h1

It’s the end of the World as we know it(?)

2008 September 4

BBC4 tonight hosts two programmes about the new device soon to be switched on at CERN, the European Organisation for Nuclear Research. The particle accelerator, called the Large Hadron Collider or LHC, will investigate the frontier of particle physics. The LHC will collide particles are the highest energies yet: More than 7 TeV. This will allow scientists to probe conditions just one billionth of a second after the Big Bang.

The first programme screens at 8pm BST (GMT +1 hour). The first programme, called Lost Horizons: The Big Bang, charts the story of the theory of the Big Bang. The second programme, called The Big Bang Machine, looks at the LHC itself. Readers who cannot view BBC4, or who miss the programmes, may be able to watch them on the BBC i-Player service.

The LHC has proven a controversial project. First thought of in the early 1980s, it was approved in December 1994. Work began on its construction in April 1998. First tests were run on 8-11 August this year.

The LHC will work, like other colliders, by crashing particles against one another. Beams travel in opposing direction, and the results analysed. The first beam circulation test is due on the 10th (next Wednesday). And the first high-energy collisions due on 21 October.

Among the array of strange new particles physicists hope to observe are Higgs bosons. These are predicted in the “standard model” but have not yet been observed. Other searches are planned, including for extra dimensions, magnetic monopoles, strangelets and micro black holes. It is these last three that have produced some controversy.

The LHC Controversy

Concerns have been raised as to the safety of the LHC. These surround suppositions that it may produce dangerous phenomena including:

  • strangelets,
  • micro black holes,
  • vacuum bubbles,
  • magnetic monopoles.

The LHC Safety Study Group of independent scientists concluded in a 2003 report that there is “no basis for any conceivable threat“. They reaffirmed this in a 2008 update to the report. Two subsequent papers also confirmed their findings. However, one researcher caused a stir on 10 August, concluding: “At the present stage of knowledge there is a definite risk from mBHs production at colliders”. On 21 March an injunction was filed to stop the LHC’s start-up. The US government called for its summary dismissal after the 2008 report. On 26 August a suit was filed against CERN in the European Court of Human Rights in Strasbourg. This alleged that the LHC poses grave risks for the safety of the 27 members of the European Union and its citizens. The request was summarily rejected on the 29th. Though the case that it violates the right to life is still pending.

So what is the controversy? (Here comes the science bit, so pay attention!)

The immediate “threat” would come if there was a sudden release of the energy inherent in the system. The total energy carried by the two beams will reach 724 MJ. This is the same as 173 kg of TNT. Though unlikely that an accidental release could occur, it would damage the CERN facility itself.

The greater controversy, however, comes from the nature of the strange phenomena some believe the LHC could produce.

Strangelets

Strangelets are a hypothetical form of something called strange matter. If they exist and if they were produced at the LHC, they could conceivably cause a runaway fusion process. This would convert all the nuclei (atoms) in the planet to strange matter. And it would turn the Earth into a strange star. The creation elsewhere in the universe of quark stars (by natural phenomena) are one theory offered for gamma ray bursts. And strange matter is a candidate for the mysterious dark matter of cosmology. Neutron stars that don’t emit radio waves may be quark stars.

But the suggestion that the LHC could destroy the Earth in this way is highly controversial. The probability of strangelet creation decreases at higher energies. The LHC will work at higher energies than the Relativistic Heavy Ion Collider (RHIC) and similar colliders that have been running since the 1980s. This means the LHC is less likely to produce them. And models suggest strangelets are only stable at energies much less than the 14 TeV of the LHC.

But, scientists will be looking for short-lived, unstable strangelet production from the LHC.

Micro Black Holes

It may be possible that the LHC could produce micro black holes. It depends on whether extensions to the standard model of physics are correct or not. But the standard model suggests any produced would decay quickly by Hawking radiation. This is thermal (heat) radiation. It is still theoretical as it has never been observed and no experiment has yet been devised to allow it to be. The controversy centres around the possibility that micro black holes could stay in the Earth’s gravitational pull and accumulate (accrete) matter from the planet.

The LHC Safety Assessment Group notes the broad agreement among physicists that Hawking radiation exists. And the also argue that even stable micro black holes could not accumulate matter “in a manner dangerous for the Earth”. They also say “they would also have been produced by cosmic rays and have stopped in the Earth or some other astronomical body, and the stability of these astronomical bodies means that they cannot be dangerous.”

Vacuum Bubbles

Another proposed catastrophe from the LHC was also proposed before the RHIC was turned on. If I understand this right (and I have to admit I’m struggling here!), it could create a region of space (around CERN or wider) in which the laws of physics differ from the norm we know. But the energies needed to create such a region are far higher than those produced by the LHC. Given we have seen cosmic rays at much higher energy, scientists argue, there is no threat.

Magnetic Monopoles

A magnetic monopole is simply a magnet with one pole (all magnets we know of have two: north and south). Although theoretically possible, none has yet been observed. They are thought to be too massive (heavy) to be produced in any particle accelerator. Which begs the question what is so bad if one were to be?

Conclusion

So, the LHC is thought to be safe by the vast majority of mainstream science. But just for fun, if the world did end on 21 October at the first full energy test – what would you do with the last day of your life?

Sources

http://en.wikipedia.org/wiki/Hawking_Radiation
http://en.wikipedia.org/wiki/Large_hadron_collider
http://en.wikipedia.org/wiki/Magnetic_monopole
http://en.wikipedia.org/wiki/Micro_black_holes
http://en.wikipedia.org/wiki/Relativistic_Heavy_Ion_Collider
http://en.wikipedia.org/wiki/Safety_of_the_Large_Hadron_Collider
http://en.wikipedia.org/wiki/Strangelet
http://en.wikipedia.org/wiki/Vacuum_bubble
http://www.bbc.co.uk/bbcfour/listings/programme.shtml?day=today&service_id=4544&filename=20080904/20080904_2100_4544_24651_60
http://www.bbc.co.uk/bbcfour/listings/programme.shtml?day=today&service_id=4544&filename=20080904/20080904_2000_4544_24656_60

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: