A nebula is a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter.
An imaginary line about which a body rotates.
Equatorial regions are located in a band around the Equator and cover about 6% of the Earth’s surface. They are often in lowland areas and have a climate that is hot and wet all year round. Tropical rainforests grow in the equatorial regions.
A minor planet is an astronomical object in direct orbit around the Sun that is neither a planet nor exclusively classified as a comet.
The upper hard earth’s crust is cracked into very large pieces, which are known as ”Plate Tectonics. These tectonic pieces are in continuous motion. Some of them are moving closer to each other, such motion is known as the convergent boundary, while others are moving apart from each other, such motion is known as “divergent boundary”. There is a third type of motion that is transverse motion. Two plates in transverse motion are known as “Tranverse Boundary”.
Radiometric dating, which is also known as radioactive dating or radioisotope dating, is a technique, which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.
Isotopes are two or more different atoms of an element, in which the atomic number is equal, but their atomic weight is different from one another. Some elements are found in a single atomic form, while some elements like hydrogen, uranium, rubidium, barium etc, are have different atomic forms. Two different types of atoms on the basis of atomic weight are known as “Isotopes”.
A radioactive isotope is any of the species of the same chemical element that have different masses and unstable nuclei that emit radiation.
The presence of salts in water (seawater) is known as the salinity of the water.
Organic evolution is the theory that more recent types of plants and animals have their origins in other pre-existing forms and that the distinguishable differences between ancestors and descendents are due to modifications in successive generations.
Sedimentation is the process of settling or being deposited as a sediment. The weathered rock particles starts moving from highlands to lowlands, get deposited. This process is known as sedimentation.