Hi My Friends: A VUELO DE UN QUINDE EL BLOG., String theory
is an incomplete mathematical approach to theoretical physics, whose
building blocks are one-dimensional extended objects called strings,
rather than the zero-dimensional point particles that form the basis
for the standard model of particle physics. By replacing the point-like
particles with strings, an apparently consistent quantum theory of
gravity emerges, which has not been achievable under quantum field
theory. Usually, the term string theory includes a group of related
superstring theories and a few related frameworks such as M-theory,
which seeks to unite them all.
String theorists have not yet completely described these theories, or
determined if or how these theories relate to the physical universe.
The elegance and flexibility of the approach, however, and a number of
qualitative similarities with more traditional physical models, have
led many physicists to suspect that such a connection is possible. In
particular, string theory may be a way to "unify" the known natural
forces (gravitational, electromagnetic, weak nuclear and strong
nuclear) by describing them with the same set of equations, as
described in the theory of everything. On the other hand, the models
have been criticized for their inability, thus far, to provide any
experimentally testable predictions.
Work on string theory is made difficult by the very complex mathematics
involved, and the large number of forms that the theories can take
depending on the arrangement of space and energy. Thus far, string
theory strongly suggests the existence of ten or eleven (in M-theory)
spacetime dimensions, as opposed to the usual four (three spatial and
one temporal) used in relativity theory; however, the theory can
describe universes with four effective (observable) spacetime
dimensions by a variety of methods. The theories also appear to
describe higher-dimensional objects than strings, called branes.
Certain types of string theory have also been shown to be equivalent to
certain types of more traditional gauge theory, and it is hoped that
research in this direction will lead to new insights on quantum
chromodynamics, the fundamental theory of the strong nuclear force.
The idea behind all string theories is that each elementary "particle"
is actually a string of a very small scale (possibly of the order of
the Planck length) which vibrates at resonant frequencies specific to
that type of particle. Thus, any elementary particle should be thought
of as a tiny vibrating object, rather than as a point. This object can
vibrate in different modes (just as a guitar string can produce
different notes), with every mode appearing as a different particle
(electron, photon, etc.). Strings can split and combine, which would
appear as particles emitting and absorbing other particles, presumably
giving rise to the known interactions between particles.
In addition to strings, this theory also includes objects of higher
dimensions, such as D-branes and NS-branes. Furthermore, all string
theories predict the existence of degrees of freedom which are usually
described as extra dimensions. String theory is thought to include some
10, 11, or 26 dimensions, depending on the specific theory and on the
point of view.
Interest in string theory is driven largely by the hope that it will
prove to be a consistent theory of quantum gravity or even a theory of
everything. It can also naturally describe interactions similar to
electromagnetism and the other forces of nature. Superstring theories
include fermions, the building blocks of matter, and incorporate
supersymmetry, a conjectured (but unobserved) symmetry of nature. It is
not yet known whether string theory will be able to describe a universe
with the precise collection of forces and particles that is observed,
nor how much freedom the theory allows to choose those details.
String theory as a whole has not yet made falsifiable predictions that
would allow it to be experimentally tested, though various planned
observations and experiments could confirm some essential aspects of
the theory, such as supersymmetry and extra dimensions. In addition,
the full theory is not yet understood. For example, the theory does not
yet have a satisfactory definition outside of perturbation theory; the
quantum mechanics of branes (higher dimensional objects than strings)
is not understood; the behavior of string theory in cosmological
settings (time-dependent backgrounds) is still being worked out;
finally, the principle by which string theory selects its vacuum state
is a hotly contested topic (see string theory landscape).
String theory is thought to be a certain limit of another, more
fundamental theory — M-theory — which is only partly defined
and is not
well understood.
Michio Kaku: Mr
Parallel Universe
Large Hadron Collider could unlock
secrets of the Big Bang
Michio Kaku: Mr
Parallel Universe
Our universe is doomed, says Professor
Michio Kaku.
Fortunately, he's
working on several escape routes: time travel, wormholes, and another
universe entirely. The physicist on a mission to 'read the mind of God'
shares his (very) deep thoughts. There is a contradiction in Professor
Michio Kaku's appearance, as if he had been drawn by a composite
artist, based on the memories of an unreliable witness. It is to do
with the smoothness of his skin being at odds with the silver hair that
flows down to his shoulders. The latter reflects his age, 61; the
former suggests he is a teenager. Perhaps he has the face he deserves.
There is kindness in his eyes and a smile tugs gently at the corners of
his mouth as he talks.
His optimism about the future of the human race knows no bounds. And as
he leads the way to the planetarium in the basement of the physics
department of New York's City University, he hums to himself and
rattles a large set of keys. He likes to give lectures down here. He
also likes to come here on his own, to gaze at the cosmos and think. He
is a deep, deep thinker. You could say he casts miles below the surface
of normal thought. He has to. His ambition is to crack the elusive
'theory of everything', the one that defeated even Einstein, his mentor
of sorts.
Today the planetarium does not lend itself to deep thinking because
there is construction work going on directly above it: a raspy drilling
sound, metal on metal, that vibrates the walls for minute-long bursts.
We try to ignore it as we talk about his work. Although he is known as
a populariser of science - he writes bestselling books with titles such
as Hyperspace and Parallel Worlds, and presents programmes for BBC4
with equally imposing titles: Time and Visions of the Future - he is
very much a practising theoretical physicist. He co-founded field
string theory, after all. We'll come to that in a minute. For now it is
enough to say that Stephen Hawking believes string theory may hold the
key to the theory of everything: that is, to the single equation that
unifies the very big (the theories of general relativity and gravity)
with the very small (quantum mechanics).
This is what the CERN
experiment in Switzerland is all about, where physicists are recreating
the conditions of the Big Bang in a Super Collider, or atom-smasher,
that is 27 kilometres in circumference.
Although Prof Kaku is awaiting the results with eagerness, he does wish
the experiment had taken place in America, as had originally been the
plan. 'In the world of theoretical physics there is a certain amount of
snobbery aimed at those of us who try to engage the public,' he says in
a soft Californian accent. 'In 1994, we were going to build one near
Dallas that would have been several times bigger than the one in
Switzerland, and therefore several times more useful. But we needed to
win Congress over to get 20 billion dollars' worth of funding for it.
On the last day of the hearings, a Congressman asked one of the
physicists if we would find God with our machine. The physicist
answered that we would discover the Higgs Boson [the sub-atomic
particle]. Our machine was duly cancelled.'
How would Michio Kaku have answered the question? 'I would have said
this machine will take us as close as is humanly possible to the
creation of the universe. This is a genesis machine. And yes, it may
even let us read the mind of God... I think they would have opened
their cheque books.' That answer would have been true to form. Prof
Kaku has a gift for communicating complex scientific ideas in a way
that lay people can understand. He argues, moreover, that good physics
should be simple, so simple that it can be understood as an image. I'll
let him explain. 'A good physicist is driven by a childlike fascination
and imagination. If we find ourselves getting jaded or bored we have to
try to recapture that childishness. Einstein used to do that. He could
be quite childish. He wanted to get access to that feeling of
wonderment. 'He also believed that if a theory couldn't be broadly
explained to a child it wasn't working. He believed that there should
be a picture behind the theory. So his special relativity, for example,
can be understood as a 16-year-old boy out-racing a light beam. Out of
this arose the image of space and time being curved like the surface of
an egg, warped by the presence of stars and planets, and finally
Einstein's general theory of relativity, a mathematical description of
the structure of the universe only one inch long on the page.' He
smiles gently and looks up at the ceiling of the planetarium. 'But for
the last 30 years of his life Einstein lost his picture. There was no
picture guiding him; he said as much in his memoirs. That is why he
wandered into various mathematical fields and got lost.'
So what is the picture guiding Kaku's string theory? 'Just that.
String. Sub-atomic particles composed of tiny vibrating strings.'
Sub-atomic particles, moreover, that can be in more than one place at a
time, if you believe, as he does, in the possibility of there being
parallel universes and (at the latest count) 11 dimensions. A further
complication is that these strings are small - inconceivably small.
This means we have no chance of observing strings with current
technology, thus rendering string theory untestable and, its critics
argue, pretty meaningless. 'But string theory has no rival,' Kaku
counters. 'It's the only game in town. It is a strange theory that goes
way beyond what Einstein was doing. It is so fantastic that some
physicists can't get their heads around it and prefer not to work on
it. I think Einstein would have got there eventually.'
The drilling and grinding above us builds in volume, the laws of
physics in action. The drilling is then joined by electric sawing. 'I'm
sorry about the reconstruction,' he shouts. 'I did ask them to work
somewhere else this morning.' Oh, that's what it is, I shout back. I
thought it was his brain heating up. He smiles again. 'Yeah, that as
well.'
The noise has now become intolerable, so we give up and walk along
corridors and up the stairs to his office. Endearingly, he is
embarrassed to show it to me because it is so untidy. But actually it
is all you could hope for: very mad professorish. There are teetering
stacks of books on the floor, powerful computers humming away, framed
citations on the wall, a blackboard covered in equations, piles of
files and the odd coffee cup. It is like a three-dimensional
representation of chaos theory.
The importance Prof Kaku places on childishness in theoretical physics
extends to science fiction, and this, in part, is the subject of his
new book, Physics of the Impossible. It argues that because there is no
law of physics preventing the existence of concepts such as time
travel, teleportation and invisibility, physics has to take their
possibility seriously. He thinks that those technologies that are
considered impossible today might become commonplace centuries, or even
decades, in the future. 'A lot of this stuff sounds like science
fiction,' he says, 'and that is no coincidence because a lot of
physicists became interested in their subject through a love of science
fiction. I used to watch a lot of it on TV. Flash Gordon was my
favourite. I realised it was the scientist who really made the series
work. With the force of his mind he could build rocket ships and ray
guns. Flash got all the credit, and the girls. But it made me realise
that physics was behind the architecture of the 20th century, with its
X-rays and television and moon landings.'
Does he ever worry that he is devoting too much of his energy to his
television work and books and neglecting his serious theoretical
calling? He smiles the gentle smile. 'Einstein played the violin. Most
physicists I know, for some strange reason, like mountain climbing. But
two of my acquaintances have died mountain climbing, so I prefer to
popularise science.'
So it's his hobby? 'I also like to figure-skate.'
All those patterns. 'Exactly. It's Newtonian physics. Objects spin
faster as they shrink, in much the same way that skaters spin faster
when bringing in their arms. That's how black holes spin, too.'
Michio Kaku was born near San Francisco, but his parents were
originally from Japan. His father was a trucker and a gardener. His
mother was a maid. Both were interned at the start of the war. 'My
parents were poor and hadn't had the benefit of a university education.
I realised early on in life that I would have to make it on my own
without help from them.' It was the death of Einstein that prompted his
interest in physics. 'It came at the right age for me because I was
eight and so I hadn't yet become distracted by girls. I wanted to know
why everyone was talking about this man with the crazy hair in such
reverential tones. In the news reports they flashed up a picture of
Einstein's desk and on it was a manuscript, which was described as his
"unfinished work". That was the moment I became hooked. I wanted to
finish that work.'
By the time he was 16, Kaku had bought 400lb of steel and 22 miles of
copper wire and had built his own atom smasher in the family garage. It
was powerful enough to pull fillings out of teeth, but the only thing
it smashed was the house. 'It broke every fuse and ruined every
circuit-breaker,' he says, shaking his head at the memory. His
experiment attracted the attention of the physicist Edward Teller, 'the
father of the hydrogen bomb'. He took Kaku under his wing and secured a
place for him to read physics at Harvard. Kaku graduated summa cum
laude in 1968, studied for a doctorate at Berkeley and then took up a
lectureship at Princeton. He later discovered that all Teller's
scholarship students were earmarked for the 'Star Wars' programme at
Los Alamos. Kaku was offered a chance to work there, but turned it
down. 'I've always thought science was about creation, not
destruction,' he says.
He gives examples in his new book of scientists who were so ahead of
their time that no one would listen to them; they would become
depressed and even, in two cases, suicidal. Is that how he feels
sometimes? 'I have felt frustrated sometimes but never depressed.
Cassandra was the priestess who was blessed with seeing the future but
cursed because no one would believe her. People laughed at us when we
discovered in the early Seventies that our strings could only vibrate
coherently in [as was thought then] 10-dimensional hyperspace. You
couldn't get a job if you were involved in string theory. It was
considered too outrageous. So a lot of my friends ended up driving
cabs. For 20 years it was like that.' With the taunts of fellow
physicists, including the Nobel laureate Richard Feynman, ringing in
his ears, Kaku started work on another theory, only to realise he was
looking at the same phenomenon, except at a higher vibration on the
string. This amounted to proof. The academic world soon stopped
laughing.
Prof Kaku may well one day achieve immortality through his work, as
Einstein did, but he would rather achieve it in the way Woody Allen
recommended: by not dying. He does have two children (the oldest at
medical school), and, he reflects, our descendants are a form of
genetic immortality. But such is his faith in science that he thinks
that, if he could stay alive for another 20 years, medical advances by
then might mean it were possible to live until 150. Perhaps with this
in mind, he took a DNA test not long ago to determine whether he might
suffer from Alzheimer's, as his grandparents did. It transpired that he
didn't have that gene.
Nevertheless, losing his mental faculties is, he says, his greatest
fear. 'We scientists play in the world of equations. They dance in our
heads constantly. If you can't do that, if you no longer have the
abstract ability to manipulate equations, you are like a painter who is
blind or a musician who is deaf.' If I asked his wife if he was easy to
live with what would she say? 'I think she would say yes, but add that
I can be distracted at times, staring out the window, glassy eyed,
playing with equations. I think she can empathise. We are hardwired to
seek beauty. I seek it in equations. My wife is a former kimono
teacher: she used to dress young women in beautiful kimono outfits, so
even if she doesn't understand my equations she can relate to my search
for beauty.'
Prof Kaku seems completely lacking in cynicism. There really is a
childish wonder to his expressive face. And take this line he has on
the future of the planet: it has no future. In five billion years' time
the sun will swell into a raging inferno, the oceans will boil and the
mountains will melt. According to the laws of physics, he says, this
scenario is inevitable. It is the law of physics that one day we must
leave the Earth or die. 'Yet it need not be a death warrant for all
human life. We could escape through a wormhole. Perhaps civilisations
billions of years ahead of ours will harness enough energy to punch a
hole in space and escape, in a hyper-dimensional space ark, to a new
universe. 'Calculations show that these gigantic machines must be the
size of star systems. Unfortunately, other calculations show that the
wormhole might only be microscopic in size. If so, an advanced
civilisation might resort to shooting molecular-sized robots, called
"nanobots", through the wormhole. These could carry the entire genetic
database of the human race. Once on the other side, these nanobots
would then create huge DNA factories to grow clones of their creators.
Although the physical bodies of these individuals will have died, their
genetic twins will live on.'
I ask if that isn't just as outlandish an idea as life after death.
'The difference is we have no mathematics to calculate life after
death. No mathematics of God. But we do have a testable mathematics, in
principle, about wormholes, even though it is all speculation billions
of years into the future. You ask me about God. Well, I would ask you
how do you define God? If he is the personal God of intervention in
people's lives, how do you write the mathematics for it? You can't. But
if you define God as harmony then you are on to something. That becomes
a testable theory. Is there harmony and symmetry in the universe? If
that is your idea of God then that is testable.'
Bill Bryson once said that Michio Kaku's theories were 'worryingly like
the sort of thoughts that would make you edge away if conveyed to you
by a stranger on a park bench'. In fact, he's infectiously
enthusiastic, and convincing, as he bubbles to find ways of expressing
his concepts in lively images. As I listen, I recall where I have read
ideas as fanciful as his before: in The Hitchhiker's Guide to the
Galaxy. He is a fan, it turns out. Met the author once. Douglas Adams,
of course, imagined a giant computer that was able to calculate the
answer to the question of life, the universe and everything. The answer
was 42. 'I love that,' Kaku says. 'It turned out that the answer on its
own was meaningless. What was needed was a proper question. Maybe one
day physics will come up with a simple answer like that. An equation.
E=mc2 is the secret of the stars, the reason why they shine and why we
have energy here in this room, but what does it actually mean to
people? It means everything and nothing, like 42.
'I think we create our own meaning, and if we do it well that brings us
happiness. It is too easy to have a guru on a mountaintop saying the
answer is this and this. That's a cop out. The meaning of life is to
struggle and find your own meaning of life.'
Information of: Frost's Medidations
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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