intergalactic matter

Many cosmic rays are in fact extremely high-energy photons—gamma rays—that can be absorbed by interstellar or intergalactic matter as they travel through space.

She says one of her subjects is nothing less than “the physical laws of the universe,” a remark underscored by her list of the ingredients of a green-gold-brown parabolic monolith: “Aurora particles, stardust, cosmic radiation, intergalactic matter, ionic waves, organic carbamate, gravity and time.”

But this duration is misleadingly long: as signals travel across millions of light years of space, intergalactic matter tends to smear radio waves across the spectrum, a phenomenon known as dispersion.

That discovery was based on the structure of the pulses themselves: Among the range of frequencies that make them up, longer wavelength photons lag behind the shorter ones, thanks to the drag of intergalactic matter.

“It’s true,” Mr. Byrne sings at one point, “I am a shaky ladder/intergalactic matter/outside of space and time.”