Chapter 1: Section 7: Page 62: Line 100 (1082)

 "A walking interferometer, as you'd say," suggested Ed Addle.

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"interferometer"
Merriam-Webster's definition: "an apparatus that utilizes the interference of waves (as of light) for precise determinations (as of distance or wavelength)". The interferometer was the device used in the Michelson-Morley experiment to determine if the movement of the Earth caused a change in the speed of light as it moved through the theoretical Æther. Ed's suggesting that Blinky now has the same sort of ability. He can see distortions in space-time because each eye sees the same light from the same source but from two separate perspectives.

A Michelson interferometer invented by Albert Abraham Michelson in 1887.

Here's a quote from the Michelson interferometer Wikipedia page that sort of sums up why Pynchon's concentrating on this event at the beginning of the book, much like he began with the Columbus Exposition in Chicago because it signaled the end of the Frontier and the advancement of electricity:

"The null result of that experiment essentially disproved the existence of such an Æther, leading eventually to the special theory of relativity and the revolution in physics at the beginning of the twentieth century."

Thomas Pynchon has carefully chosen this time and place as the beginning of not just a new century but an entirely new world brought on by a new understanding and perspective, a changed observation, of that world.