The Big Bang theory is the prevailing cosmological model for the earliest known periods of the universe and its subsequent large-scale evolution. It states that the Universe was in a very high density state and then expanded. If the known l...

The Universe is all of time and space and its contents. The Universe includes planets, stars, galaxies, the contents of intergalactic space, the smallest subatomic particles, and all matter and energy. The majority of matter and energy is m...

The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for l...

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the world, the Blue Pl...

Earth is the third planet from the Sun. It is the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the world or the Blu...

Venus is the second planet from the Sun and the sixth largest. On June 8 2004, Venus will pass directly between the Earth and the Sun, appearing as a large black dot travelling across the Sun's disk. This event is known as a "transit of Ve...

Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of icy trans-Neptunian objects. It was the first such object to be discovered. It is the largest and second-most massive known dwarf planet in the S...

The Nine Planets is an overview of the history, mythology, and current scientific knowledge of each planet and the major moons in our solar system. Each page has my text and NASA's images, some have sounds and movies, most provide reference...

Saturn is the sixth planet from the Sun and the second largest. In Roman mythology, Saturn is the god of agriculture. The associated Greek god, Cronus, was the son of Uranus and Gaia and the father of Zeus (Jupiter). Saturn is the root...

Uranus is the 7th planet from the Sun. It was discovered in 1781 by William Herschel and named for the Greek god personifying heaven. A blue-green gas giant, it has almost 15 times the mass of Earth and over 50 times its volume. It is less...

Neptune is the eighth planet from the Sun and the fourth largest (by diameter). Neptune is smaller in diameter but larger in mass than Uranus. In Roman mythology Neptune (Greek: Poseidon) was the god of the Sea. After the discovery o...

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often described as the "Red Planet" because the iron oxide prevalent on its surface gives it a...

The Cambrian is the first geological period of the Paleozoic Era, lasting from 541 to 485 million years ago (mya) and is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by...

Pangaea or Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It formed approximately 300 million years ago and then began to break apart after about 100 million years. Unlike the present Earth, much...

The Permian is a geologic period and system which extends from 299 to 252 million years ago. It is the last period of the Paleozoic Era, following the Carboniferous Period and preceding the Triassic Period of the Mesozoic Era. The concept o...