Hello Sam,

thanks for the entertaining calculation and for cross-checking the information I had given you. All I had to do was look at my watch!

I disagree with you though in the sense that this effect is really on the tunnel or rather, the Earth crust. It is really the tunnel that moves and the operator has to move the beam to keep it in the center of the tunnel (or beam pipe to be precise).

Cheers, Pauline

]]>thanks very much for your prompt reply. I just did a rough Newtonian calculation of how much the moon’s tidal acceleration will affect the orbits

of the particles in LHC. Calculated

d=1/2 g t^2,

where

g=G M/R^3 S,

where G is Newtons constant, M is the mass of the moon, R, the earth moon distance and S the diameter of LHC, (around 9 km).

The effect, is of course small but builds up over time because of the t^2. If we ask when will the distortion d of the orbit

equal the beam width of 1 mm, the answer turns out to be

about

5000 seconds,

ie. between one hour and two. Of course, they may correct more often than this, but the fact that it

agrees with your observations makes me believe that the effect is on the particle orbits rather than the

LHC tunnel.

Is there some way of estimating the effect of the moon’s gravity on the tunnel?

with best wishes

Sam

Sorry the graph is not easy to see. The labels are also missing… but the blips are roughly 1-2 hours apart. This is what I recall from being on shift that night and correspond roughly to showing about 12 hours on the plot.

Cheers, Pauline

]]>how often do they have to correct for the moon’s effect. (Every 20 minutes or every few hours).

The graph on my screen is so small that I cant read the axes labels.

Sam ]]>