Discussion:
Time Travel in "2001"
(too old to reply)
MGenevieve
2003-12-05 22:53:06 UTC
Permalink
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).

Best,

Genevieve

November 24, 2003

Borrowed Time: Interview with Michio Kaku


A theoretical physicist contemplates the plausibility of time travel


By JR Minkel

A motion picture adaptation of Michael Crichton's time travel
adventure story Timeline opens November 26. Crichton cites theoretical
physicist Michio Kaku of the City University of New York as one
inspiration for the science behind the story. Kaku, a string theorist,
is the author of several physics books for a popular audience,
including Hyperspace and Visions: How Science Will Revolutionize the
21st Century, and host of a weekly science radio show. He recently
spoke with Scientific American.com about the possibility of time
travel and his thoughts on science and popular culture. An edited
transcript of that conversation follows.
------------------------------------------------------------------------


Scientific American.com: How has speculating about time travel changed
over the years?

Michio Kaku: About 10 years ago, if you were a serious physicist
talking about time travel, you'd be laughed out of the scientific
establishment. People would snicker behind your back, your scientific
career would be ruined, and you wouldn't get tenure. In the last
decade or so, there's been a sea change with regards to the scientific
attitude toward time travel, and I think Michael Crichton picked that
up. And I tried to convey that in my book Hyperspace. Originally, the
burden of proof was on physicists to prove that time travel was
possible. Now the burden of proof is on physicists to prove there must
be a law forbidding time travel.

SA: When did scientists first start thinking about time travel in a
rigorous way?

MK: In 1949 Einstein's colleague at Princeton was Kurt Gödel, one of
the greatest logicians of the last thousand years. Gödel found a
solution to Einstein's equations [of general relativity] in which the
universe rotated. And if the universe rotated, then in a rocket ship,
if you went around the universe, you would come back before you left.

Now Einstein was very troubled by this. The river of time, Newton
thought, was straight and uniform; it never deviated, it always flowed
at the same rate, and it carried everything in its way. Einstein comes
along and says, "Not so fast, the river of time meanders, speeds up
and slows down around stars and galaxies." The new wrinkle that Gödel
showed in 1949 was that the river of time could have whirlpools. These
are called "closed timelike curves." And in his memoirs, Einstein says
that yes, these are solutions to his equations, but we can dismiss
them on physical grounds: the universe expands; it doesn't rotate.

Then scientists looked back at earlier solutions to Einstein's
equations and found that there were other solutions which also allow
for time travel. In 1937 [W. J.] van Stockum took an infinitely long
cylinder that was spinning like a maypole and [it was later found
that] if you danced around the maypole you would come back before you
left. In 1963 Roy Kerr, a mathematician, found that a spinning black
hole collapses into a ring of compressed matter, not a dot. If you
fall through the ring, you could wind up backwards in time or perhaps
on another universe. The mathematicians call [such spaces] multiply
connected spaces. The physicists call them wormholes. In the late
1980s Kip Thorne at Caltech and his colleagues found yet another class
of Einstein's equations where these time machines were traversable.
Like an elevator connecting parallel universes, these solutions have
an up button and a down button. Under certain conditions, you can go
through them easily, just like in the movies. You can look through the
looking glass and then come back.

SA: Where would the wormhole come from in that case?

MK: We would get the wormhole by grabbing it from the vacuum, because
they're everywhere. We think that at very small distances, 10-33
centimeters, spacetime becomes foamy. The dominant structures at those
quantum distances are probably wormholes, little bubbles, universes
that pop into existence and then pop right back out of existence. Now
if you could manipulate [the so-called] quantum foam, then you could
go through one of these bubbles. And in Kip Thorne's original proposal
for a time machine, he said that maybe we would obtain a wormhole by
grabbing one of these bubbles and expanding it, stabilizing it with
negative energy.

SA: Negative energy?

MK: Negative energy is energy below the vacuum state, or the state of
motionless nothing. Let's say we have two parallel plates that are
uncharged. We say they are at a state of zero energy because nothing
moves. But when you actually calculate this [state using quantum field
theory], you have "virtual particles" that dance everywhere. These
virtual particles create a pressure that is greater outside the plates
than it is between the plates. Therefore the plates collapse. But the
plates were in a state of zero energy; therefore as they collapse,
they're going to a lower energy state. This is called the Casimir
effect. It is minuscule; it takes a laboratory of sophisticated
equipment to pick it up. But this exists. This is not science fiction.
We've seen negative energy in the laboratory, and this is what I think
Michael Crichton picked up on, that there is a kernel of truth there.
SA: The idea in Timeline is that you can "fax" particles into the
past. What is the kernel of truth there?
MK: In the last 10 years, there has been enormous progress in
something called quantum teleportation. This is not science fiction
anymore. Now, to be real, we're not talking about sending Captain Kirk
across space and time. But we are talking about sending individual
photons across space. In a few decades, maybe we will teleport the
first virus, if the virus consists of a few thousand molecules. But at
the present time, that's the limit of what we can do. And we can only
teleport things in space, not time. But the concept of faxing matter
is not totally out of the question. And that was also raised in my
book. So there is a little bit of truth there.

SA: In Timeline the characters travel back to France in A.D. 1357
because the wormhole happens to let out there. They have six hours to
return, but their six hours in the past are synchronized with the
present. How plausible is all that?

MK: It depends. There are many designs for time machines. Wormholes
from the vacuum would connect randomly with any point in space and
time, so the other end would connect God knows where. Probability-wise
the wormhole would be more likely to connect with the universe back in
time, rather than the present. And if the mouths of the wormhole are
stationary relative to each other, time will pass at the same rate at
each mouth.

SA: How practical would it be to build one of these time machines?

MK: In fact the energies we are talking about are the energies of
stars. It would take a civilization far more advanced than ours,
unbelievably advanced, to begin to manipulate negative energy to
create gateways to the past. But if you could obtain large quantities
of negative energy--and that's a big "if"--then you could create a
time machine that apparently obeys Einstein's equation and perhaps the
laws of quantum theory. You need string theory to ultimately control
all the divergences [i.e., to make sure a hail of gravitons doesn't
fry you when you open or close the time machine]. Some cynics say
quantum effects may still make the machine blow up. But at this point
the burden of proof has shifted: people who are skeptical of time
travel have to prove it's impossible. And so far they have failed.

SA: Wouldn't time travel lead to paradoxes?

MK: There are about four or five main classes of paradox. The most
famous is called the Grandfather Paradox, and that's when you go back
in time and kill your parents before you were born. If you kill your
parents before you were born, how could you be born and kill your
parents before you were born? There are two schools of thought on
this. First is the Russian school. Igor Novikov [of Copenhagen
University] is a well-known cosmologist. He proposes that free will is
somehow abridged by going backwards in time. Something happens to
prevent you from killing your parents before you are born. Or let's
say, for example, that you went backwards in time to when Queen
Elizabeth's forces defeated the Spanish Armada. And let's say you give
a submarine to the Spanish with machine guns; then of course you're
altering human history and we are all speaking Spanish now. Novikov
says that's not possible, because when you go backwards in time and
give the submarine to the Spanish, something prevents you. Well, my
attitude is, in the future, a vanced civilizations might simply mail
the submarine to the Spanish without any free will being abridged;
inanimate matter will go through the time machine and change the past.
That's why I tend to doubt the Novikov interpretation. It's simply too
much to assume that the laws of the universe conspire to prevent
paradoxes.


SA: Then what resolves the paradox?

MK: I prefer the "many worlds" interpretation. [Editor's note: Quantum
physics describes a particle by a probabilistic wave function, such
that its position is indeterminate until the wave function "collapses"
and the particle assumes a definite, though randomly determined,
position.] The many worlds theory simply says that maybe the wave
[function] never collapses. Maybe the wave just keeps on bifurcating
every time it hits an obstacle. So the timeline is constantly
bifurcating because the wave is bifurcating all the time. We just
happen to be in one thread of this wave. And we have the illusion that
we are the only ones. In this other thread, they think they are the
only universe. The reality is, nobody's function has collapsed.

In time travel scenarios, you would simply go from one thread to the
next, one timeline to the next timeline. And the two look awfully
similar. If the many worlds theory is correct, it means that if you go
backward in time and kill your parents before you were born, they are
somebody else's parents. The timeline has diverged. Your parents gave
birth to you, in your universe, in your timeline. So if you have the
many worlds theory, there are no paradoxes, just different timelines.

SA: What's the value to physicists of thinking about time machines?

MK: In physics we have a theorem that if it's not forbidden, it's
mandatory. So when we postulate that we understand the laws of
everything, that means it must answer all "how" questions. It must
answer where did the universe come from, where did the big bang come
from, what is the singularity of a black hole? And here we have this
huge gap in the question of causality; attempts so far to create a
"chronology protection" hypothesis to forbid time travel have failed.
Therefore we don't really know the laws that well. When you look at
the calculation, it's amazing that every time you try to prove or
disprove time travel, you've pushed Einstein's theory to the very
limits where quantum effects must dominate. That's telling us that you
really need a theory of everything to resolve this question. And the
only candidate is string theory. So that's why we should study these
things, even if we can't build one of them for millennia.

SA: And does string theory give any insight so far into these
questions?

MK: No. String theory gives you trillions of solutions. Each solution
is a well-defined solution to Einstein's equations and the quantum
theory. So there is a multiverse [many possible universes, perhaps
coexisting] in string theory. However, string theory is also
compatible with the Copenhagen interpretation [an alternative to many
worlds]. So string theory does not rule out either interpretation.
Personally, I believe that whether or not the many worlds theory is
correct will be decided by string theory. And string theory seems to
lean toward the multiverse idea.

SA: So why do you think we haven't seen any time tourists?

MK: If you go down the road and see an anthill, do you go down to the
ants and say, "I bring you trinkets: I bring you nuclear energy, I
give you DNA technology?" The answer is no, and for the most part you
might even step on them. The distance between the ant and us,
scientifically speaking, is comparable to the distance between us and
a civilization that can manipulate the Planck energy [required to
probe very small distances and operate a time machine]. We are
arrogant and self-centered to believe that they would be interested in
us enough to want to visit us and give us technology. For the most
part, they may not care. However, I should point out that if one day
someone knocks on your door and claims to be a great great great great
granddaughter who has decided to visit you in the past, don't slam the
door. Because who knows? Maybe they have access to a time machine.

SA: How do you feel about the influence of popular culture and science
fiction on physics?


MK: Scientists, historically, are embarrassed by science fiction; they
want to distance themselves as much as possible. However, when you
read the biographies of great scientists, you realize that a lot of
them, as children, were fascinated by science fiction. I just finished
writing a biography of Einstein called Einstein's Cosmos (due in April
2004), and I had to look up the biographies of many great scientists.
I was shocked to find, for example, that Edwin Hubble, when he was a
young man, read Jules Verne. And he was fascinated by the concept of
going into outer space, the concept of going to the moon, stuff like
that. That childhood fascination was so great that he gave up a
promising law career to become an astronomer. So I think that even
though scientists are embarrassed to admit this, as children many were
influenced by Jules Verne and even Star Trek. I think there's nothing
to be ashamed of. That's one reason why we should take science fiction
seriously.

But the other reason is to combat scientific ignorance in the general
public. Anything that promotes a kernel of science, even though it's
exaggerated and hyped by Hollywood, I think is a step forward. We in
the ivory tower ultimately have to realize that in some sense we have
to sing for our supper. The cancellation of the SSC was a wake-up call
for all high energy physicists. Unfortunately, I think that we
scientists have failed to engage the public. And I think that has
negative consequences.

SA: How so?

MK: Take a look at George Gamow, who is now recognized as one of the
great cosmologists of the last hundred years. I speculate that he
probably didn't win the Nobel Prize because people could not take him
seriously. He wrote children's books. His colleagues have publicly
stated his writing children's books on science had an adverse effect
on his scientific reputation, and people could not take him seriously
when he and his colleagues proposed that there should be a cosmic
background radiation, which we now know to be one of the greatest
discoveries of 20th-century physics.

When Carl Sagan was engaging the public years ago, he was denied
admission to the National Academy of Sciences. In the debate, it came
out that many [scientists] could not take him seriously. They saw him
on television; how seriously can you take someone you see on
television? You see actors on television. So I think it had a negative
effect on his scientific career.

SA: It sounds like things have changed, though.

MK: The sea change came when Steven Hawking wrote the book A Brief
History of Time. He was a serious cosmologist who took the time to
write a book for the general public, and it was among the best-selling
books of all time. Even the publishing world had to take note of that
book. I think that has made it possible for more scientists to engage
the public, to the point where reputable scientists can write books
about science and not have to suffer like Gamow suffered decades ago.

SA: Does this have anything to do with your radio program and why you
do that?

MK: Yes, I like to engage the public because when I was in high school
I had all these questions about anti-matter, higher dimensions and
time travel. Every time I went to the library, every time I asked
people these questions, I would get some strange looks. Nobody could
answer any of these questions. So I said to myself as a child that
when I become a theoretical physicist, and I do research, I want to be
able to answer these questions for children who ask these questions
and get no answer.

SA: Do you have a favorite time travel movie?

MK: Oh, that's a hard one. There is a problem being a physicist, and
that is when you see these movies, you say, "Well, that's not right."
And it really ruins it. But I like the Back to the Future series. Here
was a movie where you actually saw the scientist building and doing
things; he was an essential character in the entire series. Doc Brown
was this crazy man, but at least they showed him. He was there. He was
making the series work.


SA: Even though in Hyperspace you say that the sort of time travel
found in Back to the Future wouldn't really work?

MK: Neither of the two theories [single or multiple timelines] is
compatible with slowly fading away as you slowly change the past. In
part two, Doc Brown does draw a timeline forking and he does say
explicitly that we went from one timeline to the next. I thought that
it was interesting that in the movie they take a position, and their
position is many worlds.
------------------------------------------------------------------------
JR Minkel is a freelance writer based in New York City.
------------------------------------------------------------------------
© 1996-2003 Scientific American, Inc. All rights reserved.
Reproduction in whole or in part without permission is prohibited.
(uh-oh)
Mike Jackson
2003-12-05 23:19:08 UTC
Permalink
Post by MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
Best,
Genevieve
Thanks for posting this. If any of you are fans of Michio Kaku or TechTV's
"The Screen Savers" where he's a frequent guest when silly movies like "The
Matrix" come out. He has a site at http://www.mkaku.org/

I never have any idea of he really knows what he's talking about but he sure
is entertaining to listen to and often quite funny. I've often thought he
will probably inherit the mantle of the next famous smart guy that no one
understands what the hell he is talking about because he is so personable
like Sagan and so on.
--
"In order to make an apple pie from scratch,
you must first create the universe."
-- Carl Sagan, Cosmos
Don
2003-12-06 04:34:08 UTC
Permalink
Post by Mike Jackson
Post by MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
Best,
Genevieve
Thanks for posting this. If any of you are fans of Michio Kaku or TechTV's
"The Screen Savers" where he's a frequent guest when silly movies like "The
Matrix" come out. He has a site at http://www.mkaku.org/
I never have any idea of he really knows what he's talking about but he sure
is entertaining to listen to and often quite funny. I've often thought he
will probably inherit the mantle of the next famous smart guy that no one
understands what the hell he is talking about because he is so personable
like Sagan and so on.
--
"In order to make an apple pie from scratch,
you must first create the universe."
-- Carl Sagan, Cosmos
Sagan smoked alot of weed.
Wordsmith
2003-12-09 00:08:12 UTC
Permalink
Post by Don
Post by Mike Jackson
Post by MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
Best,
Genevieve
Thanks for posting this. If any of you are fans of Michio Kaku or TechTV's
"The Screen Savers" where he's a frequent guest when silly movies like "The
Matrix" come out. He has a site at http://www.mkaku.org/
I never have any idea of he really knows what he's talking about but he sure
is entertaining to listen to and often quite funny. I've often thought he
will probably inherit the mantle of the next famous smart guy that no one
understands what the hell he is talking about because he is so personable
like Sagan and so on.
--
"In order to make an apple pie from scratch,
you must first create the universe."
-- Carl Sagan, Cosmos
Sagan smoked alot of weed.
Kaku smokes sushi. *LOL* (Kidding! I like Kaku when he's on the radio.)

Wordsmith :)
JeffreyMeyer
2003-12-06 10:01:10 UTC
Permalink
Kaku is a very interesting fellow and he's made numerous appearances
over the years on Art Bell's crazy radio program... unfortunately he
seems to mention Star Trek and its ilk repeatedly while for the most
part ignoring any of the serious SF films... anyway, he's one of the
few "hard science" guys to actually guest on a show otherwise
populated by obvious (though nonetheless entertaining) quacks and
frauds. Much as I enjoy Whitley Streiber's tall tales... ha ha.

Also, coincidentally, about three or four weeks ago a weekend guest on
the show -- unfortunately I cannot remember which guest (John Lear?)
-- was discussing conspiracies and the Illuminati, etc. and
specifically mentioned Eyes Wide Shut! It amazes me how little
attention this aspect of the film receives in most of the mainstream
reviews...
M4RV1N
2003-12-06 04:59:22 UTC
Permalink
MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
Unless I've missed it I don't believe there is such an essay, though Nelson and
Ciment (among several others) have discussed the depiction of the "timeless
state" of Bowman's experiences in the Room at the End. Even though the
progression is linear, Bowman appears to me to "realize" his own transformation
in steps which seem to age him by decades. This can be read as reducing or
trivializing the time spent in the room, or, (my view) no actual time occurred
at all: Bowman was transformed to the Starchild level at the end of the
stargate journey and the Room at the End is his human mind's final mythopoeic
"dream" of that transformation. This is the way I've viewed the time
distortion in "2001" anyway.

But then this isn't the sort of time travel you're interested in with Michio
Kaku and modern physics. In order to apply that you would have to inpret the
instances in which one version of Bowman observes another version as his
becoming unstuck in time, or in the Many Worlds Interpretation, visiting other
Bowmans in their universes. I don't think this is Kubrick's intention with the
scene though, and I'll stick by the version in the preceding paragraph.
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
In the Playboy interview he mentions Einstein time dilation (which is not into
the past), and the speculation then that UFOs might be time shuttles from a
future age. UFOs, just as an aside, were taken very seriously in '68 and not
yet the goofy new religion they've become today.
SA: Then what resolves the paradox?
MK: I prefer the "many worlds" interpretation. [Editor's note: Quantum
physics describes a particle by a probabilistic wave function, such
that its position is indeterminate until the wave function "collapses"
and the particle assumes a definit
though randomly determined,
position.] The many worlds theory simply says that maybe the wave
[function] never collapses. Maybe the wave just keeps on bifurcating
every time it hits an obstacle. So the timeline is constantly
bifurcating because the wave is bifurcating all the time. We just
happen to be in one thread of this
wave. And we have the illusion that
we are the only ones. In this other thread, they think they are the
only universe. The reality is, nobody's function has collapsed.
In time travel scenarios, you would simply go from one thread to the
next, one timeline to the next timeline. And the two look awfully
similar. If the many worlds theory is correct, it means that if you go
backward in time and kill your parents before you were born, they are
somebody else's parents. The
timeline has diverged. Your parents gave
birth to you, in your universe, in your timeline. So if you have the
many worlds theory, there are no paradoxes, just different timelines.
I've written a philosophical essay on this, and I'll quote a bit of it just for
fun:

~~~

... The implication here is unlikely outcomes are just as real in obtaining
as likely ones. MWI's implications, not surprisingly, bifurcate just as
rapidly as its universes. Max Tegmark has put forward a "quantum suicide"
thought experiment in which the random spin of a particle dictates whether or
not the experimenter will be shot in the head. Multiple trials are performed.
From the perspective of the experimenter's assistant, the experimenter is soon
killed. From the viewpoint of the experimenter the dreaded outcome never
happens-and can never happen. Her consciousness continually shifts into
parallel universe alternatives in which random chance allows her to live. To
verify the randomness of the results (and the validity of MWI) she must merely
move her head out of the line of fire of the gun for a few trials in order to
confirm that it does randomly fire. As trials proceed, in most universes, and
in increasingly larger number of them, there is one less experimenter. She
herself cannot experience death as her consciousness necessarily shifts (or
stays, depending on how you size up MWI theoretics) with her surviving
version(s).

The implications of this oddity take us to the Quantum Theory of Immortality,
which states that somewhere in the "multiverse" (all variations) each
consciousness will constantly shift into an unending avoidance of death. The
mathematical odds against the specific "escape" are irrelevant. This makes us
all immortal, but only from our own point of view. Objectively, people will
see you die, and you will see people die. Subjectively, you are destined to
ricochet from one nonfatal outcome to another. Of course there must be some
universes where people notice one person who is incredibly lucky, surviving
gunshot, after disease, after car accident, and old age as well, and never
dies. But the odds to you being an observer by being in one of those universes
are countless trillions to one, against. Meanwhile, your fate is to become
such an anomaly, leaving behind endless clones in other universes to go to
their graves, as to confirm for you the reality of MWI and QTI.

~~~

Sciene fiction writer Larry Niven had some fun with this notion in the short
story "All the Myriad Ways." But even if Q-immortality is right, all good
things have to come to an end, and the heat death of the universe gets the last
survivor, somehow someway.

Mark Ervin
MGenevieve
2003-12-08 18:19:59 UTC
Permalink
Post by M4RV1N
MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
Unless I've missed it I don't believe there is such an essay, though Nelson and
Ciment (among several others) have discussed the depiction of the "timeless
state" of Bowman's experiences in the Room at the End. Even though the
progression is linear, Bowman appears to me to "realize" his own transformation
in steps which seem to age him by decades. This can be read as reducing or
trivializing the time spent in the room, or, (my view) no actual time occurred
at all: Bowman was transformed to the Starchild level at the end of the
stargate journey and the Room at the End is his human mind's final mythopoeic
"dream" of that transformation. This is the way I've viewed the time
distortion in "2001" anyway.
But then this isn't the sort of time travel you're interested in with Michio
Kaku and modern physics. In order to apply that you would have to inpret the
instances in which one version of Bowman observes another version as his
becoming unstuck in time, or in the Many Worlds Interpretation, visiting other
Bowmans in their universes. I don't think this is Kubrick's intention with the
scene though, and I'll stick by the version in the preceding paragraph.
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
In the Playboy interview he mentions Einstein time dilation (which is not into
the past), and the speculation then that UFOs might be time shuttles from a
future age. UFOs, just as an aside, were taken very seriously in '68 and not
yet the goofy new religion they've become today.
...I appreciated the resonses to this thread, thanks to all. Extra
thanks for your intelligent comments, Mark. I need to do some more
(basic) reading on this topic.

Best wishes,

Genevieve
Darin Boville
2003-12-10 04:45:51 UTC
Permalink
Post by M4RV1N
MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
Unless I've missed it I don't believe there is such an essay, though Nelson and
Ciment (among several others) have discussed the depiction of the "timeless
state" of Bowman's experiences in the Room at the End. Even though the
progression is linear, Bowman appears to me to "realize" his own transformation
in steps which seem to age him by decades. This can be read as reducing or
trivializing the time spent in the room, or, (my view) no actual time occurred
at all: Bowman was transformed to the Starchild level at the end of the
stargate journey and the Room at the End is his human mind's final mythopoeic
"dream" of that transformation. This is the way I've viewed the time
distortion in "2001" anyway.
But then this isn't the sort of time travel you're interested in with Michio
Kaku and modern physics. In order to apply that you would have to inpret the
instances in which one version of Bowman observes another version as his
becoming unstuck in time, or in the Many Worlds Interpretation, visiting other
Bowmans in their universes. I don't think this is Kubrick's intention with the
scene though, and I'll stick by the version in the preceding paragraph.
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
In the Playboy interview he mentions Einstein time dilation (which is not into
the past), and the speculation then that UFOs might be time shuttles from a
future age. UFOs, just as an aside, were taken very seriously in '68 and not
yet the goofy new religion they've become today.
SA: Then what resolves the paradox?
MK: I prefer the "many worlds" interpretation. [Editor's note: Quantum
physics describes a particle by a probabilistic wave function, such
that its position is indeterminate until the wave function "collapses"
and the particle assumes a definit
though randomly determined,
position.] The many worlds theory simply says that maybe the wave
[function] never collapses. Maybe the wave just keeps on bifurcating
every time it hits an obstacle. So the timeline is constantly
bifurcating because the wave is bifurcating all the time. We just
happen to be in one thread of this
wave. And we have the illusion that
we are the only ones. In this other thread, they think they are the
only universe. The reality is, nobody's function has collapsed.
In time travel scenarios, you would simply go from one thread to the
next, one timeline to the next timeline. And the two look awfully
similar. If the many worlds theory is correct, it means that if you go
backward in time and kill your parents before you were born, they are
somebody else's parents. The
timeline has diverged. Your parents gave
birth to you, in your universe, in your timeline. So if you have the
many worlds theory, there are no paradoxes, just different timelines.
I've written a philosophical essay on this, and I'll quote a bit of it just for
~~~
... The implication here is unlikely outcomes are just as real in obtaining
as likely ones. MWI's implications, not surprisingly, bifurcate just as
rapidly as its universes. Max Tegmark has put forward a "quantum suicide"
thought experiment in which the random spin of a particle dictates whether or
not the experimenter will be shot in the head. Multiple trials are performed.
From the perspective of the experimenter's assistant, the experimenter is soon
killed. From the viewpoint of the experimenter the dreaded outcome never
happens-and can never happen. Her consciousness continually shifts into
parallel universe alternatives in which random chance allows her to live. To
verify the randomness of the results (and the validity of MWI) she must merely
move her head out of the line of fire of the gun for a few trials in order to
confirm that it does randomly fire. As trials proceed, in most universes, and
in increasingly larger number of them, there is one less experimenter. She
herself cannot experience death as her consciousness necessarily shifts (or
stays, depending on how you size up MWI theoretics) with her surviving
version(s).
The implications of this oddity take us to the Quantum Theory of Immortality,
which states that somewhere in the "multiverse" (all variations) each
consciousness will constantly shift into an unending avoidance of death. The
mathematical odds against the specific "escape" are irrelevant. This makes us
all immortal, but only from our own point of view. Objectively, people will
see you die, and you will see people die. Subjectively, you are destined to
ricochet from one nonfatal outcome to another. Of course there must be some
universes where people notice one person who is incredibly lucky, surviving
gunshot, after disease, after car accident, and old age as well, and never
dies. But the odds to you being an observer by being in one of those universes
are countless trillions to one, against. Meanwhile, your fate is to become
such an anomaly, leaving behind endless clones in other universes to go to
their graves, as to confirm for you the reality of MWI and QTI.
~~~
Sciene fiction writer Larry Niven had some fun with this notion in the short
story "All the Myriad Ways." But even if Q-immortality is right, all good
things have to come to an end, and the heat death of the universe gets the last
survivor, somehow someway.
Mark Ervin
Hello Mark,

Not being a Physics person, when I hear this sort of thing I always
think, "This sort of thing will look rather silly many years hence
when they figure out what they've been missing."

But here's the sort of thing a non-physics guy always wants to
ask--here's my chance: With all these (infinite?) alternate "worlds"
where does all the energy come from? Doesn't the many worlds thing
mean that for every alternative in my world (the one I think I'm in)
there has to be all the "overhead" that goes with each existence? That
is, in one I paint my house green, the other blue, we now have two
houses in the universe instead of one? Actually we have quite a few
(infinite?) more than that since I assume we are diverging at every
trivial "fork in the road"...

--Darin
M4RV1N
2003-12-12 02:53:34 UTC
Permalink
Darin Boville
Hello Mark,
Not being a Physics person, when I hear this sort of thing I always
think, "This sort of thing will look rather silly many years hence
when they figure out what they've been missing."
That could very well be so. I think it needs to be said in the same breath
that if the MWI is false then the right answer simply has to be far stranger
still. I'm not sure if I'm quite ready for that one...

We should also remember that the way the universe actually works is simply not
required to like the way we expect it based on our everyday and limited
experiences of it. Kubrick liked to quote the Haldane statement about the
universe being not only stranger than we imagine, but stranger than we can
imagine.
But here's the sort of thing a non-physics guy always wants to
ask--here's my chance: With all these (infinite?) alternate "worlds"
where does all the energy come from? Doesn't the many worlds thing
mean that for every alternative in my world (the one I think I'm in)
there has to be all the "overhead" that goes with each existence?
For reasons I won't go into, the other universes, vast quentillions of them,
would be folded into ours in other dimensions. They would be right "where we
are" and using the same energy, in some sense. The phrase, "you can't get
there from here" applies in a really big way, unless you find a really big
black hole and are good at math.

That
is, in one I paint my house green, the other blue, we now have two
houses in the universe instead of one? Actually we have quite a few
(infinite?)
I would doubt actual infinity is involved. I doubt infinite infinity,
infinitely.

more than that since I assume we are diverging at every
trivial "fork in the road"...
Your complaint here about the MWI is powerful and very well taken. Basically,
it's the Ocaam's Razor objection (that the simplest explanation is the right
one and that entities necessary to explain something shouldn't be multiplied
excessively). Well the MWI is about the most overbearing and grotesque
violation of Occam's Razor the human race could ever come up with. It doubles
the universe at every chronon of time when a single particle changes its state
in some way.

But the thing is Occam's razor is a generality; it's an admonition that's
usually< right. Human DNA apparently has a whole bunch of coded info that's
either gibberish or totally irrelevant to making more humans, and that's one
violation of Occam's razor.

But getting back to what I was saying earlier, if the MWI is wrong, something
has to take up the explanatory slack of the grandfather paradox. It's a fact
that some particles travel backwards in time. It's a fact that physics could
allow a big clot of particles (like me) to go back in time. If I could go back
in time I could kill my grandfather. A single time line can't deal with this
reality. Violating reality is an infinitely worse problem than violating
Occam's razor. Can't do it.

A crystalline determinist universe deals with it by suggesting that I must fail
(somehow) to kill my grandfather even though I can go back. But this
explanation has a variety of problems, one of which is the possibility of a
LaPlacen Superphysicist. A LaPS is a possible hypothetical person who can
deduce the state of all elementary particles past and present and future.
Forget that it would take a rather large headed person for the moment. Such a
fellow could see what could prevent the intended murder and work around it. If
he couldn't do that then we can't ever be conscious of anything, and we can't
actually do anything either. This lacks some basic appeal, to me.

I think the question that can emerge here, and I hope you are sitting down when
you see this one, is, is the MWI *actually the simplest explanation*?

Occam has turned in his grave six times by now.

Mark Ervin
Darin Boville
2003-12-12 07:40:29 UTC
Permalink
Post by M4RV1N
Darin Boville
Hello Mark,
Not being a Physics person, when I hear this sort of thing I always
think, "This sort of thing will look rather silly many years hence
when they figure out what they've been missing."
That could very well be so. I think it needs to be said in the same breath
that if the MWI is false then the right answer simply has to be far stranger
still. I'm not sure if I'm quite ready for that one...
We should also remember that the way the universe actually works is simply not
required to like the way we expect it based on our everyday and limited
experiences of it. Kubrick liked to quote the Haldane statement about the
universe being not only stranger than we imagine, but stranger than we can
imagine.
But here's the sort of thing a non-physics guy always wants to
ask--here's my chance: With all these (infinite?) alternate "worlds"
where does all the energy come from? Doesn't the many worlds thing
mean that for every alternative in my world (the one I think I'm in)
there has to be all the "overhead" that goes with each existence?
For reasons I won't go into, the other universes, vast quentillions of them,
would be folded into ours in other dimensions. They would be right "where we
are" and using the same energy, in some sense. The phrase, "you can't get
there from here" applies in a really big way, unless you find a really big
black hole and are good at math.
That
is, in one I paint my house green, the other blue, we now have two
houses in the universe instead of one? Actually we have quite a few
(infinite?)
I would doubt actual infinity is involved. I doubt infinite infinity,
infinitely.
more than that since I assume we are diverging at every
trivial "fork in the road"...
Your complaint here about the MWI is powerful and very well taken. Basically,
it's the Ocaam's Razor objection (that the simplest explanation is the right
one and that entities necessary to explain something shouldn't be multiplied
excessively). Well the MWI is about the most overbearing and grotesque
violation of Occam's Razor the human race could ever come up with. It doubles
the universe at every chronon of time when a single particle changes its state
in some way.
But the thing is Occam's razor is a generality; it's an admonition that's
usually< right. Human DNA apparently has a whole bunch of coded info that's
either gibberish or totally irrelevant to making more humans, and that's one
violation of Occam's razor.
But getting back to what I was saying earlier, if the MWI is wrong, something
has to take up the explanatory slack of the grandfather paradox. It's a fact
that some particles travel backwards in time. It's a fact that physics could
allow a big clot of particles (like me) to go back in time. If I could go back
in time I could kill my grandfather. A single time line can't deal with this
reality. Violating reality is an infinitely worse problem than violating
Occam's razor. Can't do it.
A crystalline determinist universe deals with it by suggesting that I must fail
(somehow) to kill my grandfather even though I can go back. But this
explanation has a variety of problems, one of which is the possibility of a
LaPlacen Superphysicist. A LaPS is a possible hypothetical person who can
deduce the state of all elementary particles past and present and future.
Forget that it would take a rather large headed person for the moment. Such a
fellow could see what could prevent the intended murder and work around it. If
he couldn't do that then we can't ever be conscious of anything, and we can't
actually do anything either. This lacks some basic appeal, to me.
I think the question that can emerge here, and I hope you are sitting down when
you see this one, is, is the MWI *actually the simplest explanation*?
Occam has turned in his grave six times by now.
Mark Ervin
I just hope that this is one of those examples in science wehere we
get a awfully complicated answer to a puzzeling set of phenomena--and
them wham, someone figures out the elegant solution that sorts it all
out...

--Darin
Wordsmith
2003-12-12 17:44:32 UTC
Permalink
Post by Darin Boville
Post by M4RV1N
Darin Boville
Hello Mark,
Not being a Physics person, when I hear this sort of thing I always
think, "This sort of thing will look rather silly many years hence
when they figure out what they've been missing."
That could very well be so. I think it needs to be said in the same breath
that if the MWI is false then the right answer simply has to be far stranger
still. I'm not sure if I'm quite ready for that one...
We should also remember that the way the universe actually works is simply not
required to like the way we expect it based on our everyday and limited
experiences of it. Kubrick liked to quote the Haldane statement about the
universe being not only stranger than we imagine, but stranger than we can
imagine.
But here's the sort of thing a non-physics guy always wants to
ask--here's my chance: With all these (infinite?) alternate "worlds"
where does all the energy come from? Doesn't the many worlds thing
mean that for every alternative in my world (the one I think I'm in)
there has to be all the "overhead" that goes with each existence?
For reasons I won't go into, the other universes, vast quentillions of them,
would be folded into ours in other dimensions. They would be right "where we
are" and using the same energy, in some sense. The phrase, "you can't get
there from here" applies in a really big way, unless you find a really big
black hole and are good at math.
That
is, in one I paint my house green, the other blue, we now have two
houses in the universe instead of one? Actually we have quite a few
(infinite?)
I would doubt actual infinity is involved. I doubt infinite infinity,
infinitely.
more than that since I assume we are diverging at every
trivial "fork in the road"...
Your complaint here about the MWI is powerful and very well taken. Basically,
it's the Ocaam's Razor objection (that the simplest explanation is the right
one and that entities necessary to explain something shouldn't be multiplied
excessively). Well the MWI is about the most overbearing and grotesque
violation of Occam's Razor the human race could ever come up with. It doubles
the universe at every chronon of time when a single particle changes its state
in some way.
But the thing is Occam's razor is a generality; it's an admonition that's
usually< right. Human DNA apparently has a whole bunch of coded info that's
either gibberish or totally irrelevant to making more humans, and that's one
violation of Occam's razor.
But getting back to what I was saying earlier, if the MWI is wrong, something
has to take up the explanatory slack of the grandfather paradox. It's a fact
that some particles travel backwards in time. It's a fact that physics could
allow a big clot of particles (like me) to go back in time. If I could go back
in time I could kill my grandfather. A single time line can't deal with this
reality. Violating reality is an infinitely worse problem than violating
Occam's razor. Can't do it.
A crystalline determinist universe deals with it by suggesting that I must fail
(somehow) to kill my grandfather even though I can go back. But this
explanation has a variety of problems, one of which is the possibility of a
LaPlacen Superphysicist. A LaPS is a possible hypothetical person who can
deduce the state of all elementary particles past and present and future.
Forget that it would take a rather large headed person for the moment. Such a
fellow could see what could prevent the intended murder and work around it. If
he couldn't do that then we can't ever be conscious of anything, and we can't
actually do anything either. This lacks some basic appeal, to me.
I think the question that can emerge here, and I hope you are sitting down when
you see this one, is, is the MWI *actually the simplest explanation*?
Occam has turned in his grave six times by now.
Mark Ervin
I just hope that this is one of those examples in science wehere we
get a awfully complicated answer to a puzzeling set of phenomena--and
them wham, someone figures out the elegant solution that sorts it all
out...
--Darin
"Elegant" is tossed around a lot in cosmological circles, almost to the
point of being a buzzword, but when it's all figured out, assuming it *ever*
is, we'll be suprised at ourselves for not having uncovered it sooner.

Wordsmith :)
Matthew Dickinson
2003-12-12 19:17:27 UTC
Permalink
Post by M4RV1N
But getting back to what I was saying earlier, if the MWI is wrong, something
has to take up the explanatory slack of the grandfather paradox. It's a fact
that some particles travel backwards in time. It's a fact that physics could
allow a big clot of particles (like me) to go back in time. If I could go back
in time I could kill my grandfather. A single time line can't deal with this
reality. Violating reality is an infinitely worse problem than violating
Occam's razor. Can't do it.
A crystalline determinist universe deals with it by suggesting that I must fail
(somehow) to kill my grandfather even though I can go back. But this
explanation has a variety of problems, one of which is the possibility of a
LaPlacen Superphysicist. A LaPS is a possible hypothetical person who can
deduce the state of all elementary particles past and present and future.
Forget that it would take a rather large headed person for the moment. Such a
fellow could see what could prevent the intended murder and work around it. If
he couldn't do that then we can't ever be conscious of anything, and we can't
actually do anything either. This lacks some basic appeal, to me.
The same cause and effect process that enables the bit clot of
particles of your grandparents (and parents) to have sex and create
you would also (as the domino effect would not ultimately be broken)
cause you to go back in time to kill said grandparents. The "original"
timeline would include your time traveling already. This no longer
seems bizarre when you consider the difficulty we have in predicting
the future in the first place, or our ability at reconstructing the
past with great detail. That one clot of particles destroyed the
original particles that led to its creation (and movement) doesn't
suggest that it would immediately "disappear" (and what would
disappearing be? Another hole in "reality" here) or somehow cease to
exist. For practical purposes, the multiverse idea of every change
branching itself into a new universe only matters in so far as there
are observers (i.e. witnesses) to its changes. That is, there is no
contradiction in reality if there are no witnesses. Any particle sent
back in time disturbs the previous particles which should ultimately
have been related, however distant, to its ("future" and "present")
being, but if time travel is a fundamental aspect of the universe,
then the "meta" time stream contains time traveling events within it.
And if returning to the "present" from which he (or it) left causes a
duplication of particles, why is this unallowed? Can we not
theoretically duplicate particles in the laboratory? The infinite time
traveling cycles this situation might imply are also allowed, even
though they seem absurd. If, though, in the laboratory we one day, by
chance!, send a particle back in time, and it doesn't return, we will
know that this particle somehow obliterated the cause and effect
stream that caused its original existence.

You know what? The best time traveling movie is "Bill and Ted's
Excellent Adventure." It's the only one that seems to realize the
comical absurdity of these (apparent) paradoxes.

Matthew
Wordsmith
2003-12-14 22:19:39 UTC
Permalink
Post by Matthew Dickinson
Post by M4RV1N
But getting back to what I was saying earlier, if the MWI is wrong, something
has to take up the explanatory slack of the grandfather paradox. It's a fact
that some particles travel backwards in time. It's a fact that physics could
allow a big clot of particles (like me) to go back in time. If I could go back
in time I could kill my grandfather. A single time line can't deal with this
reality. Violating reality is an infinitely worse problem than violating
Occam's razor. Can't do it.
A crystalline determinist universe deals with it by suggesting that I must fail
(somehow) to kill my grandfather even though I can go back. But this
explanation has a variety of problems, one of which is the possibility of a
LaPlacen Superphysicist. A LaPS is a possible hypothetical person who can
deduce the state of all elementary particles past and present and future.
Forget that it would take a rather large headed person for the moment. Such a
fellow could see what could prevent the intended murder and work around it. If
he couldn't do that then we can't ever be conscious of anything, and we can't
actually do anything either. This lacks some basic appeal, to me.
The same cause and effect process that enables the bit clot of
particles of your grandparents (and parents) to have sex and create
you would also (as the domino effect would not ultimately be broken)
cause you to go back in time to kill said grandparents. The "original"
timeline would include your time traveling already. This no longer
seems bizarre when you consider the difficulty we have in predicting
the future in the first place, or our ability at reconstructing the
past with great detail. That one clot of particles destroyed the
original particles that led to its creation (and movement) doesn't
suggest that it would immediately "disappear" (and what would
disappearing be? Another hole in "reality" here) or somehow cease to
exist. For practical purposes, the multiverse idea of every change
branching itself into a new universe only matters in so far as there
are observers (i.e. witnesses) to its changes. That is, there is no
contradiction in reality if there are no witnesses. Any particle sent
back in time disturbs the previous particles which should ultimately
have been related, however distant, to its ("future" and "present")
being, but if time travel is a fundamental aspect of the universe,
then the "meta" time stream contains time traveling events within it.
And if returning to the "present" from which he (or it) left causes a
duplication of particles, why is this unallowed? Can we not
theoretically duplicate particles in the laboratory? The infinite time
traveling cycles this situation might imply are also allowed, even
though they seem absurd. If, though, in the laboratory we one day, by
chance!, send a particle back in time, and it doesn't return, we will
know that this particle somehow obliterated the cause and effect
stream that caused its original existence.
You know what? The best time traveling movie is "Bill and Ted's
Excellent Adventure." It's the only one that seems to realize the
comical absurdity of these (apparent) paradoxes.
Matthew
*Back to the Future* seemed self-aware, in a jocular manner, of the
implications of time travel. What we need is a movie that really digs
down deep into the philosophical meat of the matter. We can only (sadly)
speculate as to what kind of a time traveling tale SK would have made.

Wordsmith :(
Ken Michael Nielsen
2003-12-13 00:31:51 UTC
Permalink
I haven't followed this thread from the beginning, so I'm not sure if
I'm just repeating something that has already been discussed, but
there is an absolutely mindblowing article on parallel universes on
the Scientific American web site:

http://www.scientificamerican.com/article.cfm?articleID=000F1EDD-B48A-1E90-8EA5809EC5880000&catID=2

It deals with the different 'levels' of PUs, which are a necessary
consequence of modern cosmology. If I understand the author's point
correctly, modern cosmology implies that there are infinite copies of
you and me elsewhere in the 'multiverse' - this follows from the
recent discovery that the uni/multiverse is indeed infinite; hence,
all structures such as you, me, the solar system - and SK! - are bound
to repeat themselves, since the particles constituting these entities
can only be combined in a finite number of ways. And this is just the
simplest Level I PU, i.e., regions of space that are beyond the
visible universe because the light from there hasn't reached us yet.
As the universe expands, any given point will, in principle and given
sufficient time, come within 'reach', that is, become part of our
local universe which is merely what we are able to observe (the limit
being where recession velocity equals the speed of light), but is
really only 'our' local island in the vast multiverse.

Oh, and while the multiverse is infinite, there may be infinitely many
distinct multiverses. This is Level II. Levels III and IV are weirder
still (different quantum states and different mathematical
structures). Somebody with more knowledge of cosmology please correct
me if this summary is flawed.

Reading this article was almost a transcendental experience for me. It
stayed with me for a long time, and triggered what I personally call
the "2001 feeling" which is this sense of awe that I have known since
the first space flights and particularly since seeing 2001 for the
first time at 12. One of the nice things about AMK is that you can
sense that others than you know this feeling which is so difficult to
describe to others, but which is very real, and, dare I use the word,
precious. In other words, the SciAm article should appeal to 2001
junkies.

Regarding the possibility or impossibility of time travel, there is an
interesting article in New Scientist, Vol. 179 No. 2413 (Sept. 20,
2003) pp. 28-32, titled "No going back." Seems that many scientists
have a feeling that something as yet unknown may 'prohibit' time
travel after all.

Ken
PT Caffey
2003-12-06 11:26:12 UTC
Permalink
Post by MGenevieve
I was reading this fascinating interview with Michio Kaku in
Scientific America and I am wondering (forgive my ignorance): have any
_serious_ essays been published solely on the subject of time travel
in "2001"
It's an obvious topic and I have read discussions and
_interpretations_ regarding this topic but did Kubrick talk about time
travel in interviews about 2001 in 1968. (I cannot find my 2001 book
right now).
Best,
Genevieve
Great interview! Thanks for posting.
Jan
2003-12-15 07:04:00 UTC
Permalink
Post by MGenevieve
In 1963 Roy Kerr, a mathematician, found that a spinning black
hole collapses into a ring of compressed matter, not a dot.
That's fine except we don't know that the ring (or dot in the
Schwarzschild case) consists of "compressed matter". According to
current established theory it's actually beyond all space and time.
It's not a part of spacetime. No physical events take place there. In
fact there is no "there" there.
Post by MGenevieve
If you
fall through the ring, you could wind up backwards in time or perhaps
on another universe. The mathematicians call [such spaces] multiply
connected spaces.
Multiply connected spaces are something else. Kaku should hang out
around the mathematics department cafeteria more often :-)
Post by MGenevieve
The physicists call them wormholes. In the late
1980s Kip Thorne at Caltech and his colleagues found yet another class
of Einstein's equations
solutions
Post by MGenevieve
where these time machines were traversable.
Like an elevator connecting parallel universes, these solutions have
an up button and a down button. Under certain conditions, you can go
through them easily, just like in the movies. You can look through the
looking glass and then come back.
SA: Where would the wormhole come from in that case?
MK: We would get the wormhole by grabbing it from the vacuum, because
they're everywhere. We think that at very small distances, 10-33
centimeters, spacetime becomes foamy.
This is where it gets annoying. He begins a wild speculation here
without the slightest warning and talks as if this stuff was
established more or less as firmly as Einstein's equations. This is
very misleading and is in fact the single weakest link in entire
theoretical physics: the quantum mechanics of gravity. "Foamy"
spacetime is one way of attempting resolution of this conundrum but if
science history can be any guide it's more likely that the complete
theory of quantum gravity will be something quite unexpected and
entirely new - possibly no strings, no gravitons, no big bang, etc.
(this is exactly what happened in 1905 when Einstein cut short all the
wild speculation regarding aether by coming up with a new thing called
special relativity theory).
Post by MGenevieve
MK: [i.e., to make sure a hail of gravitons doesn't
fry you when you open or close the time machine].
Spoken as if we had a good theory of gravitons. In fact nobody knows
how to quantise general relativity - "gravitons" come from quantising
an *approximation* of general relativity, not general relativity
itself. It's probably another instance of "aether thinking". We just
don't know yet.
Post by MGenevieve
SA: Wouldn't time travel lead to paradoxes?
MK: There are about four or five main classes of paradox. The most
famous is called the Grandfather Paradox, and that's when you go back
in time and kill your parents before you were born. If you kill your
parents before you were born, how could you be born and kill your
parents before you were born? There are two schools of thought on
this. First is the Russian school. Igor Novikov [of Copenhagen
University] is a well-known cosmologist. He proposes that free will is
somehow abridged by going backwards in time.
Here I agree with Kaku that Novikov's idea is silly. Free will with
*just* oh-so-convenient properties. Do we even *know* what free will
*is*?
Post by MGenevieve
So when we postulate that we understand the laws of
everything, that means it must answer all "how" questions. It must
answer where did the universe come from, where did the big bang come
from, what is the singularity of a black hole?
That assumes the big bang really happened and that singularities
exist. These claims are based on at least two important assumptions:

1. quantum mechanics does not exist (or if it does, it does not
significantly alter general relativity in the microscale),

2. the speed of light, Planck's constant, and the gravitational
constant have never changed in the past and, moreover, they are the
same everywhere in the universe,

...and a bunch of other (technical) assumptions.
Post by MGenevieve
SA: So why do you think we haven't seen any time tourists?
MK: If you go down the road and see an anthill, do you go down to the
ants and say, "I bring you trinkets: I bring you nuclear energy, I
give you DNA technology?" The answer is no, and for the most part you
might even step on them. The distance between the ant and us,
scientifically speaking, is comparable to the distance between us and
a civilization that can manipulate the Planck energy
Again, how very convenient. Our threshold of being able to comprehend
advanced aliens just *happens* to be located at the point of the
ability to manipulate the Planck energy! This is completely pulled out
of thin air.
Post by MGenevieve
For the most part, they may not care.
Why not? Personally I would love to visit a Neanderthal family. I mean
it sincerely, it would be fascinating. And visiting someone even so
much further in the past would be even incomparably more fascinating.

Jan Bielawski

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