From about 10í^35 of a second after the moment of creation, we can tell a
good scienti¿ c story. Something appeared. It was tiny (the size of an atom
perhaps) and inconceivably hot. It was expanding rapidly and cooling fast.
At this point, energy and matter were indistinguishable. As this “something”
cooled, “things” and “forces” appeared, in a series of “phase changes,” rather
like the change steam undergoes as it turns into water. Gravity appeared from
the chaos, as did the “strong” and “electromagnetic” forces.
From 10í^33 to 10í^32 seconds, the Universe expanded faster than the speed of
light, growing from the size of an atom to the size of a galaxy. This phase is
known as “inÀ ation.” Within the ¿ rst second, quarks—the building blocks
of atomic nuclei— were created in positive and negative forms. These then
proceeded to annihilate each other, leaving just a few survivors. These forlorn
survivors formed protons (which are positively charged) and neutrons (which
are electrically neutral).
Electrons (lighter than protons and negatively charged) were created in
an equally violent process. A few minutes after the big bang, the Universe
consisted of a hot “plasma” (a mixture of energy and charged subatomic
particles, a bit like the center of the Sun today).
About 380,000 years later, the Universe was cool enough for positively
charged protons to capture negatively charged electrons, creating the
¿ rst, simple atoms of hydrogen and helium. Because the positive charges
of protons are cancelled by the negative charges of electrons, atoms are
electrically neutral, so electromagnetic radiation (of which light is just one
form) could now travel freely through the Universe without getting tangled
in networks of electromagnetism. The Universe cooled, entering a “dark
age” that lasted several hundred million years.
Other entities and forces were created that we don’t understand. We call this
missing stuff “dark matter” or “dark energy.” We know it’s there because
studies of the movements of galaxies show that something is exerting a
powerful gravitational pull. This stuff may account for up to 95% of the
Universe’s total mass. Seventy percent of that total may consist of undetected
forms of energy. Twenty-¿ ve percent may consist of matter in forms we
cannot detect because they emit no radiation (such as cold, dead stars or