Warped in space

After I finish writing each gem-like entry in this blog, I look around for an appropriate photograph or drawing to illustrate it. This time, however, I fell in love with the drawing (by NASA) first. The text that now follows is merely a pretext -- as it were -- for publishing the drawing.

The drawing shows Earth surrounded by a schematic of the space-time continuum. The little dragon fly-like doo-hicky swimming in space-time around the Earth is Gravity Probe B, an orbiting satellite launched jointly by Stanford and NASA in 2004. The purpose of the probe was to determine whether Einstein's theory of general relativity could be verified empirically. The final empirical data were received early last month.

Einstein's theory indicates, first, that any body of mass warps the time-space continuum surrounding it (thus creating what we view as its gravititational field), and, second, that as such a body rotates, it drags time-space around with it in a circle.

Imagine the Earth as if it were immersed in honey. As the planet rotated its axis and orbited the Sun, the honey around it would warp and swirl, and it's the same with space and time," said Francis Everitt, a Stanford physicist and principal investigator for Gravity Probe B.
--Stanford Report (5-4-11)

The gravity probe satellite contained four highly precise gyroscopes. Gyroscopes have the quality of maintaining an invariable orientation, pointing in the same fixed direction in space once operational. These were originally aimed at a single distant star. As they circled the Earth, the gyroscopes departed from their original orientation very slightly -- but measurably -- in almost precisely the amount predicted by Einstein's theory.

The differences in the actual data accumulated by Gravity Probe B from those expected from Newtonian physics -- differences attributable to relativistic "swirling" effects -- may seem miniscule, but it's been important that these differences be understood and recognized in developing precise applications for the GPS system. Measurements from the satellite have provided support not only for Einstein's theory, moreover, but for the Big Bang theory as well.

The schematic illustration showing directions in time-space being warped by the Earth's mass and rotation is figurative. The warping actually occurs in four dimensions -- three dimensions in space plus time. But it makes a pretty picture. And, from now on -- whenever I swirl a spoon around in a jar of honey -- I'll think of Dr. Everitt's evocative metaphor.