(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational pull on surrounding objects. Dark matter is thought to exist in a vast network of filaments throughout the universe, pulling luminous galaxies into an interconnected web of clusters, interspersed with seemingly empty voids.

Researchers at the University of Pennsylvania have measured the "weight" of these cosmic voids and filaments for the first time, showing the former are not as empty as they look.

The studies of voids and filaments are currently available on the ArXiv and were conducted by graduate student Joseph Clampitt and professor Bhuvnesh Jain of the Department of Physics and Astronomy in Penn's School of Arts & Sciences.

Gravitational lensing, the tiny distortions of distant galaxy images due to intervening matter, allows scientists to weigh galaxies by measuring how much their light bends. Voids, on the other hand, are enormous, seemingly empty spaces in the universe with scarcely any galaxies visible — an arrangement that makes measuring their contents through lensing more difficult.

While galaxies and filaments have more mass than the average regions of the universe, voids have less mass than average. This unbalanced distribution causes matter to rapidly move away from voids and towards the concentrations of mass along the cosmic filaments that lie between them.

"This means that voids act like objects with an effectively negative mass," Clampitt said, "such that even light rays bend away from them. They act roughly like concave lenses, the opposite of big galaxies, which act like convex lenses."

Clampitt and Jain detected the tiny distortions produced by voids on the images of nearly 40 million galaxies in the Sloan Digital Sky Survey. This breakthrough came just a few months after they, along with Masahiro Takada of Tokyo University's Institute for the Physics and Mathematics of the Universe, detected the lensing signal from the dark matter filaments that connect galaxies.

"The measurements came as a wonderful surprise," Jain said. "Theoretical studies had predicted that we'd have to wait for much bigger surveys well into the future to detect void lensing. Joseph's ingenious analysis techniques extracted a subtle signal no one had seen before."

The team's trick to wringing these measurements out of existing data was a new way of processing the images of galaxies. The images from the Sloan Digital Sky Survey contain distortions from the atmosphere and telescope imperfections that are larger than the cosmological signal the researchers aimed to detect. Exploiting symmetries of the lensing effect, they were able suppress these terrestrial distortions so the ones stemming from the cosmic voids and filaments were clearer.

Their results show that voids are not as empty as they appear. Dark matter and other dim structures permeate all the way to the center of the voids.

"Although the density of this matter is far less than average," Clampitt said, "it is somewhat surprising that the voids are not as empty as the galaxy distribution suggests."

"The density at the center of a typical void," Jain said, "is about half the mean density in the universe, but that still leaves the voids with an enormous deficit in mass, about a thousand trillion times the mass of the sun."

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## Benni

Albert Einstein 97

"If we are to have in the universe an average density of matter which differs from zero, however small may be that difference, then the universe cannot be quasi-Euclidean. On the contrary, the results of calculation indicate that if matter be distributed uniformly, the universe would necessarily be spherical (or elliptical). Since in reality the detailed distribution of matter is not uniform, the real universe will deviate in individual parts from the spherical, i.e. the universe will be quasi-spherical. But it will be necessarily finite. In fact, the theory supplies us with a simple connection between the space-expanse of the universe and the average density of matter in it."

Above is quoted directly from Einstein's General Theory of Relativity. This study basically confirms what Einstein states in his GR about the average density of matter & the manner of energy distribution within the limited cosmos.

## shavera

## Benni

.....this means you completely misunderstood the context of this article. There is no evidence that the universe is "not quasi-spherical", the evidence of Energy Distribution points to the conclusion that the 1st & 2nd laws of Thermodynamics apply everywhere in the universe or energy distribution cannot occur for expansion & the rotation of galaxies & orbits of planets around stars. I have lots of experience working in Thermodynamics, so don't try to distort its proven laws in favor of theories about "a flat universe", such arguments do not fit the proven laws of Thermodynamics & you can't prove otherwise.

## IMP-9

Except from numerous cosmological tests which point to a flat or just open universe. Thermodynamics does not require the universe to be closed.

## Benni

.......until you can prove the 1st & 2nd Laws of Thermodynamics do not apply to the entirety of the Universe you cannot prove this. Your statement simply proves how your limited knowledge of Thermodynamics really is. My challenge to you would be to prove how entropic systems function if they are not "closed"? Without closed boundaries "entropy" is never established & if entropy cannot be established "work" cannot be accomplished.

When the random entropic process is established, energy distribution & gravity forces are always geometrically spherical, this is what lead Einstein into the derivation of General Relativity calculations using non linear partial differential equations establishing how the universe must function in accord with "testable" laws.

## rah

## AeroSR71

Actually, you can prove it, and we have. If you measure the spots on the CMB and their within one degree in length, than you can confidently say that the global geometry of the universe is flat. WMAP has proven this to a high precision http://map.gsfc.n...ape.html

## Benni

You can prove the laws of Conservation of Energy as detailed in the 1st & 2nd Laws of Thermodynamics cannot apply to the structure of the Universe as described by Einstein? OK, you're on, prove it....you know more than Einstein, now show us your math.

......and do you even understand what they are talking about? It has nothing to do with the universe as a whole. It merely indicates that the universe is so much bigger than what they assume it to be that this is the best measurement they can come up with.

And if you'd have studied as much Thermodynamics as I have, youi'd know this is fiction.

## Antuka

Apr 18, 2014## Antuka

Apr 18, 2014## IMP-9

Fantastic, you don't even know what you're talking about. Closed and spherical do not mean the universe has an edge, it describes the global curvature of the universe. You do not need boundaries for entropy, that is complete nonsense.

## MRBlizzard

I'm not an expert on this, but I was thinking:

1) "Why is the sky dark" leads us to understand that the expansion of the universe moves the further stars away from us (cosmic expansion), which is enough to darken the night sky.

2) Arguments of a similar nature would allow us some approximation of a closed system arising from the speed of light limitation on a test space containing light and reflecting particles. If the volume was opaque, i.e., the early universe, this would reach some sort of equilibrium. The inertia of the particles also set some sort of bound on the density / outer edge of a system. Thank you for your consideration.

## Benni

OK, prove it.........let us know where to go to find the calculus for your derivations ( I presume I'll be looking for non-linear differential equations) proving entropy does not need boundaries.

## Benni

I think I understand that you are trying to determine what the boundary that defines the edge of the universe consists of?

Mass that is transformed to energy can of course revert & be transformed again to mass. Energy reaching the defining boundary of the universe may be doing just that, the boundary absorbs energy & when mass is added to it, it thus can become bigger & expands.

## IMP-9

You can't prove a negative, it's your claim, you need to prove the positive. So go ahead, prove entropy needs boundaries.

## IMP-9

You can't prove a negative, it's your claim, you need to prove the positive. So go ahead, prove entropy needs boundaries.

## Benni

.........and again you've maxed your limit of quixotic quotes. I imagine that by now you've been to WikiPedia & seen the derivations of the calculations used to produce the equations for "entropy".........and you realized energy science is far beyond your make believe world & the pseudo-science Star Trekkies mesmerize themselves with. What is your age?

## IMP-9

## Whydening Gyre

following a few laws of physics, entropy creates it's own boundaries via chirality...

## Returners

All you have to do to prove the universe is not past eternal is one step:

Imagine two photons moving in opposite directions...

That completes the lesson for the day.

## Woutertje

## Drjsa_oba