How do you explain the concept of a fourth dimension to humans who are only able to see in 3-D? Physical space can be measured in height, width, and depth. What is there beyond or in addition to those three dimensions? How can we understand the existence of a dimension we cannot picture?

Thankfully, we had Carl Sagan, one of the greatest science communicators of his time, to help us visualize a fourth dimension. Perhaps best known for his research into extraterrestrial life, Sagan was among the first to demonstrate that life could have existed on Mars. Sagan possessed a unique gift for demystifying complex scientific concepts, making them accessible and thrilling for the general public. He could be described as a scientific Mister Rogers: friendly, a wonderful storyteller, and able to distill difficult lessons into their simplest form.

In 1980, on Episode 10 of the groundbreaking PBS show “Cosmos,” Sagan embarked on a mission to explain the seemingly impossible fourth dimension. It’s a hypnotic, entertaining, and incredibly enlightening watch:

Many of us have commonly heard of time being considered the fourth dimension. That’s not so hard to understand. In order to locate an object in the universe, you’d need to know three dimensions of........

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