Readers respond to the June 2026 issue

POLE POSITION

“Early Plates,” by Marissa Grunes [Advances], states that Earth’s magnetic north pole is “technically” now in the Southern Hemisphere. Can readers get an explanation of this?

ALEX SMITH LITTELTON, MASS.

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GRUNES REPLIES: The terms “north” and “south,” as applied to magnetic poles, are somewhat arbitrary designations. Imagine a bar magnet: Magnetic force flows out of what we call its “north” pole. The force bends around the magnet (forming a magnetic field) and flows back into the magnet through its “south” pole. This is why opposite poles attract and similar poles repel each other.

In the case of Earth, since the last magnetic reversal about 780,000 years ago, lines of magnetic force flow out from the Antarctic, bend around our planet and reenter Earth in the Arctic. So our world’s “north” magnetic pole is in the Antarctic, and its “south” magnetic pole is in the Arctic.

Magnetic compasses arose from the discovery that free-floating magnetic materials align themselves along the north-south axis of the globe. The poles on a bar magnet received their names from the direction in which they would point. But remember that opposite poles attract! So the pole of a magnet that’s called “north” may point toward the cardinal direction of geographic north, but the pole that’s pulling it is, magnetically speaking, “south.”

To avoid confusion, we’ve continued to use the geographic designations of “north magnetic pole” for the pole in the Arctic and “south magnetic pole” for the pole in the Antarctic. But technically, the planet’s “south” magnetic pole is in the Northern Hemisphere, and vice versa.

SAFEGUARDING THE MOON

In the June issue, I was especially fascinated by the articles about the Artemis II moon mission and the space dreams it has inspired [“Back to the Moon” report]. But I was troubled by how little attention was paid to the U.S.’s history of irresponsible resource extraction, which is especially concerning now that billionaires and others are obviously advocating for the rapid exploitation of whatever the moon may hold. I would love to see substantial guardrails erected to protect the moon in a way that we’ve so far failed to protect our home planet.

For instance, “Eyes in the Sky,” by Joseph Howlett, reports that researchers hope to make the moon a site for a new gravitational-wave detector. I believe that goal can be reached only if mining is severely restricted or even prohibited on the moon because, as demonstrated by the Laser Interferometer Gravitational-Wave Observatory (LIGO), even minuscule tremors interfere with measurements. Similarly, Howlett describes how the lunar farside is an ideal location for a highly sensitive radio telescope because radio communications from Earth can’t reach it. But that promise can be realized only if that portion of the lunar sky is kept free of a maze of communications satellites.

MICHAEL KEARNS COLUMBUS, OHIO

PIECE OF HISTORY

“Tetris Paradox,” by Jack Murtagh [Advances; September], refers to the shapes used in the game as its “pieces.” These shapes are, in fact, called tetrominoes. The shapes were first introduced 30 years before Tetris by the late mathematician Solomon Golomb, and within a couple of years they were popularized in Scientific American! So it’s unfortunate to see them called Tetris pieces.

I have a book with MIT Press exactly about this: Soviet Blocks, a legal and geopolitical history of Tetris.

JULIEN MAILLAND PROFESSOR OF MEDIA LAW & MANAGEMENT, INDIANA UNIVERSITY BLOOMINGTON

AUTISM AND CONTEXT

“Visualizing the Spectrum,” by Allison Parshall and Amanda Montañez [Graphic Science; April], shows how autism spectrum disorder has many dimensions rather than being a single linear spectrum. It’s encouraging to see that autism research has begun, over the past decade, to recognize that complexity and the fact that divergence in quite a few of those dimensions does not represent a “disease” that needs treatment.

As a neurodivergent individual myself, I note that there’s still one set of dimensions the field is missing: context. The article represents 39 traits from the Autism Symptom Dimensions Questionnaire, and my answers to some of these questions, especially those relating to interpersonal relationships, can differ markedly depending on the situation. For example, a couple of the questions lump family and friends into one group, but my answers differ depending on whether I’m interacting with my spouse, other family, friends or unfamiliar people and also depend on whether those interactions are in a group setting versus one-to-one.

“JIM” VIA E-MAIL

ORBITAL DATA CENTERS

Partly inspired by “Battle for the Night Sky,” by Jonathan O’Callaghan [September], our online Discussions space asked readers, “Should we build data centers in space?” The following responses were edited for space and clarity.

I can’t believe it would be less costly to put a data center in space rather than on the ground. And there are other factors to consider. The most common objections to data centers on Earth focus on electricity consumption and cooling. Neither concern goes away in orbit.

I think the objections to massive data-center construction here on Earth’s surface are well founded. Regulation is badly needed here. And if I’m wrong and space-based data centers turn out to be economically feasible, regulation will be needed there, too.

GARY NOVOSIELSKI VIA DISCUSSIONS

There is no way to stop the advancement of our technology, whether it is good or not. Perhaps we have no realistic choice about building data centers somewhere. Then, considering the environmental impact of these massive projects, space is a better place.

“NOBU” VIA DISCUSSIONS

Assuming they work, building, launching and operating space-worthy data centers would exact a stupendous environmental cost during production and after. Much smarter solutions abound. China is powering data centers, here on Earth, with renewable energy and placing them underwater to minimize climate and land-use impact. It apparently understands that however data centers are built, preservation of habitable environment has to come first, or there will be no one needing them.

DOROTA NIECHWIEJ CLEGG VIA DISCUSSIONS

ERRATUM

“Spying on the Universe,” by Jonathan O’Callaghan [September], should have said that astronomers met at Princeton University to discuss what they could do with telescopes from the National Reconnaissance Office in 2012.