What are the social consequences when science allows us to see things that had previously been invisible?

Scientists have revealed microscopic life, nanoscale molecules and galaxies billions of light years away. These images have revolutionized the disciplines in which they were made, but they also transformed the public's imagination, letting them see new things to think and dream about.

The intertwined social, scientific and artistic impacts of 19th century photography is the subject of a new exhibit, Brought to Light Photography and the Invisible, 1840-1900, at San Francisco's Museum of Modern Art*.*

In this five-part series, we walk through the exhibit with its curator, Corey Keller. Keller spent five years scouring dusty archives, primarily in Europe, to dig up dozens of haunting photographs from the period. Many of the images have never been seen, except by their creators. Up first is the X-ray, which allowed us to see through our skin and muscle to the bones that lay within.

In 1895, Wilhelm Conrad Roentgen discovered the X-ray, a form of electromagnetic radiation with a very short wavelength.

Waves that are shorter can penetrate denser materials. X-rays are perfectly tuned to barrel through soft tissues like muscle and fat, but get slowed down by denser materials like bone. That allowed early scientific photographers — and your dentist — to employ these rays to see skeletons without cutting into flesh.

To the common people at the time, this was (and probably should remain) astonishing. Within three months, Keller said, DIY X-ray kits were available on the market. The rich and famous had their hands X-rayed, their skeletons draped in rings. Photographers, who had access to most of the tools needed to make the images, began to train this new form of light on just about anything that might be beautiful.

"They were X-raying everything just to see what it looked like," Keller said.

In this series of images, we see the strange hodgepodge of subjects that early X-rayers tackled. At the top of the post is a chameleon, and further down the page, the boot of a shoemaker who built his own x-ray machine for fun. Below, you'll find a river dolphin fetus, two fish and the hand of the wife of Nicholas II, the last czar of Russia.

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