Medescape

Skepticism, Medicine and Science News

Water Droplets And Black Holes

Researchers at the University of Nottingham have published a paper where they use water droplets to simulate the dynamics of black holes. By using magnetic fields and electrodes they managed to spin levitating water droplets, and this produced some interresting results. As the droplet was spun at different velocities, the shape changed to form, among others, triangles,  squares and pentagons. This was due to the surface tension of the water droplet, and the scientists say this is very much like what happens at the event horizon of a black hole. The droplet experiment could hence be used to model such systems, a valuable tool in learning more about the dynamics of black holes. 

There is a video of the dropet spinning here

You spin me right round, baby. 

December 15, 2008 Posted by | Physics | , , , , , , , , , , , , , , | 1 Comment

LHC: Damage Report

Earlier this year the Large Hadron Collider was fired up, but sadly it did not take long before it broke down. In fact, only nine days after the opening CERN was forced to shut it down again due to an accident during one of the test runs. An electrical connection melted, which subsequently led to failures in the pipes containing liquid helium. Because the superconducting magnets require temperatures at about -271°C (that is only about 2 kelvins!) to function properly, they failed dramatically when the helium cooling system was damaged. When the magnets started overheating, they damaged nearby equipment with a massive burst of pressure. The forces at play were so great that several of the magnets supports were literally ripped from the ground were they were secured. 

But, they say they will be able to fix the problem, an have the LHC up and running again next summer.

December 11, 2008 Posted by | Physics | , , , , , , , , , , , | Leave a comment

Photons to Power Nanomachines

Photons are elementary particles and the basic units of light, and they are capable of exerting forces. Recently, this force was shown to be strong enough to power a small, mechanical resonator, in other words a proof of concept that may lead to a new way of powering nanoscale machines. The research was done by Hong Tang et al at Yale University. They designed and tested a device that was able to take advantage of the optical gradient force to create vibrations. The device channelled incoming light through an extremely thin passage, only about 110 nanometres wide, in a photonic circuit. This caused the material to resonate at right angles to the beam. Even though the force generated is extremely small, the researchers claim it is strong enough to power small-scale devices, and since light can easily be beamed at large areas at a time, several devices could be powered with little effort. 

A picture of the photonic circuit with one of the resonators highlighted. 

The full article can be found here.

November 29, 2008 Posted by | General Science, Physics | Leave a comment

Completely Random

Randomness is a tricky thing. It is easily found in the world around us, but if you want to actively generate, say, a random sequence of numbers, it suddenly becomes quite elusive. The more advanced hand-held calculators have a program that generates, seemingly, random numbers by using specific algorithms, but the fact is that this is not true randomness, but rather pseudorandomness. This means that although the number sequence generated may seem random to a person, a statistical analysis may reveal subtle patterns and skews in the data. For the applications of a pocket calculator, this is probably not a big deal. However, random numbers are a big part of modern cryptography, and are used in, for example, Internet banking. It would be inherently bad if your personal bank ID could be easily predicted by a large statistical analysis of ID-data, so true randomness would be an advantage for these applications.

One common pseudorandom number generator is the linear congruential generator (LCG). It uses the following algorithm to generate seemingly random numbers (click the link for a proper explanation of the equation): 

This is one of the oldest methods for generating random numbers, but it has several problems, and is subsequently not recommended when high-quality randomness is needed.  

A more recent algorithm is the Mersenne twister developed in 1997. It is by far more complicated than the LCG, but also produces a better result. It passes a lot of different tests for true randomness, including the Diehard tests and even some of the more rigorous TestU01 Crush randomness tests (go here for a brief description of these tests, and for the really daring, go here for a more….detailed document). 

To generate a truly random sequence of numbers, a hardware random number generator is required. These devices uses random processes in nature to generate randomness. These processes can range from radioactive decay, thermal noise, avalanche noise and atmospheric noise. These devices have been known to silently break over time though, and the true randomness of the numbers generated should therefore be tested from time to time. 

Another problem with these devices have been that they do not generate random numbers very fast. Typical existing devices only generate a random string of numbers with a speed of 10s-100s megabits per second. To deal with this problem, a new method for generating random numbers have recently been developed. According to the researchers, the method is capable of generating random numbers with a speed of up to 1.7 gigabits, which is 10 times faster than previous devices. The method was developed by researchers at Saitama University in Japan, and uses semiconductor lasers. The process itself is really quite simple, and consist of an external mirror that reflect some of the light back inside the laser. This feedback causes the light to oscillate randomly, and this is then converted into an AC current and further to a binary signal. In total, the process uses two of these lasers to produce a single, random number sequence. According to the researchers, Atsushi Uchida and Peter Davis, the system can be built into cryptographic systems for secure network links with very little extra cost.

November 24, 2008 Posted by | General Science, Math, Physics | , , , , , , , , , , , , , , , , , , , , , , , , , , | Leave a comment

New Method for Creating Antimatter Developed

Antimatter consists of antiparticles in the same way matter consists of particles, and the antimatter equivalent of, for example, a proton found in normal matter would be an antiproton. When matter meets antimatter the result is total annihilation and radiation in the form of gamma rays. As a result, producing antimatter is not easy, but scientists have recently developed a new method that produces far more of it than previous methods. 

The research was done by a team led by physicist Hui Chen at Lawrence Livermore National Laboratory in Livermore, California. They managed to create an estimated 100 billion positrons, which is the antimatter equivalent of electrons, by modifying and perfecting earlier methods. Previously, the team created positrons by shooting a short, ultra-intense laser at a paper-thin sheet of gold, but recent computer simulations suggested that they would be able to produce far more positrons by using a thicker sheet. So, when the paper-thin foil was substituted for a millimetre-thick one, they were able to create an estimated 100 billion positrons. 1 million of these were physically measured by their detectors, and the final number was inferred from that. In comparison, when the laboratory first created positrons about 10 years ago, they were able to detect only 100 particles. 

The laser used in the experiment ionizes and accelerates electrons that are subsequently driven through the gold sample. Here, they interact with the gold nuclei to give off packets of energy that then decay into matter and antimatter. 

When the universe was created in the Big Bang, the theory goes that equal amounts of matter and antimatter were created. However, after some time, due to a not fully understood process called bayrogenesis, there was a small shift in the matter-antimatter equilibrium, resulting in the dominance of quarks and leptones over antiquarks and antileptones. Even though the dominance was only about 1 particle per 30 million, it led to the development of the matter-based universe we know today. This new method of creating positrons will thus perhaps enable physicist to conduct more research into antimatter, and maybe improve our understanding of the early development of the universe. 

A bubble chamber-photograph showing the movement of elementary particles, including positrons. For more information, go here. Credit: CERN

November 18, 2008 Posted by | Physics | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , | 1 Comment

New Solar Breakthrough

A major problem with solar cells has been the fact that a lot of the sun light shone upon the surface of the cells is reflected and thus cannot be absorbed. Silicon cells for example only absorbs about 67.4% of the total sun light it receives, which means that 32.6% is just reflected. Well, researchers at Rensselaer Polytechnic Institute have created a nanoengineered coating material that boosts the absorptiveness of silicon cells up to 96.2%, and this increase was consistent through the entire light spectrum. Another advantage is that the coating makes the cells absorb light equally good at all angles. Normally, solar cells have to be aligned so that light hits them perpendicularly, often achieved by using mechanised rigs that moves over the course of the day. This new coating would thus allow for stationary solar cells, which would cut the costs significantly. This, in addition to higher absorption, is an important step in the right direction for achieving cost-effective solar cells. 

November 5, 2008 Posted by | General Science, Physics | , , , , , , , , , , , , , , , , , , | Leave a comment

Nobel Prize in Physics

The 2008 Nobel Prize in Physics is awarded to:

1/2 Yoichiro Nambu “for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics”

1/2 Makoto Kobayashi and Toshihide Maskawa “for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature”

Congrats!

Now, I was planning on writing something about what these discoveries actually imply, but I just found it so hard to wrap my mind around that I could not do it justice in just a couple of paragraphs. I therefore choose to give some links to sites that explains this better than I would be able to do:

New Scientists short overview of quantum physics. 

Wikipedias entry on spontaneous symmetry breaking.

And for the really daring, here‘s an article about the origins of families of quarks and leptons.

The original paper by Maskawa and Kobayashi is not free, as of yet, but can be bought here.

Edit: The major science websites have now had time to write their own articles about the science behind the award this year, and some examples can be found here and here.

October 7, 2008 Posted by | General Science, Physics | , , , , , , , , , , | Leave a comment