How to Make Light Late ⚡ экспресс
The Shapiro delay is a slowdown of light passing near massive bodies, caused by the curvature of spacetime. All existing measurements of this effect have been astrophysical and limited to an accuracy of 10⁻⁵. Now, a laboratory method has been proposed: a Sagnac fiber interferometer capable of sensing the delay with a thousand times higher precision—down to 10⁻⁹. It's like turning a cosmic experiment into a tabletop device and testing general relativity under terrestrial conditions for the first time.
Mass curves spacetime like a heavy stone pressing into an asphalt road. Light passing by skirts around this dent, its path lengthens, and it arrives late. Astronomers have observed this Shapiro effect many times near the Sun and planets.
A new plan proposes to recreate this delay on a lab bench. Two beams are simultaneously launched into a closed fiber-optic loop: one clockwise, the other counterclockwise. A massive object placed nearby curves space within the loop, and one of the beams arrives with a delay of billionths of a second. The technology is well-honed: similar devices already detect vibrations of space.
Instead of satellites and telescopes, Einstein's theory of gravity could be tested in an ordinary room. The precision is enough to spot deviations hinting at new physics. Remarkably, the light delay near bodies was originally proposed by Einstein himself in 1916—long before the first spaceflights.
🎯 The strongest Shapiro effect from our star: a signal to Venus and back is delayed by about 200 microseconds due to the Sun's gravity.