Mark Trapp

History, science, and a problematic Cosmos

Like many others, I was both interested and concerned when it was announced there'd be a reboot of Cosmos. I wasn't yet born when it first aired, but I nevertheless saw it when I was a kid and loved it. I read Sagan's book of the same name and Contact, which lead to reading the works of Stephen Hawking, Richard Feynman, and many others. I thought, as I'm sure many others did, how is the guy who made Family Guy of all things going ruin it?

After seeing the first episode this past weekend, I'm still on the fence. While I don't think Seth McFarlane ruined the memory of the original, and the choice of Neil deGrasse Tyson to take on the mantle of trying to follow Carl Sagan's superb narration was flawless, it nevertheless comes off as problematic.

When I watched the episode, I laughed out loud at a number of segments, leading me to begin writing what follows. There are some really boneheaded mistakes in the episode, and it's a bit amusing to call them out. But after a few days of expanding this list, talking to other people about it, and some reflection, I'm convinced that's not merely why I found it problematic.

And, as several people have reminded me, first and foremost Cosmos is an introduction to science. It's not meant to be absolutely cutting edge or a deep dive into the minutiae of various aspects of astrophysics or cosmology. Because of that, it's tempting to give it a pass when it makes these mistakes.

But at the same time, Cosmos—at least this version—is not merely a piece of throwaway content to merely say, "yeah, we got science talk in primetime!" Or rather, it shouldn't be, and we do ourselves a disservice to couch it in those terms. For many, who are like myself watching the original Cosmos, this might be the first time being exposed to more than is learned in a middle school science course.

To make the claim, as is done in the opening act of the first episode, that science is a rigorous and unyielding search for truth and then get the results from that pursuit wrong all the while excusing the mistakes in the name of dumbing it down for a wider audience or making it entertaining comes off as hypocritical. In other words, science is not an unyielding search for truth unless it's too boring, nor is it okay okay to ignore the results when we don't want to explain why it really matters.

So I hope the list of mistakes, ambiguities, and outright fictions are taken in the spirit in which they were written: that the results and fruits of science and history are exist whether or not they are convenient or easy to explain. These things are complicated because the the Universe is complicated, and we're better off appreciating that complexity for what it is rather than saying science is the practice of "well, it's good enough."


Beings who live in fire and ice

About 45 seconds in, deGrasse's narration mentions that we will "encounter beings who live in fire and ice." The image displayed is an animation of this guy:


This is a tardigrade, or waterbear: a microscopic organism part of a group known as "extremophiles." Extremophiles have the ability to live in habitats humans and most other organisms would find completely inhospitable: the waterbear, for example, can live under miles of ice, withstand temperatures close to the boiling point of water, and even survive the vacuum of space.

However, while the "ice" part of the narration is correct, there is no known organism that can withstand, much less live in, even the lower bounds of temperatures associated with fire (~750°C). Even the hardy waterbear has only survived a few minutes at ~150°C. So unfortunately, we won't encounter beings that live in fire.

Stars that never die

In the very next animation, Tyson states we'll also "explore the planets of stars that never die." Depending on how you define "die", this is either another impossibility or, in actuality, not that wild and fantastical. There are many types of stars and equally as many different expected lifecycles for stars. Some stars might explode into supernovae, some may even turn into black holes. But many will burn through their fuel and eventually shrink down to a small fraction of their former selves called a black dwarf.

The supernova is pretty uncontroversially a "death" of a star: there is nothing left but a cloud of star material that may then go on to form something else, like a new star. So that leaves the other two scenarios: black holes and dwarfs. It is in these two scenarios where we need to hone our understanding of the word "die". What does it mean for a star to "die"? Do we mean the same thing as a super nova, where there is no single "thing" we can point to and say, "that's a star"?

If so, black holes and black dwarfs would qualify as "stars that never die", though black holes are theorized to be able to "evaporate" via a mechanism known as Hawking radiation. In this case, you won't have to go very far to explore the planet of a star that never dies: the Sun is one of them. The Sun is main-sequence star: it is expected to follow a stellar life cycle that will eventually lead to its perpetual existence as a black dwarf. But black dwarfs and non-evaporating black holes stretch the boundaries of what one might consider "alive" in a stellar sense: they emit no light, have no internal combustion. They're alive in the sense that a charred ember is when compared to a roaring fire.


At 3 minutes in, we see the next big mistake: the executive producer is Brannon Braga. Just kidding (but only slightly).

A bit later, we're treated to a very impressive nova remnant/iris combination that forms the basis for Cosmos's title card as the Ship of the Imagination passed by the camera on the right, making a "whooshing" sound as it does so. Things don't "whoosh" in space. Sound requires a medium through which to travel, something space is definitely missing. In fact, this happens every single time an external shot of the Ship of the Imagination is used. I won't call it out again, but keep that in mind as you watch the rest of the episode.

The Cosmic Address

Earth / Ship of the Imagination

Tyson is shown on the bridge of the Ship of the Imagination, explaining how things work on it. He then shows a picture of the Earth from 250 million years ago, and another of the Earth "how it could appear 250 million years from now", complete with evidence that human life is still there. This is all well and good (it's a ship of the imagination after all), but I want to call back to something he said in the opening. If you remember, this was the contract as described by him:

This adventure is made possible by generations of searchers strictly adhering to a simple set of rules:

  • test ideas by experimental observation,
  • build on those ideas that pass the test,
  • reject the ones that fail,
  • follow the evidence to wherever it leads, and
  • question everything

Accept these terms and the cosmos is yours.

Less than 3 minutes after laying these terms out, Cosmos is already violating them. The picture of Earth from 250 million years into the future is a fantasy: it's not based on any experimental or observable data.

The Solar System


Around the 6 minute mark, Tyson begins to narrate our journey through the solar system. He has something to say about almost every planet, except Mercury. "The Sun holds all the worlds in our solar system in its gravitational embrace, starting with Mercury." And that's it. We don't even get a clear shot of the closest planet to the Sun. Why no love for Mercury? Someone on the Cosmos staff is clearly an Anti-Mercurite.


Continuing on to Mars, where Tyson says that Mars has "as much land as Earth itself." This necessitates some clarification. Mars is not as large as Earth: in fact, it only has ~38% of the surface area of Earth. However, because the Earth is mostly covered in water, the land Mars does have is about as much as the dry land on Earth.

Asteroid Belt

The Ship of the Imagination reaches the asteroid belt, where we see a very crowded array of rocks and debris that wouldn't be out of place in a remade Empire Strikes Back. However, the asteroid belt is not that dense. In fact, the Asteroid Belt is mostly empty: while the density of the belt is not uniform, Marc Rayman of the JPL estimates an average distance of about 1.9 million km, or 8 times the distance from the Earth to the Moon. It's just that space is so big that "mostly empty" still translates into a lot of asteroids.


Past the asteroid belt we arrive at Jupiter and are treated to a number of lingering shots of Jupiter's Great Red Spot. However, while there are some impressive winds associated with the Great Red Spot, what's portrayed is way too fast. In the animations, we see the clouds rotate about the eye of the storm fairly quickly, indicating a rotational period of only a minute or two. But the Great Red Spot is so vast that its rotational period is about six days. From the vantage point of Tyson (who gets up from his seat to view the spectacle) there wouldn't be much movement at all.

Uranus and Neptune

We then reach Uranus and Neptune, who, like Mercury, are given a bit of a raw deal by being grouped together. One thing to note here is that Uranus's rings, while clearly visible in the flyby, are actually so faint they were discovered by accident while looking for something else. Unlike Saturn, whose rings are made of highly-reflective ice, Uranus's rings are mostly made up of light absorbent rock.

The Kuiper belt and Pluto

Past Neptune we reach the Kuiper belt, which for some reason is never referred to by name in this episode. Like the asteroid belt, the density shown is way too high: the Ship of the Imagination's evasive maneuvers are all for naught.

Oddly, the density drops down to a more reasonable level when Pluto is reached. This is totally fascinating to me. If you're older than, say, 12, you remember a time when Pluto was considered a planet in the same vein as the other eight. However, this was a bit controversial and arbitrary amongst astronomers: Pluto always seemed like the odd one out. But given there was nothing else found like it, nobody made too much of a fuss. However, as astronomers identified more and more objects in the vicinity of Pluto, its status as a planet became called into question. It was totally shot when Kuiper belt objects Sedna and Eris were found to be about the same size of Pluto (or, in the case of Eris, possibly even larger).

Tyson, as director of the Hayden Planetarium, caused a bit of a stir himself when he omitted Pluto from the planetarium's planetary exhibit. His decision was vindicated by the 2006 IAU vote on how planets should be classified. Under the IAU definition, Pluto would not be counted as a "major planet" (the same category as Earth or Jupiter) because it has not "cleared the neighborhood" around its orbit: i.e., there's other stuff floating about where Pluto orbits.

So you have this shot of Tyson whizzing through this minefield of a Kuiper belt (which isn't nearly as dense) only to get to Pluto—which is supposed to be part of that minefield—but is instead shown to have a clear orbit. One wonders if someone in the graphics team did that intentionally just to mess with people.

Voyager I

Voyager I is then shown, complete with its famous golden record. However, the record is shown rotating under its cover with music blaring. This isn't the case at all: there is nowhere near enough power to maintain the continuous playing of a record for decades. And as noted above, there is no medium through which the music would play even if there were. In reality, directions for playing the recorded are etched on the cover, complete with some basic diagrams about how to measure time and where we are in the galaxy.

A couple of interesting notes about the contents of the golden record:

  • It also contains a number of video segments.
  • The song playing in Cosmos is Blind Willie Johnson playing "Dark was the night, Cold Was the Ground". It is, in fact, one of the song samples features on the golden record.

Oort Cloud

Not a whole lot wrong with this segment, but I wanted to talk about the explanation of why nobody has ever seen the Oort Cloud. As Tyson explains, the Oort cloud is incredibly sparse. Why did they completely flub the visual depiction of the asteroid belt and the Kuiper belt only to explicitly call attention to the density of the Oort Cloud? It's a strange decision.

One nitpick with the explanation: it's not merely that the Oort cloud is incredibly sparse. After all, we're able to visually confirm objects within the asteroid and Kuiper belts without issue even though they too are sparse. The issue is that it's sparse and the objects are too far away.

Milk Way Galaxy

Exoplanets and rogue planets

This segment is a bit hamfisted and disjointed. It starts off innocently enough, with a factually correct description of how many planets theorized to be orbiting other stars in the galaxy. But then Tyson wonders, "what do we know about life? We've met only one kind so far: Earthlife." and then immediately starts talking about rogue planets.

To be clear: weird, strange new forms of life that defy our conventional understanding of the term are not limited to rogue planets. We may find such things even in our own backyard, on satellites like Jupiter's Europa, or even Saturn's Titan.

A bit later, he defines rogue planets as "orphans, cast away from their mother stars during the choatic birth of their native star systems" and "molten at the core and frozen at the surface". While it's certainly possible there are exemplars of such rogue planets, our evidence so far points to most of them being Jupiter-sized (or larger) gas giants. We also have evidence to believe that many of these rogue planets are actually "failed" stars called "brown dwarfs", never bound to any star system but not massive enough to sustain the fusion reaction required for an active star.

Milky Way Visuals

The section on the Milky Way concludes with a stark, "infrared" visual where Tyson states "every single dot, not just the bright ones, is a star." This is wrong. Half the visual is covered in a vast, dark cloud of interstellar dust, commonly referred to as the Great Rift.

Later, the camera pans far outside of the Milky Way and Tyson states that "we're now a hundred thousand light years from home." In reality, in that visual we would be much farther away than that. The Milky Way Galaxy itself is 100,000 light years across. I'd argue the Ship of the Imagination is at least half a million light years away, if not farther.

Local Group

First, Andromeda is not "the galaxy next door". It's close, relatively speaking, and it is the closest spiral galaxy to us, but there are a dozen other galaxies closer. The closest, the Canis Major Dwarf Galaxy, is a mere 25,000 light years away: there's less distance between us and it than us and the center of the Milky Way.

Second, when Tyson says "a smattering of other, smaller [galaxies]", he means 54.

The Multiverse

Skipping over the Virgo Supercluseter and the Observable Universe segments, Tyson makes a pretty big claim:

Many of us suspect that all of this—all the worlds, stars, galaxies, and clusters in our observable Universe—is but one tiny bubble in an infinite ocean of other Universes: a multiverse.

While the multiverse has support from a number of prominent scientists, its existence is controversial. There is no evidence—direct or otherwise—to suggest that the multiverse is real. Reasonable scientists often disagree on whether it exists, or whether we can even know it exists. This is not a "Flat Earthers vs. reality" type of debate, and it's a bit disingenuous to put that out there without mentioning the controversy especially considering the terms of rejecting ideas that fail the test of experimental observation Tyson required us to accept at the start of the episode.

The Early Modern Period

This section is rough and strays heavily into outright fiction. Because of the sheer number of inaccuracies and falsehoods presented in this section, I'm going to list them off by bullet point rather than recap every few seconds:


  • Non-geocentric views of the Universe have had a long tradition dating back to classical Greece, a thousand years before the timeline presented by Tyson and it was not "obvious that Earth was motionless."
  • In 1599, the claim that "everyone knew the Sun and stars were just lights in the sky [that] revolved around the Earth" is false. Even discounting the efforts by the ancient Greeks, Romans, and early medieval astronomers, Copernicus had been working on his heliocentric model 30 years prior, and astronomers like Kepler and Tycho Brahe had published their findings endorsing the heliocentric model by 1596.
  • Likewise, Copernicus built his work upon the findings of others, and he credited them directly and extensively. He did not make a "radical proposal".

Giodorno Bruno, Part 1

  • Giodorno Bruno was not the first, much less the only, person to envison an infinite cosmos. As Corey Powell notes, Nicolas of Cusa envisioned the same thing a century earlier.
  • Bruno's undoing was not "[daring] to read the ancient books banned by the Church" or specifically reading the works of Lucretius. His first brush with the religious authorities was when he was accused of advocating a specific type of heresy unreleated to cosmology and when he was found to have an annotated text of Erasmus, a prominent figure in early Protestantism.
  • He was not accosted and thrown out of his order: he fled and voluntarily gave up the habit when he learned an investigation into the above was underway. In fact, he picked up his habit again at the convincing of his fellow Dominican brothers.
  • Likewise, the picture of him cold and alone by a campfire having visions is a fiction. Bruno was initially successful wherever he went. As Powell continues:

    Despite his heresies, Bruno was neither impoverished nor alone. In reality, he had a series of powerful patrons. In 1579, he was appointed a professor of philosophy in Toulouse, France. In 1581, King Henry III of France offered him a lucrative lectureship at the Sorbonne. In 1583 he visited England, lived with the ambassador to France, and met regularly with the Court…and so on. The gaunt, lonely fellow you see on screen in Cosmos is not the real Bruno.

    Nor was Bruno the simple, humble figure shown on TV. A major reason he moved around so much is that he was argumentative, sarcastic, and drawn to controversy. He engaged in bitter academic disputes, many of which had nothing to do with his cosmic framework. One example He fled France because of a violent dispute about the proper use of a compass (seriously).


At this point, I want to interject and explain what excommunication is, because Tyson never explains what it meant for Bruno to be excommunicated by three different groups.

In the context of Christianity, the Communion is what unites Christians with Jesus Christ. The details vary from denomination to denomination, but it's essentially the thing that makes Christians Christians.

That bond can be severed, however: if, for example, you decide that you don't want to be a Christian anymore, you'd no longer be in communion with the Church. Similarly, there are certain beliefs that a Church may hold to be core to its understanding of Christianity: by rejecting those beliefs, you'd fail to be in communion with the Church as well.

That breaking of the bonds is called excommunication. Generally, the consequences for excommunication are as follows:

  • You can't participate in any of the Sacraments. Sacraments are specific Christian rites—like receiving the Holy Eucharist—that are manifestations of God's divine favor.
  • You may be ostracized by those who don't want to associate with people who are not of the same faith. One practical implication of this, as Giodorno Bruno occasionally ran into, may be that you can't attend or teach at an institution associated with the denomination from which you were excommunicated.

Excommunication is not, and never was, a euphemism for capital punishment. It's also intended to be temporary (what Roman Catholics refer to as a "medicinal penalty"): atone for whatever you did and it's lifted. Atonement generally consists of recognizing whatever you did was wrong (confession) and making up for the act (penance). Of course, if you don't believe you did anything wrong or you simply don't want to be a part of the denomination, you wouldn't do any of that and you'd simply stay excommunicated.

However, back when most of the Western World was under autocratic rule, if you kept making waves and stirring the pot and being a general rabble-rouser, someone in a position of authority was going to decide that something is going to need to be done about you. Because virtually all monarchs believed they ruled with divine favor, they considered themselves defenders of the faith as they saw it. This meant civil authorities having laws against spiritual wrongs like heresy and blasphemy, almost all of which were cruel and unusual.

Giodorno Bruno, Part 2

Now that all of that is out of the way, let's pick up Cosmos's story of Bruno again:

  • Bruno was automatically excommunicated by the Roman Catholic Church when he professed himself to be a Calvinist during his travels.
  • Bruno was temporarily excommunicated by the Calvinists when he distributed a pamphlet attacking a prominent professor and refused to apologize. We do not know the contents of the pamphlet other than that he called the professor a "pedagogue" and that it contained a couple of dozen perceived errors made by the professor.
  • Bruno was subsequently excommunicated by the Lutherans, well after his journey to England, when they accused him of being a Calvinist.
  • With respect to his time in England, he enjoyed a fair amount of success and published a number of works. There is no evidence to suggest the scene depicted in Cosmos ever happened. He only left after a riot stormed the French embassy at which he had his residence.

Giodorno Bruno's trial and execution

After a number of failed teaching gigs in France and Germany, he returned to his native Italy where he continued his streak of pissing off the locals and losing bids for teaching positions to people like Galileo Galilei. Tyson suggests he may have returned because he was homesick: I'd argue it's because he pissed off everyone elsewhere and had nowhere else to go.

Tyson refers to Bruno's imprisonment by the Inquisition as "falling into the clutches of the thought police." This is a bit disingenuous. Bruno wasn't arrested and tried merely for having heretical ideas. He was arrested and tried because, as discussed above, he wouldn't stop talking about them. To be clear, this is no more defensible: we now have centuries of political philosophy that cogently argues for the freedom of expression. But this was yet another missed opportunity to give an accurate portrayal of history.

Tyson then asks, "why was the Church willing to go to such lengths to torment Bruno? What were they afraid of?" The answer suggested by Tyson is that "if Bruno was right, then the sacred books and the authority of the Church would be open to question." Again, this is disingenuous at best, and patently false at worst. Bruno was not the first, nor would he be the last, person to speak out against the Church. Heck, while Bruno was doing his thing, the Protestant Reformation—which really did cripple the notion of an omnipresent, omnipotent Church—was in full swing.

Oddly, after glossing over the theological issues with Bruno's philosophy throughout the segment, there's a scene in which the supposed heresies of which Bruno was convicted are listed, three of which are theological in nature and never mentioned before this point:

  • Questioning the Holy Trinity
  • Divinity of Jesus Christ
  • Believing that God's Wrath is not eternal; everyone will be saved
  • Asserting the existence of other worlds

To be clear, this is a fiction. We don't know what heresies Bruno was convicted of: the record of his trial has been lost. Various historians have created their own speculative lists, indicating that his assertion of an infinite Universe or multiple worlds was but one issue among several theological errors. But we do know that the Church had no stance on the Copernican model of the Universe at the time of his conviction, so he could not have been convicted of a heresy related to that.

We also know that Bruno was not highly regarded by other scientists at the time, like Kepler and Galileo, contrary to Tyson's claim that Galileo realized 10 years later that Bruno had "been right all along."

Tyson wraps up the segment on Bruno with the following monologue:

Bruno was no scientist. His vision of the cosmos was a lucky guess, because he had no evidence to support it. Like most guesses, it could well have turned out wrong. But once the idea was in the air, it gave others a target to aim at, if only to disprove it.

I found this to be the most problematic aspect of the entire Bruno segment. As I've repeatedly called back to, the terms by which we were supposed to be on this journey through the cosmos was that we "test ideas by experimental observation, reject the ones that fail, [and] follow the evidence to wherever it leads." Bruno did none of that. He simply had a crazy idea that happened to be similar to what we now believe to be the case. Nobody took Bruno's ideas and ran with them. Actual scientists at the time correctly rejected Bruno's vision of reality precisely because it was baseless.

So what should we take from this? That Kepler and Galileo were wrong? That if someone has a crazy idea and no evidence to support it, we should still treat it as a valid hypothesis? What does that mean for flat Earthers, or the multitude of crank theories that are unfalsifiable in principle?

The Cosmic Calendar

For the most part, the Cosmic Calendar is a faithful retelling of cosmology as we know it. There are a few points to touch on, though.

First, the description of how the Moon formed—where it was simply a collection of random debris that coalesced in a singular object—is a bit of an oversimplification of the currently accepted lunar origin hypotheses. The most widely accepted hypothesis of how the Moon was formed is called the giant impact hypothesis, where a planet the size of Mars called Theia collided with Earth and its resultant ejecta coalesced to for the Moon. Cosmos shows a planetoid hitting Earth, but what they showed is much smaller than the proposed Theia.1

Second, Tyson mentions that we "invented Astronomy." The use of "invented" is problematic: we didn't make astronomy up like we did with, say, astrology. I'd strongly argue "discover" is a more appropriate description of our relation to astronomy and the other sciences.

Third, another slight nitpick: Tyson dates a "revolution in the way we live" (the so-called Neolithic Revolution) at around 10,000 years ago. It actually occurred 12,000–13,000 years ago. A drop in the bucket on the cosmological scale, but still 20–30% longer than Tyson describes.


This was a long, tedious exercise. I doubt I'll do another for the other episodes. While some (or, perhaps, most) of what I wrote here may seem pedantic or missing the point, the one thing I hope people take away from this exposition is that while Cosmos is a great eye opener if you have never experienced the wonders of our Universe, but you would do yourself a grave disservice if you take it at face value or use it as a reference. Science and history are complicated, messy subjects that are nevertheless worth exploring to their fullest extent: don't let your only exposure to it be an carefully edited hour of passive viewing for a few weeks.

  1. It's important to note that the giant impact hypothesis is not without its problems, even if the general idea is currently considered to be the most feasible. 

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