[NOTE: This post is the fourth in a four-part series. Previous posts are: 1) Einstein's Crazy Idea, 2) Visual "Proof" of Gravitational Lensing, and 3) Gravitational Lensing in Action. The same posts, slightly modified, also appear on the Frontier Fields blog.]
For the final part of this series of blog posts, let's bring things back to Earth. The demonstration of a physical process will always seem a bit arcane when using unfamiliar objects as the example. Most folks don't have a working relationship with galaxies, let alone the strange varieties one gets in the distant universe. Instead of taking the viewer into the universe, it can be more intuitive to bring the cosmic phenomenon closer to home.
Suppose that, say, a black hole decided to take a short vacation. Perhaps it got tired of the enormous responsibilities of being such a tremendous distortion of space-time. It needed a weekend off to cool its jets (absurdly geeky pun intended - sorry). Around Baltimore, where I work, the black hole might go down to the Inner Harbor, enjoy the sights and activities, indulge in a crab feast, and leave completely rejuvenated. Now, while I haven't yet tried to visualize a black hole eating crabs, and the concomitant singularity eruptions due to Old Bay seasoning, we can approximate what tourists might have seen during the visit.
This scientific visualization presents a black hole of about the mass of Saturn passing through Baltimore's Inner Harbor. The initial view from Federal Hill shows the usual boats, shops, and office buildings along the water. As the black hole passes across the harbor, the view of the background buildings is distorted due to gravitational lensing. Light is redirected such that, in the region around the singularity, imagery is flipped top/bottom and left/right, with multiple views of the same object. This transformation of a familiar skyline scene can help one imagine the transformation of unfamiliar galaxies in the distant universe.
Note: As in the previous simulated lensing image, a simplified, planar approach of gravitational lensing is used for this visualization. However, in this case, the foreground objects were not removed. The visual distortion of ship's masts on the near side of the harbor would not occur. We humbly ask your indulgences.
While in graduate school, I had to solve problems using the complex collection of general relativity equations - but only a few times. And all of those instances were for problems with enough symmetry that things could be considerably simplified. I gained an appreciation for the essential character, and some of the beauty, of the mathematics behind it. However, as stated in the first post in this series, the whole concept still has a feeling of weirdness.
Perhaps that notion would have dissipated had I specialized in relativity. Instead, as I developed into a scientific visualization specialist, I've gotten to revisit things from a public presentation, rather than research, perspective. The visual allure of gravitational lensing can attract an audience for topics typically mired in equations. It shows how a simple magnifying glass can have a truly cosmic analogue. It helps explore the perspective changing shift in gravity from Newton's force to Einstein's geometric re-interpretation. It opens the pathway to deeper philosophical thoughts about the fabric of space-time and the very underpinnings of our universe. Now, that's quite the opportunity for an outreach astrophysicist like me.
In this case, weird is cool.