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Category: cosmology

Welcome to Quantum Hell.

Martin Bojowald, a professor of phycics at Penn State University, presents his fascinating ideas about “Loop Quantum Cosmology” in Once Before Time: A Whole Story of the Universe. “Will we ever,” Bojowald asks, “with a precision that meets scientific standards, see the shape of the universe before the big bang? The answer to such questions remains open. We have a multitude of indications and mathematical models for what might have happened. A diverse set of results within quantum gravity has revealed different phenomena important for revealing what happened at the big bang. But for a reliable extrapolation, parameters would be required with a precision far out of reach of current measurement accuracy.

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The cosmos came into sharper focus this week with astronomers releasing the highest resolution astronomical image yet. The product of 15 earthbound radio telescopes and a Russian satellite, the image of a black hole in a galaxy 900 millions light years away is detailed enough to show the equivalent of a US 50-cent piece on the Moon.

According to Instituto de Astrofísica de Andalucía (IAA-CSIC), which is leading the project, the image is the product of six European radio telescopes, the nine dishes of the US National Science Foundation’s Very Long Baseline Array (VLBA), and the Spektr-R satellite of the RadioAstron mission.

The data from these were combined by the Max Planck Institute for Radio Astronomy in Bonn using a technique called interferometry, which is a way of turning a number of optical or radio telescopes distributed across an area into one gigantic telescope. It does this by combining the images from these telescopes so they interfere with one another. By analyzing the amplitude and phase of the interference patterns, scientists can generate a new image of much higher resolution.

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Understanding time is one of the big open questions of physics, and it has puzzled philosophers throughout history. What is time? Why does it appear to have a direction? The concept is defined as the “arrow of time,” which is used to indicate that time is asymmetric – even though most laws of the universe are perfectly symmetric.

A potential explanation for this has now been put forward. Physicist Sean Carroll from CalTech and cosmologist Alan Guth from MIT created a simulation that shows that arrows of time can arise naturally from a perfectly symmetric system of equations.

The arrow of time comes from observing that time does indeed seem to pass for us and that the direction of time is consistent with the increase in entropy in the universe. Entropy is the measure of the disorder of the world; an intact egg has less entropy than a broken one, and if we see a broken egg, we know that it used to be unbroken. Our experience tells us that broken eggs don’t jump back together, that ice cubes melt, and that tidying up a room requires a lot more energy than making it messy.

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The universe might have started with a bang, but once the echoes faded it took quite some while until the symphony began. Between the creation of the cosmic microwave background (CMB) and the formation of the first stars, 100 million years passed in darkness. This “dark age” has so far been entirely hidden from observation, but this situation is soon to change.

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Black holes may sport a luxurious head of “hair” made up of ghostly, zero-energy particles, says a new hypothesis proposed by Stephen Hawking and other physicists.

The new paper, which was published online Jan. 5 in the preprint journal arXiv, proposes that at least some of the information devoured by a black hole is stored in these electric hairs.

Still, the new proposal doesn’t prove that all the information that enters a black hole is preserved.

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Although we experience time in one direction—we all get older, we have records of the past but not the future—there’s nothing in the laws of physics that insists time must move forward.

In trying to solve the puzzle of why time moves in a certain direction, many physicists have settled on entropy, the level of molecular disorder in a system, which continually increases. But two separate groups of prominent physicists are working on models that examine the initial conditions that might have created the arrow of time, and both seem to show time moving in two different directions.

When the Big Bang created our universe, these physicists believe it also created an inverse mirror universe where time moves in the opposite direction. From our perspective, time in the parallel universe moves backward. But anyone in the parallel universe would perceive our universe’s time as moving backward.

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A new theory from physicists at the U.S. Department of Energy’s Brookhaven National Laboratory, Fermi National Accelerator Laboratory, and Stony Brook University, which will publish online on January 18 in Physical Review Letters, suggests a shorter secondary inflationary period that could account for the amount of dark matter estimated to exist throughout the cosmos.

“In general, a fundamental theory of nature can explain certain phenomena, but it may not always end up giving you the right amount of dark matter,” said Hooman Davoudiasl, group leader in the High-Energy Theory Group at Brookhaven National Laboratory and an author on the paper. “If you come up with too little dark matter, you can suggest another source, but having too much is a problem.”

Measuring the amount of dark matter in the universe is no easy task. It is dark after all, so it doesn’t interact in any significant way with ordinary matter. Nonetheless, gravitational effects of dark matter give scientists a good idea of how much of it is out there. The best estimates indicate that it makes up about a quarter of the mass-energy budget of the universe, while ordinary matter — which makes up the stars, our planet, and us — comprises just 5 percent. Dark matter is the dominant form of substance in the universe, which leads physicists to devise theories and experiments to explore its properties and understand how it originated.

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