6 Forces Are Also Caused by Particles
47
therefore easily be that they do not have an electromagnetic-like force, but only
a strong force. In which case dark matter would form big blobs.
The issue of range is much better understood from fundamental principles,
in terms of the masses of the exchange particles. The heavier the exchange
particle, the shorter the range. There is a principle called “gauge invariance”
which, for example, explains why the electromagnetic forces have infinite
range. (See later for an explanation of gauge invariance). Similar is the case
for gravitational forces, where Einstein’s coordinate invariance plays the same
role. Of course, you could always ask, who decided that these principles must
be obeyed in nature? That is the next level question which more fundamental
theories like string theory attempt to answer in terms of their own set of
fundamental principles. We could of course ask the same question of string
theory as to who decided the principles of string theory. These questions could
go on.
The question of force strength is, however, a different story and it is a
big mystery. Why do the different force strengths turn out to be what they
are? Is there a fundamental reason behind it, like for the range, which can
be uncovered from a set of principles and equations, or is there some “divine
hand” which sets them at what they are, so humanity could exist? In other
words we do not know any principle like gauge invariance for electricity, which
would tell us what the strength of electric force is. The last alternative which
is clearly not very satisfactory to a scientific mind is called the “anthropic
principle” as mentioned earlier. We will discuss more of this later on in the
book. Could it be that there are many universes, in which case, the anthropic
picture makes more sense? We do not know the answer to these questions.
Thus, we have not made any progress in understanding strengths of forces,
even to the first stage of having a principle, as we have for the range of the
forces. Even getting to the stage of finding a principle that would determine
the strength of forces is a challenge to the human mind and continues to be
an obsession to many physicists over the ages.
A related question which is often debated is whether over the age of the
universe, the strengths of forces change or they have remained same from
beginning to the end. If, for example, they changed with time, it would be
hard to believe that some unknown hand (or a specific universe) has not only
fixed the desired initial value of the strength but also the rate of change of
the strength over time. That would be an extra burden on enthusiasts of the
anthropic principle and multiverse.
47
therefore easily be that they do not have an electromagnetic-like force, but only
a strong force. In which case dark matter would form big blobs.
The issue of range is much better understood from fundamental principles,
in terms of the masses of the exchange particles. The heavier the exchange
particle, the shorter the range. There is a principle called “gauge invariance”
which, for example, explains why the electromagnetic forces have infinite
range. (See later for an explanation of gauge invariance). Similar is the case
for gravitational forces, where Einstein’s coordinate invariance plays the same
role. Of course, you could always ask, who decided that these principles must
be obeyed in nature? That is the next level question which more fundamental
theories like string theory attempt to answer in terms of their own set of
fundamental principles. We could of course ask the same question of string
theory as to who decided the principles of string theory. These questions could
go on.
The question of force strength is, however, a different story and it is a
big mystery. Why do the different force strengths turn out to be what they
are? Is there a fundamental reason behind it, like for the range, which can
be uncovered from a set of principles and equations, or is there some “divine
hand” which sets them at what they are, so humanity could exist? In other
words we do not know any principle like gauge invariance for electricity, which
would tell us what the strength of electric force is. The last alternative which
is clearly not very satisfactory to a scientific mind is called the “anthropic
principle” as mentioned earlier. We will discuss more of this later on in the
book. Could it be that there are many universes, in which case, the anthropic
picture makes more sense? We do not know the answer to these questions.
Thus, we have not made any progress in understanding strengths of forces,
even to the first stage of having a principle, as we have for the range of the
forces. Even getting to the stage of finding a principle that would determine
the strength of forces is a challenge to the human mind and continues to be
an obsession to many physicists over the ages.
A related question which is often debated is whether over the age of the
universe, the strengths of forces change or they have remained same from
beginning to the end. If, for example, they changed with time, it would be
hard to believe that some unknown hand (or a specific universe) has not only
fixed the desired initial value of the strength but also the rate of change of
the strength over time. That would be an extra burden on enthusiasts of the
anthropic principle and multiverse.