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| Onsigbare Krag [boodskap #116915] |
Wo, 23 April 2008 07:27  |
duif
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'God-deeltjie' is in sig, glo fisikus
Apr 10 2008 07:28:19:857AM - (SA)
Genève. - Die bekende Britse fisikus prof. Peter Higgs het dié week
gesê dit sal binnekort moontlik wees om die bestaan te bewys van 'n
onsigbare krag wat massa aan die heelal gee en dus lewe moontlik maak.
Higgs het die bestaan van dié Higgs-energieveld sowat 40 jaar gelede
reeds voorspel.
Hy glo 'n subatomiese deeltjie, bekend as die Higgs-boson, wat sy
oorsprong in dié onsigbare krag het, sal deur die Europese Organisasie
vir Kernnavorsing (Cern) se nuwe Groot Hadron-botser (GHB) in
Switserland ontdek word.
Die GHB, 'n 27 km lange sirkelvormige tonnel waarin twee strome
kerndeeltjies teen 99,9% van die spoed van lig in teenoorgestelde
rigtings geskiet en teen mekaar laat bots sal word, sal na verwagting
volgende jaar volledig in werking wees.
"Die Higgs-boson-deeltjie sal waarskynlik sommer vinnig raakgesien
word - ek is 90% seker dat die GHB dit sal ontdek," het Higgs gesê.
Die 78-jarige fisikus se pogings in die 1960's om te verduidelik
hoekom dié krag moet bestaan, het destyds by Cern op dowe ore geval.
Vandag word die bestaan van hierdie onsigbare krag wyd deur
wetenskaplikes aanvaar.
Daar word gereken die Higgs-energieveld het net millisekondes ná die
oerknal - die ontstaan van die heelal sowat 13,7 miljard jaar gelede -
ontstaan.
Met Cern se GHB sal gepoog word om omstandighede in die tyd van die
oerknal te simuleer om van die geheime van die heelal te ontsyfer.
Indien die Higgs-boson deur die GHB ontdek word, sal dit Higgs se
teorie bewys.
Die Higgs-boson is tot selfs Higgs - 'n ateïs - se spyt deur sommige
mense die "God-deeltjie" gedoop.
Hy het met sy teorie vorendag gekom om te kan verduidelik hoekom massa
verdwyn as materie in sy kleinste boustene - molekules, atome en
kwarke - opgebreek word.
Higgs het voorgestel materie was op die oomblik van die oerknal
gewigloos, en dat die meeste daarvan daarna baie skielik massa bygekry
het.
Materie moes volgens hom deur 'n energieveld beweeg wat aan deeltjies
vasgeklou en dit swaar gemaak het.
As dit nié gebeur het nie, sou materie vry in die ruimte rondgedryf
het en sterre en planete sou nooit gevorm het nie.
Higgs hoop die ontwykende Higgs-boson word voor sy 80ste verjaardag
aanstaande jaar ontdek. "As dit nié gebeur nie, sal ek baie, baie
verbaas wees." - Reuters
http://www.news24.com/Beeld/Sci-Tech/0,,3-2356_2303266,00.ht ml
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| Re: Onsigbare Krag [boodskap #116932 is 'n antwoord op boodskap #116915] |
Wo, 23 April 2008 12:18  |
Ferdi
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On Wed, 23 Apr 2008 09:27:06 +0200, Dave wrote:
> Hy glo 'n subatomiese deeltjie, bekend as die Higgs-boson, wat sy
> oorsprong in dié onsigbare krag het, sal deur die Europese Organisasie
> vir Kernnavorsing (Cern) se nuwe Groot Hadron-botser (GHB) in
> Switserland ontdek word.
Re Cern:
Geniet die onderstaande
------------------------------------------------------------ --------------------
2008: Does time travel start here?
* 09 February 2008
* From New Scientist Print Edition. Subscribe and get 4 free
issues.
* Michael Brooks
AS YOU may have heard, this will be the year. The Large Hadron
Collider - the most powerful atom-smasher ever built - will be
switched on, and particle physics will hit pay-dirt. Yet if a pair of
Russian mathematicians are right, any advances in this area could be
overshadowed by a truly extraordinary event. According to Irina
Aref'eva and Igor Volovich, the LHC might just turn out to be the
world's first time machine.
It is a highly speculative claim, that's for sure. But if Aref'eva and
Volovich are correct, the LHC's debut at CERN, the European particle
physics centre near Geneva in Switzerland, could provide a landmark in
history. That's because travelling into the past is only possible - if
it is possible at all - as far back as the creation of the first time
machine, and that means 2008 could become Year Zero: a must-see for
the discerning time traveller.
Aref'eva and Volovich are sensible and well-respected mathematicians,
based at the Steklov Mathematical Institute in Moscow, so they are not
actually suggesting that visitors from the future are imminent. What
they are saying is that since causality - the idea that effect must
follow cause - is one of the most fundamental principles of physics,
the notion that it might be tested at the LHC is worth pushing as far
as possible. Their work has yet to be recognised by a peer-reviewed
journal, but that hasn't stopped some other physicists from taking a
keen interest.
For decades, physicists have strived to come up with plausible
mechanisms for time travel. Our best description of how space and time
behave comes from Einstein's general theory of relativity, so
researchers have been looking for some flaw in it - or some as yet
unappreciated aspect - in the hope that this might do the trick. The
time machine blueprints flowing from such endeavours have never got
off the drawing board, but with the LHC we might have finally done it,
albeit accidentally.
When the LHC is running at full throttle, it will imbue each of the
particles travelling around its 27-kilometre circumference with around
7 teraelectronvolts (TeV) of energy. That may not be much in everyday
terms: 1 TeV barely matches the kinetic energy of a flying mosquito.
However, when concentrated into a subatomic particle - a trillionth
the size of a mosquito - it can do extraordinary things to the fabric
of the universe.
According to general relativity, everything in the universe is played
out on a stage that has three dimensions of space and one of time. The
strange thing about this space-time is that it gets warped by the mass
and energy of the universe's contents. This is what lies at the root
of gravitational attraction. The mass of the Earth, for instance,
distorts the surrounding space, causing everything in its vicinity to
feel a pull towards it.
It's harder to visualise the distortion of time, but it does happen to
a tiny extent in the presence of any matter or energy. What's more, a
large enough concentration of mass or energy can distort time so much
that it loops back on itself like a rubber sheet rolled up to make a
cylinder. These loops are known to physicists as "closed timelike
curves" and they ought, at least in theory, to allow us to revisit
some past moment in time.
The first person to show how a closed timelike curve could form was
the Austrian mathematician Kurt Gödel. In 1949, he demonstrated that
if the universe were spinning, relativity should allow this spin to
create conditions in which time looped back on itself. If you could
get yourself onto this loop, you would keep revisiting the same moment
until you got off.
The idea that relativity allowed time travel bothered Einstein when
Gödel showed him the results of his calculations, but it wasn't really
a problem: to the best of our knowledge, our universe is not spinning,
so time travel couldn't happen this way. Neither did the world end in
1976 when Frank Tipler of Tulane University in New Orleans, Louisiana,
showed how an extremely massive and infinitely long, fast-rotating
cylinder would create a similar opportunity to travel through time: it
is, after all, not a machine that is going to get built any time soon.
Things got more interesting in 1988, when Kip Thorne and colleagues at
the California Institute of Technology in Pasadena showed that
wormholes, or tunnels through space-time, would allow time travel
(Physical Review Letters, vol 61, p 1446). In this case a wormhole
would close a loop in time. Travelling through it is a bit like taking
a tunnel under a hill: you could get to the other side by going over
the hill, but the tunnel gets you there faster. If you choose your
wormhole carefully - or take an existing one and move its entrances
around - you could even emerge from the wormhole before you went in at
the other end.
Space-time shock
This is where the LHC comes in. It could, Aref'eva and Volovich
believe, create wormholes and so allow some form of time travel. Each
particle travelling through the LHC creates a kind of shock wave in
space-time, a gravitational ripple that distorts the space and time
around it. When two such waves are heading towards each other, the
outcome could be spectacular. Under certain conditions, the colliding
gravitational waves will rip a hole in space and time.
What those conditions are depends on the precise nature of space-time
- something we don't yet know enough about. While Einstein's
relativity theory provides a description of space-time's properties on
a large scale, this is only an approximation. Finding out just how
much energy it might take to rip holes in the fabric requires an
understanding of quantum gravity - a microscopic description of
space-time that is still beyond our reach.
Nevertheless, it is conceivable that the LHC could achieve the
conditions needed for ripping a hole in space-time. The conventional
view among physicists is that quantum gravity does not become
important until you deal with phenomena that occur at energies of
around 1016 TeV. However, a team led by Nima Arkani-Hamed from the
University of California, Berkeley, has shown that quantum gravity
could kick in at energies as low as 1 TeV (Physical Review Letters,
vol 84, p 586).
Aref'eva and Volovich's speculation about strange space-time effects
began with the realisation that the LHC might be powerful enough to
make mini black holes. Two protons colliding with a combined energy of
14 TeV might create black holes 10-18 metres in diameter. That idea is
intriguing enough, but it is only one possibility. Last year, Aref'eva
and her colleagues were again playing about with Einstein's equations,
looking for ways in which closed timelike curves might arise (see
Diagram). It was then that they came across the possibility that the
LHC might create a time machine (www.arxiv.org/abs/0710.2696). "We
realised that closed timelike curves and wormholes could also be a
result of collisions of particles," Aref'eva says.
The possibilities this raises are being taken seriously by some
physicists. "This is an interesting paper," says J. Richard Gott of
Princeton University in New Jersey, who suggested as long ago as 1991
that accelerating particles could be a route to time travel. In a
paper published at the time in Physical Review Letters, he suggested
that if super-energetic particles were aimed so that they missed each
other by a small amount, they would warp the space-time around them
enough that the interaction of their two warped space-times could form
a closed timelike curve.
In Gott's calculations, however, the final outcome wasn't clear: the
deformed space-times might well form a black hole instead of a time
machine. "The twisting of space and time required to make a time
machine are similar to that required to make a black hole," Gott says.
Now Aref'eva and Volovich have calculated that wormholes and mini
black holes have an equal chance of being created by the LHC, and that
a wormhole might even appear as frequently as every couple of seconds.
None of this means we're going to be time travelling by Christmas,
however. There are still plenty of obstacles to opening a time portal.
Not least of them is the fact that these are mini wormholes, so only
subatomic particles are small enough to travel through them. Probably
the best we can hope for is that this might provide a signature of the
wormholes' existence, Volovich says. If some of the energy from
collisions in the LHC goes missing, it could be because the collisions
created particles that have travelled into a wormhole.
The second obstacle is also to do with wormhole size. The mouth of a
wormhole is like the mouth of a rubber balloon, in that it has a
tendency to pull itself closed. The only way to avoid this is to prop
the wormhole open with some strange kind of matter that exerts a push
rather than a pull.
Is there any such stuff available? At this point, Aref'eva and
Volovich extend their speculation into the mysteries of the "dark
energy" that seems to be accelerating the expansion of the universe.
Dark energy could, they say, be just what is needed to keep the
entrance to a wormhole open, but to find out if that is even possible
we need to know the answer to another crucial question: as space-time
expands, does the density of dark energy increase, decrease or stay
constant?
When physicists look at the way expanding space-time behaves, most
interpret the observations as suggesting that the energy contained in
every cubic centimetre of space-time stays constant: it is
"persistent", not, as one might expect, "diluted" by the expansion of
the universe. There are, however, a minority of physicists who are
putting their money on a third possibility - that as space-time
expands, every cubic centimetre gains ever more energy. If dark energy
did have this "phantom" nature, space-time would contain an inherent
push that could keep the mouths of LHC wormholes open - and perhaps
even grow them big enough for people to pass through. "The
observational evidence still allows for phantom energy," says Robert
Caldwell, a physicist at Dartmouth College in Hanover, New Hampshire.
Wormhole fingerprint
Unfortunately, we just don't know yet which of the three possibilities
is right. Francisco Lobo of the University of Lisbon in Portugal is
among the minority who favour the existence of phantom energy - the
kind Aref'eva and Volovich say would prop wormholes open. However,
just as we're getting ready to go back to the future, Lobo throws his
own spanner in the works. "Even if one could, in principle, detect a
wormhole signature it does not guarantee the presence of a time
machine," he says. We might see the fingerprint of a wormhole at the
LHC, just as we might see the indicator of a black hole being formed,
but that's not enough to create a useful loop in time, Lobo reckons.
A wormhole is a loop protruding from "normal" space-time, like a
handle protruding from a teacup. If you want to turn the wormhole into
a time machine, you have to make sure the two ends of the handle meet
the cup at just the right points in time. "One would have to create a
time-shift between the wormhole mouths," Lobo says.
Various schemes have been proposed to create such a time-shift, but
all of them are exotic to say the least. Anchoring one end of a
wormhole to a neutron star might do the job, for instance. The intense
gravitational field of the star slows time, so the wormhole mouth near
the star would develop a time difference with respect to the other
mouth. It is conceivable that a time traveller could then jump in,
emerge at some point in her past, then travel through normal space to
the other end of the wormhole and hang around waiting to watch herself
jumping in. It's not the kind of operation we are going to be capable
of in the foreseeable future, as Lobo points out.
Yet who knows? Perhaps future civilisations might work out how to
stabilise and grow a wormhole, then manipulate the two mouths in order
to create a time tunnel. If a combination of fast-moving particles and
phantom energy does create a wormhole in Geneva this year, such an
advanced civilisation could find it in their history books, pinpoint
the moment, and take advantage of their technology to pay us a visit.
This possibility forces us to confront the many paradoxes that time
travel raises. The classic example is the time traveller who goes back
to kill his grandfather before his own father is conceived - thus
ensuring he is never born. Scenarios such as this prompted Stephen
Hawking to suggest in 1992 that the laws of physics actually conspire
against time travel. His "chronology protection conjecture" says that
creating loops in time that would allow time travel has a kind of
negative feedback, giving rise to physical phenomena that act to block
the loops - as if there were a causality enforcement agency.
Aref'eva doesn't fear these time cops, though. "In general relativity,
one cannot just assert that chronology should be preserved without
careful analysis," she says. There are many solutions of Einstein's
equations that permit such paradoxes to arise, she points out; it is
arrogant to declare that these situations can't be manifest in reality
just because we can't see how they will play out. Perhaps, she says,
the paradoxes will answer questions about free will or allow us to
sift through the interpretations of quantum theory. Maybe you would
find yourself unable or unwilling to kill your grandfather, or end up
in a parallel universe where killing your grandfather would make no
difference in the universe from whence you came. Until we build a time
machine, we just can't know.
For now our best hope of finding out about the limits of temporal law
enforcement is to let the physicists and engineers carry on with their
preparations at the LHC. Sure, there are unresolved issues about the
scale at which quantum gravity kicks in; we are still arguing over
whether the universe contains phantom energy; and we don't even know
if we have the likelihood of black holes and wormholes pinned down
accurately. Nevertheless, the slim possibility remains that we will
see visitors from the future in the next year.
Wouldn't it be better to be prepared than not? Perhaps now is the time
to increase the staffing levels at Geneva's tourist information
centre. And if you are a grandfather, you might want to check the
small print on your life insurance.
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| Re: Onsigbare Krag [boodskap #116939 is 'n antwoord op boodskap #116932] |
Wo, 23 April 2008 16:30 |
duif
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On Wed, 23 Apr 2008 14:18:13 +0200, Ferdi wrote:
> On Wed, 23 Apr 2008 09:27:06 +0200, Dave wrote:
>
> world's first time machine.
>
>
> The first person to show how a closed timelike curve could form was
> the Austrian mathematician Kurt Gödel. In 1949, he demonstrated that
> if the universe were spinning, relativity should allow this spin to
> create conditions in which time looped back on itself. If you could
> get yourself onto this loop, you would keep revisiting the same moment
> until you got off.
>
Dankie Ferdi, ek het dit geniet. Eintlik is dit 'n oorweldigende
skrywe. Soveel dat ek dit twee keer gelees het, en die tweede keer
heelwat stadiger as die eerste keer. En toe save ek dit, om dit weer
te lees, want dit is vreeslik interessant. Baie meer as wat die
fiktiewe ruimte reise vir die comic lesers aan die begin van die
vorige eeu moes gewees het.
> Nevertheless, the slim possibility remains that we will
> see visitors from the future in the next year.
As iemand jou nou sou besoek en sê dat hy uit die toekoms kom, en hier
is om jou te waarsku dat jy verkeerde perd speel, sal jy hom na 'n
sielkundige stuur:-)
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| Re: Onsigbare Krag [boodskap #116970 is 'n antwoord op boodskap #116939] |
Vr, 25 April 2008 16:57 |
Ferdi
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On Wed, 23 Apr 2008 18:30:24 +0200, Dave wrote:
> As iemand jou nou sou besoek en sê dat hy uit die toekoms kom, en hier
> is om jou te waarsku dat jy verkeerde perd speel, sal jy hom na 'n
> sielkundige stuur:-)
He,he..
New Scientist het ook 'n satiriese rubriek waarin hulle in die
volgende uitgawe geskryf het die PR van Cern het glo self gejoke en
gesê hulle sal 'n verwelkomingskomitee moet reg hê.
Toe sê NS hulle sal die speeches maar kort moet hou, gegee dat die
besoekers uit die toekoms sal weet wat gesê gaan word...
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