MOTION MOUNTAIN

356 challenge hints and solutions
4.5 V
F I G U R E 177 How to get electrical shocks
from a 4.5 V pocket battery.
Vol. II, page 103
Vol. VI, page 107
Vol. V, page 308
Vol. VI, page 20
in this case the signals from the electric cap to the computer – and the password checking system.
Both are as vulnerable as any other password system. (If you want to learn about security, read
the writings of Bruce Schneier, most of which are available on the internet.)
Challenge 231, page 230: The maximum electric and magnetic field values are those that exert
the maximum possible forcec 4 /4G on an elementary chargee.
Challenge 233, page 232: See challenge 29.
Challenge 235, page 233: One can measure smallest charges, showing that they are always multiples
of the same unit.This method was used by Millikan. One can also measure current fluctuations,
and show that they follow from shot noise, i.e., from the flow of discrete charges.
Challenge 238, page 234: Earth’s potential would beU=−q/(4πε o R)=60 MV, where the number
of electrons in water must be taken into account.
Challenge 239, page 234: There is always a measurement error when measuring field values,
even when measuring a ‘vanishing’ electromagnetic field. In addition, quantum theory leads to
arbitrary small charge density values through the probability density due to wave functions.
Challenge 243, page 237: The issue is: is the ‘universe’ a concept? In the last volume of this adventure
we will show that it is not.
Challenge 245, page 244: When thinking, physical energy, momentum and angular momentum
are conserved, and thermodynamic entropy is not destroyed. Any experiment showing anything
different would point to unknown processes. However, there is no evidence for such processes.
Challenge 246, page 245: The best method cannot be much shorter than what is needed to describe
1 in 6000 million, or 33 bits. The Dutch and UK post code systems (including the letters
NL or UK) are not far from this value and thus can claim to be very efficient.
Challenge 247, page 245: For complex systems, when the unknowns are numerous, the advance
is thus simply given by the increase in answers. For the universe as a whole, the number of open
issues is quite low, as shown later on; inthis topic there hasnot been much advancein the past
years.Buttheadvanceisclearly measurableinthiscaseaswell.
Challenge 248, page 246: Is itpossibleto usetheterm ‘complete’ whendescribing nature?Yes,
itis.Foraclear-cut answer,seethelastvolumeofouradventure.
Challenge 250, page 247: There are many baths in series: thermal baths in each light-sensitive
celloftheeyes,thermalbathsinsidethenervestowardsthebrainandthermalbathsinsidebrain
cells.
Challenge 252, page 248: Yes.
Challenge 254, page 255: Chips based on trits would have to be redesigned from scratch. This
would beawasteofresources andofprevious work.
Motion Mountain – The Adventure of Physics copyright © Christoph Schiller June 1990–November 2015 free pdf file available at www.motionmountain.net