When you read through this
article, you will pick up several comments from me that show my position.
The importance of this result is
that it shows explicitly that the ‘pixel’ background is transparent and non
refractive to gamma rays. This happens
to be a core prediction of my own work on the metric underlying our ultimate understanding
of physics. The pixel itself only
changes curvature in combination with other pixels and will generally not
affect a passing photon as an actual particle will.
I always like good news.
Have three little photons broken theoretical physics?
They've just arrived after epic journey to Earth, and offer surprising
tale about structure of universe
ESO / A. Roquette
An artist’s impression of a gamma ray burst.
By Natalie Wolchover
Seven billion years ago, three cosmic travelers set out together on an
epic journey to Earth. They just arrived, and the trio has a surprising tale to
tell about the structure of the universe. Their story could overturn decades of
work by theoretical physicists.
But first, an introduction: Scientists have long wondered about the
nature of space and time. Albert Einstein envisioned the two concepts as an
interwoven fabric that extends smoothly and continuously throughout the
universe, warping under the weight of the matter it contains. The smoothness of
this stretchy "space-time" fabric means that no matter how closely
one inspects it, no underlying structure emerges. The fabric is completely pure
even at infinitesimal scales. [ this is where I part company with present
theory as it is absolutely wrong and what is then produced is nonsense -
arclein]
The snag in this picture of a space-time fabric is that it doesn't jive
with quantum
mechanics, the set of laws describing the bizarre behavior of subatomic
particles. To explain gravitational interactions between planets and stars, Einstein's
theory works beautifully; but try to describe quarks or electrons zipping
about on a fabric with no elemental structure, and the equations turn to
nonsense. [ my contribution was to provide the metric that overcomes this
completely - arclein]
Modern "theories of everything" try to reconcile Einstein's
big picture view of the universe, built of space-time, with the small-scale
picture of the universe described by quantum mechanics. Most of these theories,
collectively called "quantum gravity," posit that space-time must not
be smooth after all, but must instead be comprised of discrete, invisibly small
building blocks — sort of like 3-D pixels, or what scientists have dubbed a
"foam." [ I am able to exactly model the pixel assuming only rigorous
existence and then use my metric to generate the resulting space time universe
- arclein]
But real or not, such space-time pixels seemed to be permanently out of
human reach. For reasons having to do with the uncertainty that exists in the
locations of particles, theories suggest the pixels should measure the size of
the "Planck length," or about a billionth of a billionth of the
diameter of an electron. With the key evidence for quantum gravity buried at
such an inaccessible scale, physicists were at a loss for how to confirm or
refute their ideas.
Then, a paper published 15 years ago in the journal Nature proposed an
ingenious method of detecting space-time pixels. Giovanni Amelino-Camelia, a
theoretical physicist at Sapienza University in Rome, and colleagues said
the building blocks of space-time could be discovered indirectly by observing
the way light of different colors disperses as it travels through the pixels on
its journey across
the universe, just as light spreads into its component wavelengths when it
passes through the crystalline structure of a prism.
As long as one is sure all the photons, or particles of light, left
their source at exactly the same time, measuring how much photons of different
wavelengths spread out during their commute to Earth would reveal the presence,
and size, of the pixels they passed through. [ the difficulty is that
individual pixels are plausibly neutral in effect - arclein ]
Such studies hadn't been feasible, until now.
"Very few of us were suggesting that the structure of space-time
could be detected, and now 15 years later facts are proving us right,"
Amelino-Camelia told Life's Little Mysteries.
Burst of light
Seven billion years ago, 7 billion light-years away, a gamma-ray burst sent a blitz of photons tearing into space. Some of them headed for Earth.
Gamma-ray bursts occur when an extremely massive, rotating star
collapses in on itself, unleashing in less than a minute as much energy as our
sun will radiate in its entire 10-billion-year lifetime. These shockwaves of
gamma rays and other energetic photons are the brightest events in the
universe. When gamma ray bursts have occurred in the Milky Way galaxy,
scientists speculate that they might have altered Earth's climate and induced
mass extinctions. Thankfully, the bursts are so rare that they typically occur
a safe distance away — far enough that only a light mist of photons reaches our
planet.NASA's
Fermi Gamma-ray Space Telescope was launched into orbit in 2008 to
scan the skies for these mists of shockwaves past.
Robert Nemiroff, an astrophysicist at Michigan Technological
University, and colleagues recently took a look at data from a gamma-ray burst
detected by the Fermi telescope in May 2009.
"Originally we were looking for something else, but were struck
when two of the highest energy photons from this detected gamma-ray burst
appeared within a single millisecond," Nemiroff told Life's Little
Mysteries. When the physicists looked at the data more closely, they found a
third gamma ray photon within a millisecond of the other two.
Computer models
showed it was very unlikely that the photons would have been emitted by
different gamma ray bursts, or the same burst at different times. Consequently,
"it seemed very likely to us that these three photons traveled across much
of the universe together without dispersing," Nemiroff said. Despite
having slightly different energies (and thus, different wavelengths), the three
photons stayed in extremely close company for the duration of their marathon
trek to Earth.
Many things — e.g. stars, interstellar dust — could have dispersed the
photons. "But nothing that we know can undisperse gamma-ray photons,"
Nemiroff said. "So we then conclude that these photons were not dispersed.
So if they were not dispersed, then the universe left them alone. So if the
universe was made of Planck-scale quantum foam, according to some theories, it
would not have left these photons alone. So those types of Planck-scale quantum
foams don't exist." [ This actually confirms my own thinking
regarding the effective neutraliy of the pixel background – Arclein]
In other words, the photons' near-simultaneous arrival indicates that
space-time is smooth as Einstein suggested, rather than pixilated as modern
theories require — at least down to slightly below the scale of the Planck
length, a smaller scale than has ever been probed previously. The finding
"comes close to proving (that space-time is smooth) for some range of
parameters," Nemiroff said.
The finding, published in June in the journal Physical Review Letters,
threatens to set theoretical physicists back several decades by scrapping a
whole class of theories that attempt to reconcile Einstein's theory with
quantum mechanics. But not everyone is ready to jettison quantum gravity. [
It astonishes me to this day forty years
on that I dismissed quantum theory as anything other than a useful empirical
tool that was at least suggestive but otherwise a theoretical dead end -
arclein ]
Other effects?
"The analysis Nemiroff et al. are reporting is very nice and a striking confirmation that these studies of Planck-scale structure of space-time can be done, as some of us suggested long ago," said Amelino-Camelia, an originator of the idea that gamma rays could reveal the building blocks of space-time. "But the claim that their analysis is proving that space-time is 'smooth with Planck-scale accuracy' is rather naive."
To prove that Planck-scale pixels don't exist, the researchers would
have to rule out the possibility that the pixels dispersed the photons in ways
that don't depend in a straightforward way on the photons' wavelengths, he
said. The pixels could exert more subtle "quadratic" influences, for
example, or could have an effect called birefringence that depends on the
polarization of the light particles. Nemiroff and his colleagues would have to
rule out those and other possibilities. To prove the photon trio wasn't a
fluke, the results would then require independent confirmation; a second set of
simultaneous gamma-ray photons with properties similar to the first must be
observed.
If all this is accomplished, Amelino-Camelia said, "at least for
some approaches to the quantum-gravity problem, it will indeed be a case of
going back to the drawing board."
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