Novel in which dark matter is giant sentient single-celled organisms and humans learn their language

Question

It has been over ten years since I read this book (and I believe that it was an old book even then), so the title, and many of the details, completely escape me.

In this novel, the main characters consist of a crew of a ship whose sole purpose is to make first contact with new alien species and learn/teach their language, so that they can establish regular communication norms with that species.

The crew discovers, somehow, that dark matter is made of a bunch of gigantic sentient, hyper-intelligent single-celled organisms. They communicate with them.

Even though we can't detect dark matter, the book contrives a way for them to communicate with the humans. To the best of my recollection, what happens is that the cells are so massive that their gravity traps errant charged particles. They can then vibrate those particles somehow, and the resulting electromagnetic radiation is what the humans detect.

Much of the book is the explanation of the process by which they attempt to communicate. They start with what they consider to be the most universal language: basic arithmetic. I don't remember how it proceeds from there, but I remember the explanation of the process of first-contact communication being a central part of the book.

The species is single-celled and hyper-intelligent. That means each individual is a cell, and you can hold a high level, thought-provoking conversation with one. They also refer to each other as individuals, and have identities for each of them. (Much like we have names for each other.)

I don't exactly remember the size scale of each cell. But at the very least, they are planetary in size. That is, one individual is at least the size of a planet. They may be as big as stars, though I don't recall.

Answer 1

I wonder if this could be Starplex by Robert J. Sawyer.

I have to confess I don't remember the details of the book as it's a long time ago I read it, but from skimming through it the book is about the discovery of dark matter organisms that the book calls Darmats. The first discovery is in chapter 12:

In the framed-off area was a dark-matter sphere, seen from almost directly above its equator. Actually, it wasn’t anywhere near a perfect sphere: this one was flattened at the poles. Light and dark latitudinal cloud bands crossed its face. According to the scale bars, this was one of the largest spheres they’d found, measuring 172,000 kilometers in diameter.

172,000 kilometers in diameter is about 13 times bigger than the Earth, so these are indeed planetary sized organisms. The Darmats aren't single celled, but you may be remembering a scene where one of the Darmats reproduces by fission like a cell:

When the image reappeared, the two spheres were joined by only about a tenth of the original globe’s diameter. Everyone watched, rapt, silence broken only by the gentle whir of the air-conditioning equipment, as the process reached its inevitable conclusion. The two spheres broke free from each other. One immediately started curving toward the bottom of the frame; the other, toward the top. As they distanced themselves from each other, the orange reference dots on each of their equators began to take longer and longer to complete their paths—the rotation was slowing down.

Rissa turned to face Keith, her eyes wide. “It’s like a cell,” she, said. “A cell undergoing mitosis.”

“Exactly,” said Rhombus. “Except that in this case, the mother cell is some hundred and seventy thousand kilometers in diameter. Or, at least it was before this started happening.”

The remainder of the book then concerns the (successful) attempts to communicate with the Darmats.

At the end it turns out that:

The Darmats created the universe!

“Yes,” barked Jag, “quantum physics demands qualified observers. Yes, intelligence is necessary to determine which possibility becomes reality. But in our arrogance we thought that the universe could work for fifteen billion years without us, and yet that it somehow was geared to give rise to us. Such hubris! The intelligent observers are not us—tiny beings, isolated on a handful of worlds in all the vastness of space. The intelligent observers are the dark-matter creatures. They have been spinning galaxies into spirals for billions upon billions of years. It is their intellect, their observations, their sentience that drives the universe, that gives quantum potentialities concrete reality. We are nothing—nothing!—but a recent, localized phenomenon—a spot of mold on a universe that doesn’t need us, or care that we exist. Cat’s Eye was absolutely right when he said we were insignificant. This is their universe—the darmats’ universe. They made it, and they made us, too!”