London: The moon, which is known for its ability to cast an impact on the Earth`s tides, has been causing yet another effect over the last few years – disrupting experiments at the Large Hadron Collider.
The gravitational effect of the moon may be generally weak on the Earth`s surface, but with the collider stretching out in a ring with a 27 kilometre circumference, the effects are strong enough to be felt.
The scientific research facility on the Swiss-French border is picking apart neutrons and electrons while hunting for the elusive Higgs Boson particle, and technician Pauline Gagnon, working on the collider, blogged her surprise when she realised the cause for less “particle collisions” were happening on her shift.
“The shift crew (about ten people plus dozens of experts on call) must keep the detector running smoothly, tackling every problem, big or small, as fast as possible,” the Daily Mail quoted her as writing on her blog.
“Data was coming in at a high rate and all sub-detectors were humming nicely. Not a glitch in hours so we were getting slightly sleepy nearing the end of the shift around 10pm.
“So when a colleague from the trigger system - the system that decides which events are worth keeping - called to inquire about recurrent splashes of data, I was rather puzzled.
“I quickly went around, asking a few shifters to check their system. Nobody had a clue.
“We measure how many collisions are happening per second in each experiment from the two beams of protons circulating in opposite direction in the LHC tunnel,” she wrote.
On the graphs detecting particle interactions, there were regular dips on both of the Hadron`s two main measuring systems.
“Since both were registering these dips, it had to be coming from a common source, the LHC,” Gagnon said.
“So I called the LHC control room to find out what was happening. “Oh, those dips?”, casually answered the operator on shift. “That`s because the moon is nearly full and I periodically have to adjust the proton beam orbits.
“This effect has been known since the LEP days, the Large Electron Positron collider, the LHC predecessor.
“The LHC reuses the same circular tunnel as LEP.
“Twenty some years ago, it then came as a surprise that, given the 27 km circumference of the accelerator, the gravitational force exerted by the moon on one side is not the same as the one felt at the opposite side, creating a small distortion of the tunnel.
“Since the moon`s effect is very small, only large bodies like oceans feel its effect in the form of tides.
“But the LHC is such a sensitive apparatus, it can detect the minute deformations created by the small differences in the gravitational force across its diameter. The effect is of course largest when the moon is full.
“What came as a surprise to me was to witness the dynamic aspect of it.
“As the moon was rising in the sky, the force it exerted changed ever so slightly, but even these infinitesimal changes were big enough to require a periodic correction of the orbit of the proton beams in the accelerator to adapt to a deformed tunnel.
“Other surprising disturbances were also observed in the LEP days like one that appeared every day at fixed times. It took months and a train company strike to figure it out.
“These perturbations were created by the passage of the fast train linking Geneva to Paris, the TGV, since it releases a lot of electrical energy into the ground.
“The LHC is also sensitive to the hydrostatic pressure created by the water level in nearby Lake Geneva that also deforms the tunnel shape.
“So next time you want to know if the moon is full, just check the luminosity plot from the LHC to see if you can spot those small glitches caused by the operator correcting the beam orbit,” she added.