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

News from Space: New Map of the Universe Confirms The Big Bang!

planckAfter 15 months of observing deep space, scientists with the European Space Agency Planck mission have generated a massive heat map of the entire universe.The “heat map”, as its called, looks at the oldest light in the universe and then uses the data to extrapolate the universe’s age, the amount of matter held within, and the rate of its expansion. And as usual, what they’ve found was simultaneously reassuring and startling.

When we look at the universe through a thermal imaging system, what we see is a mottled light show caused by cosmic background radiation. This radiation is essentially the afterglow of the Universe’s birth, and is generally seen to be smooth and uniform. This new map, however, provides a glimpse of the tiny temperature fluctuations that were imprinted on the sky when the Universe was just 370,000 years old.

big_bangSince it takes light so long to travel from one end of the universe to the other, scientists can tell – using red shift and other methods – how old the light is, and hence get a glimpse at what the universe looked like when the light was first emitted. For example, if a galaxy several billion light years away appears to be dwarfish and misshapen by our standards, it’s an indication that this is what galaxies looked like several billion years ago, when they were in the process of formation.

Hence, like archaeologists sifting through sand to find fossil records of what happened in the past, scientists believe this map reveals a sort of fossil imprint left by the state of the universe just 10 nano-nano-nano-nano seconds after the Big Bang. The splotches in the Planck map represent the seeds from which the stars and galaxies formed. As is heat-map tradition, the reds and oranges signify warmer temperatures of the universe, while light and dark blues signify cooler temperatures.universe

The cooler temperatures came about because those were spots where matter was once concentrated, but with the help of gravity, collapsed to form galaxies and stars. Using the map, astronomers discovered that there is more matter clogging up the universe than we previously thought, at around 31.7%, while there’s less dark energy floating around, at around 68.3%. This shift in matter to energy ratio also indicates that the universe is expanding slower than previously though, which requires an update on its estimated age.

All told, the universe is now believed to be a healthy 13.82 billion years old. That wrinkles my brain! And also of interest is the fact that this would appear to confirm the Big Bang Theory. Though widely considered to be scientific canon, there are those who dispute this creation model of the universe and argue more complex ideas, such as the “Steady State Theory” (otherwise known as the “Theory of Continuous Creation”).

24499main_MM_Image_Feature_49_rs4In this scenario, the majority of matter in the universe was not created in a single event, but gradually by several smaller ones. What’s more, the universe will not inevitable contract back in on itself, leading to a “Big Crunch”, but will instead continue to expand until all the stars have either died out or become black holes. As Krzysztof Gorski, a member of the Planck team with JPL, put it:

This is a treasury of scientific data. We are very excited with the results. We find an early universe that is considerably less rigged and more random than other, more complex models. We think they’ll be facing a dead-end.

Martin White, a Planck project scientist with the University of California, Berkeley and the Lawrence Berkeley National Laboratory, explained further. According to White, the map shows how matter scattered throughout the universe with its associated gravity subtly bends and absorbs light, “making it wiggle to and fro.” As he went on to say:

The Planck map shows the impact of all matter back to the edge of the Universe. It’s not just a pretty picture. Our theories on how matter forms and how the Universe formed match spectacularly to this new data.

planck_satThe Planck space probe, which launched in 2009 from the Guiana Space Center in French Guiana, is a European Space Agency mission with significant contribution from NASA. The two-ton spacecraft gathers the ancient glow of the Universe’s beginning from a vantage more than a million and a half kilometers from Earth. This is not the first map produced by Planck; in 2010, it created an all-sky radiation map which scientists, using supercomputers, removed all interfering background light from to get a clear view at the deep background of the stars.

However, this is the first time any satellite has been able to picture the background radiation of the universe with such high resolution. The variation in light captured by Planck’s instruments was less than 1/100 millionth of a degree, requiring the most sensitive equipment and the contrast. So whereas cosmic radiation has appeared uniform or with only slight variations in the past, scientists are now able to see even the slightest changes, which is intrinsic to their work.planck-attnotated-580x372

So in summary, we have learned that the universe is a little older than previously expected, and that it most certainly was created in a single, chaotic event known as the Big Bang. Far from dispelling the greater mysteries, confirming these theories is really just the tip of the iceberg. There’s still the grandiose mystery of how all the fundamental laws such as gravity, nuclear forces and electromagnetism work together.

Ah, and let’s not forget the question of what transpires beneath the veil of an even horizon (aka. a Black Hole), and whether or not there is such a thing as a gateway in space and time. Finally, there’s the age old question of whether or not intelligent life exists somewhere out there, or life of any kind. But given the infinite number of stars, planets and possibilities that the universe provides, it almost surely does!

And I suppose there’s also that persistent nagging question we all wonder when we look up at the stars. Will we ever be able to get out there and take a closer look? I for one like to think so, and that it’s just a matter of time!

To boldly go!
To boldly go!

Sources: universetoday.com, (2), extremetech.com, bbc.co.uk