Albert Einstein's calculations regarding the speed-of-light axiom demonstrated one rule of the universe that cannot be violated: time is not absolute. There's no such thing as a Greenwich Mean Time in space; television sci-fi producer Gene Roddenberry's fictional dream of a universal stardate calendar is an impossibility, too (well, you'd have to find an energy field that exists-instantly-throughout space to get around Einstein's no absolute time rule).
Regarding Einstein's calculations, two observers in space cannot synchronize their on-board clocks to a standard time. The two observers, separated in space, are also separated in time; they cannot see both clocks showing synchronized time. Thus, the two clocks will never be in agreement-well, unless both observers and their clocks occupy the same space in time.
The accuracy of atomic clocks is frequently touted to be accurate to within 0.000000001 or 10-9 of a second (a billionth) or more. Sounds wonderful, except for the fact that the accuracy works only when an observer is standing alongside the clock. Move away from the atomic clock, and light will affect the observed and the instrument's accuracy will begin to drift.
One example frequently cited regarding atomic clocks and absolute time is to place a clock and an observer at opposite ends-at the goal posts on a football field.
The billionth of a second accuracy of the atomic clock in the football stadium will appear less accurate when measured by the observer at the opposite goal post. The drift may be a microsecond or 1,000 billionths of a second in time. Ok, sounds like splitting hairs, you might be muttering-but over vast distances the accuracy drift becomes, well, astronomical.
If you leave the atomic clock at the football goal post and then rocket the observer to the Moon-250,000 miles away-the clock's accuracy drift will show 1.33 seconds. Still hairsplitting, you say?
Now imagine moving the observer out through the solar system, past Pluto, and on into the mysterious Kuiper Belt region of comets and ice asteroids-and beyond. Atomic clocks become the final arbiters of Einstein's calculations about the lack of absolute time in our universe.
Can anything travel faster-than-light (FTL) to get around the limits of keeping absolute time in space? Maybe but only on a quantum level.
Some experiments since the 1980s have demonstrated that FTL may be possible, but only across amazingly short, quantum distances. To move large amounts of data or humans in a spacecraft FTL will remain in the realm of science fiction for the foreseeable future.
What's in the Sky: After 9 p.m., in the WNW, the crescent Moon offers some beauty and challenges throughout April. Venus hovers below the Pleiades.
Louis Varricchio, M.Sc., was a science writer at the NASA Ames Research Center in California. He is a member of the NASA JPL Solar System Ambassador program in Vermont.