The electroweak force is pretty
romantic because it's really the unification of two forces, electromagnetic
force, and the weak force. At really
high (like, universe-creating high) energy, they're the same thing, but at
energies where you and I live, they look pretty different, so we'll talk about
them separately.
1. Electromagnetic force:
The electromagnetic force is 1037 (*ahem* that's
a 1 with 37 zeroes after it) times stronger than the gravitational force that
keeps you anchored to the earth. So for
the record, if you want to compliment someone, telling them you're magnetically
attracted is making a stronger point than telling them that you gravitate
toward them.
They say opposites attract, and whether that's true in love
or not, the electromagnetic force causes opposite charges and opposite magnetic
poles to be attracted to each other.
North poles of a magnet are attracted to south poles, and positive
charges are attracted to negative charges.
On the other hand, the same force causes things with like magnetic
polarity or like electrical charge to be repulsed. The electromagnetic force causes electrons to
be attracted to the nucleus in atoms. It
also causes protons in the nucleus to be repulsed by each other. The nucleus stays together regardless of this
repulsion between positive charges because of the strong force, which we will
discuss in a future post.
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| Electromagnetic force causes opposites to attract... At least when it comes to magnets and electrical charges. |
Quantum electrodynamics says that massless virtual photons
mediate the electromagnetic force. All
four fundamental interactions are mediated by different particles, the mass of
which determine the range of the interaction.
Massless particles, gravitons and photons, mediate gravitation and
electromagnetism, respectively, so the range is essentially infinite. Of course, the strength of the field drops in
an inverse square relationship with the distance from the source, so at large
distances from the source, the force becomes extremely weak and we tend to
largely ignore them. In other words,
physical separation does not "make the heart grow fonder," at least
not when it comes to electromagnetism.
2. Weak force
The weak force also relies upon exchange
of extremely massive mediating particles called W particles, and has an
extremely limited distance (~10-18 m). Quarks (the stuff that protons and neutrons
are made of) come in six different "flavors," (strange, charm, up,
down, top, and bottom) and the weak force is the way quarks change flavors.
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| Flavor changes by the weak force |
The weak force is important in
things like beta emission, a kind of radioactive decay. Protons and neutrons are composed of up and
down quarks. Protons are two up quarks
and one down quark, and neutrons are two down quarks and one up quark. In the process of beta emission, a down quark
of a neutrons changes to an up quark, changing a neutron into a proton. In addition to the emission of a beta
particle (now we know it is an electron) and a neutrino, this flavor change
results in the transmutation of an atom, changing its identity from one element
to another element. For example,
Carbon-14 in living organisms (and otherwise) decays to Nitrogen-14 over
time. Carbon dating (the only type of
dating some people will ever do *zing*) takes advantage of the steady decay of
Carbon-14 to Nitrogen-14 to estimate the age of things like bone fragments and
wood artifacts.
Stay tuned, because in the next
installment we will talk about the strong force, which is the strongest of all
four fundamental forces of nature.
