This student text describes Epoch Eight in our Evolving Universe. It is the second student text of the Tracing the Origins of Our Universe activity.

We will start in Epoch Eight as we trace the origins of quarks and electrons back to the beginning of the universe. Epoch Eight is the present epoch, the epoch in which we live.

For each epoch you will have a tactile card as well as a descriptive text to help you visualize where quarks and electrons were located and the role they played in the universe during that particular period.

Some of the critical factors that change as we go backwards in time include the following:

the time span of each epoch, which decreases as we go from Epoch Eight back to Epoch One;

the temperature, which increases as we go from Epoch Eight back to Epoch One;

the form of matter may change during an epoch;

the location and relative freedom of quarks and electrons may change during an epoch;

and the size of the universe. One of the precepts of the standard cosmological model is that the universe is expanding, so we would expect that as we go trace the origins of the universe, the universe will be smaller.

Epoch Eight has the longest time span of the universal epochs. It started when the universe was about three hundred thousand years old. Scientists think that the universe is fifteen billion years old.

So that makes Epoch Eight about fourteen billion, seven hundred thousand years long. Lots of changes occurred during this time.

During Epoch Eight, the average temperature of the universe decreased from three thousand kelvins to three kelvins. Three thousand kelvins is relatively hot by our standards and three kelvins is very cold. It is only three degrees above absolute zero.

This means that there must be some very large, very cold areas of the universe because here on earth, temperatures even around the north and sound poles usually don’t get much below two hundred kelvins.

And we have already found that the temperatures in stars like our Sun can be as high as ten million kelvins.

Even at the beginning of the epoch, when the average temperature was about three thousand kelvins, quarks and electrons were not free. They were found in the hydrogen and helium atoms that were the major constituents of the hot gas that made up the universe.

This is a description of figure on Tactile Card Eight. Have your card available so you can follow the description. Feel the number Eight in the upper left corner of the card.

The figure in box A on Tactile Card Eight represents a hydrogen atom. The circle represents the farthest distance the electrons can travel away from the nucleus.

The set of two up quarks and one down quark represent a proton. The small dash at the upper right of the circle represents an electron.

The figure in box B of the Tactile Card Eight card represents a helium atom, with four sets of quarks making up the nucleus. The two sets of two up quarks and one down quark indicate two protons.

The two sets of one up quark and two down quarks indicate two neutrons. There are two electrons outside the nucleus but inside the atom.

This is the end of the description of Tactile Card Eight. Place your Epoch Eight tactile card on a table or other surface that has enough space for eight cards.

As the temperature decreased during Epoch Eight, the gaseous clouds of hydrogen and helium became stable regions in which matter was more concentrated.

Epoch Eight is called the structural epoch because some cosmic matter condensed into liquids and solids during this epoch.

The gravitational attraction between the masses of atoms caused more hydrogen and helium clouds to concentrate and start rotating. These large, rotating accumulations of hydrogen and helium were the building blocks of today’s galaxies, which then formed clusters and superclusters of galaxies.

These cosmic structures and the interstellar gases in the spaces between them were formed from the hydrogen and helium atoms made of quarks and electrons. And, oh yes, plant and animal life developed, at least here on earth.

Quarks and electrons are now found in the atoms that make up your body, in the atoms of everything on the Earth and of the Earth and other solar planets, galaxies and cosmic superstructures as well as in the interstellar gases. Quarks make up the nuclei of all these atoms.

But where did the hydrogen and helium atoms come from? How and when did quarks and electrons form these atoms? Let’s trace them back another epoch in time.