Cosmology: The Timeline of Everything We Know - From Quarks to Quasars

Cosmology: The Timeline of Everything We Know - From Quarks to Quasars
 

Image: Gary S Chapman/Photographer (Source)

First would be that prior to the big bang it is possible there was no previous era. Matter, energy, space and time began abruptly. Another posits that of Quantum emergence – space and time develop out of a primeval state describe by a quantum theory of gravity. Then there is the landscape multiverse of string theory – due to differences of quantum tunneling and quantum fluctuations between different energy states, this theory reorganizes a multiverse of universes in a new type of field ordered from most energetic to least energetic. As this new type of postulated field (called inflation) decays it releases the remainder of its energy and “buds” off the eternal, infinite space and expands rapidly. And lastly the cyclic universe, were the big bang is just the latest in the continual expansion, collapse and renewed expansion of space and time. The beginning is not really the beginning at all, only the latest stage in a continuing cycle.

Quantum gravity takes singularity out of black holes - space - 29 May 2013 - New Scientist

Quantum gravity takes singularity out of black holes - space - 29 May 2013 - New Scientist

Falling into a black hole may not be as final as it seems. Apply a quantum theory of gravity to these bizarre objects and the all-crushing singularity at their core disappears.

In its place is something that looks a lot like an entry point to another universe. Most immediately, that could help resolve the nagging information loss paradox that dogs black holes.

Though no human is likely to fall into a black hole anytime soon, imagining what would happen if they did is a great way to probe some of the biggest mysteries in the universe. Most recently this has led to something known as the black hole firewall paradox – but black holes have long been a source of cosmic puzzles.

According to Albert Einstein's theory of general relativity, if a black hole swallows you, your chances of survival are nil. You'll first be torn apart by the black hole's tidal forces, a process whimsically named spaghettification.

Eventually, you'll reach the singularity, where the gravitational field is infinitely strong. At that point, you'll be crushed to an infinite density. Unfortunately, general relativity provides no basis for working out what happens next. "When you reach the singularity in general relativity, physics just stops, the equations break down," says Abhay Ashtekar of Pennsylvania State University.

The same problem crops up when trying to explain the big bang, which is thought to have started with a singularity. So in 2006, Ashtekar and colleagues applied loop quantum gravity to the birth of the universe. LQG combines general relativity with quantum mechanics and defines space-time as a web of indivisible chunks of about 10^-35 metres in size. The team found that as they rewound time in an LQG universe, they reached the big bang, but no singularity – instead they crossed a "quantum bridge" into another older universe. This is the basis for the "big bounce" theory of our universe's origins.

Information paradox

Now Jorge Pullin at Louisiana State University and Rodolfo Gambini at the University of the Republic in Montevideo, Uruguay, have applied LQG on a much smaller scale – to an individual black hole – in the hope of removing that singularity too. To simplify things, the pair applied the equations of LQG to a model of a spherically symmetrical, non-rotating "Schwarzschild" black hole.

In this new model, the gravitational field still increases as you near the black hole's core. But unlike previous models, this doesn't end in a singularity. Instead gravity eventually reduces, as if you've come out the other end of the black hole and landed either in another region of our universe, or another universe altogether. Despite only holding for a simple model of a black hole, the researchers – and Ashtekar – believe the theory may banish singularities from real black holes too.

That would mean that black holes can serve as portals to other universes. While other theories, not to mention some works of science fiction, have suggested this, the trouble was that nothing could pass through the portal because of the singularity. The removal of the singularity is unlikely to be of immediate practical use, but it could help with at least one of the paradoxes surrounding black holes, the information loss problem.

A black hole soaks up information along with the matter it swallows, but black holes are also supposed to evaporate over time. That would cause the information to disappear forever, defying quantum theory. But if a black hole has no singularity, then the information needn't be lost – it may just tunnel its way through to another universe. "Information doesn't disappear, it leaks out," says Pullin.

The US military's new agony beam weapon - health - 16 May 2013 - New Scientist

Sign in to read: Pain ray: The US military's new agony beam weapon - health - 16 May 2013 - New Scientist
THE pain, when it comes, is unbearable. At first it's comparable to a hairdryer blast on the skin. But within a couple of seconds, most of the body surface feels roasted to an excruciating degree. Nobody has ever resisted it: the deep-rooted instinct to writhe and escape is too strong.
The source of this pain is an entirely new type of weapon, originally developed in secret by the US military – and now ready for use. It is a genuine pain ray, designed to subdue people in war zones, prisons and riots. Its name is Active Denial. In the last decade, no other non-lethal weapon has had as much research and testing, and some $120 million has already been spent on development in the US.
Many want to shelve this pain ray before it is fired for real but the argument is far from cut and dried. Active Denial's supporters ...

Dark energy is still the greatest cosmic mystery - physics-math - 13 May 2013 - New Scientist

Dark energy is still the greatest cosmic mystery - physics-math - 13 May 2013 - New Scientist

A new field, a new force, the power of our own ignorance? It’s two-thirds of the cosmos but it just keeps us guessing

IT IS 15 head-scratching years since we noticed that some mysterious agent is pushing the universe apart. We still don't know what it is. It is everywhere and we can't see it. It makes up more than two-thirds of the universe, but we have no idea where it comes from or what it is made of. "Nature has not been ready to give us any clues yet," says Sean Carroll, a theoretical physicist at the California Institute of Technology in Pasadena.

We do at least have a name for this most enigmatic of beasts: dark energy. Now the hunt for it is really on. Later this year, astronomers will begin a new sky survey to look for signs of the stuff among exploding stars and ancient galaxy clusters. A pack of space missions and gigantic Earth-based telescopes will soon join the chase. Meanwhile, some physicists are pursuing an unorthodox idea: that we might snare dark energy in the lab.

As yet, our knowledge of the quarry is desperately scarce. It is limited to perhaps three things. First, dark energy pushes. We first noted that in 1998, in the unexpected dimness of certain supernova explosions which told us they were further away than we expected. Space seems at some point to have begun expanding faster, as if driven outwards by a repulsive force acting against the attractive gravity of matter.

Second, there is a lot of the stuff. The motion and clustering of galaxies tells us how much matter is abroad in the universe, while the cosmic microwave background radiation emitted 380,000 years after the big bang allows us to work out the total density of matter plus energy. This second number is much bigger. According to the latest data, including microwave observations from the European Space Agency's Planck satellite, about 68 per cent of the universe is in some non-material, energetic, pushy form. That works out at about 1 joule per cubic kilometre of space.

Third, dark energy makes excellent fuel for the creative minds of physicists. They see it in hundreds of different and fantastical forms.

The tamest of these is the cosmological constant, and even that is a wild thing. It is an energy density inherent to space, which within Einstein's general theory of relativity creates a repulsive gravity. As space expands there is more and more of the stuff, making its repulsion stronger relative to the fading gravity of the universe's increasingly scattered matter. Particle physics even seems to provide an origin for it, in virtual particles that appear and disappear in the bubbling, uncertain quantum vacuum. The trouble is these particles have far too much energy – in the simplest calculation, about 10¹²⁰ joules per cubic kilometre.

Wet and wild views from the Herschel space telescope

Wet and wild views from the Herschel space telescope
Herschel, the largest infrared telescope ever launched into space, has imaged its last. Take a tour of some of its most impressive finds, from tangles of glowing gas to water-soaked worlds – and even a hole in space.