As always, on Sundays we take a look at the biggest news from the world of physics. To receive these news to your email box, register for our email newsletter.
All the green activists have a reason to be a bit happier this week thanks to a group of physicists from Harvard. Federico Capasso and his colleagues suggested a possible way of extracting renewable energy from the Earth’s infrared emissions into outer space.
The idea is that heated by the sun, our planet is warm compared to the frigid vacuum beyond and thus radiates infrared radiation, which could be turned into electricity. To achieve this, Capasso and his research team are proposing a device that would generate electric power by releasing infrared light. “The device could be coupled with a solar cell, for example, to get extra power at night, without extra installation cost,” said the lead author Steven J. Byrnes.
CMB could act as a lab for detecting gravitons
Out of all the known fundamental forces, gravity has always been the hardest to understand and to relate to other forces. An example of this is the fact that, even though there are numerous theoretical reasons why gravitons (particles mediating gravity) should exist, they haven’t been detected yet.
One of the reasons for this is that a typical detector that could detect a single graviton would be so big that it would collapse into a black hole. For this reason, physicists have been looking for indirect methods of detecting gravitons. One of the most interesting approaches has been recently proposed by the famous cosmologist Lawrence Krauss and his colleague Frank Wilczek. In a paper titled “Using Cosmology to Establish the Quantization of Gravity”, physicists proposed that the cosmic microwave background could act as a “detector” for gravitons.
To find evidence of the existence of gravitons Krauss and Wilczek suggested studying the polarization of the microwave background. “While the realization that gravitational waves are produced by inflation is not new, and the fact that we can calculate their intensity and that this background might be measured in future polarization measurements of the microwave background is not new, an explicit argument that such a measurement will provide, in principle, an unambiguous and direct confirmation that the gravitational field is quantized is new,” he said. “Indeed, it is perhaps the only empirical verification of this very important assumption that we might get in the foreseeable future.”
For the last decade the leading hypothesis for the ultimate fate of the universe has been the so called “big rip” hypothesis. The idea behind this is that the expansion of the universe will most likely keep accelerating in the future, eventually tearing apart galaxies, planets and even subatomic particles.
Recently this idea has been challenged by Nemanja Kaloper and Antonio Padilla, who worked on a reformulation of general relativity to address the problem of vacuum energy density. In Kaloper and Padilla’s approach the cosmological constant is the historical average of the matter energy density in the universe, thus canceling out the input from quantum fluctuations. The result was a relatively small cosmological constant that now predicted the big crunch as the ultimate fate of the universe.