics and news are often driven by hyperbole, innuendo, and conspiranoia, his caution would seem more apropos than ever. Stranger ---
**Author:** ![Horatius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/horatius/32/3572_2.png) [@Horatius](https://boards.straightdope.com/u/Horatius)\ **Post date:** [April 11, 2023, 12:46am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/3 "2023-04-11T00:46:16Z")
> [@Stranger\_On\_A\_Train](#): > > Well, okay, we shouldn’t “…impose a double standard by asking for something extra.” But that’s not really what “extraordinary” really means. > 1a **:** going beyond what is usual, regular, or customary > extraordinary powers > > b\*\*:\*\* exceptional to a very marked [extent](https://www.merriam-webster.com/dictionary/extent) > extraordinary beauty A signal from an alien species _would_ be extraordinary, because we’ve never seen one before. It would clearly be “beyond what is usual, regular, or customary” in astronomy or astrophysics, in which every signal we’ve seen so far has been natural in origin. We’d need to confirm the signal, in case it was just a artefact, but even one confirmed artificial signal would be enough. ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [April 11, 2023, 4:59am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/4 "2023-04-11T04:59:21Z")
I take issue with his stance that if an advanced alien entity were to visit Earth, it would almost assuredly end bad for us. His litmus is to look what has happened in history when ever colonizers have visited less advanced societies. This argument assumes aliens would have the same psyche as humans do. I see no reason to make that assumption. In fact, the contrary is true. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 11, 2023, 5:53am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/5 "2023-04-11T05:53:15Z")
> [@Grrr](#): > > I take issue with his stance that if an advanced alien entity were to visit Earth, it would almost assuredly end bad for us. > > His litmus is to look what has happened in history when ever colonizers have visited less advanced societies. The reality would probably be even worse. When human societies meet the more powerful one tends to dominated the other or subjugate it for labor but to at least preserve some subset of the population for utility. An extraterrestrial intelligence with the ability to transit interstellar distances may be so technologically advanced that they wouldn’t even regard humanity as worthy of regard or protection, or worse yet a potential threat to be eliminated before it grows into something dangerous. It is highly doubtful that there is anything humans could offer that would justify preservation unless the extraterrestrials have some innate reason for doing so. Fortunately, we don’t see any evidence of extraterrestrial societies radiating in electromagnetic bands, and the distances between stars and the energies required to travel between them in timeframes of less than thousands of years are so enormous that interstellar transit without some kind of superluminal travel is extremely problematic, so even if high intelligence is relatively common, the odds of overlapping with another civilization over distance and time is highly unlikely. Stranger ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [April 11, 2023, 5:56am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/6 "2023-04-11T05:56:28Z")
Why are you assuming aliens think like we do? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 11, 2023, 5:59am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/7 "2023-04-11T05:59:04Z")
“When did you stop beating your wife?” Stranger ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [April 11, 2023, 6:07am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/8 "2023-04-11T06:07:13Z")
Okay, so you don’t have an answer then. Got it. ---
**Author:** ![nightshadea](https://avatars.discourse-cdn.com/v4/letter/n/7ba0ec/32.png) [@nightshadea](https://boards.straightdope.com/u/nightshadea)\ **Post date:** [April 11, 2023, 6:08am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/9 "2023-04-11T06:08:37Z")
> [@Stranger\_On\_A\_Train](#): > > An extraterrestrial intelligence with the ability to transit interstellar distances may be so technologically advanced that they wouldn’t even regard humanity as worthy of regard or protection, or worse yet a potential threat to be eliminated before it grows into something dangerous so pretty much the “most aliens believe human thought to be dangerous disease that must be exterminated” speech from MIB 1 as an example ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 11, 2023, 6:15am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/10 "2023-04-11T06:15:10Z")
> [@Grrr](#): > > Okay, so you don’t have an answer then. Got it. No, I objected to your mischaracterization that I was “assuming aliens think like we do,” when I quite explicitly did not say that. > [@nightshadea](#): > > so pretty much the “most aliens believe human thought to be dangerous disease that must be exterminated” speech from MIB 1 as I suspect than an extraterrestrial intelligence might not even care about “human thought” or regard it as worthy of consideration. They might regard humanity as less significant or worthy of consideration than a anthill or hair lice, and dispense with us as casually as we would exterminate such pests. Stranger ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [April 11, 2023, 6:26am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/11 "2023-04-11T06:26:19Z")
> [@Stranger\_On\_A\_Train](#): > > No, I objected to your mischaracterization that I was “assuming aliens think like we do,” when I quite explicitly did not say that You did the exact same thing Sagan did. You literally used an example of what humans have done in the past as a reason to believe what aliens might do to us in the future. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 11, 2023, 6:48am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/12 "2023-04-11T06:48:53Z")
> [@Grrr](#): > > You did the exact same thing Sagan did. You literally used an example of what humans have done in the past as a reason to believe what aliens might do to us in the future. No, I didn’t. What I wrote was: > [@Stranger\_On\_A\_Train](#): > > When human societies meet the more powerful one tends to dominated the other or subjugate it for labor but to at least preserve some subset of the population for utility. An extraterrestrial intelligence with the ability to transit interstellar distances may be so technologically advanced that they wouldn’t even regard humanity as worthy of regard or protection, or worse yet a potential threat to be eliminated before it grows into something dangerous. I contrasted that one human society conquering another at least has the motivation of utilizing the population of the less powerful society for its own ends (typically as slave labor or to convert to their ideology) versus an extraterrestrial intelligence or society which would be unlikely to have even that motivation to preserve the inferior human society it encounters. Indeed, a highly advanced extraterrestrial intelligence might not even regard humanity as being truly intelligent, and too limited to even be worthy of attempt at communication or ‘domestication’ for any purpose. Stranger ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [April 11, 2023, 7:36am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/13 "2023-04-11T07:36:49Z")
I discussed one of the problems with the book Cosmos 11 years ago in a post: > [@infinite regression](https://boards.straightdope.com/t/infinite-regression/644712/28): > > As long as we’re talking about smoking pot and thinking about infinite regression, there’s a passage in Cosmos (second to the last paragraph in Chapter X) by Carl Sagan where he says, “There is an idea - strange, haunting, evocative - one of the most exquisite conjectures in science or religion. It is entirely undemonstrated; it may never be proved. But it stirs the blood. There is, we are told, an infinite hierachy of universes, so that an elementary particle, such as an electron, in our uni… The idea that an atom could be a universe of its own (or a solar system of its own) is arbitrary. It is based on the idea from a century or so ago that an atom is like the solar system with electrons spinning around the nucleus. Nothing like this is currently believed by physicists. Some things that Sagan said were silly. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [April 11, 2023, 9:20am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/14 "2023-04-11T09:20:39Z")
> [@Stranger\_On\_A\_Train](#): > > An extraterrestrial intelligence with the ability to transit interstellar distances may be so technologically advanced that they wouldn’t even regard humanity as worthy of regard or protection, or worse yet a potential threat to be eliminated before it grows into something dangerous. It is highly doubtful that there is anything humans could offer that would justify preservation unless the extraterrestrials have some innate reason for doing so. That is one possibility. Another possibility is that interstellar travel is so difficult and energy intensive that the travellers arrive with very limited resources indeed, having exhausted almost all of their fuel and shed most of the mass of their spacecraft in order to decelerate. Such a mission would arrive with almost nothing, except perhaps a cache of stored information which they could use to rebuild their infrastructure; like a seed or a spore, their craft would be small but packed with potential. If we encountered interstellar travellers of this kind they could have much to offer us, but they could also benefit greatly from our assistance and co-operation. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [April 11, 2023, 9:59am UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/15 "2023-04-11T09:59:17Z")
I understand that most historians do not accept his statement that the burning of the Alexandria Library was the death knell of advanced civilisation in the Ancient World, and his list of scholars and philosophers who worked there is largely inaccurate. However I do note that there are many people who can only be described as Sagan H8ters who despise everything he has written simply because he was a Democrat and progressive. They often harp on about his strange voice and his use of marijuana, neither of which are relevant to his legacy. And there seem to be far too many nowadays who readily accept the presence of alien visitors in our skies, including quite a few in positions of power at the Pentagon and US government. These are the people who should heed Sagan’s advice about extraordinary evidence. ---
**Author:** ![Miller](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/miller/32/481_2.png) [@Miller](https://boards.straightdope.com/u/Miller)\ **Post date:** [April 11, 2023, 8:09pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/16 "2023-04-11T20:09:13Z")
> [@Grrr](#): > > Why are you assuming aliens think like we do? Assuming that aliens would act better than human colonists did is, also, assuming that aliens think like us. “We should be nice to people who are different from us,” is as much a human concept as, “We should exploit people as much as we can.” Any theory about a first contact scenario that works out well for humans is based on an assumption that the aliens have specific human traits like altruism, or interest in foreign cultures, or the concept of personal rights, or other human concepts that would mediate how much damage the aliens are willing to inflict on human civilization in pursuit of whatever goal brought them to our solar system. ---
**Author:** ![Kron](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kron/32/12444_2.png) [@Kron](https://boards.straightdope.com/u/Kron)\ **Post date:** [April 11, 2023, 8:15pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/17 "2023-04-11T20:15:53Z")
> [@Grrr](#): > > This argument assumes aliens would have the same psyche as humans do. > > I see no reason to make that assumption. In fact, the contrary is true. I don’t follow. 100% of all technologically advanced sentient species that we know of behave as described; so there is at least some evidence-based reasoning behind the characterizations you are objecting to. The contrary literally requires evidence-free wishful thinking. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 11, 2023, 8:21pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/18 "2023-04-11T20:21:30Z")
I don’t understand the assumption that no alien would be expansionist. Not a single one. Sure, there may be aliens out there that are pacifists, all the way up until they are annihilated by the ones that aren’t. All it takes is one expansionist species, we have evidence from our own existence that they _can_ exist, so I’d like to see the proof that is being used to say that they don’t. ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [April 11, 2023, 8:23pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/19 "2023-04-11T20:23:33Z")
> [@Stranger\_On\_A\_Train](#): > > McMahon writes: > > > _a stupendous announcement: they have found a signal of extraterrestrial life. What happens next? I expect there will be a mass outbreak of Sagan’s dictum and wall-to-wall demands for extraordinary evidence (including from scientists themselves). But these demands may be unreasonable. We don’t know if life is rare or common in the universe, probable or improbable. There is very little evidence either way, so the claim isn’t really “extraordinary” in the sense required for Sagan’s dictum to apply._ I think McMahon has missed the point. The extraordinary part isn’t “there’s extraterrestrial life”, the extraordinary part is “I found proof of extraterrestrial life.” That claim, that YOU found the proof is what needs extraordinary evidence. Rock solid evidence, virtually unassailable, that you have given us THE ANSWER to one of humanity’s great questions. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [April 11, 2023, 8:23pm UTC](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476/20 "2023-04-11T20:23:34Z")
> [@Stranger\_On\_A\_Train](#): > > Fortunately, we don’t see any evidence of extraterrestrial societies radiating in electromagnetic bands, and the distances between stars and the energies required to travel between them in timeframes of less than thousands of years are so enormous that interstellar transit without some kind of superluminal travel is extremely problematic, so even if high intelligence is relatively common, the odds of overlapping with another civilization over distance and time is highly unlikely. That’s assuming that the aliens are biological in nature, and not, say, self-replicating artificial intelligences, who could explore the galaxy at a much more leisurely pace. [Next page](https://boards.straightdope.com/t/what-did-carl-sagan-get-wrong/982476.md?page=2)