字幕表 動画を再生する 英語字幕をプリント [ music ] A Space Time Vortex Around Earth - presented by Science@NASA Would you believe Earth sits in the middle of a space-time vortex? Einstein predicted this almost a hundred years ago, and it turns out to be true. On May 4th, 2011, researchers announced that NASA's Gravity Probe B spacecraft has detected the vortex and its shape precisely matches the predictions of Einstein's theory of gravity. "The space-time around Earth appears to be distorted just as general relativity predicts," says Stanford University physicist Francis Everitt, principal investigator of the Gravity Probe B mission. Time and space, according to Einstein's theories of relativity, are woven together, forming a four-dimensional fabric called "space-time." The mass of Earth dimples this fabric, much like a person sitting in the middle of a trampoline. If Earth were stationary, that would be the end of the story. But our planet spins, and the spin should pull the dimple around into a 4-dimensional swirl. This is what GP-B went to space in 2004 to check. The idea behind the experiment is simple: Imagine trying to spin a toy top on the dimpled surface of that trampoline. It's going to wobble, right? Something similar happens when you try to spin a gyroscope in curved space-time. Its spin axis will drift or "precess." Gravity Probe B carried some super-spherical gyros into Earth orbit to see what they would do. In practice, this simple idea is extremely difficult. According to calculations, the twisted space-time around Earth should cause the axes of the gyros to drift by a tiny amount - really tiny. It's like measuring the thickness of a sheet of paper held edge-on 100 miles away. Even the slightest disturbance could ruin the experiment. "We had to invent whole new technologies to make this possible," says Everitt. The Gravity Probe B team developed a "drag free" satellite that could brush against Earth's atmosphere without disturbing the gyros. They figured out how to keep Earth's magnetic field from penetrating the spacecraft. And they created a device to measure the spin of a gyro - without touching the gyro. Pulling off the experiment was a big challenge. But after a year of data-taking and nearly five years of analysis, the Gravity Probe B scientists appear to have done it. The gyros precessed; the vortex is real; and we are in it. Einstein was right again. For more information about the space-time vortex and what it means to us on Earth, visit Science.nasa.gov
B1 中級 サイエンスキャスト時空の渦 (ScienceCasts: Space-Time Vortex) 343 23 薛惠綸 に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語