According to the best theories that the scientists have, the Big Bang happened about 13–14 billion years ago. Back in the beginning, the basic elementary particles that all matter is made from did not have any mass. But they then acquired their mass by pushing their way through a strange thick ‘mud’ that is part of the Fabric of Space-Time. This gloopy sticky ‘mud’ is called the ‘Higgs Field’. It manifests itself as the hypothetical Higgs Particle, named after the Scottish physicist Peter Higgs. He first discussed this proposition back in 1964.
But how do you explain this complicated stuff in plain English? This was the problem that William Waldegrave, the British Science Minister, had in 1993, so he offered prizes to anybody who could explain this concept on a single A4 sheet of paper. A total of 125 scientists entered the competition, and Minister Waldegrave awarded prizes (bottles of champagne) to five of them.
The winning entry was proposed by David Miller, a physicist from University College London. He compared the Higgs Field to a cocktail party made up of Tory party members, all of whom love Margaret Thatcher enormously.
Margaret Thatcher enters the room alone (i.e. she begins with no mass). As she crosses the room, Tory party members attach themselves in loving adoration of her (i.e. they give her ‘mass’).
So the Higgs Field imparts a drag to any matter passing through it, giving it ‘mass’. Unlike other fields (e.g. gravity, electric, magnetic), the Higgs Field has exactly the same value throughout the Universe. What varies is how different particles interact with it.
Hopefully the LHC will find the Higgs Particle in its brief lifetime of 10-24 seconds, during which it will travel 10-15m before it breaks apart.
Particle Spin-Off
One useful thing that has emerged from the work of particle physicists is the World Wide Web. By the way, the World Wide Web is not the internet. The World Wide Web is the software that lets you use the internet.
The Center for Nuclear Energy Research (CERN) in Europe, which has run various Colliders, is now running the LHC. (Note: CERN is the European Organization for Nuclear Research. It’s name is derived from the acronym for the French Conseil Européen pour la Recerche Nucléaire.) Back in 1990, CERN was the largest internet node in Europe. In those days, only scientists used the internet, and then only as a way to communicate and share data among themselves. Tim Berners-Lee was a computer scientist at CERN. On 25 December 1990, he set up the very first successful link between an HTTP (Hyper Text Transfer Protocol) and a server across the internet. The World Wide Web was born.
So the World Wide Web is a useful spin-off from Particle Physics.
End of Everything
So just how will the LHC cause the End of Everything? The claims against the LHC fit into the Really Big Problem basket, so let me deal with them one at a time.
Doom 1: Black Hole (Part 1)
There are people who claim that the LHC will create a Black Hole, which will then gobble up our planet.
But there are two reasons why you don’t have to worry about the LHC making Black Holes. First, it’s probably theoretically impossible to make them and, second, if we could make them they would be incredibly tiny and would evaporate in a time too short to measure with our current technology.
In reality, the LHC simply does not have enough grunt to create a Black Hole.
Let me explain. The smallest possible length in our Universe is probably (let me emphasise probably) the so-called Planck Length. According to various theories, any distance or object smaller than this is lost in a bubbling sea of quantum vacuum (more about this later).
So, therefore, the smallest possible Black Hole is the size of this Planck Length, which is about 1.6 x 10-35m. OK so far?
Theory tells us that a Black Hole of this size (i.e. 1.6 x 10-35m) would have a mass of ten millionths of a gram. To create this much mass with a collider would need energies of 1016 TeV (a TeV is a unit of energy equal to one trillion electron volts)—but the LHC can generate only 14 TeV. The LHC, the world’s most powerful collider, is too feeble by a factor of a thousand million million.
But just suppose that it is possible to make a Black Hole with the LHC. After all, as CERN itself honestly acknowledges, perhaps ‘the Planck mass is not a fundamental quantity but is derived from an underlying theory with more than four space-time dimensions. In such theories the higher dimensional Planck mass may be much smaller, raising the question of whether gravitational instabilities may develop much more readily.’ ‘Gravitational instabilities’ is polite language for Black Hole.
Destruction of the Universe?
On 18 July 1999, the London newspaper The Sunday Times ran the rather negative headline of ‘Big Bang machine could destroy Earth’. They were referring to the imminent starting up on Long Island, New York, of a very large particle accelerator called the Relativistic Heavy Ion Collider (RHIC). Like the LHC today, the RHIC was also supposed to destroy the world. There was so much alarmist writing in the media that Bill Clinton, the President of the USA at the time, asked for a specific briefing on these safety issues.
However, nothing went wrong. The RHIC has been running quite happily since then, lots of good research has happened, and both the Earth and the Universe survived and are still here.
Doom 1: Black Hole (Part 2)
Would this Black Hole survive? No, it would evaporate because it was so small. It would give off energy. You see, contrary to popular belief, a Black Hole can evaporate and get lighter—thanks to ‘Hawking Radiation’.
A Black Hole with the mass of a car (about 1,000 kg, and about 10-24 m in diameter) would evaporate in one billionth of a second—and during that evaporation time would be 200 times brighter than the Sun. Suppose the LHC did make a Black Hole of the Planck Length. It would evaporate in 10-42 seconds. A 14 TeV Black Hole (the energies involved at the LHC) would evaporate in 10-100 seconds.
So even if the LHC did make a Black Hole, it would evaporate in a time too short to measure.
Hawking Radiation
Hawking Radiation is radiation emitted by Black Holes. How can this be if nothing can ever leave a Black Hole? It turns out that Black Holes are not completely black but have a hint of grey about them.
Quantum Mechanics tells us that a particle and its corresponding antiparticle can pop into existence out of nothing. They can do this only if they both recombine and annihilate each other and vanish in an extremely short time. (They kind of ‘borrow’ energy from the vacuum, and then give it back almost immediately.)
Every now and then the particle and antiparticle will pop into reality just outside the Event Horizon of a Black Hole. On average, one will vanish into the Black Hole and one will not. So we, as external observers, will see that the Black Hole suddenly spits out a particle which has energy.
The name for this radiation is the famous ‘Hawking Radiation’.
The time for a Black Hole to evaporate using this very slow mechanism is roughly the cube of its mass (in Solar Masses) multiplied by 1066. So a Black Hole weighing 10 Solar Masses will need 1069 years to evaporate by Hawking Radiation alone. But over the eons, a Black Hole this large would have gravitationally sucked in much more than enough mass from around it to compensate for this incredibly slow rate of evaporation.
The Large Hadron Collider
The Large Hadron Collider (LHC), the biggest and most complicated particle physics experiment ever seen. The LHC will accelerate bunches of protons the highest energies ever generated by a machine, then collide them head-on 30 million times a second.
Each collision will explode out thousands of particles at almost the speed of light.
Doom 2: Vacuum Collapse of our Universe (Part 1)
But what about the claim that the LHC could collapse the quantum vacuum that underlies the Fabric of our Universe?
First I have to explain what this quantum vacuum is. It turns out that a vacuum is not just nothing. A vacuum is actually a seething sea of temporary particles and antiparticles, which continually pop into exist
ence and then vanish. These particles and antiparticles exist for such a short time, before they wink out of existence again, that they don’t disturb the weird laws of Quantum Physics and the Uncertainty Principle. Each particle is the exact opposite of its antiparticle—so each pair (of a particle and an antiparticle) adds up to zero. This frothing sea of short-lived particles and antiparticles is involved in making the ‘zero-point energy’.
Let’s pretend that we have a metal box, out of which we have sucked every single molecule of air. Even though the metal box is empty of matter, it is riddled with various energies, e.g. heat. Those energies will lessen as we cool down the box. But even if we cool our so-called vacuum down to absolute zero, we find that there is still a huge amount of energy running through the supposedly empty space. Because this energy is still around at absolute zero, it’s called the ‘zero-point energy’.
Doom 2: Vacuum Collapse of our Universe (Part 2)
It’s quite easy to prove that this zero-point energy actually exists. In 1948, Hendrik B.G. Casimir from the Philips Research Laboratories in the Netherlands proposed that if you put two metal plates very close to each other, the zero-point energy would push them together!
Consider the zero-point energy in two locations—between the plates, and outside the plates. If the plates are very close together, only the very short wavelengths of energy can fit—the long wavelengths are too long to squeeze in. So between the plates, only some of the possible wavelengths of zero-point energy can happen, and they push the plates apart. But outside the plates, all the possible wavelengths of zero-point energy can happen—this energy tries to push the plates together. Casimir reckoned that there should be more energy on the outside of the plates than between them, so they should get pushed together.
In 1958, another Dutch physicist, M.J. Sparnaay, finally did the experiment in a pretty high vacuum. It turns out that if you get two metal plates, each 1 cm square, and place them 0.5 micron apart (just a fraction of the size of a human hair), the force pushing them together is equivalent to a weight of 0.2 mg. Of course, the closer the plates are together, the more of the zero-point energy of the outside Universe you can keep out, and so the force pushing the plates together is greater. And an experiment in 1996 by Steve Lamoreaux, now at Los Alamos National Laboratory in New Mexico, agreed with the predicted results to within 5%.
At the moment, we really don’t know how much energy there is in the vacuum. Some scientists say that the amount of energy is insignificant, but other scientists reckon that there may be enough energy in a single cubic centimetre of vacuum to boil all the water in all the oceans on Earth. To really find out, we need to do both theory and experiment.
Crash and Burn
Two protons colliding at high speed can produce various hadrons plus very high mass particles like Z bosons.
Performing these collisions may finally unveil the secret of dark matter, the mysterious entity that makes up 85% of the Universe. This would then help to explain the current mystery of the motions of galaxies.
Theory vs Experiment
The Nobel Laureate experimental physicist Leon Lederman wrote: ‘If I occasionally neglect to cite a theorist, it’s not because I’ve forgotten. It’s probably because I hate him.’
Theoretical physicists do the deep thinking, while experimental physicists do the hard experiments. The theorists need the data from the experimentalists to come up with the theories, and the experimentalists need the theories to devise the experiments that generate data.
They need each other, but they don’t always see eye to eye. Some experimentalists see theorists as bludging brats who drink coffee all day, coming up with crazy ideas that they don’t have to be held responsible for.
Doom 2: Vacuum Collapse of our Universe (Part 3)
So the Universe is filled with this quantum vacuum energy. The Universe was a lot hotter soon after the Big Bang, so presumably the quantum vacuum energy was a lot greater back then. And as the Universe cooled down, then presumably the quantum vacuum energy reduced to the lowest stable level.
But what if it didn’t? What if it got hung up in an energy level that is both unstable and not the lowest possible level? And what if, after a few years of operation, the LHC somehow ‘kicked’ the quantum vacuum a little and shoved it into the lowest possible energy level.
Perhaps a terrible wave of destruction would propagate away from the LHC in all directions, collapsing the quantum vacuum into a lower energy state—and destroying our Universe as it spreads at the speed of light.
There are two objections to this scenario—one theoretical, the other based on data.
The theoretical objection is that our scientists have already come up with various theories that describe the subatomic world very well. Our Universe is already in the correct and stable vacuum state.
The practical objection looks at cosmic rays. Cosmic rays are high-energy particles that have been hitting the solar system for all of its nearly five-billion-year history. Many of these collisions have hundreds of millions of times the maximum energies produced in the LHC. Because the quantum vacuum has survived these enormously powerful cosmic ray collisions, it should survive anything that the LHC can throw at it.
Doom 3: Strange Matter
This claim refers to ‘strange matter’ being accidentally created and then taking over the Universe.
‘Quarks’ are a type of subatomic particle that make up some of the matter in our Universe. There are six types, called ‘up’, ‘down’, ‘top’, ‘bottom’, ‘charm’ and yes, ‘strange’. The proton (which is in every atom in the Universe) and the neutron (which is in every atom in the Universe, apart from hydrogen) are made mostly from various combinations of ‘up’ and ‘down’ quarks.
The worry here is that the LHC might accidentally create matter made from ‘strange’ quarks—henceforth known as ‘strange matter’. When the superhot fireball cools down, it might condense into strange quarks, which might then cool down into strange matter. What if this strange matter had a natural lower energy level than regular matter? And once we had a ‘seed’ of strange matter, what if it set off an unstoppable chain reaction? And what if it converted all the matter on Earth, and then the entire Universe, into strange matter. (It would work like the fictional Ice-9, in the sci-finovel Cat’s Cradle by Kurt Vonnegut Jr.)
Once again, there is nothing to worry about.
First, we have looked vigorously for strange matter, and have never found it anywhere in the Universe. In addition, theory tells us that strange matter is unstable in small quantities, thanks to surface effects.
Second, theory tells us that high-energy colliders like the RHIC and the LHC are a poor way to make strange matter. Low-energy colliders would be a better way—but they have been running for decades and have never produced strange matter.
Third, cosmic rays come in a wide range of energies—from much weaker than the energies produced in the LHC to hundreds of millions of times greater. Cosmic rays have not yet set off a chain reaction of strange matter conversion. Even though they have been hitting the various moons and planets in our solar system for billions of years, the moons and planets are still here.
Too Costly?
The total cost of the LHC is about US$8 billion. Yes, that is a lot of money. And yes, it is roughly the cost of three of the American B-2 stealth bombers. Each one costs about US$2.6 billion, or to be strictly accurate, US$2.595 billion, or US$2,595 million. (That’s in 1996 dollars, which are worth more than today’s dollars.)
My guess is that when our great-grandchildren look back to the early 21st century, they will see that the world got more benefit from the LHC, than it did from three B-2 bombers.
We’re Safe, Hooray!
And even bigger energies are unleashed inside exploding nuclear weapons, inside our Sun, and around Black Holes—and the Universe has shown itself to be remarkably robust.
High-energy physics is on the verge of a major breakthrough. The LHC might find hidden extra
dimensions, or the truth about the Missing Stuff that makes up 96% of the Universe, or point us towards the Quantum Theory of Gravity, or tell us why gravity is so much weaker than the other forces, or tell us where all the antimatter went. It is The Large in search of The Tiny. It could take us to the Golden Age of Physics. Or it might give us the Next Cool Thing, even better than the World Wide Web.
So let’s give it a whirl and see what we find…
Black Hole = Power Pack
In the sci-fi TV series Star Trek, the spaceship Enterprise uses antimatter engines. They are efficient and do indeed convert all their fuel to pure energy.
On the other hand, the Romulan warbirds have a Black Hole (or ‘artificially generated quantum singularity’, as they verbosely call it) for their power supply. Black Holes have the advantage as a power pack that they are very compact (infinite density helps). This is balanced by a few disadvantages—it’s not really possible to control the power output of a Black Hole, and when they run out they evaporate in an enormous blast of gamma rays.
If Black Holes did form (you know, all that extra dimension stuff), they would have a very characteristic decay signature as they evaporated, involving an electron, a muon and a photon.
If, against all odds, the LHC makes a Black Hole, and if, against all odds, we learn the technology to capture one, then it might make a nice power supply—if we can iron the bugs out of it!
Science is Golden Page 17