Interpreting What the Webb Telescope Sees

A lot of creativity and art goes into crafting those images. For very good scientific reasons, the Webb telescope is designed to work mainly with infrared radiation, which gives a picture that complements visible light, illuminating different features. To see the distant past of the universe and catch galaxies in their youth, this is how to look. Light from those sources has been stretched by the universe’s expansion into the infrared region of the electromagnetic spectrum. To view it, you need to go into space and avoid the infrared glare of closer warm bodies.

There is a mismatch between the exquisitely detailed infrared images the Webb scope produces and what human eyes can perceive. We ordinarily feel infrared radiation as heat but don’t see it. (Pythons and vampire bats do, using it to home in on the heat generated by their prey.) To bridge the human sensory gap, astronomer-artists assign visible, false colors to the different sorts of infrared light. The result both caters to our natural vision and transcends it. There is a scientific purpose to that exercise; humans have powers of visual pattern recognition that computers can’t yet match. There’s also, of course, a cultural purpose—to make the hidden beauty of the universe more accessible.

For scientists and hard-core science fans, though, the point is not the processed images but the underlying information. That information, detailed and quantitative, is nourishing food for thought, both for computers and for the more analytical parts of human brains. The scientific program of Webb will address many questions, probably including new ones that its own observations will pose. Personally, I’m especially interested in two “sure things” and two related long shots.

Presently, two different ways of measuring the age of the universe don’t quite agree. Methods based on studying signals from the very early universe (specifically, cosmic microwave background radiation) give a larger value than methods based on studying signals from the relatively recent universe (specifically, distant galaxies and supernovae). The discrepancy, known as the “Hubble tension,” is about 10%—not enormous but larger than the claimed precision of the measurements. Webb observations should significantly firm up—or modify—the recent-universe result, which involves more complicated data analysis.

Webb’s infrared imaging also will open a new window on other (relatively) cold, dim astronomical objects. Especially interesting is the possibility of studying the atmospheres of planets outside our solar system: exoplanets. Webb will surely identify lots of new ones, including small Earthlike planets that so far have been elusive. Life on Earth has drastically changed its atmosphere, mainly through photosynthesis, in ways that ordinary chemistry might find hard to mimic. Unusual exoplanet atmospheres might hint at distant life.

Those are pretty sure bets. Here are two intriguing long shots. First: If the Hubble tension gets firmed up, it could indicate that there was more “dark energy”—a substance thought to accelerate the universe’s expansion—in the early universe than today. That is contrary to existing theory, but I wouldn’t bet against it heavily. It would inject some welcome (dark) energy into fundamental physics.

Second: Notoriously, human technology is beginning to alter Earth’s atmosphere significantly. Big projects can involve big flows of energy and matter, so plausibly someday human engineering will alter the solar system in ways that a Webb-like instrument could detect from afar. Wouldn’t it be poetic for our own restless intelligence to unearth signs of restless intelligence elsewhere?