Archive for October 9th, 2011

October 9, 2011

How to spot a multiverse

According to Kurt Vonnegut, “The universe is a big place, perhaps the biggest.”

However, it may not be the only place, nor even the biggest.

How to spot a multiverse – physicsworld.com

How can we tell if another universe has collided with our own? Physicists in Canada and the US believe they have the answer – it would leave “a unique and highly characteristic” imprint in the microwave background that pervades the cosmos. The physicists claim that the prediction can be tested using existing and future space telescopes, which contradicts a widespread view that the existence of a multiverse is untestable.

Chuck Bennett, an astrophysicist at Johns Hopkins University in Maryland, US, who was not involved with the study, believes the prediction helps bring multiverse theory into the realms of conventional, falsifiable science. “Science relies on being able to falsify ideas through experiment or observations of nature,” he says. “The fact that these potentialities exist enables us to call this ‘science’. That, to me, is a significant statement.”

The possibility of a multiverse comes from both string theory and inflation theory, the idea that our universe underwent a rapid expansion just after the Big Bang. Inflation theory does a good job of explaining why space is fairly smooth on large scales, but researchers can’t explain what started the expansion and what stopped it. These problems have led physicists to consider the possibility that inflation could occur at other places and times, generating new universes in addition to our own.

In order for a scientific hypothesis to be more than just theoretical speculation, there need to be testable predictions. Most people have assumed that even if other universes exist in a multiverse, there would be no way that we could detect evidence of their existence. However, that’s a speculative assumption too.

Three researchers have now suggested where and how to look for evidence.

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October 9, 2011

Science begins at world’s most complex ground-based astronomy observatory

The electromagnetic spectrum comprises “radiation” of many types whose fundamental similarity is usually overlooked – from radio at the low-energy end to gamma rays at the high end. Whether one measures it in frequency, wavelength, or photon energy, the difference from one end to the other is more than 15 orders of magnitude. In principle, there is neither an upper nor lower limit, though the extremes are uncommon in nature.

All forms of EM radiation result fundamentally from the oscillations of electrical charges. All forms carry information encoded in these oscillations. Radio waves have lengths typically measured in meters. They were the first type of EM radiation used for communication, because the atmosphere is transparent to them. The length of microwaves is measured in centimeters, and although the atmosphere is mostly transparent to microwaves, they do not easily penetrate solid objects. There’s an atmospheric window for visible light and infrared radiation, with wavelengths measured in a few hundreds of nanometers. But at shorter wavelengths (ultraviolet, ~400 nm) the atmosphere again becomes opaque – fortunately for living things.

Astronomy can, in principle, be done at any wavelength, from radio to gamma rays, and there is astronomically interesting information at all wavelengths. In cases where the atmosphere is transparent to the radiation, astronomy can be done from the ground (though higher elevations are better, to be above dust, water vapor, and clouds). Otherwise it must be done from space.

One especially interesting case is the millimeter and sub-millimeter wavelength band, lying between microwaves and far infrared. Very little astronomical work has been done in this band, because the atmosphere is mostly opaque to those wavelengths, and because it has been technically difficult to build receivers for this range.

However, by using the latest technology and locating facilities at high elevations above most of the atmosphere, astronomers are about to gain access to this range for the first time.

ALMA Opens Its Eyes

Humanity’s most complex ground-based astronomy observatory, the Atacama Large Millimeter/submillimeter Array (ALMA), has officially opened for astronomers. The first released image, from a telescope still under construction, reveals a view of the Universe that cannot be seen at all by visible-light and infrared telescopes. Thousands of scientists from around the world have competed to be among the first few researchers to explore some of the darkest, coldest, furthest, and most hidden secrets of the cosmos with this new astronomical tool.

At present, around a third of ALMA’s eventual 66 radio antennas, with separations up to only 125 metres rather than the maximum 16 kilometres, make up the growing array on the Chajnantor plateau in northern Chile, at an elevation of 5000 metres. And yet, even under construction, ALMA has become the best telescope of its kind — as reflected by the extraordinary number of astronomers who requested time to observe with ALMA.

What types of astronomical questions can be investigated in this newly opened territory?

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