Physics News of the Week: Dark Matter, Black Holes and Invisibility

| February 1, 2015 | 0 Comments

This week we have some amazing breakthroughs from from both theoretical physicists and experimentalists. As always, here are the top 3 news stories with the corresponding links to the original articles. If you would like to receive these news stories straight to your email, register for our newsletter here.

1. Engineering Discovery Brings Invisibility Closer to Reality (Jan 26)

What can be more thrilling that the idea of invisibility? After all, everyone has dreamt of having the power of turning invisible. Well, it turns out, the idea of invisibility is not a dream, but rather a scientific fact. Scientists, in the last couple of decades, have extensively studied metamaterials, artificial materials engineered to bend electromagnetic, acoustic and other types of waves in ways not possible in nature. Metamaterials, by having this unique ability of controlling wave propagation, open the doors to invisibility. Needless to say, we are not there quite yet — invisibility of large objects remains a significant engineering challenge.

One of the main challenges associated with the exotic metamaterials (which can have a negative refractive index) is energy loss experienced by waves propagating through the material. However, Hao Xin, a professor of electrical and computer engineering at the University of Arizona, has recently made a crucial discovery bringing invisibility a step closer to reality. As Xin reported with his co-authors in an article, “Microwave Gain Medium With Negative Refractive Index”, he has developed a way to avoid the energy loss and even turn it to gain in energy for light passing through the metamaterial.

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Invisibility: not sci-fi anymore?

2. Could a New Proposed Particle Help Detect Dark Matter (Jan 29)

Researchers at the University of Southampton have proposed a new fundamental particle which could explain why no one has managed to detect ‘Dark Matter’, the elusive missing 85 per cent of the Universe’s mass. The proposed particle has a mass of 100eV/c^2, only about 0.02 per cent that of an electron. While it does not interact with light, as required for Dark Matter, it does interact surprisingly strongly with normal matter. Indeed, in stark contrast to other candidates, it may not even penetrate Earth’s atmosphere. Earth-bound detection is therefore not likely, so the researchers plan to incorporate searches into a space experiment planned by the Macroscopic quantum resonators (MAQRO) consortium, with whom they are already involved.

3. Black Holes Do Not Exist Where Space Time Doesn’t Exist (Jan 30)

Defining what a black hole is without referring to the concept of an event horizon is not possible.  The event horizon, or a “point of no return” is an essential feature of a black hole, but, according to physicists Ahmed Farag Ali, Mir Faizal, and Barun Majunder, defining and measuring the horizon might be trickier than one might expect. In their newest paper Ali, Faizal and Majunder discuss a new generalization of Einstein’s theory of gravity called “gravity’s rainbow.” This generalization, being another candidate for quantum gravity, predicts that space does not exist below a certain minimum length, and time does not exist below a certain minimum time interval.

“General relativity predicts that the geometry of space and time curves in the presence of matter, and this causes gravity to exist. Gravity’s rainbow predicts that this curvature also depends on the energy of the observer measuring it. So, in gravity’s rainbow, gravity acts differently on particles with different energies,” said Ali. Such a difference, being negligible for small masses and energies, could in principle be measured for such massive objects as black holes.

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