As of 2014, there is no single piece of concrete evidence to prove the existence of alien life, although most scientists today agree that the potential of discovering life outside Earth is much greater than previously thought. According to Discovery News, alien life is considered highly probable and will likely be discovered by the year 2024.Know More
Fictional accounts of aliens found in mainstream media aren't considered an accurate representation of alien life. Some scientists believe that aliens will be simple life forms such as bacteria or single celled organisms while others believe that more complex forms of life exist. Within the Milky Way galaxy, there are several planets that may be able to support some type of life.
NBC News has stated that over half of the galaxies visible from Earth's telescopes may have planets and solar systems similar to our own. Scientists often determine the probability of alien life by examining the availability of water on other planets. Currently, there are several planets that are thought to have some form of water available, including Mars and Titan, one of Saturn's moons.
The debate of whether alien life exists is hinged on the lack of definite proof of other species outside Earth. According to New Scientist, there are some examples that point to irrefutable evidence. For example, methane has been found on Mars. The presence of methane is linked to the metabolic process that occurs when life forms process organic compounds for energy. This evidence is controversial and has only been accepted as proof of alien life by a portion of scientists.Learn More
Also known as HR Diagram, the Hertzsprung-Russel diagram is believed to be one of the most important tools used in the study of evolution. Independently developed in the early 1920s, the HR Diagram is primarily used to plot the temperature of stars against their luminosity. It is also used to plot the color of the stars against their magnitude.Full Answer >
The perigee is the closest the moon gets to Earth, while the apogee, on the opposite side of the moon's orbit, is the farthest away it moves from Earth. Perigee and apogee can be used to describe the orbits of other objects orbiting Earth, such as man-made satellites.Full Answer >
The albedo of Earth is the percentage of sunlight it reflects back into outer space. Scientists believe this is about 31 percent overall. Generally, sunlight that strikes light-colored objects on the planet, such as snow or ice, can have an albedo of up to 90 percent.Full Answer >
The term "geocentric" means "earth-centered," while "heliocentric" means "sun-centered." In medieval astronomy, two models were proposed regarding the structure of the universe: the geocentric model claimed that Earth was the center of the cosmos, while the heliocentric model suggested that the sun was the center of the universe.Full Answer >