One Apollo 11 Experiment Is Still Going 50 Years Later

The Lunar Laser Ranging Experiment lets NASA precisely measure the distance between Earth and the moon

5 min read
Image of the laser deployed from the facility and pointing toward the sky.
Goddard’s Laser Ranging Facility in Greenbelt, Md., directing a laser (green beam) toward the Lunar Reconnaissance Orbiter spacecraft in orbit around the moon (white disk). The moon has been deliberately over-exposed to show the laser.
Photo: Tom Zagwodzki/Goddard Space Flight Center

THE INSTITUTEIf nothing else will convince someone that humans once walked on the moon, NASA’s lunar ranging experiment (LURE) should. It’s because of that experiment that scientists know the precise distance between the Earth and the moon with centimeter accuracy.

The LURE’s first demonstration began on 1 August 1969, when a pulse of trillions of photons was shot out of a telescope at Lick Observatory on Mount Hamilton, outside of San Jose, Calif. The laser pulse traveled to the moon and returned after reflecting off a 1-meter-wide array of mirrors—retroreflectors—that Apollo 11 astronauts had placed on the lunar surface 12 days earlier.

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The Transistor of 2047: Expert Predictions

What will the device be like on its 100th anniversary?

4 min read
Six men and a woman smiling.

The luminaries who dared predict the future of the transistor for IEEE Spectrum include: [clockwise from left] Gabriel Loh, Sri Samavedam, Sayeef Salahuddin, Richard Schultz, Suman Datta, Tsu-Jae King Liu, and H.-S. Philip Wong.

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The 100th anniversary of the invention of the transistor will happen in 2047. What will transistors be like then? Will they even be the critical computing element they are today? IEEE Spectrum asked experts from around the world for their predictions.

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