پنجمین عنصر به طبیعت اشاره دارد، همراه با زمین، آب و هوا یک
احتمال دیگر این است که در مجاورت انرژی
خلا یا میدان
خیالی ، چگالی آنها در طول زمان افزایش یابد که سبب شتاب گیری
کیهان شود و با سرعت بیشتری بتواند نیروی اتمی در هم بشکند و باعث
پایان کیهان در هر بیست هزار میلیون سال شود، چیزی که به آن تبدیل
بزرگ می گویند.
Cosmologists believe that some
three quarters of the universe are made up of a mysterious
dark energy which would explain its accelerated
expansion. The truth is that they do not know what it
could be, therefore they put forward possible solutions. One
is the existence of quintessence, an invisible gravitating
agent that instead of attracting, repels and accelerates the
expansion of the cosmos. From the Classical World until the
Middle Ages, this term has referred to the ether or fifth
element of nature, together with earth, fire, water and air.
Another possibility is the presence of an energy or phantom
field whose density increases with time, causing an
exponential cosmic acceleration. This would reach such speed
that it could break the nuclear forces in the atoms and end
the universe in some 20,000 million years, in what is called
the Big Rip.
Now researchers from Barcelona
and Athens suggest that both possibilities are only a mirage
in the observations and it is the quantum vacuum which could
be behind this energy that moves our universe. The
experimental data that underlie these two hypotheses comes
from satellites such as Planck of the European
Space Agency (ESA) and Wilkinson
Microwave Anisotropy Probe (WMAP) of
NASA. Observations from the two probes are essential for
solving the so-called equation of the state of dark energy,
a characterising mathematical formula, the same as that
possessed by solid, liquid and gaseous states.
Now researchers from the University of Barcelona (Spain) and
the Academy of Athens (Greece) have used the same satellite
data to demonstrate that the behaviour of dark energy does
not need to resort to either quintessence or phantom energy
in order to be explained. The details have been published in
the Monthly
Notices of the Royal Astronomical Society journal.
"Our theoretical study demonstrates that the equation of the
state of dark energy can simulate a quintessence field, or
even a phantom field, without being one in reality, thus
when we see these effects in the observations from WMAP,
Planck and other instruments, what we are seeing is an
mirage," told SINC Joan Solà, one of the authors from
University of Barcelona.
"What we think is happening is a dynamic effect of the
quantum vacuum, a parameter that we can calculate,"
explained the researcher. The concept of the quantum vacuum
has nothing to do with the classic notion of absolute
nothingness. "Nothing is more 'full' than the quantum vacuum
since it is full of fluctuations that contribute
fundamentally to the values that we observe and measure,"
Solà pointed out.
These scientists propose that dark energy is a type of
dynamical quantum vacuum energy that acts in the accelerated
expansion of our universe. This is in contrast to the
traditional static vacuum energy or cosmological constant.
The drawback with this strange vacuum is that it is the
source of problems such as the cosmological constant, a
discrepancy between the theoretical data and the predictions
of the quantum theory that drives physicists mad.
"However, quintessence and phantom fields are still more
problematic, therefore the explanation based on the dynamic
quantum vacuum could be the more simple and natural one,"
concluded Solà.
The image at the top of the page shows the results from
NASA's Galaxy Evolution Explorer and the Anglo-Australian
Telescope atop Siding Spring Mountain in Australia
confirming that dark energy (represented by purple grid) is
a smooth, uniform force that now dominates over the effects
of gravity (green grid). The observations follow from
careful measurements of the separations between pairs of
galaxies (examples of such pairs are illustrated here).
Spyros Basilakos, Joan Sola. "Effective equation of state
for running vacuum: "mirage" quintessence and phantom dark
energy". Monthly Notices of the Royal Astronomical Society
437(4), February 2014. DOI:10.1093/mnras/stt2135.
The Daily Galaxy via FECYT - Spanish Foundation
for Science and Technology
Image credit: NASA/JPL-Caltec