Answer to Question 1
In the first phase of the big bang, the Universe was filled completely with gamma ray photons with very high energies.
As the highest energy gamma ray photons interacted, they produced proton-anitproton and neutron-antineutron pairs. Almost all of the pairs would annihilate and create new photons, but one in a billion pairs would leave a proton or neutron of matter behind.
As the Universe expanded and cooled, the photons dropped in energy and could no longer produce massive particles. The protons and neutrons created in the last phase remained. The photons could create electron-positron pairs. This process continued until the photon energy dropped below the threshold for creating electron-positron pairs. As with protons and neutrons, one in a billion electrons was left behind.
As the photon energy cooled, the protons, neutrons and electrons remained to begin nucleosynthesis.
Answer to Question 2
Visible light:
We can see light and color, and color is reflected in our eyes.
Earth is not in blackness.
Ultraviolet light:
We need to wear sunscreen.
Humans have evolved with different skin pigments.
Infrared:
We feel heat.
Earth isn't a frozen rock
Steps involved in in vitro fertilization.
The steps of an enzyme-catalyzed reaction
Vaccine Information Sheet (VIS) provided by the CDC for the varicella vaccination.
Steps in the humoral and cell-mediated immune responses.
Describe the functions of fat in the body
Primary steps in fibrinolysis