Beyond the God Particle (55 page)

16
. “Clue,” or “Cluedo,” is great preparation for a budding physicist. See
http://en.wikipedia.org/wiki/Cluedo
(site last visited 3/26/2013).

17
. Lederman and Hill, “
Symmetry and the Beautiful Universe
,” chap 8, note 2; T. D. Lee and C. N. Yang, “Question of Parity Conservation in Weak Interactions,”
Physical Review
104 (1956); J. Bernstein, “
Profiles: A Question of Parity
,”
New Yorker Magazine
38 (1962); M. Gardner,
The New Ambidextrous Universe: Symmetry and Asymmetry, from Mirror Reflections to Superstrings
(New York: W. H. Freeman and Co., 1991).

18
. Even a complex break shot, where a cue ball scatters the ten pool balls, could in principle occur in a time-reversed way, but it is simply extremely improbable that it could be arranged to occur—this is why complex systems look funny when they run backward in time—the reversed physical processes are allowed, but it would be virtually impossible to set everything in motion to make things happen that way. The evolution of life is such a process—it is governed by the laws of physics, but it happens very slowly over many, many “collisions” of large macromolecules under rare circumstances. Once certain self-replicating macromolecules are formed, the process can build greater complexity through “random selection.”

19
. In physics we always pose, and solve, “if-then” problems. Let's consider the following elementary physics question (Q1):
If
a particle at time
t
₁
is located at
x
₁
traveling at a velocity,
V
,
then
where will the particle be at time
t
₂
? The answer is
x
₂
=
x
₁
+
V
(
t
₂
–
t
₁
). But even this simple result illustrates some deep philosophical issues as to how we describe nature.

Consider now
a time-reversed question
(Q2): “
If
at time
t
₁
the particle is located at
x
₂
and traveling with velocity
–V
(velocities change sign when we reverse the direction of time, as you well know by running a DVD backward and seeing a car driving in reverse down the highway),
then
where will it be at time
t
₂
?” Now the answer, by common sense, must be
x
₁
. And indeed, we see, upon a little rearranging, that our previous formula gives us
x
₁
=
x
₂
–
V
(
t
₂
–
t
₁
).

This is indeed the correct answer for the time-reversed question, yet it came from the original problem's solution after a little rearranging of the math. The answer for the forward-in-time question contains the answer for the backward-in-time question—we get both from one in the same physics equation! Our physical description of this system is the same if time is running forward as when time is running backward. In the second question, Q2, we set up
initial conditions
that were the
opposite
to those in the first question, Q1, that is, in Q2 we put the particle at the location,
x
₂
, where it ended up in Q1, and we reversed the direction of motion, replacing
V
by –
V
. We find that after an equivalent time interval, the particle in Q2 gets to location
x
₁
, where it started in Q1. This shows that we can do time-reversed physics without actually reversing the flow of time. We need only reverse the directions of motions and swap the final destinations for the initial one.

20
. The particle
K
⁰
and the antiparticle
actually oscillate back and forth between one another,
K
⁰
↔
. If CP is an exact symmetry, then the oscillation phase from the
K
⁰
into the
should be
exactly the same
as the reverse oscillation phase, from the
into the
K
⁰
. Experimentally, however, it is found that the oscillation phase to go from
K
⁰
↔
is slightly different, at one part in a thousand, than the oscillation phase from
↔
K
⁰
. J. H. Christenson, J. W. Cronin, V. L. Fitch, and R. Turlay, “Evidence for the 2π Decay of the K(2)0 Meson,”
Physical Review Letters
13 (1964): 138–40. This is not CP invariant. In refined experiments with neutral K-mesons, direct confirmation of the violation of T-symmetry has also been confirmed. The combined symmetry transformation, CPT, is a symmetry of the decays. CP violation is now turning up in other particles, called B-mesons, containing the heavy beauty quark. Search online for “CP violation.”

CHAPTER 10. NEUTRINOS

1
. See “Supernova” and references therein,
http://en.wikipedia.org/wiki/Supernova
(site last visited 3/28/13). Or search online for “supernova” for some great images. We are mainly describing Type II supernovae in the text. There are several kinds of supernovae with differing evolutionary processes, as detailed in the article.

2
. See “Galaxy,”
http://en.wikipedia.org/wiki/Galaxy
(site last visited 3/28/13). Search online for “galaxies” for images.

3
. See “Eta Carinae,”
http://en.wikipedia.org/wiki/Eta_carinae
(site last visited 3/28/13). Under the heading “Possible Effects on Earth,” “It is possible that the Eta Carinae hypernova or supernova, when it occurs, could affect Earth, which is about 7,500 light years from the star…. a certain few [scientists] claim that radiation damage to the upper atmosphere would have catastrophic effects as well. At least one scientist has claimed that when the star explodes, ‘it would be so bright that you would see it during the day, and you could even read a book by its light at night.’” A supernova or hypernova produced by Eta Carinae would probably eject a gamma ray burst (GRB) out from both polar areas of its rotational axis. Calculations show that the deposited energy of such a GRB striking Earth's atmosphere would be equivalent to one kiloton of TNT per square kilometer over the entire hemisphere facing the star, with ionizing radiation depositing ten times the lethal whole body dose to the surface. This catastrophic burst would probably not hit Earth though, because the rotation axis does not currently point toward our solar system. If Eta Carinae is a binary system, this may affect the future intensity and orientation of the supernova explosion that it produces, depending on the circumstances.