Fumfer Physics 16: Gravitational Lensing as Information, What Warped Photons Reveal

Gravitational lensing can be read as an informational process: gravity reshapes photon trajectories, encoding maps of mass and curvature into observable distortions, magnifications, and time delays. On galactic and cluster scales, lenses reveal dark matter distributions; on cosmic scales, cumulative lensing and expansion geometry alter apparent sizes and brightnesses across look-back time. Compact objects—black holes, neutron stars, brown dwarfs—add microlensing noise that, in aggregate, conveys counts of nonluminous matter, though single remnants rarely dominate. Observing a younger, smaller universe at greater distances that still spans our sky reflects both curvature and expansion history. In short, warped light is measured information.

Scott Douglas Jacobsen: Describe to me in detail how gravitational lensing can be seen—on a cosmological scale—as an informational process, particularly in the ways photons are warped so distinctly. How does that fit into the larger picture?

Rick Rosner: I have seen postulates that much of the dark matter may actually be collapsed matter—stars that have burned out and collapsed into neutron stars or even denser remnants. You also have supermassive black holes at the centers of galaxies. Moreover, there are brown dwarfs, although I am not sure they are compact enough to contribute significantly to gravitational lensing.

Under that view, we should see more lensing than the standard Big Bang model predicts. On the other hand, an individual neutron star does not create a massive lensing footprint. If it is in another galaxy, it is not detectable from here—it is simply too small. I have not read enough about what can be seen at those distances.

However, the entire universe itself is lensed by the overall curvature of space-time. We are used to imagining “flat” three-dimensional space. When you look one mile away, everything one mile away forms a sphere with you at the center and a radius of one mile. At two miles, it is a larger sphere, and the surface area you see increases with the square of the distance.

Now, scale that to billions of light-years. At one billion or two billion light-years away, what you are looking at should appear enlarged. In a Big Bang universe, when you observe something two billion light-years away, you’re seeing it as it was two billion years earlier—two billion fewer years of expansion.

So you’re not looking at a sphere that increases at the standard rate. You’re looking at a sphere that’s slightly shrunk compared to the near space around you. But it still occupies the full 360 degrees of your vision. So it appears enlarged.

The objects you’re seeing are part of a smaller version of the universe, because that region hasn’t expanded as much as our local region. But it still surrounds you. The farther back you look, the more this effect increases, until you’re looking at a tiny, early universe that still occupies your whole field of view in every direction.

So this shrunken universe should still appear large. Imagine the big sphere in Las Vegas.

Picture yourself standing inside it, at the center, looking at images projected at different distances. First, they show youthings ten feet away—a living room or bedroom, with walls all around. Then they show you a field, where everything is a hundred feet away, with trees in the distance. Then a thousand feet away—buildings.

A building a hundred feet tall, at that distance, might occupy the exact angle of vision as a chest of drawers did in the first room. Then, when you look all the way back to about a million years after the Big Bang, you’d see a soupy, nebulous universe. But it would still fill your entire 360-degree field of view.

So, for it to occupy your whole field, things would appear enlarged. I don’t know—I haven’t thought through every detail. It might be an effect of lensing, but I’d need to think more about whether that’s accurate or just me talking out of turn.

Still, I expect more small-scale lenses. IC predicts vast numbers of neutron stars and “blackish holes” orbiting farther from galactic centers than the luminous stars. But can we see them? I don’t know.

I don’t know how close a star-sized black hole would need to be for us to detect lensing around it. I assume that the lensing astronomers see across the universe comes from galaxy-scale objects, not individual star remnants. But I’m not sure.

So, the overall idea—looking back into deep time—is that lensing, through gravitation, contributes to the curvature of the universe. And since nothing has a trajectory outside the universe, you could argue that light that has travelled for 14 billion years has been bent along the way by that curvature.

Rick Rosner is an accomplished television writer with credits on shows like Jimmy Kimmel Live!, Crank Yankers, and The Man Show. Over his career, he has earned multiple Writers Guild Award nominations—winning one—and an Emmy nomination. Rosner holds a broad academic background, graduating with the equivalent of eight majors. Based in Los Angeles, he continues to write and develop ideas while spending time with his wife, daughter, and two dogs.

Scott Douglas Jacobsen is the publisher of In-Sight Publishing (ISBN: 978-1-0692343) and Editor-in-Chief of In-Sight: Interviews (ISSN: 2369-6885). He writes for The Good Men Project, International Policy Digest (ISSN: 2332–9416), The Humanist (Print: ISSN 0018-7399; Online: ISSN 2163-3576), Basic Income Earth Network (UK Registered Charity 1177066), A Further Inquiry, and other media. He is a member in good standing of numerous media organizations.