Spacetime-Travel
& Relativity (Part 2)
Kirk: Mister
Sulu, set the course for What-The-Heck star system, warp five.
Sulu: aye
aye, captain... The course is set. The What-The-Heck star system is five
hundred light-years away and we will get there in about one week.
Kirk: That's
not fast enough. Mister Scott, how much more power can you give?
Scott: Captain,
we have plenty of power to blow up the Enterprise if you like.
Kirk: Mister
Sulu, warp nine and up.
Spock: Captain,
according to my calculations, the ship may not be able to withstand the
warp nine speed. There is a probability of 0.0511010342 that the ship will
blow up.
Kirk: That's
enough, Spock. Go ahead, Mister Sulu.
(Excerpt from
a Star-Trek episode extracted from D.T.Vo's memory.)
.....................................
(Continued...)
My empty head
friend has always been a sore loser. This evening, however, he seems quite
different. Even after losing three consecutive arguments, he was smiling.
I think he has some tricks hidden somewhere in his hollow brain that I
don't know and he is going to dump it on me soon.
-Duc: Alright,
spit what's in your brain out now, my friend.
-Nobrain:
Do you believe in time travel, that is, going backward as well as forward
in time?
-Duc: No way,
Jose. And don't tell me that you believe in that kind of stuff. Those are
science fictions, man.
-Nobrain:
You know that good science fiction has to have its idea somewhat scientifically
acceptable. The warp space and time travel in science fictional movies
like Star-Trek may have some truth in them. What if I can prove time travel
can be made real? Would you believe then?
-Duc: What?
You mean that you believe the Star-Trek garbage stuff where it takes one
week for the Enterprise to travel thousands of light year distance... I
can understand if the Enterprise can travel very near the speed of light
then it may take them only one week to travel, while for the rest of the
universe, thousands of year has gone by. But in the show, the people on
earth or on the far-away planet also record only one week passing by for
them. Relativity does not allow that, man. How are you going to explain
that? If you can prove it, scientifically, then I will believe.
I think my
friend is bluffing. Maybe he has had one beer too many. I'll get him a
glass of water the next time he ask for a drink. My friend does not waste
much time. He seems happy to start the discussion.
-Nobrain:
You know that the faster you travel, the slower you will see the time passing
by and when you get to the light speed, the time will stand still for you.
So if you can move faster than light speed, what do you suppose will happen
then?
-Duc: No way
can any one or any thing move faster than the speed of light. Albert Einstein
said so. So the IF you said can never happen.
-Nobrain:
O.K., so nothing can ever go faster than light. But that does not mean
faster than light travel is impossible.
-Duc: What
the hell are you talking about? Relativity says that the time it takes
to go from place to place can not be less than the time it takes light
to pass between them.
-Nobrain:
Agree! But do you know that Albert Einstein's relativity theories have
a hole in it... I mean a loophole, where the conventional rules break down.
That loophole is given the name black hole, inside which anything impossible
is possible. A black hole is a hole in space-time which gives birth to
another kind of holes, the wormholes, which in turns can form shortcuts
connecting different regions of space together. So if you can find a short
cut like a wormhole to go from place to place then you may be able to travel
faster than light. And faster than light (FTL) travel means time travel,
that is, you can go back in time.
-Duc: Alright,
slow down. One thing at a time, and don't try to confuse me. If you are
really knowledgeable about this stuff, then answer these questions one
by one so I can understand them. 1/ Tell me what is warp speed and how
scientific it is about the time experienced by the people in Star-Trek
when it really contradicts the theories of relativity. 2/ What are wormholes?
Are they what you see in the yard in the morning after a heavy rain? 3/
How can a wormhole be used for FTL travel? 4/ And how FTL can be used for
time travel?
-Nobrain:
That's easy, my man. The answer to your first question about Star-Trek
is somewhat complicated so I'll leave it to the end. To answer the second
question, what are wormholes, I have to start with an other kind of holes,
the black holes. There are four kinds of black holes which are named for
after the ones who worked out the mathematical descriptions of them. They
are the Schwarzschild black hole which has no electrical charge and no
spin, the Reissner-Nordstrom black hole which has charge but no spin, the
Kerr black hole which has spin but no charge, and the Kerr-Newman black
hole which has both charge and spin. Each kind of black hole has a slightly
different internal structure and affects particles and light in different
fashions...
This guy said
all those things in one breath. I think he just memorized the whole thing,
word by word, from a text book and then recited the whole thing trying
to impress me. It's nothing. Any first grade kid can recite any thing from
any text book just like him.
-Nobrain:
... The Schwarzschild black hole is the simplest form of black hole. It
has one "event horizon" within it nothing, including light, can
escape. This type of black hole, no spin and no charge, is not likely to
exist. One particular property of this black hole is that it has a connection,
called the Einstein-Rosen bridge or wormhole, connects this universe with
another universe. The problem is that you can not use this kind of wormhole
to travel because whatever enters beyond the event horizon can travel only
in one direction heading toward the singularity and be annihilated. The
second kind of black holes is called the Reissner-Nordstrom black hole.
This kind of black hole has charge but no spin and is even less likely
to exist than the Schwarzschild black hole. A Schwarzschild black hole
has one event horizon. If a small electrical charge is added to the black
hole, the event horizon begins to shrink inward and a second event horizon
appears near the singularity. As the amount of charge in the black hole
increases, the outer event horizon continues to shrink, and the inner event
horizon begins to expand outward. With enough electrical charge, the two
event horizons will merge into one. Keep adding more charge now, the now-single
event horizon will shrink more and more and eventually will vanish into
the singularity. The result: a naked singularity.
Two other
kinds of black holes that are more likely to exist than the just mentioned
two are the Kerr and Kerr-Newman black holes which have spins. A spinning
black hole has two event horizons like the Reissner-Nordstrom black hole.
Also, the singularity of a spinning black hole would have the form of a
ring instead of a point. One characteristic of a spinning black hole, which
is different than the Schwarzschild black hole, is that, the inside of
the inner event horizon is traversable and you can steer your spaceship
to avoid the singularity and the annihilating death. This property enable
the possibility of building a traversable wormhole via a spinning black
hole connecting this universe with another one or this part of the universe
with another part thousand or million light years away.
-Duc: Do you
mean a traversable wormhole exists inside a spinning black hole? Is the
wormhole inside the event horizons or is it outside?
-Nobrain:
Inside, of-course. It is inside the inner event horizon.
-Duc: Then
if you get through a wormhole and travel to the other side, how are you
going to get out? Isn't the other end of the wormhole also buried inside
the event horizon? So with your traversable wormhole, you may be able to
avoid the singularity and can travel back and forth between the two ends
of the wormhole, but you can never get pass the event horizons to get out
to see the other universe. Your wormhole shortcut idea is cut short and
it doesn't work, my friend.
-Nobrain:
Ooooppps... Get me another bud, man.
(to be continued)
