Nobel Prize for discovery of accelerating universe; mysterious origin still unknown
October 4, 2011 | 2:26 pm
The 2011 Nobel Prize in Physics has been awarded to three scientists: Saul Perlmutter, Brian Schmidt and Adam Riess. Their observations of distant exploding stars led them to the startling discovery that the expansion of the universe is accelerating. This discovery laid the groundwork for the idea that a mysterious force called dark energy, which makes up 75 percent of the universe – yet has never been detected – is fueling the acceleration.
Perlmutter, a researcher at Lawrence Berkeley National Laboratory and the University of California, headed the Supernova Cosmology Project, which began observations in 1988. Schmidt, of the Australian National University, started the High-Z Supernova Search Team in 1994; it was later joined by Riess, of Johns Hopkins University and the Space Telescope Science Institute, who played a crucial role in the observations.
Between them, the two teams found more than 50 supernovae whose light was weaker than expected – an indication not only that the universe was expanding, as had been expected, but that it was expanding ever faster. The discovery came as a complete surprise, even to the discoverers, and its announcement in 1998 profoundly shook our view of the universe. In 2007, symmetry published a scan of the page of Riess’s logbook with the data and notes that led to his Nobel Prize-winning discovery.
“I’m thrilled for Adam, Brian and Saul and the teams they have led,” said Roger Blandford, director of the Kavli Institute of Particle Astrophysics and Cosmology at SLAC National Accelerator Laboratory. “It was a great discovery, and it’s looking like a vindication of the original proposal Albert Einstein made 94 years ago.”
Several research projects are aiming to find out the origin of the force that drives the universe apart. The SDSS-II collaboration, which includes Riess, used the telescope of the Sloan Digital Sky Survey, located in New Mexico, to gather information on supernovae and the expansion of the universe. Earlier this year, SDSS scientists published the largest color image of the sky ever made.
Perlmutter is a member of the Dark Energy Survey, which will use a powerful digital camera mounted on a telescope in Chile to record 300 million galaxies. The survey will start taking data in 2012. The Dark Energy Camera, built at Fermilab in Batavia, Ill., will peer deeper into the sky and unveil more galaxies at greater distances than any previous project, including the Sloan Digital Sky Survey.
“The origin of cosmic acceleration presents a deep mystery for cosmology and fundamental physics,” said Joshua Frieman, director of the Dark Energy Survey. “Is the universe filled with gravitationally repulsive dark energy? Do we need a new theory of gravity to replace Einstein’s? The Dark Energy Survey aims to address these questions by measuring the 14-billion-year history of cosmic expansion with high precision.”
This symmetry article describes the DES in more detail. It says:
[The Dark Energy Survey] will collect data on the distances of supernovae from Earth; the large-scale clustering of galaxies; the abundance of massive galaxy clusters; and the bending of light caused by galaxies and clusters of galaxies. DES scientists will use these four methods to determine how fast the universe has been expanding and the rate at which galaxies and clusters formed over cosmic time. Two of those methods will yield answers that are independent of the role that gravity played in the evolution of the universe. The other two will provide answers that depend on the theory of gravity.
Another group of scientists is advancing plans for the Large Synoptic Survey Telescope. The LSST will meet the need for more dark energy data over its estimated 10-year lifetime by collecting some 2000 images of each of five billion galaxies. The LSST project has about 400 members and expects to grow to more than 1000. Led by a team at SLAC, LSST collaborating institutions from all over the world are working on pieces for the LSST digital camera. According to this article:
The LSST mirrors will capture and focus starlight down into the largest— and perhaps the most expensive—digital camera ever built. Six feet tall, weighing more than 6000 pounds, the LSST camera will produce 3.2-billion-pixel images and generate, on an average viewing night, about 15 terabytes of raw data, or 25,000 CDs worth. To display one of the LSST full-sky images on a television would require not just a high-definition screen, but 1500 of them.
Much of the initial funding to get the LSST rolling came from private sources, primarily the Charles Simonyi Fund for Arts and Science and from Microsoft founder Bill Gates. Long-term plans show the bulk of LSST funding coming from the National Science Foundation and the US Department of Energy.
–Glennda Chui and Kurt Riesselmann
A short version of this article first appeared in SLAC Today.
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2 Comments »
October 5th, 2011 at 8:01 am
It’s strange that you see the universe as expanding, even accelerating while expanding, while all the time it’s contracting. You’d not believe and consider me idiotic. However, it’s true. My site will tell you a bit, the rest shall be soon out in a book.
October 5th, 2011 at 12:56 pm
The Accelerating Universe caused by Decreasing Cosmic Gravity?
By Louis Nielsen, Denmark
The discovery of the accelerating Universe could be an indication of a cosmic decreasing gravity.
Observations of supernovae, belonging to distant galaxies, show that they are situated at distances that are greater than what would be expected according to current cosmological models.
This must mean that the galaxies in question have moved faster than expected.
The analysis of the observations shows that the rate of expansion of the Universe appears to vary with position. More distant objects are receding from us faster than nearby ones. That is, the expansion of the Universe was faster at earlier times than it is now in our epoch.
To save the traditional cosmological models the scientists try to introduce different solutions, supported by new and old effects, such as ‘dark energy’, ‘dark-matter’ and the re-introduction of the ‘cosmological constant’ in Einstein’s general field equations, etc.
But maybe the accelerated expansion of the Universe is an indication of a cosmic decrease of Newton’s gravitational ‘constant’.
Decrease of Cosmic Gravity and decrease of the Hubble parameter.
In my treatise “Quantum Cosmology with Decreasing Gravity” I assume that Newton’s
gravitational ‘constant’ G is a variable decreasing quantity. (You can study more in my treatise in the given link).
The decrease of G with respect to the age T of the Universe is (in the continuous approximation) given by the equation:
(1) (1/G)*(dG/dT) = – (1/3)*(1/T) (dG/dT is the time derivative of G)
In equation (1) the variable T is the actual age of the Universe. We note that G does not decrease linearly with the age of the Universe. The relative decrease of G had been faster when the Universe was younger. When the Universe came into being, during the first cosmic quantum time intervals, G decreased extremely fast, corresponding to what in the standard cosmological theory is called an ‘inflation phase’.
In our epoch G decreases very slowly, so slow that it has not hitherto been possible to measure directly.
If we could measure the relative decrease of G with very high precision then the age of the Universe can be calculated from equation (1).
Due to a decrease of the cosmic gravitational forces, the distance between two gravitating mass systems – for example two galaxies will increase as the Universe ages.
As the relative decrease of Newton’s gravitational ‘constant’ is not a linearly function of time, this is also not the case for the increase in distance between two gravitational attracting systems.
We can assume that the variable Hubble parameter H has connection to the decreasing gravitational ‘constant’ G according to the relation:
(2) H = – (1/G)*(dG/dT) = (1/3)* (1/T)
The radial velocity v of an object is then given by a modified Hubble-relation:
(3) v = – (1/G)* (dG/dT)*D = (1/3)*(1/T)*D
In equation (3) D is the distance to the object from an observer. According to equation (3) v depends on both the distance D to the object and the actual age T of the Universe when the light was emitted.
From equation (3) we see that when T was smaller then v was higher. Therefore objects in the younger Universe had moved a greater distance than calculated from the ordinary Hubble-relation.
The light from a supernova in distant galaxies will therefore be observed as fainter because it is more distant away than calculated from the ordinary Hubble-relation.
As our knowledge of the physical objects in the Universe is mainly obtained by analysis of the light emitted by the objects, it is also necessary to take into account the gravitational conditions when the light was emitted. For instance the gravitational shift of wavelength depends on the strength of the gravitational field in the position from which the light is emitted.
Also other physical effects depend on the actual value of G.
Best regards
Louis Nielsen
Denmark