November 9, 2011
by Sean Carroll
At the turn of the 20th century, finding a new form of radiation could put a physicist’s career on the fast track. Wilhelm Röntgen changed the world by discovering X-rays in 1895. Soon thereafter, Ernest Rutherford and Paul Villard identified three different kinds of radiation, dubbed alpha, beta, and gamma rays, emitted by radioactive compounds. In 1903 French scientist René Blondlot added to the frenzy with his announcement of N-rays, a strangely democratic form of radiation emitted by wood, iron, living organisms—just about anything at all.
Some 300 scientific papers were written about N-rays. There was just one problem: They weren’t real. A skeptical physicist named Robert Wood visited Blondlot’s lab and secretly removed a key part of his apparatus; this had no effect on Blondlot’s perception of N-rays, showing that they were purely a product of the imagination.
Blondlot’s reversal of fortune served as a reminder that the world isn’t really full of countless kinds of radiation waiting patiently to be discovered. Nature is more parsimonious than that. Even as forms of radiation seemed to proliferate, theory was driving physics the other way, toward consolidation. X-rays and gamma rays were soon recognized as different forms of electromagnetic radiation, like radio waves and visible light but more energetic. Beta rays are simply fast-moving electrons, and alpha rays are fast-moving helium nuclei. Beneath the dazzling array of new phenomena lurked just a few simple ingredients.
The trend toward unification and simplification is a major theme of modern physics. At the same time, nature has ways of surprising us, and it pays to be watchful. We know a lot about the physics of the macroscopic world, but can we be sure that we aren’t missing one of those crucial ingredients? The answer is yes: In certain well-defined cases, we can be very sure. Physicists long ago mapped the entire electromagnetic spectrum. The modern version of the search for new kinds of radiation is the search for new forces of nature. And while there may be unknown forces waiting to be discovered, we can say with great confidence that such forces must be so feeble that only a professional physicist like me would really care.
Here’s how I can justify such a grandiose pronouncement. According to modern physics, the world is fundamentally composed of particles interacting via forces. Over the course of the 20th century, researchers discovered many new particles interacting in many different ways. But it gradually became clear that the vast majority of such particles are merely different combinations of smaller ones, and the great variety of interactions boils down to just a few forces. When the dust settled in the 1970s, we were left with two kinds of elementary particles: quarks, which group into heavier composites like protons and neutrons; and lighter particles called leptons, like the electron and the neutrino, which can move freely without bunching into heavier combinations.
July 6th, 2011
Russian scientists expect humanity to encounter alien civilisations within the next two decades, a top Russian astronomer said on Monday.
“The genesis of life is as inevitable as the formation of atoms … Life exists on other planets and we will find it within 20 years,” said Andrei Finkelstein, director of the Russian Academy of Sciences’ Applied Astronomy Institute, according to the Interfax news agency.
Speaking at an international forum dedicated to the search for extraterrestrial life, Finkelstein said 10% of the known planets circling suns in the galaxy resemble Earth.
If water can be found there, then so can life, he said, adding that aliens would most likely resemble humans with two arms, two legs and a head.
“They may have different colour skin, but even we have that,” he said.
Finkelstein’s institute runs a programme launched in the 1960s at the height of the cold war space race to watch for and beam out radio signals to outer space.
“The whole time we have been searching for extraterrestrial civilisations, we have mainly been waiting for messages from space and not the other way,” he said.
In March a Nasa scientist caused controversy after claiming to have found tiny fossils of alien bugs inside meteorites that landed on Earth.
Richard Hoover, an astrobiologist at the US space agency’s Marshall space flight centre in Alabama, said filaments and other structures in rare meteorites appear to be microscopic fossils of extraterrestrial beings that resemble algae known as cyanobacteria.
Writing in the Journal of Cosmology, Hoover claimed that the lack of nitrogen in the samples, which is essential for life on Earth, indicated they are “the remains of extraterrestrial life forms that grew on the parent bodies of the meteorites when liquid water was present, long before the meteorites entered the Earth’s atmosphere.”
Great things are expected of terahertz waves, the radiation that fills the slot in the electromagnetic spectrum between microwaves and the infrared. Terahertz waves pass through non-conducting materials such as clothes , paper, wood and brick and so cameras sensitive to them can peer inside envelopes, into living rooms and “frisk” people at distance.
The way terahertz waves are absorbed and emitted can also be used to determine the chemical composition of a material. And even though they don’t travel far inside the body, there is great hope that the waves can be used to spot tumours near the surface of the skin.
With all that potential, it’s no wonder that research on terahertz waves has exploded in the last ten years or so.
But what of the health effects of terahertz waves? At first glance, it’s easy to dismiss any notion that they can be damaging. Terahertz photons are not energetic enough to break chemical bonds or ionise atoms or molecules, the chief reasons why higher energy photons such as x-rays and UV rays are so bad for us. But could there be another mechanism at work?
The evidence that terahertz radiation damages biological systems is mixed. “Some studies reported significant genetic damage while others, although similar, showed none,” say Boian Alexandrov at the Center for Nonlinear Studies at Los Alamos National Laboratory in New Mexico and a few buddies. Now these guys think they know why.
Alexandrov and co have created a model to investigate how THz fields interact with double-stranded DNA and what they’ve found is remarkable. They say that although the forces generated are tiny, resonant effects allow THz waves to unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication. That’s a jaw dropping conclusion.
And it also explains why the evidence has been so hard to garner. Ordinary resonant effects are not powerful enough to do do this kind of damage but nonlinear resonances can. These nonlinear instabilities are much less likely to form which explains why the character of THz genotoxic effects are probabilistic rather than deterministic, say the team.
This should set the cat among the pigeons. Of course, terahertz waves are a natural part of environment, just like visible and infrared light. But a new generation of cameras are set to appear that not only record terahertz waves but also bombard us with them. And if our exposure is set to increase, the question that urgently needs answering is what level of terahertz exposure is safe.