If you don't already know why a helium balloon tethered to the floor of a minivan has the power to make your jaw drop, you're going to want to see this. Seriously – set aside five minutes of your time, have a seat and watch. You won't regret it.
American Live Wire Stephen Hawking's black holes 'blunder' stirs debate CBC.ca The U-turn from Hawking, one of the pioneers of modern black hole theory, surprised his colleagues, said Amanda Peet, a theoretical physicist and associate professor at...
Physics is the natural science that involves the study of matter and its motion through space and time, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves. Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics was a part of natural philosophy along with chemistry, certain branches of mathematics, and biology, but during the Scientific Revolution in the 17th century, the natural sciences emerged as unique research programs in their own right.
You probably read about new physics discoveries all the time on this site, but that doesn't necessarily mean that you know how we got to where we are today. This brief history of physics describes how scientists have tried to ...
Bouncing neutrons probe dark energy on a table-top, measuring gravity's effects at the quantum scale finds no deviations from Newton's laws.
In this week's Physical Review Letters2, a team led by physicist Hartmut Abele at the Technical University of Vienna shows that the ordinary laws of gravity are still valid even when measured over the scale of a few micrometres. The researchers measured quantized gravitational energy levels with a precision that is 100,000 times better than in previous experiments3.
That precision is sufficient to test some proposed explanations for dark energy — the unknown force that seems to be accelerating the expansion of the Universe. Some models of dark energy put constraints on particular gravity-like forces that would subtly distort the quantum levels at these micrometre scales. “It’s really a beautiful experimental tour de force,” says Geoffrey Greene, a physicist at the University of Tennessee in Knoxville who was not involved in the study.
'Chameleon' dark energy is one such hypothesized force. It derives its name from the way the range over which it acts is reduced drastically for dense objects, which would account for why we fail to see it in Solar System measurements. Such a 'fifth force', existing alongside the known electromagnetic, strong, weak and gravitational forces, would tweak the neutrons' energy levels from those predicted by gravity alone, says Amol Upadhye, a theoretical physicist at Ewha Womans University in Seoul, who was not part of the research team.
The team’s results put a limit on how strong that force could be. “This limit is one hundred times better than the previous such limit,” says Upadhye. This does not eliminate chameleon theories as possible explanations for the dark energy, he adds. “There are still some seven orders of magnitude to cover … but this goes a long way towards closing that gap.”
The results also constrain the properties of a potential candidate for dark matter, the substance thought to make up 85% of matter in the Universe but which seems to be undetectable except for its gravitational pull at cosmic scales. Very light hypothetical particles called axions would cause a deviation from the ordinary law of gravity at short distances. The absence of such an effect in this latest study limits how strong these interactions could be.
"It's truly remarkable that experiments such as this are possible at all," says Upadhye. The researchers call the technique gravity resonance spectroscopy, because it mirrors other kinds of spectroscopy, which measure the energy states of electrons in the electromagnetic field of an atom. These have found a wide range of uses — from determining the composition of faraway galactic objects to atomic clocks. “This first application of the new technology is a big step," says Greene.
"Excellent educational content can be found on YouTube. However, not every teacher can access YouTube in his or her classroom. That's why a few years ago I compiled a big list of alternatives to YouTube. Over the years some of those sites have shut-down, started charging a fee, or have switched into another market. So this evening I went through and eliminated some sites from the list and added a few new ones."
This exploratory’s emphasis is on the introduction of Newton's 1st, 2nd and 3rd laws. At each station students are asked to perform one or more activities and answer questions based on their observations. These stations use a variety of...
A wireless transmission with 40 Gbit/s over a distance of one kilometer, achieved by researchers of theFraunhofer Institute for Applied Solid State Physics and the Karlsruhe Institute for Technology, Germany, set a new world record and ties in seamlessly with the capacity of optical fiber transmission. In the future, such radio links will be able to close gaps in providing broadband internet by supplementing the network in rural areas and places which are difficult to access.