Secret dimensions

from: CERN

In everyday life, we inhabit a space of three dimensions – a vast ‘cupboard’ with height, width and depth, well known for centuries. Less obviously, we can consider time as an additional, fourth dimension, as Einstein famously revealed. But just as we are becoming more used to the idea of four dimensions, some theorists have made predictions wilder than even Einstein had imagined.

String theory intriguingly suggests that six more dimensions exist, but are somehow hidden from our senses. They could be all around us, but curled up to be so tiny that we have never realized their existence.

Beyond the third dimension

Some string theorists have taken this idea further to explain a mystery of gravity that has perplexed physicists for some time – why is gravity so much weaker than the other fundamental forces? Does its carrier, the graviton, exist and where? The idea is that we do not feel gravity’s full effect in the everyday world. Gravity may appear weak only because its force is being shared with other spatial dimensions.

To find out whether these ideas are just products of wild imaginations or an incredible leap in understanding will require experimental evidence. But how?

High-energy experiments could prise open the inconspicuous dimensions just enough to allow particles to move between the normal 3D world and other dimensions. This could be manifest in the sudden disappearance of a particle into a hidden dimension, or the unexpected appearance of a particle in an experiment. Who knows where such a discovery could lead!

Dark secrets of the Universe

Dark secrets of the Universe

from: CERN

It’s perhaps natural that we don’t know much about how the Universe was created – after all, we were never there ourselves. But it’s surprising to realise that when it comes to the Universe today, we don’t necessarily have a much better knowledge of what is out there. In fact, astronomers and physicists have found that all we see in the Universe – planets, stars, galaxies – accounts for only a tiny 4% of it! In a way, it is not so much the visible things that define the Universe, but rather the void around them.

Cosmological and astrophysical observations indicate that most of the Universe is made up of invisible substances that do not emit electromagnetic radiation – that is, we cannot detect them directly through telescopes or similar instruments. We detect them only through their gravitational effects, which makes them very difficult to study. These mysterious substances are known as ‘dark matter’ and ‘dark energy’. What they are and what role they played in the evolution of the Universe are a mystery, but within this darkness lie intriguing possibilities of hitherto undiscovered physics beyond the established Standard Model.

Dark matter

Dark matter makes up about 26% of the Universe. The first hint of its existence came in 1933, when astronomical observations and calculations of gravitational effects revealed that there must be more 'stuff' present in the Universe than telescopes could see.

Researchers now believe that the gravitational effect of dark matter makes galaxies spin faster than expected, and that its gravitational field deviates the light of objects behind it. Measurements of these effects show that dark matter exists, and they can be used to estimate the density of dark matter even though we cannot directly observe it.

But what is dark matter? One idea is that it could contain ‘supersymmetric particles’ - hypothesized particles that are partners to those already known in the Standard Model. Experiments at the Large Hadron Collider may be able to find them.

Dark energy

Dark energy makes up approximately 70% of the Universe and appears to be associated with the vacuum in space. It is homogenously distributed throughout the Universe, not only in space but also in time - in other words, its effect is not diluted as the Universe expands.

The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the Universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the Universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of this mysterious substance exists.

Researchers build tiny batteries with viruses

Researchers build tiny batteries with viruses

Sunday, 28. January 2007, 20:57:38
Researchers build tiny batteries with viruses

April 7, 2006

MIT scientists have harnessed the construction talents of tiny viruses to build ultra-small "nanowire" structures for use in very thin lithium-ion batteries.

By manipulating a few genes inside these viruses, the team was able to coax the organisms to grow and self-assemble into a functional electronic device.

The goal of the work, led by MIT Professors Angela Belcher, Paula Hammond and Yet-Ming Chiang, is to create batteries that cram as much electrical energy into as small or lightweight a package as possible. The batteries they hope to build could range from the size of a grain of rice up to the size of existing hearing aid batteries.

Batteries consist of two opposite electrodes -- an anode and cathode -- separated by an electrolyte. In the current work, the MIT team used an intricate assembly process to create the anode.

Specifically, they manipulated the genes in a laboratory strain of a common virus, making the microbes collect exotic materials -- cobalt oxide and gold. And because these viruses are negatively charged, they can be layered between oppositely charged polymers to form thin, flexible sheets.

The result? A dense, virus-loaded film that serves as an anode.

A report on the work will appear in the April 7 issue of Science.

Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering; Chiang, the Kyocera Professor of Materials Science and Engineering (MSE); and Hammond, the Mark A. Hyman Professor of Chemical Engineering (ChE), led a team of five additional researchers.

They are MSE graduate students Ki Tae Nam (the lead author), Dong-Wan Kim, Chung-Yi Chiang and Nonglak Meethong, and ChE postdoctoral associate Pil. J. Yoo.

In their research, the MIT team altered the virus's genes so they make protein coats that collect molecules of cobalt oxide, plus gold. The viruses then align themselves on the polymer surface to form ultrathin wires. Each virus, and thus the wire, is only 6 nanometers (6 billionths of a meter) in diameter, and 880 nanometers in length.

"We can make them in larger diameters," Belcher said, "but they are all 880 nanometers in length," which matches the length of the individual virus particles. And, "once we've altered the genes of the virus to grow the electrode material, we can easily clone millions of identical copies of the virus to use in assembling our batteries.

"For the metal oxide we chose cobalt oxide because it has very good specific capacity, which will produce batteries with high energy density," meaning it can store two or three times more energy for its size and weight compared to previously used battery electrode materials. And adding the gold further increased the wires' energy density, she added.

Equally important, the reactions needed to create nanowires occur at normal room temperatures and pressures, so there is no need for expensive pressure-cooking technology to get the job done.

The work is important, too, because energy density is a vital quality in batteries. A lack of energy density -- meaning the amount of charge a battery of a given size can usefully carry -- is what has hampered development of electric cars, since existing batteries are generally too heavy and too weak to compete with gasoline as an energy source. Still, battery technology is gradually being improved and may someday even become competitive as the price of oil escalates.

"The nanoscale materials we've made supply two to three times the electrical energy for their mass or volume, compared to previous materials," the team reported.

The researchers' work was spurred by "growing evidence that 'nanostructured' materials can improve the electrochemical properties of lithium-ion batteries," compared to more conventional batteries based on older technologies, the team wrote in Science.

But to create new battery materials, Belcher noted, special control is needed so just the right amounts of the exotic materials end up exactly where they belong. Cobalt oxide "has shown excellent electrochemical cycling properties, and is thus under consideration as an electrode for advanced lithium-ion batteries."

In earlier research, Belcher and colleagues learned they could exploit the abilities of microbes to recognize the correct molecules and assemble them where they belong.

A new means of inducing this order comes from self-assembly, a tool that is commonly used now in Hammond's lab. "By harnessing the electrostatic nature of the assembly process with the functional properties of the virus, we can create highly ordered composite thin films combining the function of the virus and polymer systems," Hammond said.

This work was funded by the Army Research Office Institute of Collaborative Biotechnologies, the Institute of Soldier Nanotechnologies and the David and Lucille Packard Foundation