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Doomsday Machine Large Hadron Collider?

A scientific essay about energies, dimensions, black holes, and the associated public attention to CERN

bridges vol. 19, October 2008  /  OpEds & Commentaries

By Norbert Frischauf

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Norbert Frischauf

It was September 10, 2008, when the world’s largest experiment, the Large Hadron Collider (LHC) started its operation. Located at CERN, the European Particle Accelerator Laboratory at the Franco-Swiss border near Geneva, the LHC particle accelerator resembles an enormous ring with a circumference of 27 km (17 miles), buried 100 m (328 feet) underground. When it runs at full power, the LHC is able to accelerate protons to a velocity that reaches 99.9 percent of the speed of light, so each particle attains an enormous kinetic energy. At regular time intervals and deep in the center of dedicated particle-detectors at specific places in the ring, the accelerated protons are forced to follow a course that ends in a head-on collision, which releases the kinetic energy in an event that resembles a “mini-Big Bang.”

{access view=guest}Access to the full article is free, but requires you to register. Registration is simple and quick – all we need is your name and a valid e-mail address. We appreciate your interest in bridges.{/access} {access view=!guest} These collisions are the very raison d’etre of the accelerator. They allow scientists to witness events like those that took place when the Universe came into existence, giving clues to the identity of its ultimate constituents that make up what we perceive as matter and force in our daily lives.

This, in a nutshell, is what the LHC is supposed to do – and is already a marvelous story in itself. What was featured in the news, however, was not the “science facts” but rather the “doomsday fiction” based on the claim by some “experts” that the LHC could possibly create mini-black holes that would ultimately lead to the destruction of Mother Earth.

I had the privilege of working at CERN from 1994 to 1998, at that time supporting two experiments at the Large Electron-Positron Collider (LEP), the precursor of the LHC. In the events surrounding the LHC start-up, I was suddenly confronted with question after question relating to the potential production of mini-black holes in the LHC. I realized that people were really concerned that the CERN scientists might endanger all life on planet Earth. Of course this is not the case. However, I don’t want you to take me at my word, but prefer that you draw your own conclusions. In the following essay, I provide some background information and clarification about what really is happening at the LHC:

Background info # 1: You need high energies to look at the smallest scale

This statement might sound odd at first, but only until one realizes that an optical microscope is limited in its optical resolution primarily by the wavelength of the light being used (wavelengths of visible light range from 380 nm to 740 nm). If one wants to study objects smaller than half the wavelength of visible light, it is necessary to utilize shorter wavelengths (= higher energies), for example electron microscopes, whose electron beam has a very short wavelength. To put it in perspective: An electron with 100 keV of energy (about 4 times the energy level of the electrons that make up the TV image that you enjoy every evening) has a wavelength of 0.0037 nm, fully 100,000 times shorter than the shortest wavelengths of visible light.

A factor of 1:100,000 sounds impressive, and enables in-depth studies in physics, chemistry, and biology. However, if one wants to look into an atomic nucleus – and such a nucleus measures only 10-6 nm, which is 1000 times smaller than an electron wavelength – it becomes evident that one must use much shorter wavelengths and accordingly very high energies. Such high energies can only be provided by a particle accelerator – and this is where the Large Hadron Collider enters the scene.

Background info #2: You need an accelerator with a diameter of 8.6 km – anything smaller will not work

Accountants aren’t the only ones who imagine how fantastic it would be if high energy physics experiments like LHC could be conducted with a tabletop system. Unfortunately the laws of nature preclude such possibilities right from the start. One of the basic laws of nature, the emission of electromagnetic radiation by an accelerated charged particle – the so-called Bremsstrahlung – manifests itself as synchrotron radiation in a ring-shaped accelerator like the LHC (which is also called a synchrotron). If particles emit radiation, they lose energy. This effect limits the maximum energy that a particle can accumulate in such a synchrotron.
One particular feature of synchrotron radiation is that the energy loss is greater when a) the accelerator is bent more strongly and thus features a smaller diameter, and b) the mass of the accelerated particle is smaller. This means that in the same synchrotron, electrons, which are 2000 times lighter than protons, emit synchrotron radiation more quickly, limiting the maximum energy per particle in a more stringent way. Therefore, if you want to study the tiniest structures of nature, you have to build a large synchrotron and use heavy particles in order to keep synchrotron radiation emission to a minimum.
Even when synchrotron radiation is minimized, it is still harmful. Because it emits X-rays among other types of radiation, it is advisable to place the synchrotron in a tunnel so that potential synchrotron radiation emissions will be stopped in solid rock – and not within an unaware neighboring community. That’s why we bury the accelerator 100 meters underground.

Background info # 3: The collision of relativistic protons is a job for high-skilled experts

As if it were on a specially designed Autobahn, a proton travels through the 27 km-long LHC with a velocity 99.9 percent the speed of light (300,000 km/s) along with 100 billion other protons. These are exposed to a nearly perfect vacuum – only one billionth atmospheric pressure. The temperature inside the LHC is nearly 1°C cooler than in the free space of our Universe. This is because the LHC runs with superconducting magnets and is therefore cooled to 1.9 K or 1.9°C above absolute zero. 

The ATLAS detector. Click here for a 3D-panorama view.

In the LHC, protons are accelerated in packages, the so-called bunches, consisting of 1011 protons each. Scientists deviate the traffic at dedicated places – deep in the center of particle detectors like ATLAS or CMS – in the ring, so that protons find themselves on a direct collision course with the proton particle beam that runs in the opposite direction (clockwise vs. counter-clockwise). As these particles travel at nearly the speed of light, 600 million collisions per second can be achieved. This sounds like a huge number, but the estimates predict that ONLY ONE out of 1013 (10,000,000,000,000) collisions will lead to a really high energy event, a proton hitting anther proton perfectly head-on. The remaining protons miss each other or touch each other only slightly.

The LHC-detector CMS just before a test with atomspheric muons. Click here for a 3D-panorama view.

Why not neglect the collisions entirely and fire the protons onto a static target? This would, in principle, make things much easier, but again the devil is in the detail: Only when particles hit each other head-on, as in a collision machine, do their energies summate. At the LHC, which is a collider, the particle energies add up to 7 + 7 = 14 TeV. However, if one of the particles is static, the required energy of the beam rises quadratically, leading to exorbitant energy requirements. To reach the 14 TeV collision energy in such a configuration, the proton beam would have to be 7460 times more powerful – an energy of 104,444 TeV. Needless to say, these energies represent levels that only the Cosmos can play with (e.g., supernovae or quasars), but nothing that is within the reach of humanity.

The Controversy: Extra dimensions and black holes – doomsday machine LHC?

What got the controversy ball rolling was a lawsuit filed by two Hawaiian residents claiming that a powerful particle accelerator like the LHC would be able to produce black holes.

The concept behind this hypothesis derives from the possible existence of hidden dimensions, which is postulated by certain theories such as string theory.
String theory – a quantum theory that calls for minuscule, one-dimensional swinging strings to describe the elementary constituents of the Universe – introduces six to seven additional spatial dimensions in order to achieve mathematical consistency. When taking the already existing four-dimensional space-time into account, the Universe would then feature 10 or 11 dimensions. Apparently we do not perceive these additional dimensions, and several explanations have been proposed. For example, these additional dimensions may be twisted or rolled-in in a complicated manner; or we may all live on a “brane,” a three-dimensional space embedded into a higher dimensional one, like the two-dimensional flat surface of a tablecloth being embedded in the three-dimensional space of daily life.

Regardless which explanation is true, if these additional space dimensions really do exist they might manifest themselves in a different strength of the gravitational force, which changes with the number of dimensions. Hence, if extra dimensions exist they will alter Newton’s law of gravity at least at very small distances, and only hypothetically – such an effect has never been observed so far.

A region of space in which the gravitational field is so strong that nothing, not even light, can escape it. 
A characteristic radius associated with every mass. It is the radius for a given mass where, if that mass could be compressed to fit within that radius, nothing could stop it from continuing to collapse to a black hole.
Although this hypothesis lacks any empirical evidence, it is exactly THE point of contact with which the denouncers start. Black holes are assumed to form whenever mass (= energy) density exceeds a certain value, that is if the mass is compressed in a dense sphere whose radius undercuts what physicists call the Schwarzschild radius. When particles collide, the energy density at the actual point of collision is extremely high. Assuming that is possible to bring particles with a high energy (=mass) so close together during the LHC collisions that the Schwarzschild radius is eventually undercut due to the extra-space-dimension-enhanced-gravitational-force, then a microscopic small black hole will form. In the follow-up horror scenario, this mini-black hole nestles itself into the Earth’s core and starts to devour the Earth from its very center. And, what is worse, all that mankind can do is watch and despair.

A scientific analysis: How to potentially generate a microscopic black hole

Even though I agree that a bit of horror can provide some pleasurable thrills from time to time, this horror scenario goes seriously overboard. When analyzing the required cascade of events, the whole scenario starts to look more like a conspiracy thriller than a scientific argument.

But let’s take a closer look:

1) The first show-stopper is that these extra space dimensions have to exist. In case there are only three dimensions (just as we perceive), the horror movie will have to take its first commercial break here.

2) Next, these extra space dimensions need to manifest themselves by a magnified near field gravitational force. The primary evidence against this claim is the former LEP experiment at CERN. Here, high energy electrons and positrons were put on a collision course and therefore came very close to each other – but extra-space-dimension-enhanced-gravitational-forces have not been observed.

3) Even if a black hole were to form because of the
extra-space-dimension-enhanced-gravitational-force, this mini-black hole would be very, very short-lived because of the Hawking radiation. At a mass of 10,000 protons, the lifetime of the black hole would be a mere 10-26 seconds before it decayed in a particle-ray flash. It should be noted here, that the Hawking radiation was first postulated in 1974 and still maintains its position in the scientific world.

Radiation predicted to be emitted by black holes due to quantum effects. Via Hawking radiation, black holes lose mass. If this happens faster than a black hole can gain mass, the black hole will shrink and eventually evaporate.  
An extremely light, neutral elementary particle which can pass matter without almost any interaction. Thus it is very challenging to detect.

4) With a projected lifetime of 10-26 seconds, the black hole does not have enough time to devour any matter around it – which spells “The End” for the horror movie.
The horror film can only continue if the Hawking radiation does not exist. There is, however, no single theory (!) that predicts stable microscopic black holes. In case these did exist, however, they would be either electrically charged or neutral, which leads us to points 5 and 6:

5) Stable microscopic black holes without any electric charge (neutral) will interact with the Earth in only a very limited way, leaving the Earth quickly as the collision releases a large amount of energy. Because the gravitational force is by far weaker than the electromagnetic or the strong force, and because an electrically neutral stable microscopic black hole would be subject only to gravity, it is not much different from a neutrino – except for the mass.

6) Stable microscopic black holes WITH electric charge, however, will interact with the matter of the Earth. Due to the electromagnetic interaction, they will be stopped rather quickly. ONLY IN THIS CASE, the question of a black hole within the Earth’s sphere of influence is a valid one. To reach this point, however, both extra-space-dimension-enhanced-gravitational-forces and perfect particle collisions were required, Hawking radiation must not exist, and the microscopic black hole must be both stable and charged.

In light of all these “ifs,” should you still be concerned, I can assure you by a simple observation that there is no imminent danger. This simple observation relates to the fact that Earth still exists – and has already done so for a period of 4.5 billion years.

An observation with far-reaching consequences: Earth still exists!  

Although this statement sounds trivial, it is the simplest and clearest argument for the safety of the LHC. In the whole controversy about production of stable microscopic black holes in the most powerful particle accelerator in the world, one thing tends to be forgotten:  The Earth is bombarded constantly by a stream of high energy particles coming from the Sun as well as other celestial bodies.

High energetic cosmic particles encounter the Earth’s atmosphere leading to „Northern lights“ or aurora borealis.

Space is flooded with protons, electrons, and high energy atomic nuclei, which can cause damage to energy supply systems, satellites, and space vessels. The protection of the Earth’s magnetic field and its atmosphere prohibits the ionizing radiation from hitting the Earth’s surface – or else life would be impossible. The severity of the bombardment is clearly visible at the two polar circles, where the “Northern lights” showcase the energetic interaction between the incoming particles and the Earth’s atmosphere.

Compared to the energies of these incoming particles, the power level of the world’s largest experiment can be described as a “toy” at best. Particles from the cosmic background radiation can easily have one million times more power then the collision energy of LHC protons. The mechanism leading to these high energies is still unclear; scientific studies are currently underway to identify potential sources such as pulsars and/or supernovae.

White dwarf
An old star in its final evolutionary state. It is a very dense object consisting usually of carbon and oxygen. The nuclear fusion process has come to an end. Hence, its luminosity is much weaker than the luminosity of the sun.
Neutron star
An old star in its final state consisting almost entirely of neutrons. Its matter density is very high. A typical neutron star has a mass between 1.35 and about 2.1 solar masses, with a corresponding radius of about 12 km only.
Highly magnetized fast rotating neutron star that emits radio waves.  
An extremely high energetic and very bright explosion of a star after the end of the nuclear fusion process.  

What significance does the existence of the cosmic radiation have for the controversy?

Simply speaking, it means that we don’t have to be concerned: The Earth has been bombarded over its 4.5 billion year existence by a whole bunch of cosmic radiation particles with much higher energy levels than what the LHC can produce.

In case all of the aforementioned “ifs” were true, the Universe would already have unleashed a multiplicity of stable microscopic black holes on the Earth. Bearing in mind that the Earth has already existed for 4.5 billion years, there would have been plenty of time for at least one stable microscopic black hole to devour one or more planets in the aftermath such an event. The sheer observation that the Earth and the other planets still DO exist, and that super-dense celestial objects like white dwarfs and neutron stars, with lifetimes of at least 1 billion years, are also observed in numerous quantities in the Universe, therefore refutes the existence of stable microscopic black holes.
In the hour in which I have written, or you have read, these sentences, the Universe has conducted more than 36 x1015 LHC experiments. And obviously, if you’re still reading, it does
still exist.

After 8 years of construction, the first proton collection was started in the LHC on August 8, 2008.
At that time, the Universe had already existed for more than
13 billion and the Earth for more than 4.5 billion years. 
The first collisions were bound to happen after September 11, 2008.
The Universe as a whole conducts more than 10,000 billion LHC experiments every second.
In the best case, one collision in the LHC can unleash energies as high as 14 TeV.
The highest energy particles of the cosmic radiation enter the Earth’s atmosphere with an energy of 1 Joule or more. This energy level is at least 1000 times greater than the equivalent energy in LHC collisions.
The LHC experiment averages 600 million collisions per second.
Cosmic radiation has performed 1 million LHC experiments on the Earth within the last 4.5 billion years.

Conclusion: 0:4 – A spectacular home defeat, which to me demonstrates one thing: Even the largest scientific experiment of mankind amounts to nothing when compared with the size and the energies of the Universe.  For me, this is a comforting result.

About the author:

Norbert Frischauf is a high energy physicist by education and and works as managing director at QASAR Technologie(s), a new found high-tech venture in Vienna, Austria.


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