Atoms
Bill Bryson uses atoms in the novel to symbolize the eternity of life. Everything that exists on Earth is made of atoms. Interestingly, Bill Bryson describes the eternity of atoms implying that human life does not end at death. When a person dies, his body decomposes, and the atoms of the decomposing corpse are released to the ecosphere to create other organisms. Consequently, a person today has atoms from his ancestors who died thousands of years ago. In other words, our ancestors are living in us today. In the same way, future generations will have our atoms, which implies that human life is eternal.
The mattress
In the novel A Short History of Nearly Everything by Bill Bryson, the mattress is a symbol of space-time. Many people assume that space is empty. However, the relativity theory by Einstein proves that space is made of interwoven fabric, which forms the universe's structure. The relativity theory further explains how gravitational pull is created. For instance, a mattress sags when a heavy object is placed on it. In that case, a ball on the mattress rolls towards the sagging part, the center of gravity.
The metaphor of the freeway
The metaphor of the freeway represents the dangers of Earth's orbit. The author uses this metaphor to explain how dangerous the Earth's orbit is. The freeway is the route followed by the meteors, which often collide while passing on the Earth's orbit. The colliding of the meteors is very dangerous because it causes the life of some organisms to become extinct. For instance, Bryson explains how the colliding of meteors led to the extinction of dinosaurs sixty-five million years ago. Meteors pass through the Earth's orbit three times a week, thus posing a great danger to living organisms if any collision occurs.