quantum black holes

What we don’t know about black holes:

Of all the places in the entire universe, there is probably nowhere more mysterious than the inner workings of a black hole. This is because the two most accurate theories humans have ever created disagree about what happens in the center of one.

When a large star runs out of fuel, it no longer has the energy to resist its own gravity and starts pulling in on itself. If nothing stops the collapse before a certain point, the gravity will become so strong that not even light can escape. At this point, the star becomes a black hole; a massive celestial body that has the ability to tear apart stars.

For the most part, we have a good idea for what happens in the space around a black hole. Einstein’s theory of General Relativity tells us that black holes, as well as other massive objects, bend the fabric of space and time, leading to strange events such as time dilation. But the main point of controversy isn’t what happens around a black hole, but what happens in the very middle; the singularity.

General Relativity states that if a piece of matter falls into a black hole, it gets crushed into a single point in the center. Here, any information about what fell in is completely obliterated. However, quantum mechanics tells a different story. It is a well known rule in quantum physics that quantum information can’t be destroyed, and there must be some ambiguity to a particle’s position. Clearly, something is off here.

There are a lot of different theories that attempt to solve this riddle, often involving extra dimensions or new particles beyond the Standard Model, but none of them seem to be currently testable. But it’s possible that someday, someone will give us a new, testable theory, and it will give us insight into the inner working of black holes, and maybe even the first few moments of the Big Bang.


Ask Ethan: What Happens When A Black Hole’s Singularity Evaporates?

“What happens when a black hole has lost enough energy due to hawking radiation that its energy density no longer supports a singularity with an event horizon? Put another way, what happens when a black hole ceases to be a black hole due to hawking radiation?”

One of the most puzzling things about Black Holes is that if you wait around long enough, they’ll evaporate completely. The curved spacetime outside of the event horizon still undergoes quantum effects, and when you combine General Relativity and quantum field theory in exactly that fashion, you get a blackbody spectrum of thermal radiation out. Given enough time, a black hole will decay away completely. But what will that entail? Will an event horizon cease to exist, exposing a former black hole’s core? Will it persist right until the final moment, indicative of a true singularity? And how hot and energetic will that final evaporative state be?

Incredibly, even without a quantum theory of gravity, we can predict the answers! Find out on this week’s Ask Ethan.

unstablestar  asked:

Can black holes die? if not, then is it possible for black holes to continue merging and expanding until all matter in the universe is pulled into one big massive black hole? if black holes can die then what happens with the matter that has been pulled in by the gravitational force? would a white hole then be produced after the black hole dies?

Black holes can, in fact, die! The way they die, however, is theoretical and not proven, but it’s possible and it’s called Hawking radiation. To summarize // oversimplify (because it’s really complicated), according to quantum physics we know that particle-antiparticle pairs pop in and out of existence all the time, and usually annihilate each other almost immediately. They are able to come into existence by “borrowing” energy from the universe, and when they annihilate they “return” that energy back.

Now, what if a particle-antiparticle pair comes into being right at the edge of a black hole’s event horizon, and one particle falls in and the other escapes? Well, now you’ve just “created” one particle that’s entered the universe, and one particle that’s entered the black hole (and can’t escape). Since these two particles can’t annihilate, they can’t “return” their borrowed energy to the universe. However, you can’t just spontaneously create energy; it has to come from somewhere. That somewhere is, you guessed it, the black hole. So, the amount of energy in the black hole decreases by the amount of energy required to create the particle-antiparticle pair. Since mass and energy are equivalent (e=mc2), the mass of the black hole decreases ever so slightly - the mass of an electron, positron, or other subatomic particle. 

This process takes billions of years, and it will be another several billion years before we’re able to see black holes finish evaporating. This process is expected to be faster the smaller the black hole is - once a black hole is small enough, this process happens faster and faster, until the black hole gives off lots and lots of radiation and “explodes” (think: gamma rays, really bright, as bright or brighter than a supernova), and no longer exists. While this isn’t proven and is entirely theoretical, it’s pretty cool that black holes, the killers of the universe from which nothing should be able to escape, are slowly losing mass over billions and trillions of years, one subatomic mass at a time.

Black holes are a passage to another universe, says Stephen Hawking
Humans could escape from black holes, rather than getting stuck in them, according to a new theory proposed by Stephen Hawking.

Unfortunate space travellers won’t be able to return to their own universe, according to Hawking. But they will be able to escape somewhere else, he has proposed at a conference in Stockholm.

Black holes in fact aren’t as “black” as people thought and could be a way of getting through to an alternative universe.

“The existence of alternative histories with black holes suggests this might be possible,” Hawking said, according to a report from Stockholm University. “The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn’t come back to our universe. So although I’m keen on space flight, I’m not going to try that.

Hawking’s proposal is an attempt to answer a problem that has tormented physicists about what happens to things when they go beyond the event horizon, where even light can’t get back. The information about the object has to be preserved, scientists believe, even if the thing itself is swallowed up — and that paradox has puzzled scientists for decades.

Now Hawking has proposed that the information is stored on the boundary, at the event horizon. That means that it never makes its way into the black hole, and so never needs to make its way out again either.

That would also mean that humans might not disappear if they fall into one. They’d either stay as a “hologram” on the edge, or fall out somewhere else.

“If you feel you are in a black hole, don’t give up,” he told the audience at the end of his speech. “There’s a way out.”

Finally! Hawking finally said it! YES!

Black Holes: A Summary

I got asked this lovely question yesterday afternoon and instead of just answering it, I wanted to write a comprehensive post about black holes and their many intricacies.  So, here we go: let’s talk about black holes!


We’re going to work with General Relativity (mostly) because it simplifies these concepts down into something a lot more understandable.  General Relativity is the perception of gravity as not an inherent force, but instead caused by the curvature of spacetime, a two-dimensional interpretation of the four dimensions of Minkowski spacetime (space in x, y and z directions and time).  The extent of the curvature of spacetime is directly related to the mass of the object.  Quantum theory will come up briefly, but not in the creation of black holes nor in the analysis of their properties.  

We’re also going to assume that the black holes discussed are gravitational, static and eternal.  This means that the black holes have gravity generated by their mass, do not spin and do not deteriorate over time.  I will discuss black hole deterioration in a separate section, but that concept won’t be relevant in the earlier sections.  

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Simulating a black hole

40 years ago Stephen Hawking predicted that black holes emit a special kind of radiation. Consequently black holes are theoratically able to shrink and even vanish. This radiation arises when virtual particles (pairs of particles developing because of quantum fluctuations inside the vacuum; usually they nearly instantly destroy each other) are near the event horizon. Then the virtual particle pair gets divided: one disappears in the black hole (and its quantum mechanical information) and the other one becomes real. Thus the black hole radiates but unfortunately this radiation is so low that astronomical observations are nearly impossible.
Therefore scientists have to simulate black holes to get empirical evidence. The physicist Jeff Steinhauer of the Technion, the University of Technology of Haifa in Israel exactly did this. He realized an idea of physicist Bill Unruh with an acoustical event horizon. He uses a fog made of rubidium atoms which is only slightly above the absolute zero. Because they are trapped inside an electromagnetic field these atoms become a Bose-Einstein Condensate. Inside of this condensate the acoustic velocity is only a half millimeter per second. With the help of accelerating some above this speed an artificial event horizon is created. The low temperatures lead to quantum fluctuations: pairs of phonons develop. In the simulation these pairs also get divided: one gets caught by the supersonic event horizon; the other one becomes some kind of Hawking radiation.
It is still not sure if this experiment really simulates black holes. According to Ulf Leonhardt it does not proof for sure that the two phonons are entangled. Thus it is not sure if the pairs arised out of one fluctuation. Leonhardt even doubts that the fog of atoms is a real Bose-Einstein Condensate. Leonard Susskind thinks this experiment does not reveal the mysteries of black holes: for instance it does not explain the information paradox, because acoustic black holes do not destroy information.

Single particles of light (photons) simulate quantum particles travelling through time were just used by scientists from the University of Queensland, Australia. They showed that one photon can pass through a wormhole and then interact with its older self.

The study of closed timelike curves (CTC’s) provides valuable insight into particles that can loop back on themselves, breaking free of linear time. One aspect of general relativity that has long intrigued physicists is the relative ease with which one can find solutions to Einstein’s field equations that contain closed timelike curves (CTCs) causal loops in space–time that return to the same point in space and time.

Closed timelike curves are a necessary concept to understand this experiment.
CTCs are used to simulate powerful gravitational fields, like the ones produced by a spinning black hole, that could theoretically (based on Einstein’s theory of general relativity), warp the fabric of existence so that space-time bends back on itself. This creates a CTC, almost like a pathway to travel back through time. The source of time travel speculation lies in the fact that our best physical theories seem to contain no prohibitions on traveling backward through time. The feat should be possible based on Einstein’s theory of general relativity, which describes gravity as the warping of spacetime by energy and matter. An extremely powerful gravitational field, such as that produced by a spinning black hole, could in principle profoundly warp the fabric of existence so that spacetime bends back on itself. This would create a “closed timelike curve,” or CTC, a loop that could be traversed to travel back in time.

in our silent moments
you ask me
what i’m thinking

i grasp for words
often remaining silent
as my tongue gets tied
into shy
and playful knots
begin to wander
and i cautiously ponder
yet all i can give
are mere glimpses
of the dream that exists
when my eyes are closed

let me try to convey
all i long to say…

i imagine walking the rooms
inside my mind
with you
who understands
my every weakness
seeing them as strength
i look upon you
who fills the quantum
celestial gap
the black hole
within my heart
a universe
this niche missing
from reality
i envision a home
and complete
with all the facets
of an unblemished love
and displayed
within each photo
that is hung on the walls
love thrives inside
the pages of every book
that rests
upon the dusty shelves
for us to read
letter by letter
i imagine that
on our darkest days
when lost in life’s maze
and one may not feel like reading
the other will speak
the words aloud
so very slowly
with compassion
the sound will resonate
and saturate
our home
this love will linger about
in the air we breathe
and swirling
captured under blankets
in-between the bedsheets
it will be piling high
on the harvest table
the vital nourishment placed
bountifully upon each plate
the sustenance
in abundance
that will feed our body
heart and soul
i clearly see you
and vulnerable
yet holding inside
the courage of lion heart
within your own wounds
your weakness
your greatest
i see you
who requires to be loved
as deeply you love
who looks into my eyes
and desires not to remedy
one single thing
what is yours
i see only you
the man who is willing
as i am willing
to cross even the most
treacherous valleys
climb the highest mountains
that we might enjoy the view
both together

in the depths
of your eyes
i see sheer beauty
within every scar
they hide
i see brilliance
in the divine plan
of the past
that lead you here

i am left looking into us
reveling in the perfection
that is chaotically scattered
like diamonds among the stones
that lay upon the path
we walked
before finding




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Still not satisfied? Relive the previous year in science!

What Is Dark Matter?

There is as yet no answer to this question, but it is becoming increasingly clear what it is not. Detailed observations of the cosmic microwave background with the WMAP satellite show that the dark matter cannot be in the form of normal, baryonic matter, that is, protons and neutrons that compose stars, planets, and interstellar matter. That rules out hot gas, cold gas, brown dwarfs, red dwarfs, white dwarfs, neutron stars and black holes.

Black holes would seem to be the ideal dark matter candidate, and they are indeed very dark. However stellar mass black holes are produced by the collapse of massive stars which are much scarcer than normal stars, which contain at most one-fifth of the mass of dark matter. Also, the processes that would produce enough black holes to explain the dark matter would release a lot of energy and heavy elements; there is no evidence of such a release.

The non-baryonic candidates can be grouped into three broad categories: hot, warm and cold. Hot dark matter refers to particles, such as the known types of neutrinos, which are moving at near the speed of light when the clumps that would form galaxies and clusters of galaxies first began to grow. Cold dark matter refers to particles that were moving slowly when the pre-galactic clumps began to form, and warm dark matter refers to particles with speeds intermediate between hot and cold dark matter.

This classification has observational consequences for the size of clumps that can collapse in the expanding universe. Hot dark matter particles are moving so rapidly that clumps with the mass of a galaxy will quickly disperse. Only clouds with the mass of thousands of galaxies, that is, the size of galaxy clusters, can form. Individual galaxies would form later as the large cluster-sized clouds fragmented, in a top-down process.

In contrast, cold dark matter can form into clumps of galaxy-sized mass or less. Galaxies would form first, and clusters would form as galaxies merge into groups, and groups into clusters in a bottom-up process.

The observations with Chandra show many examples of clusters being constructed by the merger of groups and sub-clusters of galaxies. This and other lines of evidence that galaxies are older than groups and clusters of galaxies strongly support the cold dark matter alternative. The leading candidates for cold dark matter are particles called WIMPs, for Weakly Interacting Massive Particles. WIMPs are not predicted by the so-called Standard Model for elementary particles, but attempts to construct a unified theory of all elementary particles suggest that WIMPs might have been produced in great numbers when the universe was a fraction of a second old.

A typical WIMP is predicted to be at least 100 times as massive as a hydrogen atom. Possible creatures in the zoo of hypothetical WIMPs are neutralinos, gravitinos, and axinos. Other possibilities that have been discussed include sterile neutrinos and Kaluza-Klein excitations related to extra dimensions in the universe.


The Huge-LQG (Large Quasar Group)

The Huge-LQG is a possible structure that could be one of the largest in the known universe. Having originally been identified as the largest, the Hercules-Corona Borealis Great Wall is bigger at 10 billion light years.

The Huge-LQG consists of 73 quasars, a quasar being a class of active galactic nuclei is essentially a superheated region of gas and dust that surrounds a supermassive black hole typically being 10-10,000 times the size of the Schwarzschild radius of the black hole. The existence of this structure defies Einstein’s cosmological principal which states that at large scales, the universe is approximately homogenous (meaning that the fluctuation in matter density throughout space can be considered small). It’s around 9 billion light years away from us, has a length of 1.24 gigaparsecs which is 4.0443 billion light years and a solar mass of 6.1 quintillion (that’s 6.1 quintillion times the mass of our sun and our sun is approximately 2 nonillion kg’s)!


Has LIGO already discovered evidence for quantum gravity?

“According to Einstein, a black hole’s event horizon should have specific properties, determined by its mass, charge and angular momentum. In most ideas of what quantum gravity would look like, that event horizon would be no different. Some models, however, predict notably different event horizons, and it’s those departure models that offer a glimmer of hope for quantum gravity. If we see a difference from what Einstein’s theory predicts, perhaps we can uncover not only that gravity must be a quantum theory, but what properties quantum gravity actually has.”

In 2015, LIGO collected data from a total of three candidate gravitational wave events, all of which were announced and released in 2016. These events verified the great prediction of Einstein: that decaying orbits should emit gravitational radiation with specific magnitudes and frequencies that distort spacetime in a particular, measurable way. But some quantum gravitational ideas modify the event horizon and the space just outside of it, creating the possibility that merging black holes will exhibit “echoes” superimposed atop the Einsteinian signal. For the first time, a team of theorists dove into the LIGO data to test this, and may have just uncovered the first evidence for quantum gravity in our Universe.

With the next run of LIGO already underway, be prepared to find out that gravity may be inherently quantum after all!

What Would Happen To You If You Fell Into A Black Hole?

Black holes are without question some of the strangest places in the universe. So massive that they hideously deform space and time, so dense that their centers are called “points at infinity,” and pitch-black because not even light can escape them, it isn’t surprising that so many people wonder what it would be like to visit one.

It’s not exactly a restive vacation spot, as it turns out.

If you were to take a step into a black hole, your body would most closely resemble “toothpaste being extruded out of the tube,” said Charles Liu, an astrophysicist who works at the American Museum of Natural History’s Hayden Planetarium.

Liu said that when an object crosses a black hole’s “event horizon” — its outer boundary, or point of no return — the same physics that causes Earth’s ocean tides begins to take effect. Gravity’s strength decreases with distance, so the moon pulls on the side of the Earth closer to it a bit more vigorously than the side farther from it, and as a result, Earth elongates ever so slightly in the direction of the moon. The land is sturdy, so it doesn’t move much, but the water on Earth’s surface is fluid, so it flows along the elongated axis. “That’s the tidal interaction,” he said.

Rising tides are about as calming a scene as there is. A human toeing the line of a black hole? Not so much.

Near a black hole roughly the size of Earth, tidal forces are magnified off the scale. Swan-diving into one, the top of your head would feel so much more gravitational pull than the tips of your toes that you would be stretched, longer and longer. “Sir Martin Rees coined the term ‘spaghettification,’ which is a perfectly good way to put it. You eventually become a stream of subatomic particles that swirl into the black hole,” Liu said.

Because your brain would dissociate into its constituent atoms almost instantly, you’d have little opportunity to soak in the scenery at the threshold of an Earth-size black hole.

However, if you’re dead-set on visiting a space-time singularity, we recommend going big; bigger black holes have less extreme surfaces. “If you had a black hole the size of our solar system, then the tidal forces at the event horizon … are not quite that strong. So you could actually maintain your structural integrity,” Liu said.

In that case, you would get to experience the effects of the curvature of space-time, predicted by Einstein’s general theory of relativity, firsthand.

“First of all, you approach the speed of light as you fall into the black hole. So the faster you move through space, the slower you move through time,” he said. “Furthermore, as you fall, there are things that have been falling in front of you that have experienced an even greater 'time dilation’ than you have. So if you’re able to look forward toward the black hole, you see every object that has fallen into it in the past. And then if you look backwards, you’ll be able to see everything that will ever fall into the black hole behind you.

"So the upshot is, you’ll get to see the entire history of that spot in the universe simultaneously,” he said, “from the Big Bang all the way into the distant future.”

Not such a bad way to go, in the grand scheme of things.

Black Holes Aren’t Black After All, Say Theoretical Physicists

Collapsed stars are just too big to trap light forever

Black holes are a crucial part of the great cultural legacy of Einstein’s theory of general relativity. They have fascinated scientists and laypeople alike since they entered the public consciousness in the latter half of the 20th century.

But it may be time to say goodbye to the notion of regions of space so dense that even light becomes trapped within them. In the last year or so, an intense debate about the paradoxical properties of black holes has left a number of theoretical physicists, including Stephen Hawking, suggesting that black holes might not exist at all, at least not in the form that anyone had imagined.

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A recent study suggests that each black hole contains another entire universe! According to the new equations, the matter black holes absorb and seemingly destroy is actually expelled and becomes the building blocks for galaxies, stars, and planets in another reality. Essentially, every black hole contains a smaller alternate universe. And our universe might just exist inside a black hole of a galaxy in a much larger universe.

Do Black Holes Explode When They Die?

A new theory suggests that black holes might die by transforming into a ‘white hole,’ which theoretically behave in the exact opposite manner as a black hole - rather than sucking all matter in, a 'white hole’ spews it out.

The theory, as first reported by Nature.com, is based on the speculative quantum theory of gravity. Scientists believe it may help determine the great debate over black holes about whether they destroy the things they consume.

According to the theory, a 'white hole’ would explosively expel all the material consumed by a black hole.

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