News from Space: Universe’s Evolution Mapped in Detail

universe_expansionScientists have come up with the best computer model to date of the universe, one which maps the evolution of the cosmos in unprecedented detail. Known as Illustris, this virtual cosmos – which was created by U.S., English and German researchers using a network of supercomputers – includes details never before achieved in a simulation. All told, the numerical-based model covers the 13-billion-year evolution of the universe, beginning just 12 million years after the Big Bang took place.

While cosmologists have been developing and employing computer models of the universe for several decades, the outcome is usually a rough approximation of the universe that scientists observe in reality.  Illustris, however, has produced a universe that looks uncannily like the real on.  Among other things, it models how the universe expands, how galaxies are formed, their composition and distribution, and the mechanics of how stars and black holes are formed.

planck-attnotated-580x372Given all the recent breakthroughs in physics and cosmology, this ultra-detailed virtual model should come as no surprise. For example, this past April, scientists made not only made the first-ever observation of gravitational waves, they also processed data that is believed to be the first real indication of the existence of Dark Matter. In addition, the ESA’s Planck mission released the most detailed thermal imaging map of the universe last year that placed an accurate date on the universe’s age and confirmed the validity of the Big Bang Theory.

The Illustris creators say it represents “a significant step forward in modelling galaxy formation”, and provides a good visual representation of our ever-expanding (no pun!) understanding of the universe. A recent article that appeared last Wednesday in the journal Nature describes Illustris, and several videos (like those below) have been released that show the simulation in action. Check them out below:

 


Sources:
cbc.ca, IO9.com

New Video: Quantum Entanglement Explained

quantum-entanglement1If you’re like most people, the concept of quantum entanglements confuses and perplexes you. But considering its important to quantum science, the future of computing and (maybe, just maybe) space travel, it’s something we should all strive to understand. Luckily, this educational video produced by PHD Comics, and narrated by physicists Jeff Kimble and Chen-Lung Hung, explains it in easy-to-understand terms.

To break it down succinctly, quantum entanglement is the unusual behavior where elementary particles become linked so that when something happens to one, something happens to the other; no matter how far apart they are. This bizarre behavior of particles that become inextricably linked together is what Einstein supposedly called “spooky action at a distance.”

Understanding how this works may very well unlock the mysteries of the universe, shedding light on the unusual behavior of black holes, how gravity interacts with the other fundamental forces and yielding a Grand Unifying Theory/Theory of Everything (TOE)- and even let us circumvent “natural” barriers like the speed of light. So enjoy the video, and be sure to listen carefully. Simplified or not, this is still some pretty heavy stuff!


Source: universetoday.com

News From Space: Hawkings’ U-Turn on Black Holes

blackholeA recent paper published by Hawking, in which he reversed himself on several of his previous theories about black holes, has created quite a stir. In fact, his new found opinions on the subject have been controversial to the point that Nature News declared that there is no such thing as black holes anymore. This, however, is not quite what Hawking has claimed.

But it is clear that Hawking, one of the founders of modern theories about black holes, now believes that he he may have been when he first proposed his ideas 40 years ago. Now, he believes that black holes may NOT be the the final graveyard for matter that gets sucked in by the gravitational pull caused by a collapsing star, or that they prevent light from escaping.

stephen_hawkingBasically, he was wrong in how he attempted to resolve the paradox of black holes, because apparently they don’t exist. It all comes down to what is known as the “firewall paradox” for black holes.  The central feature of a black hole is its event horizon, the point of no return when approaching a black hole.  In Einstein’s theory of general relativity, the event horizon is where space and time are so warped by gravity that you can never escape.

 

This one-way nature of an event horizon has long been a challenge to understanding gravitational physics.  For example, a black hole event horizon would seem to violate the laws of thermodynamics, which state that nothing should have a temperature of absolute zero.  Even very cold things radiate a little heat, but if a black hole traps light then it doesn’t give off any heat and would have a temperature of zero.

quantum_entanglementThen in 1974, Stephen Hawking demonstrated that black holes do radiate light due to quantum mechanics. In quantum theory, the exact energy of a system cannot be known exactly, which means it’s energy can fluctuate spontaneously so long as its average remains constant. What Hawking demonstrated is that near the event horizon, pairs of particles can appear where one becomes trapped while the others escape as radiation.

 

 

While Hawking radiation solved one problem with black holes, it created another problem – aka. the firewall paradox. When quantum particles appear in pairs, they are entangled; but if one particle is captured by the black hole, and the other escapes, then the entangled nature of the pair is broken. In quantum mechanics, the particle pair would be described as in a “pure state”, and the event horizon would seem to break that state.

blackhole_birthLast year it was shown that if Hawking radiation is in a pure state, then either it cannot radiate in the way required by thermodynamics, or it would create a firewall of high energy particles near the surface of the event horizon.  According to general relativity, if you happen to be near the event horizon of a black hole you shouldn’t notice anything unusual.

In his latest paper, Hawking proposed a solution to this paradox by proposing that black holes don’t have event horizons. Instead they have apparent horizons that don’t require a firewall to obey thermodynamics, hence the declaration of “no more black holes” in the popular press. However, all these declarations may be a bit premature, as the problem Hawking’s sought to address may not exist at all.

black-holeIn short, the firewall paradox only arises if Hawking radiation is in a pure state. And in a paper presented last month by Sabine Hossenfelder of Cornell University shows that instead of being due to a pair of entangled particles, Hawking radiation is due to two pairs of entangled particles. One entangled pair gets trapped by the black hole, while the other entangled pair escapes.

The process is similar to Hawking’s original proposal, but the Hawking particles are not in a pure state, which means there’s no paradox to be had.  Black holes can radiate in a way that agrees with thermodynamics, and the region near the event horizon doesn’t have a firewall, just as general relativity requires.  So basically, Hawking’s proposal is a solution to a problem that doesn’t exist.

FTL_MEWith black holes, its always two step forwards, one step back. And this is hardly the only news in recent months when it comes to these mysterious and confounding phenomena. I imagine that the new theory from MIT, which states that wormholes may exist between black holes and be responsible for quantum entanglements (and resolve the problem of how gravity works) may also need revision next!

Too bad too. I was so looking forward to a universe where FTL wasn’t junk science…

Sources: universetoday.com, cbc.ca

The Future of Physics: Entanglements and Wormholes

worm_holeQuantum entanglements are one of the most bizarre aspects of quantum physics, so much so that Albert Einstein himself referred to it as “spooky action at a distance.” Basically, the concept involves two particles with each occupying multiple states at once. Until such time as one is measured, neither has a definite state, causing the other particle to instantly assume a corresponding state, even if they reside on opposite ends of the universe.

But what enables particles to communicate instantaneously – and seemingly faster than the speed of light – over such vast distances? Earlier this year, physicists proposed an answer in the form of “wormholes,” or gravitational tunnels. The group showed that by creating two entangled black holes, then pulling them apart, they formed a wormhole connecting the distant black holes.

quantum-entanglement1Now an MIT physicist has found that, looked at through the lens of string theory, the creation of two entangled quarks — the very building blocks of matter — simultaneously gives rise to a wormhole connecting the pair. The theoretical results bolster the relatively new and exciting idea that the laws of gravity that hold the universe together may not be fundamental, but may arise from quantum entanglement themselves.

Julian Sonner, a senior postdoc at MIT’s Laboratory for Nuclear Science and Center for Theoretical Physics, published the results of his study in the journal Physical Review Letters, where it appears together with a related paper by Kristan Jensen of the University of Victoria and Andreas Karch of the University of Washington. Already, the theory is causing quite the buzz for scientists and fans of sci-fi who would like to believe FTL is still possible.

quantum_field_theoryThis is certainly good news for scientists looking to resolve the fundamental nature of the universe by seeing how its discernible laws fit together. Ever since quantum mechanics was first proposed more than a century ago, the main challenge for physicists has been to explain how it correlates to gravity. While quantum mechanics works extremely well at describing how things work on the microscopic level, it remains incompatible with general relativity.

For years, physicists have tried to come up with a theory that can marry the two fields. This has ranged from proposing the existence of a subatomic particle known as the “graviton” or “dilaton”, to various Grand Unifying Theories – aka. Theory of Everything (TOE) – such as Superstring Theory, Loop Quantum Gravity, and other theoretical models to explain the interaction. But so far, none have proven successful.

gravity_well_cartography_2_by_lordsong-d5lrxwsA theory of quantum gravity would suggest that classical gravity is not a fundamental concept, as Einstein first proposed, but rather emerges from a more basic, quantum-based phenomenon. In a macroscopic context, this would mean that the universe is shaped by something more fundamental than the forces of gravity. This is where quantum entanglement could play a role.

Naturally, there is a problem with this idea. Two entangled particles, “communicating” across vast distances, would have to do so at speeds faster than that of light — a violation of the laws of physics, according to Einstein. In July, physicists Juan Maldacena of the Institute for Advanced Study and Leonard Susskind of Stanford University proposed a theoretical solution in the form of two entangled black holes.

big bang_blackholeWhen the black holes were entangled, then pulled apart, the theorists found that what emerged was a wormhole – a tunnel through space-time that is thought to be held together by gravity. The idea seemed to suggest that, in the case of wormholes, gravity emerges from the more fundamental phenomenon of entangled black holes. Following up on work by Jensen and Karch, Sonner has sought to tackle this idea at the level of quarks.

To see what emerges from two entangled quarks, he first generated entangled quarks using the Schwinger effect — a concept in quantum theory that enables one to create particles out of nothing. Sonner then mapped the entangled quarks onto a four-dimensional space, considered a representation of space-time. In contrast, gravity is thought to exist in the fifth dimension. According to Einstein’s laws, it acts to “bend” and shape space-time.

black_holeTo see what geometry may emerge in the fifth dimension from entangled quarks in the fourth, Sonner employed holographic duality, a concept in string theory. While a hologram is a two-dimensional object, it contains all the information necessary to represent a three-dimensional view. Essentially, holographic duality is a way to derive a more complex dimension from the next lowest dimension.

Using holographic duality, Sonner derived the entangled quarks, and found that what emerged was a wormhole connecting the two, implying that the creation of quarks simultaneously creates a wormhole between them. More fundamentally, the results suggest that gravity itself may emerge from quantum entanglement. On top of all that, the geometry, or bending, of the universe as described by classical gravity, may also be a consequence of entanglement.

quantum-entanglement3As Sonner put it in his report, the results are a theoretical explanation for a problem that has dogged scientists who quite some time:

There are some hard questions of quantum gravity we still don’t understand, and we’ve been banging our heads against these problems for a long time. We need to find the right inroads to understanding these questions… It’s the most basic representation yet that we have where entanglement gives rise to some sort of geometry. What happens if some of this entanglement is lost, and what happens to the geometry? There are many roads that can be pursued, and in that sense, this work can turn out to be very helpful.

Granted, the idea of riding wormholes so that we, as humans, can travel from one location in space to another is still very much science fiction, knowing that there may very well be a sound, scientific basis for their existence is good news for anyone who believes we will be able to “jump” around the universe in the near to distant future. I used to be one of them, now… I think I might just be a believer again!

USS_Enterprise_caught_in_artificial_wormhole-640x272Sources: web.mit.edu, extremetech.com