This is the most detailed view yet obtained of the cosmic microwave background, the light that was released after the universe finally settled down enough for the first atoms to form and for light to travel unimpeded through space. This image, released at the end of March, was produced with data from the ESA’s Planck space telescope and shows the most precise map of the slight variations present in the microwave background.
“An extreme pair of superdense stars orbiting each other has put Einstein’s general theory of relativity to its toughest test yet, and the crazy-haired physicist still comes out on top.
About 7,000 light-years from Earth, an exceptionally massive neutron star that spins around 25 times a second is orbited by a compact, white dwarf star. The gravity of this system is so intense that it offers an unprecedented testing ground for theories of gravity.”
Read the story at Space.com, or in the video above-–you do have to wait through the commercial, though.
and the University of Queensland is still performing the world’s slowest experiment.
Links: NewScientist, Catholic Herald, and University of Queensland
Image: University of Queensland
If you thought Einstein was all settled, there’s still a few wrinkles to work out. For instance, John Farrell is taking a look at the equivalence principle and new attempts to figure out just what’s going on when we say that acceleration and gravity are physically indistinguishable…
…and a scientist who claims to have found a contradiction between relativity and electrodynamics has stirred up some responses…
…and, just for fun, if you think that the Galaxy is just good for pretty pictures and intellectual puzzles, you’re clearly not a dung beetle.
Dark Universe: NASA and ESA join forces to tackle the great mysteries of dark matter and dark energy;
…while meanwhile, the mysterious shrinking of the proton remains unexplained.
Four strands–of DNA, a bit different than the textbook double-stranded kind. While this squarish form of DNA is known to be chemically possible, a new study suggest that it may actually be present in living cells, in some cases, and may play a biological role;
Three dimensions of exoplanetary atmospheres may one day be open to investigation, according to a new technique that studies the different rotation patterns of exoplanet images obtained at different wavelengths;
One billion dollars are being invested by the South Korean government into a project to make fusion a feasible means of power production.
Links: Nature, Sky & Telescope
Image: Nature/J.-P. Rodriguez
This news story has been gathering attention today: a team from Ludwig-Maximilians-Universität in Munich has created a quantum potassium gas with a temperature below absolute zero. As the claim sounds far-fetched, let’s take a closer look (with hand-drawn graphs!) and see what has happened.
Temperature is a statistical measure of the average energy of the particles in a substance. When a substance is hotter it has a higher average energy, and a lower energy when it is colder. We experience “hot” and “cold” when heat flows from the substance to us, or vice versa.
Absolute zero is the point at which a substance has no kinetic energy at all. Of course, you can’t take energy away from something that has no energy, so it follows that, seemingly, nothing can have a temperature lower than absolute zero.
But there’s more to the story.
It turns out that temperature is not simply a measure of thermal energy. It also involves entropy, a fundamental thermodynamic concept that is related to the disorder or the dispersal of energy in a system. Entropy increases as disorder increases or as energy is dispersed in a system.
Normally, temperature and entropy have a positive correlation. As energy increases, temperature increases and entropy increases. Consider a small sample of particles with a low distribution of energies. As energy is added, the temperature increases because more and more particles gain greater levels of energy. The entropy increases as well, because the particles become more distributed across the range of energy levels.
We can, therefore, think of temperature as a combined measurement of the energy and entropy of a system. As energy is added, both average energy and entropy increase together. Mathematically, this combined energy/entropy definition of temperature yields a positive number so long as the entropy and energy are both increasing.
Here’s where things get a bit stranger, though. A state of maximum entropy would occur when the particles were all evenly distributed across the range of energy levels. At this point, the particles cannot be any more dispersed than they already are. If we were to continue adding energy after this point, the system would increase in energy, but its entropy would in fact decrease because the particles would become more and more clustered at the high-energy level of the distribution. The entropy would therefore decrease, even as energy increased, as the system’s particles became less dispersed.
In this strange realm, energy and entropy have an inverse relationship. As energy increases, entropy decreases. (If we kept adding thermal energy, we’d theoretically reach a point where entropy was zero.) The upshot is that this inverse relationship between energy and entropy would mean that temperature would turn out, mathematically, to be negative.
As you can see in the high-tech graph below, temperatures in a substance with this kind of distribution would not range from zero to infinity, but would rather range from negative infinity to – 0. On the left are normal temperatures, from absolute zero up to infinity. Then the temperature scale suddenly shifts from positive infinity to negative infinity, and then tapers down to negative absolute zero (at which point there would be zero entropy.)
Of course, conditions like this don’t occur in the everyday world. Interactions between particles and between the system and its environment would normally prevent this kind of high-energy/low-entropy distribution from coming about. The team at Ludwig-Maximilians, however, was able to take the atoms of a supercold potassium gas and suspend them in a vacuum. They then used a combination of lasers and magnetic fields to cause the atoms to both obtain a high energy level and yet remain in place. Without the ability to interact with each other or their surroundings, the gas had exactly the high-energy distribution needed to find itself in the realm of negative absolute temperatures.
“After nine years of painstaking experiment, researchers in Japan reported yesterday1 that they have created a third atom of the element 113. That success, according to experts in the field, could see the element officially added to the periodic table. It would be the first artificial element to be discovered in East Asia, potentially giving the Japanese team the right to name it.
But that privilege is not assured. US and Russian researchers have also been hard at work on element 113, and say that they have created 56 atoms of it since 2003.
None of these sightings has been confirmed by the independent committee of experts appointed to rule on such matters. That shows how hard it is to prove the creation of new superheavy elements, although it also highlights the bureaucratic nature of the process set up to approve findings.”
Read the story here from Nature.
Image: public domain
Last year, astronomers reported the discovery of a pair of white dwarf stars orbiting one another at the astonishing pace of about 13 minutes per revolution. Now, a year of follow-up observations have provided indirect evidence of the power of gravitational waves in space itself.
Einstein’s view of the cosmos envisioned space itself as a sort of fabric, a substance that could be bent, twisted, warped, and otherwise affected by the matter that was in it. This was in contrast to the “emptiness” of previous Newtonian space. According to the new relativistic view, the movement of mass in space ought to produce waves in the substance of space itself, somewhat like the way the movement of a large ship produces waves in water. Ordinarily, however, these waves are so small as to be negligible. However, in high-speed, high-mass systems like that of the orbiting white dwarfs, the gravitational waves should carry away significant amounts of energy, speeding up the orbital period of the stars—and in fact, the team observing the white-dwarf pair J0651 has observed that the pair now orbits faster than it did a year ago, and by an amount in accordance with Einstein’s equations.
In the words of Warren Brown, a co-author of the study, “This result marks one of the cleanest and strongest detection of the effect of gravitational waves.”
Attempts to detect the effects of gravitational waves more directly are being carried out by the LIGO (Laser Interferometer Gravitational-Wave Observatory) project, which aims to detect gravitational waves directly by observing shifts in the phases of perpendicular laser beams travelling large distances. If a gravitational wave passes through the LIGO observatory, the laser beams will shift their relative distances slightly, causing the alignment of the laser beams to shift. The waves that move the beams will remarkably be waves travelling not through any other medium but space itself.
The white-dwarf study is available from arXiv.org: Hermes, J.J. et al. Rapid Orbital Decay in the 12.75-minute WD+WD Binary J0651+2844. (astro-ph: arXiv:1208.5051v1)
Image: D. Berry/NASA GSFC