[EAS] Large Hadron Collider Startup

Peter J. Kindlmann pjk at design.eng.yale.edu
Wed Sep 10 02:55:19 EDT 2008

Dear Colleagues -

With the word "science" found only once in Barack Obama's acceptance 
speech in Denver, and not at all in McCain's acceptance  speech in 
St. Paul, it is perhaps not surprising that this won't be a big US 
news event. So tune in to the BBC <http://news.bbc.co.uk/>.


WHAT'S NEW   Robert L. Park   Friday, 5 Sep 08   Washington, DC

Big Bang Day starts at 8:30 am on September 10 with live coverage 
from the  LHC control room on BBC radio.   TV coverage will be on 
Eurovision, better known for the Eurovision Song Contest.   It's 
rather nice to have public interest in a basic scientific experiment, 
whatever the reason.  And after Wednesday's test?  It will be time to 
start shutting the LHC down for the winter.  Maybe in the spring they 
can start a serious search for the Higgs.  Meanwhile the LHC rap is 
playing well on You Tube.

The American Institute of Physics Bulletin of Research News
Number 871 September 9, 2008      www.aip.org/pnu
by Phillip F. Schewe, James Dawson, and Jason S. Bardi

MINI BLACK HOLES NO DANGER.   The Large Hadron Collider, the largest 
and most expensive scientific instrument ever built in peacetime, 
begins operations on September 10 when a beam of high-speed protons 
begins shooting around the machine's 16 mile (27 -kilometer) circular 
tunnel beneath Geneva, Switzerland.  When the protons collide with 
each other inside the machine, one thing that scientists are certain 
won't happen is the production of miniature black holes that gobble 
up nearby matter.  A new study shows that the continuing existence of 
old stars in the sky is evidence that small black holes can't swallow 
the Earth.

That is not to say that the new collider might not actually create 
mini-black holes as no one knows for sure what will emerge from the 
debris of the LHC collisions.  Black holes are thought to represent 
the ultimate state of compressed matter, with gravity so powerful 
that any bit of matter, and even light, would be sucked inexorably 
inwards with no chance for escape if it gets too close to the black 
hole's boundary. That was the thinking about black holes before 
Stephen Hawking, the Cambridge University scientist, came forth with 
the idea that even black holes can lose energy.  The density of 
energy inside a black hole is so huge that some of it can be 
converted into creating new particles, he said.  If this conversion 
happens right at the edge of the black hole, Hawking argued, some of 
those new particles could escape, taking energy with them.  In this 
way black holes can lose energy. They can "evaporate."

There is a rule in physics that says that the smaller the black hole, 
the quicker the evaporation.  For an LHC-style black hole, estimated 
to be only a billionth of a billionth of a meter across (an 
atto-meter) the black hole would exist for a bit more than a few 
billion-billion-billionths of a second.  It wouldn't be around long 
enough to swallow any nearby matter and would pose no danger to 
ordinary matter.

But what if Hawking is wrong?  What if some black holes don't 
evaporate, but go on eating matter? What if scientists create some 
small, long-lasting black holes in Geneva, and they get loose?  This 
possibility is addressed in a new report in the journal Physical 
Review D. In their study of the matter, Steve Giddings of the 
University of California at Santa Barbara and Michelangelo Mangano of 
CERN (the parent laboratory where LHC operates) look at what happens 
if there existed a type of black hole, one we'd be concerned about, 
that could not only survive but continue to grow to a macroscopic 
size (the size of a golf ball, say) in a time shorter than billions 
of years.

If such a type of black hole existed, it would grow even quicker 
inside super-compressed stars, such as white dwarfs and neutron 
stars, where the density of matter is billions or trillions of times 
greater then the density of rock on Earth.  These celestial objects 
are created when an ordinary star runs out of fuel and starts to 
contract.  There is no LHC on such stars but a black hole could 
presumably be spawned when a passing cosmic ray, a haphazard shooting 
particle that races around the cosmos, strikes and burrows inside the 
neutron star. Since astronomers look out and see lots of perfectly 
healthy and very old white dwarfs and neutron stars of the right 
types, Giddings concludes that quickly-growing black holes, the kind 
that voraciously eat their surroundings, can't exist.  Such a 
dangerous black hole couldn't exist inside dense stars and couldn't 
exist on Earth.

Michael Peskin, a Stanford physicist who did not take part in the 
study, says that the continued existence of superdense stars act like 
the canaries that coal miners used to take underground-the idea being 
that the presence of deadly gas would more quickly overcome the 
canary, giving the miners warning of a dangerous condition.  As long 
as those stars keep sending their light, Peskin says, the Earth is 
not in danger from black holes.  (Link to Peskin comments, in APS's 
new "Physics" website at http://physics.aps.org/articles/v1/14 )
If scientists don't know for sure what particles the LHC will 
produce, why build a massive, very expensive machine to smash 
particles together in the first place? The smashing is needed because 
to explore the interior of atoms and the power of the collisions of 
particles is directly related to how deep inside the researchers can 
see.  Increasing the power of the proton beams used in the collisions 
requires increasing the size of the collider.

Why do the beams have to be so powerful?   The answer is related to 
the idea that energy can be converted from one form into another. The 
protons at the LHC whiz around their long track at a speed of 
99.999999 % of the speed of light.  Actually two beams circulate in 
the same underground tunnel in opposite directions, and when two 
protons hit each other head on, a lot of their immense energy of 
motion can, at the moment of collision, be transformed into new 
particles that weren't there a moment before. When two automobiles 
hit head-on the results are always bad.  But in the world of 
high-energy physics, instigating a violent smashup,
with lots of debris spraying out, is exactly what researchers want. 
Among the debris can be particles that might have existed billions of 
years ago but which, because of their instability, long ago decayed 
away.  Creating these rare particles again in a modern experiment is 
precisely the plan at LHC.  The thinking here is that such 
formerly-extinct species of matter can tell us things about the 
forces of nature.

PHYSICS NEWS UPDATE is a digest of physics news items arising from 
physics meetings, physics journals, newspapers and magazines, and 
other news sources.  It is provided free of charge as a way of 
broadly disseminating information about physics and physicists. For 
that reason, you are free to post it, if you like, where others can 
read it, providing only that you credit AIP. Physics News Update 
appears approximately once a week.

AUTO-SUBSCRIPTION OR DELETION: By using the expression "subscribe 
physnews" in your e-mail message, you will have automatically added 
the address from which your message was sent to the distribution list 
for Physics News Update. If you use the "signoff physnews" expression 
in your e-mail message, the address in your message header will be 
deleted from the distribution list.  Please send your message to: 
listserv at listserv.aip.org
(Leave the "Subject:" line blank.)

More information about the EAS-INFO mailing list