Just a few years ago, it was speculated that a real-life invisibility cloak could only be applied to a very narrow set of wavelengths for a few specific configurations. It was thought inconceivable that large, macroscopic objects could be cloaked to a huge variety of wavelengths.

Today, an advance in metalenses, by guiding light of various wavelengths to the proper location to get the distortion-free outcome we so keenly desire, might be just the discovery we need to herald the arrival of a true cloaking device.

As Star Trek first envisioned it, it took centuries for cloaking technology to be perfected. Here on Earth, it may require a mere decade or two. If this latest metalens advance can be rapidly applied to metamaterial cloaks, an optical, 3D cloaking device may finally become a reality in humanity’s very near future.

https://bigthink.com/starts-with-a-bang/invisibility-cloak-183582/

Yes, it does make you wonder how far they have truly progressed. Farther than this article admits, I’d reckon.

“By combining two nanofins into one element, we can tune the speed of light in the nanostructured material, to ensure that all wavelengths in the visible are focused in the same spot, using a single metalens. This dramatically reduces thickness and design complexity compared to composite standard achromatic lenses.”

While the earliest marketable applications of these metalenses should soon include cameras, VR devices, microscopes, and other medicinal and augmentative technologies, a longer-term fusion of the metalens/nanofin concept with metamaterials could be exactly the holy grail of technological combinations that a real-life cloaking device would require.

https://bigthink.com/starts-with-a-bang/invisibility-cloak-183582/

I suspect the ships bend both light and matter around them. This would explain why they seamlessly move through the air and water. But they're never seen passing through the ground. Water and air can compress without too much fuss, but rock or packed soil would do a lot of crazy things trying to compress them at high speeds.