Split Second (21 page)

37

All three residents of room
twenty-seven of the Best Border Inn stared at the screen as if they hadn’t
heard correctly.

“What?” whispered Jenna and Blake at
the same time.

“A
duplication
machine?” repeated Blake stupidly.

“Yes,” said Knight. “You heard me. A
duplication machine. You’ll understand better if we forget about microseconds
for now. Just imagine for a moment that you could send your cell phone back in
time a
week,
to your earlier self.
Wouldn’t the
you
from a week earlier
now have
two
cell phones?”

There was a pause in the
conversation as all three inhabitants considered this scenario.

“Well, sure,” said Jenna. “But
that’s a week. If I could only send my phone back a millionth of a second, I’d
have two cell phones trying to inhabit the same space. Wouldn’t that lead to an
explosion? Like a matter-antimatter explosion, I guess, only bigger?”

“Not at all,” said Knight smugly. “You’ve
been misled by the science fiction you’ve been fed all of your life. Science
fiction gets half of it right, but not all. When you travel through time, you
travel through time only.
Not
space.”

“I have no idea what that means,”
said Blake.

“Say you’re in California today. You
board a plane and arrive in Australia tomorrow. Once you’re down under, say you
activate a time machine and go back a day. Where are you?”

He didn’t wait for an answer. “Science
fiction would have you believe you’d be in Australia a day earlier. Right? You
wouldn’t end up in California, just because you happened to be there the day
earlier. You don’t retrace your actual steps. You would move through time, but
not space. Wherever you activate the time machine is where you end up, just at
an earlier time.”

“And you’re saying this isn’t
correct?” asked Jenna.

“No. I’m saying this is correct.
You maintain your precise position in space. The only thing that changes is
your position in time. But it’s not that easy. And this is where science
fiction tends to get it wrong. Because Australia,
itself
, moves. If it didn’t, you
would
end up there. But the Earth doesn’t stand still. You’d be
pinned in space. But a day earlier, Australia wasn’t anywhere
near
your pinned position. You activate
your time machine and go back a day. You arrive without changing your spatial
position in the universe. The only trouble is that yesterday, the Earth was
millions of miles distant from where it is today. Wouldn’t you find yourself in
outer space?”

He
was right
, thought Blake, his eyes wide. And from the expressions on the
faces of his companions, this was blowing their minds as well. When Knight got
no response to his question, he continued.

“The Earth rotates at roughly a thousand miles per hour. It revolves
around the sun at sixty-seven thousand miles per hour. Our solar system whips around
the center of our galaxy at four hundred and ninety thousand miles per hour.
The galaxies in our neighborhood are also racing toward something called the
Great Attractor, which has a mass one hundred quadrillion times greater than our
sun, and is a hundred and fifty million light years from us.”

Knight paused. “So how do all these motions add up? In 1989
we launched the Cosmic Background Explorer satellite, which measures something
called the cosmic background radiation. Because this radiation pervades the
entire universe, but not uniformly, scientists were able to get an exact
measure of the Earth’s speed and direction. Turns out we’re moving with respect
to the cosmic background radiation at two hundred and forty-two miles per
second. Per
second
,” he repeated.

Blake glanced at Dan Walsh, who nodded, confirming this
figure.

“So I’ll confess,” continued Knight, “my time machine can
only hit the first electron orbital, so to speak, the first landing platform
Nathan spoke about, forty-five microseconds in the past. But in that amount of
time the Earth has moved. I’ll spare you the math and just tell you:
approximately fifty-eight feet. So I can put my phone in my time machine and
press
send
. And while it does travel
back through time to a split second before, it stays pinned in space. But a
split second earlier, the Earth was fifty-eight feet away. So in this earlier
time, there are now two identical cell phones, separated by this distance.”

Walsh left his seat and seized a pad of paper on the desk. He
hastily scrawled on it and held it up for Blake to read.
Wouldn’t it materialize in mid-air?

“Wouldn’t it materialize in mid-air?” asked Blake.

“Good question,” said Knight. “By rights it should.
We’re not entirely clear on exactly how this works. Our best hypothesis is that
while it doesn’t fully move in space, only time, gravity plays a role as well,
that we haven’t fully characterized, such that it ends up fifty-eight feet
away, but the same distance off the ground as when it started. We also
shouldn’t be able to achieve any directionality. The Earth moves through the
universe the way it moves, and we should have no control. But we do. By
adjusting the polarity of the time travel field and the directionality of the
field itself—which we can do by positioning the device in a certain orientation
combined with a certain field dynamic—we can more or less point the effect.”

Walsh’s face wrinkled up in absolute confusion, and he
looked at Blake as though Knight had just told them that two plus two was five.
If the UCLA physicist was confused, what hope did Blake have?

“This makes no sense at all,” said Blake.

Knight actually smiled. “I don’t fully understand it
either. We’ve figured this part out empirically. Guess-and-check, over many
months. Time travel doesn’t seem to cut across the space-time axis, per se,
which would be through the fourth dimension, but rather through a fifth
dimension. Movement through this dimension translates in unexpected ways
through our own, so we get results that aren’t intuitive, to say the least, and
don’t even seem possible.”

“I’ll take your word for it,” said Blake, giving up.

“But you’ve actually done this?” said Jenna. “You’ve actually
sent matter back through time?”

“Many, many times,” replied Knight. “It’s become routine.”

Blake looked at another scrawled question from Walsh and
repeated it, even though he didn’t understand what Walsh was getting at. “And
what if you decide after you’ve sent something back,
not
to send it back?”

Knight grinned in delight. “Outstanding, Mr. Blake. You have
an excellent scientific mind. No wonder you’re a good detective. For Jenna’s
benefit, who probably isn’t on the same page as you are, let’s pretend again we
can send something back an hour, just because thinking in microseconds messes
with one’s mind, and makes everything harder to understand.

“So Aaron’s question is this: Say I decide that in an hour
from now, I’m going to send my phone back in time an hour. The hour passes and
I press the button, as planned. Because I did this, an hour earlier, a cell
phone magically appears in front of my earlier self. To make this as easy as
possible to picture, imagine the phone appears right next to the earlier
version of itself.
Cool
, the me in
the past thinks when the phone appears. I must have sent it back from the
future like I was planning. Now I have
two
phones.”

Knight arched an eyebrow. “But now, what if the me in the
past changes his mind? What if he now decides
not
to send it back, after all?
Now
what happens? Does the second phone disappear the moment he makes this
decision, like a photo of Marty McFly and his siblings? Or does it stick
around? And what if the hour passes and I really
don’t
send my phone back? Do I still have two phones? And if so,
how is this possible? After all, in this version of reality, I never sent it
back, so how is it still there?”

“Which would be the single timeline theory of time travel,”
said Jenna. “The one in which this type of paradox is possible. However, if a
version of the chronology protection conjecture were operating, the phone would
never appear in the past in the first place, as long as the universe
knew
you were going to change your mind
and not send it. Or, if it did appear, you
would
send it back after an hour passed. Nothing could prevent you from doing this,
including changing your mind.”

Knight shook his head in wonder. “I have to say your grasp of
time travel theory is truly impressive.”

“So what’s the answer?” said Jenna, ignoring him. “What
happens?”

“What happens is that you
can
change your mind,” said Knight. “And the second phone remains anyway, even if
you never send it back.”

“Which proves that timelines branch,” said Jenna.

“Yes and no,” replied Knight. “I see how you would think this
is the only alternative left. That this is the answer to more than a century of
time travel speculation. The instant you change the past, time branches into
two separate and distinct realities. The you on the original timeline always
sends the phone back. The you on the new timeline has two phones, forever, and
can decide to send a phone back, or not, without affecting this.”

“But you’re saying this isn’t really how it works either?”
said Jenna.

“That’s right. Turns out to be a combination of the two
theories. I won’t describe the experiments that led us to this conclusion. Just
suffice it to say that when you change the past, you get a new timeline. But
the old timeline no longer exists. No branching occurs. You reset the universe
from the point of the change onward.”

“You
are
planning
to walk through an example of this, right?” said Blake.

“Yes. So you press the button and send your phone back an
hour. Now, in the past, you have two phones. But whatever had happened before
in the upcoming hour is wiped out. The universe is reset to where it was an
hour earlier and then proceeds forward again. The original timeline is erased.
And there is no branching.”

“Which gets us back to your original question,” said Jenna.
“If this original timeline is erased, and you decide
not
to send the phone back this time, how do you have two phones?”

“Yep,” said Knight. “It’s a head-scratcher. Nonetheless, the
second phone remains, and the universe just moves on from there, as if you’ve
always had two phones, not caring about paradox. The universe would rather live
with paradox than infinite timelines, I guess. Which may explain why there is a
half-second limit. So it doesn’t have to reset too far back, and have to wipe
out too much forward history. But the bottom line is this, once a timeline
affects its own past, even though it erases itself in the process, the effect
it had still remains.”

“So if you go back in time and kill your mother,” said Jenna,
“history is rewritten from the moment of her death forward. Your own history as
you knew it no longer exists, and never existed. You are never born. But the
universe doesn’t care that you shouldn’t exist, and couldn’t have killed her. It
just accepts the reality of a universe in which you exist anyway and she is
dead. It ignores the paradox and continues forward from that point.”

“Outstanding,” said Knight, beaming. “There are world-class
physicists who couldn’t catch on this quickly.”

Jenna just sneered at the television screen as he continued.
“I hate to keep treating the universe like it is a living being, but the way I
think of it is that the universe wants to deal with changes in time in the most
efficient way possible. And it wants to maintain a single timeline, as infinite
timelines aren’t very efficient.”

“And no doubt give the universe as much of a headache as they
give me,” said Blake wryly.

Knight smiled. “Exactly. Another way to think of it, which removes
some time travel confusion from the analogy, is this: Say you’re writing a novel,
and you can only publish one version of it. You finish the novel and realize
that you gave two characters names that are too similar: John Doe and John
Dode. Too confusing. So you decide to go back in your novel and change John Doe’s
name to Steve Smith. So you tell your word processor to find every instance of
John Doe in the novel and change this to Steve Smith. You hit the button and
instantly, wherever you had John Doe, you now have Steve Smith.”

He paused to give his listeners a chance to imagine this
scenario.

“Now you want to save the file for publication,” he continued.
“First, to be efficient, the computer doesn’t bother resaving the entire novel,
since the vast majority is the same. It only saves the new name wherever it
appears. Second, once this new version is saved and published, it’s as though the
original version never existed. Steve Smith is just Steve Smith. There is no
record of him ever being John Doe. A reader would have no idea what had led to
the name Steve Smith having been chosen, could never tell that this was due to
a different version of the story that no longer existed.”

Jenna nodded thoughtfully. “So in this analogy,” she said,
“the writer is God, and the novel is the universe.”

“Yes. Or perhaps the universe is both the writer and the
novel. Either way. I admit the analogy is tortured and incomplete, but hopefully
also a little helpful.”