A camera was not always needed to "capture" a thought. In the late Victorian era, a few experimenters pressed photographic plates to foreheads and claimed the developed marks were images of the mind.

In this episode of Math! Science! History!, we trace the strange rise of "thought photography," why it sounded plausible in an age of new invisible forces, and what these experiments reveal about technology, interpretation, and scientific method.

What Develops in the Dark

What you'll learn in this episode:

1. Who tried to photograph thoughts - How Hippolyte Baraduc and Louis Darget used photographic plates as instruments, then read the resulting traces as evidence of emotion, soul, or mental imagery.

2. Why the idea felt scientific at the time - How late-19th-century discoveries made invisible phenomena feel newly recordable, especially after X-rays reshaped what "photography" could mean.

3. What can go wrong (and right!) when images look like proof - Why noisy signals, chemical artifacts, and human pattern-finding can produce results that feel conclusive long before they are.

Sources

"Psychicones: Visual Traces of the Soul in Late Nineteenth-Century Fluidic Photography" (Nicolas Pethes, Medical History, 2016)

"Imaging Inscape: The Human Soul (1913)" (The Public Domain Review on Baraduc's methods and plates)

"Discovery of the X-ray: A New Kind of Invisible Light" (National Museum of Health and Medicine)

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