Stop the LHC – until we know it’s SAFE!
July 28, 2009 by Dyau
That is what – the self-proclaimed “official site for citizens against the Large Hadron Collider” – exhorts us to do, through articles such as , , and .
A hot new niche
Using everything from , , and , the website’s have cunningly played upon the layperson’s paranoia of the “mad/evil scientist/Dr. Strangelove” cliché to sensationalize the issue and in the process have created a sizable following for the website, not to mention a good deal of publicity.
LHCDefense.org is by no means the only website cashing in on this hot new ; there is a plethora of sites that have espoused LHC-bashing and proffer their myriad points of view to the anxious reader in exchange for some . and are good examples.
These websites’ main contentions are that the theory that black holes radiate is flawed, and if they do so, they do so at a very gentle rate even at the end-stage, and that was daft after all. Or something like that. They the fact that a guy with a masters’ degree in statistics did a of a group of “physicists” and supposedly found that their estimates that Hawking radiation would fail ranged from 0% to 50%. Yeah, right. Let’s introduce democracy in physics.
Loading ...Panic on the streets of Meyrin
We have been rushed into some hasty, ill-informed decisions in our time – we emailed our bank details to our new friend in Nigeria who had $26m to smuggle out of the country by midnight, switched from to after seeing those TV adverts and just this May we stuck $225 on the Cape Caterpillars to win the International Premier League of . But even those little jaunts look like feats of when you compare them to the rumors slouching out of LHCDefense.org. If they’re to be believed, a scientist has predicted that a “” will preclude the LHC from operating. is the paper in which Holger Nielsen and Masao Ninomiya purportedly made the statement.
Which, is of course, ridiculous. Firstly, while the website states that “a” scientist has made the prediction, we find that the paper has two authors. Furthermore, a quick glance at the paper reveals that it has nothing to do with the production of micro black holes or strange matter at the LHC. Depending on your outlook, you could see this either as a case of clutching at straws; or that of stopping at nothing to further a agenda to bring all scientific research to a grinding halt. Sadly, these stories are created for consumption by the lay public, not physicists. The effect of a constant slew of such stories could well be widespread panic on the streets of , the picturesque and quiet (if you disregard airport) suburb that abuts on CERN.
The truth about black holes
Like most physics departments worth their salt, Acta Physica Building has a fire alarm. When it goes off, everyone ignores it and stays put wherever they are until assorted do-gooders (fire marshals) herd them out of the building and across Big Road. Once out of harm’s way, everyone mills around trying to find somebody important to be seen talking to, then heads to the bar.
Everyone, that is, except us, who today morning took an asbestos blanket and traipsed back into a potential inferno to risk getting reduced to a for the sake of this incredibly important revelation.
Here goes. As always, we shall start at the beginning for the sake of clarity.
Black Hole basics
The decay rate of an isolated black hole is given by
where 
is a constant:
Solving Eq. (1), we can show that a black hole’s lifetime is given by
Moreover, the temperature of a black hole is given by
A quick glance at Eq. (1) tells us that small black holes radiate more rapidly than more massive ones, and it explains why black holes end their lives in spectacular explosions.
At this juncture it is a good idea to emphasize on the word isolated.
Isolated – as in solitary, alone, removed, segregated, disengaged, sequestered, separated, insulated, undisturbed. Isolated – as opposed to connected.
A black hole in a box that contains vacuum is isolated. A black hole immersed in a radiation field is not isolated, neither is a black hole that is part of a population of black holes whose number density is large enough for them to reabsorb each other’s Hawking radiation. Consequently, a black hole lying in inter-stellar space cannot be considered to be isolated as it is immersed in the field, however weak it may be; and can also absorb inter-stellar gas and other material.
Hawking Radiation in brief
According to , there is no such thing as “nothing”. Vacuum itself has an underlying that exists even in space devoid of matter. Virtual particle – antiparticle pairs are constantly created and annihilated in vacuum. These exist for a limited time and space, introducing uncertainty in their energy and momentum due to the . They are “temporary” in the sense that they appear in calculations, but are not detectable as single particles due to their very brief existence. Indeed, they are detectable only as forces. The existence of these particles is no fiction. Though they cannot be directly observed, the effects they create are .
Consider a virtual particle – antiparticle pair that is created right at the edge of a black hole’s . Usually, such a virtual pair will self-annihilate almost instantaneously. However in this case, there is a finite probability that one of the particles will cross the event horizon and disappear into the black hole. If this happens, the other particle/antiparticle will escape from the black hole. Conservation of energy requires that the particle that fell into the black hole must have had a negative energy. The black hole thus foots the bill of the escaped particle: it loses an amount of mass-energy equivalent to that of the escaped particle.
To a user at a distance, it will appear that the black hole is radiating a steady stream of particles and antiparticles; and is shrinking over time.
That, in brief, and in lay terms, is the mechanism of . Hawking radiation is in nature and has a spectrum. The rigorous theory of the mechanism of Hawking radiation involves , which we will not delve into here.
How a black hole interacts with its environment
One way of looking at a black hole’s interaction with its environment is to compare it with (this is not entirely accurate, but works for the purpose of this illustration). Thermal energy flows from hot objects to cold ones. A hot metal rod immersed in a cool fluid such as water or air will lose heat to its environment. Similarly, a black hole radiates Hawking radiation or accretes mass-energy depending on its temperature and that of its environment.
For example, a solar-mass black hole (
≡ 
) has a temperature of 
; while the interstellar medium has a temperature of 
(the CMBR temperature). The black hole is thus colder than its environment. This means that instead of emitting Hawking radiation, such a black hole will instead accrete the interstellar CMBR photons and increase in mass.
Conversely, a -sized (
) micro black hole has a temperature of 
– which is far hotter than interstellar space. Such a black hole will radiate Hawking radiation and thereby decrease in mass.
Non-isolated black holes decay slower than their isolated counterparts, and Eq. (1) does not hold for them. The equation governing a non-isolated black hole’s decay has extra terms that account for heat sources and other factors in the black hole’s physical vicinity.
How fast (or slow) do black holes decay?
A black hole’s decay rate is inversely proportional to the square of its mass and is given by Eq. (1). In other words, small, hot black holes decay much faster then larger, colder ones. The below table makes this amply clear. Remember, this applies for isolated black holes.
Black hole lifetimes and decay rates. Note how black hole lifetimes increase dramatically with mass, while their decay rates and temperature decrease.
The above table tells some remarkable stories:
- Micro black holes have incredibly short lifetimes; in stark contrast with their more massive counterparts. A black hole weighing 1 solar mass () has a lifetime of
– which is far greater than the universe’s lifetime! Large black holes are immortal, for all intents and purposes. Moreover, their temperatures are far too low for them to decay, they actually accrete the inter-stellar Cosmic Microwave Background Radiation and assorted inter-stellar material, and grow larger. - Micro black holes decay at an astonishing rate; again in stark contrast with their more massive colleagues. A Planck-mass () micro black hole decays all its mass in
, which means that it disintegrates in an explosion almost as soon as it is created. A 17.8 gram black hole takes only 2 milliseconds to spew forth the 382 in energy that it carries (conversion factor: 1 GeV 
kilotons of TNT). In contrast, the had a blast yield of 18 kilotons of TNT, at best. To summarize, black holes decay faster as they grow smaller, and end their existence in spectacular explosions.
The revelation
Which finally brings us to the . Let us first enumerate a few facts about the LHC:
- Particle-particle collisions at the LHC will release a maximum of 14 TeV
of energy per collision (each opposing particle beam will carry an energy of 7 TeV per particle). - The colliding particles will be traveling at 99.9999991% the speed of light, or
. - The LHC’s tunnels are 3.8 m wide and contain the most perfect vacuum ever created.
- The LHC is expected to be able to produce black holes at a rate as high as one per second.
So here’s the deal. Since the particle-particle collision yield is 14 TeV, the LHC will produce black holes no larger than 
. That is sub-Planck mass. Since the LHC tunnels contain near-perfect vacuum, the black holes can be considered to be isolated, and Eq. (1) holds.
black holes have a lifetime of 
, which is shorter than the . At the maximum speed at which such a black hole can travel (), it will cover a distance of 
before it disintegrates, which is again shorter than the .
Assuming that the collisions occur at the center of the collision chamber, the black holes will be produced nearly 2 meters away from the collider’s walls. We can therefore say with 100% certainty that no black hole produced in the LHC will be able to hit the tunnel’s walls.
But what if micro black holes don’t decay?
That, after all, is what the LHCDefense folks et al have based their arguments on. Let’s humor them for once and consider this possibility to see where it takes us. We start by making the following observations:
- A
black hole has a radius of 
, which is less than the Planck length. This is 
times smaller than the radius of a hydrogen atom (radius: 
), 
times smaller than the radius of a nucleon (radius: 
), 
times smaller than the radius of an electron (radius: 
), and 
times smaller than the radius of a quark – the most fundamental known particle (radius: 
). A sub-planck-mass micro black hole would go right through atoms, atomic nuclei, and even nucleons without ever hitting anything. - Black holes interact only through the , unlike other particles on earth that have most of the other three forces (, , and ). The gravitational force is by far the weakest among the forces, which is evident from the below comparison of their coupling constants:
interact through the aptly named weak force (the name says it all!). Trillions of solar neutrinos pass right through the earth every second (and right through you!) without interacting with any particle, which gives us a fair idea of just how incredibly weak the weak force is.
So let’s now ask ourselves a question:
Question: Will a micro black hole … – whose radius is more than a hundred trillion trillion trillion times smaller than the most fundamental known particle, and whose force is a million trillion trillion trillion times weaker than the neutrino’s weak force – … ever be able to interact with any particle in the earth?
The answer is: A RESOUNDING NO!
And therefore, Hallelujah ! We are saved !! Praise the Lord !!
In Conclusion
The Large Hadron Collider is sui generis; it will expand our understanding of the universe to an extent that no other instrument has done before. It will give rise to several new theories, apart from proving or invalidating many theories that currently await judgment. The research done using this instrument will undoubtedly spawn several , both in theoretical and experimental physics. Generations from today, we will enjoy the material fruits of our labor, much as we now enjoy and other spin-offs of the that formulated over a hundred years ago.
Let us not be misled by people who do not know what they are talking about. Let us give the LHC a chance.
Dark Energy Camera scans ancient skies
Dark Energy Camera scans ancient skies
Gazing into space, scientists wonder why the universe is expanding ever faster. What mysterious force is at work? By recording the light from hundreds of millions of galaxies from a mountaintop in Chile, they hope to find out what’s going on. By Kristine Crane
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| The Fermilab team that will use the Dark Energy Camera to peer deep into the dark includes, from left, physicists John Peoples, Brenna Flaugher, Juan Estrada, and Tom Diehl. Photography by Reidar Hahn | |
Imagine a camera that takes pictures of the universe not only as we see it today but back through time, closer to when the universe began, capturing images of roughly 300 million galaxies.
At Fermilab in Batavia, Illinois, Brenna Flaugher and her colleagues are building such a device. Called the Dark Energy Camera, it will survey the skies of the Southern Hemisphere and peer far back in time, allowing scientists to see galaxies as they were when the universe was only a few billion years old.
The goal is to search for signs of dark energy—the ubiquitous, invisible substance believed to make up 70 percent of the universe.
For Flaugher, who spent 15 years studying subatomic physics, the prospects were so intriguing that she changed the focus of her career.
“I have gone from studying the smallest known things in the universe—quarks—to galaxy clusters, the biggest things we know,” she says. “The thing that makes both fun is that you get to think about the origins of the universe.”
A mysterious force
Eighty years ago, Edwin Hubble discovered that our universe is expanding, with galaxies becoming increasingly distant from each other. Scientists reasoned that the gravitational attraction among galaxies must slow this expansion. But then in 1998, two independent teams of scientists discovered a perplexing change in the expansion rate of the universe: for the first eight billion years after the big bang, gravity indeed had slowed the expansion, as predicted. Then, roughly five billion years ago, the expansion began to speed up.
What caused this acceleration?
The preliminary answer is dark energy, a mysterious “antigravity force.” When the universe was young, gravity was the dominant force. But over time, matter spread out enough to significantly diminish the gravitational attraction between galaxies. Dark energy, a repulsive force, began to overpower the gravitational force and push the galaxies ever faster apart.
Confirming the existence of dark energy and understanding its origin would have profound implications for our understanding of the universe. But an even more radical outcome would emerge if scientists discovered that dark energy does not exist. Instead, some theoretical models suggest that an extra spatial dimension causes the universe to expand ever more rapidly, unraveling Einstein’s general theory of relativity. The Dark Energy Survey, scheduled to be up and running in 2011, might reveal which explanation is correct.
“It’s throwing the tools of the digital age onto the old question of where we are,” says Craig Hogan, the director of the Center for Particle Astrophysics at Fermilab.
A fateful conversation
In the summer of 2003, former Fermilab director John Peoples and University of Chicago physicist John Carlstrom shared a cab on their way back from an astrophysics conference in Seattle. The subject of dark energy was already on Peoples’ mind, and Carlstrom was working on the South Pole Telescope, whose construction would soon begin in Antarctica. Since 2007, the telescope has recorded the microwave background radiation left over from the big bang, looking for distortions that mark giant clusters of galaxies. But the telescope is unable to determine how far away, and hence how old, galactic clusters are—information crucial for connecting its observations to dark energy calculations.
What they needed, the two physicists agreed, was a project that would fill the gap by determining how far these clusters are from Earth.
“The prospect was exciting,” Peoples recalls. At the time, he had just finished directing the Sloan Digital Sky Survey. The project, which makes observations from a telescope in New Mexico, has provided three-dimensional maps of nearly one million galaxies and 120,000 quasars in the Northern Hemisphere. Combined with data recorded at other observatories, the measurements indicate that 96 percent of the universe is composed of dark matter and dark energy.
Is gravity the problem?
Mounted on a telescope in Chile, the Dark Energy Camera will peer deeper into the sky and unveil more galaxies at greater distances than any previous project, including the Sloan Digital Sky Survey. It will collect data on the distances of supernovae from Earth; the large-scale clustering of galaxies; the abundance of massive galaxy clusters; and the bending of light caused by galaxies and clusters of galaxies.
Scientists use these four methods to determine how fast the universe has been expanding and the rate at which galaxies and clusters formed over cosmic time. Two of those methods will yield answers that are independent of the role that gravity played in the evolution of the universe. The other two will provide answers that depend on the theory of gravity.
“If all four measures show the same result, it means that our current ideas about dark energy are correct; if they differ, there is either a problem in our understanding of gravity or some other explanation,” says Flaugher, who is spearheading the camera’s construction. The $50-million Dark Energy Survey involves 120 scientists from 13 institutions in the United States, Brazil, Spain, and the United Kingdom. University College London is responsible for polishing the five lenses that make up the optical system of the camera. The Spanish groups provide the electronics that will process faint signals of light that traveled billions of years across the universe before landing in the “eyes” of the Dark Energy Camera.
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| Simulations and visualization of galaxy formations by Andrey Kravtsov, The University of Chicago, and Anatoly Klypin, New Mexico State University. |
Traveling back in time
At the forefront of Fermilab’s construction team is physicist Juan Estrada, who joined the project as a Fermilab Wilson Fellow in 2004. Estrada was a postdoctoral researcher studying the top quark at Fermilab’s DZero experiment when he became attracted by the prospect of working on the Dark Energy Camera.
As an undergraduate in Argentina, Estrada had studied the properties of the vacuum, and he was eager to re-visit an issue that he considers the biggest problem in physics: the mysterious energy that seems to come from empty space in our universe.
To do that, he first had to learn astronomy.
“Fermilab gave me the opportunity to learn something I had never done before,” Estrada says.
He learned how an astronomical camera works from a retired Fermilab engineer, Tom Droege, who practices astronomy from his home observatory. By taking apart and reassembling Droege’s camera, Estrada learned the basic steps of building a camera, valuable lessons for the construction of the Dark Energy Camera.
When complete, the Dark Energy Camera will be the size of a Smart car. What makes it so powerful are 74 delicate detectors, called charge-coupled devices or CCDs, each three by six centimeters in size and 0.250 millimeters thick. As in an ordinary digital camera, they are the camera’s “film” that records incoming light. The CCDs will sit on a plate about half a meter in diameter, located a few centimeters behind the camera’s set of lenses.
Cooled to minus 100 degrees Celsius to reduce background noise, the Dark Energy Camera’s superb CCDs will record longer wavelengths of light than other optical cameras do. This will allow it to see light from fast-receding galaxies that has shifted to longer wavelengths, toward the red end of the spectrum, in the same way a siren drops in tone as it moves away. The fastest-moving galaxies are also the farthest away, as Hubble discovered. What’s more, the light we see from the farthest galaxies is the oldest because it has taken longer to reach us. And so through this chain of inferences from reddest to fastest to farthest to oldest, the Dark Energy Camera will be able to see distant galaxies as they looked billions of years ago, closer to the universe’s infancy.
“We are mapping the distribution of the galaxies from what the local universe looks like now to a time when the universe was just a few billion years old,” says Dark Energy Survey collaborator Joe Mohr, physics and astronomy professor at the University of Illinois, Urbana-Champaign.
Reviving an old scope
Crafting the CCDs requires a unique process developed by engineers at Lawrence Berkeley National Laboratory. The final steps of the manufacturing process take place in a clean room inside a dome-shaped building at Fermilab. The lab’s technicians were already familiar with the assembly of silicon detectors used in particle physics experiments; now they produce an average of four CCDs per week for the camera.
Once all the CCDs are ready—a milestone the team expects to reach next year—technicians will finish assembling the camera and ship it to the Cerro Tololo Inter-American Observatory in Chile, where it will be placed atop a four-meter telescope called the Blanco.
The Dark Energy Camera will give new life to the 40-year-old telescope, which met the survey’s criteria beautifully, according to Peoples: “It was a marriage made in heaven.”
From Chile to Illinois
The Dark Energy Survey collaboration will use the telescope for five years between September and February, taking images on 105 nights each year and sending a few hundred images per night to the University of Illinois, Urbana- Champaign. Each image comprises 520 million pixels, equivalent to about 1 gigabyte of data, with information on the redshifts and brightness of about 200,000 galaxies and other celestial objects too faint to be seen by a simple household camera.
A supercomputer, which Mohr calls the “mother ship,” will store all these images and automatically detect the objects they contain, producing a catalog of galaxies with their brightnesses, positions on the sky, and other properties. The science team will analyze and interpret this information, searching for clues that might help explain cosmic acceleration.
So what will scientists find out?
“None of us is a prophet,” says Ofer Lahav, chair of astrophysics at the University College London, who co-chairs the scientific committee of the Dark Energy Survey collaboration with Fermilab’s Josh Frieman. Lahav says the findings will lead to a more complex view of dark energy, or perhaps a modified version of gravity.
Especially if it’s the latter, revisiting Einstein’s theory of relativity would be “a big shake-up to the foundations of physics,” says Lahav. “Either way it’s exciting.”
While future surveys aim to probe even deeper into the sky for answers about dark energy, the Dark Energy Survey will be the first to take a stab at solving the mystery, says Lahav.
“It is among the surveys that will push the subjects of dark energy and modified gravity to a new level,” he says.
But that is not all.
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| In a Fermilab clean room, Ken Schultz and Kevin Kuk check the alignment of the prototype camera’s front window. | |
The big payoff
The Dark Energy Survey collaboration expects that its data on stars, quasars, and galaxies will lead to hundreds if not thousands of scientific publications. The collaboration will make its data public a year after it has been taken, an approach also used for the data collected by the Sloan Digital Sky Survey and the Hubble Space Telescope.
The Sloan survey, which mapped a quarter of the sky, has generated more than 2400 scientific publications so far. Its results have been cited more often than those from any other observatory, including the Hubble.
The Dark Energy Survey collaboration hopes to be equally successful. Its survey of the southern sky will cover an area smaller than the Sloan survey of the northern sky, but it will go deeper, further back in time.
“It’s a small project for a really big scientific payoff,” says Flaugher. Most importantly, it might answer what she and her colleagues consider “the biggest question out there.”
Although Flaugher won’t wager a guess on whether the findings will confirm or deny the existence of dark energy, she is certain about one thing.
“I don’t want to argue about it anymore,” Flaugher says. “We need data, data, and more data.”
In a few years, she’ll have it.
to download the pdf version of this article.
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Can Hawking radiation give rise to Ultra High Energy Cosmic Rays?
July 11, 2009 by Thiago
Dyau:
The evidence so far:
- We know that Hawking radiation is emitted by all black holes. The rate at which a black hole radiates is inversely proportional to the square of its mass.
- We also know that Hawking radiation does not conserve Baryon Number. In other words, HR produces an equal number of particles and antiparticles.
- Moreover, antiparticles are routinely detected in cosmic rays of all energies. Antiprotons are one of the most precisely measured particles among the various antimatter species in cosmic rays.
Is is possible that primordial black holes in the end-stage of evaporation expire in an explosion of particles and antiparticles – which are observed here on earth as cosmic rays?
Can this mechanism explain Ultra High Energy Cosmic Rays (UHECR) – which have energies of upto 10^23 eV?
Would love to hear your thoughts!
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Daniel:
I don’t know the machanism of HR. the production of particles is continuous in energy, such as Black-Body radiation? How is the energy of the particles radiated related to the BH parameters?
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Dyau:
The rigorous theory of the HR mechanism involves quantum tunneling.
Let me explain in brief:
You must be aware of vacuum fluctuations: particle – antiparticle pairs that are constantly being created and annihilated in vacuum.
Consider a particle – antiparticle pair that is created right at the edge of a black hole’s event horizon – from the energy supplied by the black hole’s gravitational field. Usually, such a pair will annihilate almost instantaneously. However, in this case, there is a non – zero probability that one of the particles will cross the event horizon and disappear into the black hole. If this happens, the other particle/antiparticle will escape from the black hole; and the black hole will lose that much energy.
To a user at a distance, it will appear that the black hole is radiating a steady stream of particles/antiparticles; and is shrinking over time.
That, in brief, is the mechanism of Hawking Radiation.
The energy of the particles is directly proportional to the black hole’s temperature, which in turn is proportional to its surface area.
Hope this helps!
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Ragav:
Interesting idea Dyau….i have a doubt here: when the PBH ends its final stage,let’s say by explosion, then unlike the previous stage where only particles/antiparticles were radiated, now both particles and anti particles are radiated. so there is every room for them to annihilate right away and produce only photons.
so now,there is only EM radiation! if we take into consideration a single pair of particle-antiparticle, then a photon of negligible energy (but high kinetic energy due to explosion) is radiated. if we are able to calculate the energy transfer for such a process,i guess such high an energy as 10^23 ev is a little unlikely,isn’t it?!?
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Daniel:
I’ve seen that there is a strong correlation of UHECR with AGN’s (Active Galaxy Nuclei), proposed by the observatory. Also, if there were primordial BH, and if they were responsible for the Cosmic Rays, those UHECR should be isotropic in the sky. Unfortunately there are no sufficient data for that, I think.
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| Interesting idea Dyau….i have a doubt here: when the PBH ends its final stage,let’s say by explosion, then unlike the previous stage where only particles/antiparticles were radiated, now both particles and anti particles are radiated. so there is every room for them to annihilate right away and produce only photons.
so now,there is only EM radiation! if we take into consideration a single pair of particle-antiparticle, then a photon of negligible energy (but high kinetic energy due to explosion) is radiated. if we are able to calculate the energy transfer for such a process,i guess such high an energy as 10^23 ev is a little unlikely,isn’t it?!? |
Current topics of black hole research
July 11, 2009 by Thiago
Friends, thought of throwing up a few current open questions/problems in cutting-edge black hole research and seeing what you all think of them.
Firstly, let us define black holes:
Black holes are predicted by general relativity to be formed whenever sufficient mass is compressed into a small enough volume. A black hole is defined as a region of spacetime that cannot communicate with the external universe. The boundary of this region is called the surface of the black hole, or the
event horizon.
Secondly, let us define the three general categories into which black holes are classified:
- Stellar-mass black holes: These are formed by the gravitational collpase of stars, post-supernova. They are undetectable unless they orbit another start in a binary system.
- Supermassive black holes: These are believed to be present at the centers of most galaxies. They typically have masses of the order of millions of times our Sun’s mass.
- Micro black holes: These are physically the most intriguing type of black hole, they are believed to have formed in the very early universe due to quantum fluctuations in the primordial brew.
Some current open questions:
- Do black holes have internal structure?
- Do black holes retain any memory (mass/energy/charge/spin/particle type) of the matter they swallow?
- Do stationary black holes emit gravitational waves?
- Can black holes form quantized bound states?
- Can sub-Planck mass micro black holes exist?
- What happened to the micro black holes produced in the early universe? Did they evaporate; or are they still around in some form?
- Is there any link between black holes and dark matter?
- Is there any link between black holes and dark energy?
- Can black holes have multiple singularities?
- Can Hawking radiation emitted by decaying black holes give rist to Untra High Energy Cosmic Rays?
Hope this gives some food for thought. Would love to see your ideas/thoughts/comments!
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It looks possible. Black holes of course cannot be seen as they are, well, black. What can be seen is the effect black holes have on their surrounding environment, either on light by gravitational lensing, or on gas/neighboring start by the presence of accretion disks.
Your image looks like the action of a black hole on its surrounding environment; the light distortion suggests gravitational lensing at work, and the halo seems like an accretion disk. So yes, it could be an image of a black hole. Although, I’m not sure whether black holes have been captured in such detail on camera.
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Black Hole Atom
Dyau:
Friends, let me share a problem I’ve been pondering.
Consider two black holes which we define as below:
1) Black Hole 1 (BH1) has the mass of a proton (0.938 GeV) and contains a positive charge equivalent to the charge of a proton (1.602176487 × 10e−19 coulombs).
2) BH2 has the mass of an electron (511 eV) and contains a negative charge equivalent to the charge of an electron.
We can easily show that these two particles can be brought together to form a stable quantum-mechanical bound state. Since the bound state is stable, the black holes within it should not decay due to Hawking radiation. This is in essence a stable black hole atom.
Can such a bound state be formed? What would be the properties of such a particle? Would love to hear your ideas/thoughts/comments!
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Daniel :
wait… if you consider those Black Holes based only on General Relativity, how can you link it with a quantum mechanical description for a bound state?
Sorry if I’m deviating from your main idea, but I couldn’t even figure out the situation…
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Dyau :
You are right, we cannot quantize the system if we consider BHs based on GR.
Here I’m not considering BHs based on GR. I am describing a gedanken (thought) experiment:
- We take two Schwarzschild Micro BHs - MBH1 (mass: 0.938 GeV, charge: proton charge) and MBH2 (mass: 511 eV, charge: electron charge) and place them in close proximity in a box.
- The two MBHs should them form a stable quantum mechanical bound state whose properties can easily be defined using the good old Schrodinger equation.
My argument is that since the bound state is perfectly stable, the MBHs within it will not decay due to Hawking Radiation.
My questions are:
- Can such a bound state be formed?
- What would be the properties of such a particle?
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Daniel :
Let’s suppose that’s possible. Looking at the ground state of this bound state, from what we know of Quantum Mechanics, there’s a non-zero probability of finding the “electron BH” in the center of the system. It seems we get into a paradox, for the center is the “proton BH”. What would it mean “a non-zero probability to find the eBH inside the event horizon of the pBH”?
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Dyau :
You are absolutely right, there’s a non-zero probability of finding the eBH in the center of the system. Yes, it could be interpreted as a paradox.
However, this is then also true of the regular, non-black hole hydrogen atom; that there’s a non-zero probability of finding the electron in the center of the system where the proton should be.
The resolution of this apparent paradox is as follows:
- The system is a center-of-mass system: both the eBH and pBH revolve around the common center of mass.
- The eBH may sometimes be found at the physical center of the system; and so may the pBH. However this does not mean that both are simultaneously present at the center of the system. The exclusion principle prevents from happening in the H atom.
We need to study the properties of the BH atom bound state to understand what happens in this case. Do the two BHs overlap physically? If yes, they will coalesce and the bound state will be destroyed. If no, then the bound state is stable and may have interesting properties.
What are your thoughts?
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Daniel :
But that’s a main difference from the usual Hydrogen atom from that BH Atom. Even though the eBH and the pBH do not share the same space, that doesn’t mean the uncairtanty principle is beyond the Schwarzchield radius. Diferent from the e and p, a black hole has a related “size”, that’s the Schwarzchild radius. so that “center of system paradox” gets more complicated, at least that’s what I think…
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Dirk Banks :
Interesting discussion.
At a first glance, I’d say it should be possible to create such a bound state in suitable conditions.
A stable bound state of black holes? It should have the properties that we associate with SHDM.
I remember seeing a paper by a couple of Indian guys about BH bound states. The idea certainly is plausible.
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Dyau :
I agree, Daniel. This problem is much more complicated than it seems at face value. However, like Dirk mentioned, I believe such bound states are possible and can “throw light” upon Dark Matter 
I’m trying to persuade our friend to work on this problem. Hey Ragav, where are you?
Dirk, I’ve seen the papers you’re referring to. They call these bound states “holeums”. The papers are available on the Arxiv – search for holeum.
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Dyau :
I’m signing off until evening – got to go to the university! See y’all later.
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Ragav :
here i am Dyau….first things first-i sincerely appreciate the coceptual hold of our two other mutual friends here-Daniel and Dirk. So with Dyau, this is a beautiful “Triple D bound state” huh?!?
now,my views on Daniel’s arguments about the non-zero probability is that-quantum mechanically,there is always a finite probability of finding the eBH or pBH anywhere within the bounded system. We can normalize the probability to any arbirary area,WITHIN the diameter of the BHatom.
now,this is not as straight forward as it appears-because,the most important thing here is to calculate “HOW NEAR/FAR CAN THE TWO BLACK HOLES GET??”. do their vicinities allow their event horizons to overlap?let’s clarify that point first! the rest pretty much follows,i guess.
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editor :
You can’t have a proton black hole.
The Planck mass is 1.539 x 10^-8 kg which is about 10^19 proton equivalents.
The smallest BH you can have is Planck mass and 10^35m in diameter.
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Dyau :
Well all I can say is that this is a matter of conjecture. There is one school of thought that says that the Planck mass is the lower limit of mass, while there is another that says one can have sub-Planck masses. Some people believe that sub-Planck mass particles (Planckons/Cornucopions) should be considered to be stable elementary particles. There is no consensus on this, and no evidence of the veracity of eiter of these hypotheses.
Until we have iron-clad evidence one way or the other, I believe that we can safely use sub-Planck mass particles in theories. It’s better to formulate a (possibly) incorrect theory than to not explore that direction at all.
What are your thoughts on this?
See . I had no idea that someone has worked on this problem! I need to study this!
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Daniel :
So far in that article I’ve read that he considers mini-BHs forming bound-states with “regular” matter. But that is surely important to know, perhaps even before considering a miniBH-miniBH atom. Will try to read it also, at least the main parts.
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Dyau :
Yes indeed, they have considered bound states of charged black holes with “regular” matter. The concept can be applied to BH-BH bound states too, though. Will be interesting if someone has worked on that.
Still going through the paper …
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Ragav:
Hey guys,it suddenly occured to me that what if the laws of physics at the sub planck domain were a little different from the ones at the planck or the higher domains?!? like as in, suppose certain chaotic and non linear aspects dominate the sub-planck scale, so much so that the laws pf physics at such minute scales does not fall into the desciption of the ordinary quantum mechanical description at all?!?
would it be a testimony to the fact that “history repeats”, beacuse we witnessed a similar discrepancy (and a gap) when we made a transition from classical to the quantum!??!
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Dyau :
Ragav, you’ve hit the nail on the head. QM and physics as we know it are expected to break down when we cross the sub-planck threshold. At least, this what the majority of physicists believe.
Let’s take Hawking Radiation as an example, which is a semi-classical theory that involves quantum tunneling. Black holes emit HR at a rate given by
dm/dt = -k/m^2
where m is the black hole mass and k is a constant. A glance at this equation is enough to understand why large black holes are more or less stable and why micro black holes are expected to expire in a spectacular explosion.
This law may not be valid at a sub-planck mass scale. It is possible that the decay process of sub-planck mass black holes is “democratic” in nature, that is, they may exhibit varying decay behavior. There even is speculation that such black holes may not decay at all.
So yes, there could be a discrepancy and a gap when we finally make the transition and develop a theory of sub-planck physics.
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Ragav :
Hey Dyau, thanks for your encouraging and supporting remarks….it also occured to me that we can go about trying to look at the problem taking the “ensemble approach”…. let me substantiate the view:
as we know, the dynamics of Balck holes is studied on the basis of statistical arguments, like the Hawking law of black hole thermomodynamics or the Hawking-Bekenstein temperature etc: so instead of taking purely deterministic apporach to MBHs, why not take a statistical one?!? one could for example, borrow the concept of radioactive half-life or the “rate of decay of an ensemble of MBHs”!!! that way, we eliminate any discrepancies of absoluteness….not to mention the miniscule sub planck scale where the slightest fluctuations tend to perturb the system greatly! what say people?!?
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Dyau :
I can’t help agreeing with you! A statistical approach to the problem of sub-planck MBH behavior will average out their “democratic” behavior. One could certainly come up with the rate of decay of an ensemble of MBHs. However, the study of a MBH population will throw up other insteresting problems: what about the reabsorption of Hawking radiation in the MBH population? That will certainly bring the decay rate down. It will depend on several factors, primary among which will be the MBH density. Throw in some background blackbody radiation, and we’re talking about an early-universe simulation! That’s my kind of physics!
Know what Ragav, you should take up one of these problems and crack it. You have all the right ideas.
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