From
Summer Sanctuary by Laurie Gray
Chapter
8, pp. 48-52
©2010
by Socratic Parenting LLC. All rights reserved.
"What
are you studying?" Dinah asked as she sat down at the table
across
from me.
"Time
dilation and the speed of light," I said propping my head
up in
my hands.
"What
for?" asked Dinah, examining the book closest to her.
"I
have this theory that I'm hoping to prove, but it's turning
out to be
way more complicated than I thought." I flipped the book
in front of me shut and sighed. "Did you know that a light
year is a measure of distance, not time?"
Dinah
shrugged. "So what's your theory?"
"I
started reading Einstein's theory of relativity and how the
only constant
speed we know of is the speed of light." Dinah raised her
eyebrows and opened her eyes wide, trying to take it all
in. "It's
like this," I explained. "Suppose I throw a ball to you at
50 miles per hour. The ball's traveling at 50 miles per
hour,
right?"
"Okay,"
agreed Dinah.
"Now
suppose we're riding on a train that’s traveling 50 miles
per hour.
I'm holding the ball, so you and me and the ball are all
traveling at
50 miles per hour on the train, right?" I checked to make
sure she was still with me.
"Right,"
Dinah said.
"Okay,
now suppose I throw the ball to you at 50 miles per hour.
You
and I are still traveling at 50 miles per hour, but the
ball is traveling
at 100 miles per hour, right?" I was nodding, but Dinah
wasn't
convinced.
"Which
way are you facing?" Dinah asked.
"What
do you mean which way am I facing?" I thought she was just
messing
with me.
"I
mean are you throwing the ball in the same direction the
train's moving
or do you have your back to the front of the train,
throwing it back
to me?" Dinah asked. She was serious, and suddenly
it dawned on me what she meant.
"Let's
say I'm facing the front of the train and throwing the ball
in the same
direction that the train's moving," I said.
"Okay,
then I can see that the ball would be traveling 100 miles
per hour,"
Dinah conceded.
"So
how fast something is traveling is relative to how fast the
things around
it are traveling. And that's true for everything except
light.
Light always travels at 300,000 kilometers per second. If
the
train was traveling at 100,000 kilometers per second and
had a light
on the front of it, the light would still only travel at
300,000 kilometers
per second. If you were on another train traveling toward
the
light at 100,000 kilometers per second and the train with
the light
wasn't moving, the light would still travel toward you at
300,000 kilometers
per second."
"Well,
that seems a little weird," Dinah said. "So what's time
dilation?"
"Time
dilation is how time slows down the faster you move. So if
you
were in a rocket zooming by earth, you wouldn't age as fast
as I would
here on earth," I explained.
"And
that's what you're trying to prove?" Dinah asked, looking
at me
like my hair suddenly poofed up like Einstein’s.
"No,
Einstein already proved all that. I'm trying to prove that
the
Bible told us this way before Einstein figured it out," I
said.
My palms were getting sweaty. I suddenly wondered if
quoting Bible
verses to Dinah was such a great idea.
"You
mean like Einstein's theory of relativity is written in the
Bible?"
Dinah asked.
"Not
all spelled out exactly, but when I was reading all the
stuff Einstein
proved, I kept thinking of two things I'd read in the Bible-
-that God
is light, and that 1,000 years on earth is like a single
day to God.
So I want to do the math to see if the time dilation
traveling at the
speed of light would be like one day equals 1,000 years."
"So
is that like algebra or geometry or what?" Dinah wanted to
know.
"That's what I'm trying
to figure out. I thought that I just needed to look up how
long
a light year is and then compare the number of seconds in a
thousand
light years to the number of seconds in a single day on
earth.
Only a light year is how far light travels in a year.
Distance,
not time. Now I'm stuck."