Here is an example of what you can expect if tomorrow's space-flight technology-
60 employing the energy of thermonuclear
fusion, matter-antimatter annihilation, or
whatever-enables you to move at ultra-high
speeds. Imagine you're an astronaut with a
twin who stays home. If you travel back and
65 forth to the nearest star at about half the speed
of light, you'll be gone for eighteen Earth
years. When you return, your twin will be
eighteen years older, but you'll have aged
only sixteen years. Your body will be two
70 years younger than your twin's because time
aboard the flying spaceship will have moved
slower than time on Earth. You will have aged
normally, but you will have been in a slower
time zone. If your spaceship moves at about
75 90 percent of light-speed, you'll age only 50
percent as much as your twin. If you whiz
along at 99.86 percent of light-speed, you'll
age only 5 percent as much. These examples
of time-stretching, of course, cannot be tested
80 with any existing spacecraft. Yet, they are
based on mathematical projections of relativ-
ity science, as confirmed by the atomic-clock
experiments.
37. In its context in line 81, the word projections
means:
A. visual images on a television screen
B. predicted outcomes.
C. objects that stick out of the ground.
D. proofs.