Wonder of the Ancient World,” by Tony Freeth, describes the Antikythera mechanism, a Greek astronomical calculation machine. As a biologist with an interest in engineering, I was amazed by the device’s construction. Just how did the ancients make it? I doubt they had tools such as lathelike machines to cut the gears, dividing heads to index them, accurately made drills, and so on.

Gerald Legg Hurstpierpoint, England

Now that the design of the Antikythera mechanism is understood, my question is: Did it really work? And if so, how was that feat accomplished? For a device of such complexity to have functioned, the parts would have needed to be incredibly well machined. A working mechanism would seem to require the build quality of a fine watch—a device that only emerged centuries later.

NORMAN L. GILINSKY Eastsound, Wash.

FREETH REPLIES: My colleagues and I share Legg’s amazement. In the University College London Antikythera Research Team, our two Ph.D. students are exploring the issues he raises. It is difficult to see how the device’s components—such as gears, arbors and coaxial output tubes—could have been made without a lathe, and we are researching the evidence for lathes in ancient Greece. Its creators must have had some form of drill, as well as files or chisels for cutting gear teeth. The coaxial tubes raise many questions. Our students are part-time, so it may take a while to resolve these issues.

In response to Gilinsky: The Antikythera mechanism must indeed have been made with great precision for its time—it was perhaps not as accurate as a modern watch but very well made for ancient Greece. Friction must have been a huge issue—particularly because many of the parts were in contact with one another in a way that would not happen in a modern instrument.

Did it work? We cannot be sure, but two pieces of evidence suggest it likely did. The first is Roman politician Cicero’s first-century B.C.E. descriptions of Greek devices that sound similar: two made by mathematician Archimedes in the third century B.C.E. and one by philosopher Posidonius in the first century B.C.E. The second comes from modern models—particularly those of Michael Wright, a U.K.-based “historian of mechanism” and a former curator at London’s Science Museum. His models work remarkably smoothly—although he does use 19th-century lathes to make them.

Researchers on our team are exploring whether our latest theoretical model works. First, they are building a model with modern machinery to check whether there are serious design issues. Then they will build one (or parts of one) using techniques we believe were available in ancient Greece.


In “Hacking the Ransomware Problem” [Science Agenda], the editors describe strategies for addressing ransomware attacks, in which hackers encrypt data in a target’s computer system and demand payment to free it.

There are multiple issues that allow ransomware to survive. Removing the incentive for criminals to use it is great, but that works only for companies that report the attack. The vast majority seem to feel government involvement is more of a hindrance than a help. Having worked in the security and networking side of companies, I can say the biggest issue that allows ransomware to persist is companies’ reluctance to implement good security architecture and practices. This results from a combination of problems, but in general, the implementors do not know what they are implementing or why. Inevitably one area will be closed off under direction from a security person or audit, but another 50 will remain open. Companies cherry-pick good practices and do not realize that they are exponentially more secure if you implement them in tandem with complementary practices.

CTO, Alum Rock Union School District


In “Eat to Save the Planet” [Observatory], Naomi Oreskes argues that people can help mitigate the climate emergency by cutting back on red meat consumption but notes that some “have argued that calls for individual action actually distract us from corporate responsibility.”

Asking individuals to take responsibility for climate change does not distract us from pressuring larger entities to do the same. This movement requires everyone to participate to the maximum extent possible. Individuals can fight climate change in many ways that do not require a lot of time or increased expense. The tools are available to change our transportation, the energy used in gases emitted by our homes, our consumer purchases and donations to offset our carbon usage. Next time, don’t tell readers one thing they can do. Tell them the 20 things they can do.



Kudos to Amy Cooter for “Inside America’s Militias,” her article on a move to more violent extremism among such groups. Down here in rural Alabama, we own an interest in land next to a militia training camp, complete with obstacle courses, firing ranges, and fields for simulated combat and tactical drills. I’ve dealt with the spectrum of Cooter’s well-defined characters countless times over the decades and in as many contexts, from grilling them in jury selections to debates while some work on our farm equipment. As I was ticking off points of agreement with Cooter, I was anxiously awaiting her take on a topic I’ve found the militia world fixated on: Antifa, which she describes as “the antifa (antifascist) movement.”

Militia-speak can’t seem to settle on the finest-sounding string of bad words to describe antifa. Having been shot at as a veteran of the Vietnam War, I know fear and see it in the militia world when its members discuss the organization. I’d like to know if that fear is justified. Cooter’s piece leaves us with scant tidbits on the subject.

GUY V. MARTIN, JR. Montgomery, Ala.

COOTER REPLIES: What we do know is that groups that long for a fictional past, especially those with overtly racist motivations, are more organized and more threatening than those on the left. Antifa is not represented by a single organization, and engagement with it is often considered more of a transitory action, in which some people may participate for a single protest or other action rather than necessarily having a meaningful, long-term group affiliation. Strongly ideological individuals of any political persuasion have the potential for violent action. But in my opinion, the fear of antifa in militia communities and beyond is more about the social change its presence represents rather than a real or systematic threat of violence.


Lemur Rhythm,” by Jack Tamisiea [Advances], should have said that the study on indris showed the first confirmed case of a nonhuman mammal possessing categorical rhythm similar to that in human music, not categorical rhythm in general.

Ian Battaglia’s review of The High House [Recommended] incorrectly describes Florida as the novel’s setting. The character Francesca dies in a hurricane in that state, but the plot centers on the English coast.

In the March 2022 issue, two Advances articles included illustrations that should have been credited to Thomas Fuchs: “Phantom Finger,” by Matthew Hutson, and “Unusual Flow,” by Rachel Berkowitz.