Rare Earth hypothesis

The Rare Earth hypothesis suggests that life on Earth needed an improbable combination of astrophysical and geological circumstances. It is proposed by Peter Ward and Donald Brownlee.^[1] If it is true, then the chances of extraterrestrial life elsewhere is close to none.^[2]

The idea has nothing to do with the chemicals known as rare earths. The proposed idea suggests that the Earth itself is rare. Certainly, we do not know how rare it is or is not. At present we cannot see planets as small as Earth orbiting their stars. Presumably that could be decided if our powers of magnification were great enough.

Rare Earth Hypothesis Media

The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.
The dense centre of galaxies such as NGC 7331 (often referred to as a "twin" of the Milky Way) have high levels of radiation which are dangerous to complex life
According to Rare Earth, globular clusters are unlikely to support life.
According to the hypothesis, Earth has an improbable orbit in the very narrow habitable zone (dark green) around the Sun.
Depiction of the Sun and planets of the Solar System and the sequence of planets. Rare Earth argues that without such an arrangement, in particular the presence of the massive gas giant Jupiter (the fifth planet from the Sun and the largest), complex life on Earth would not have arisen.
Planets of the Solar System, shown to scale. Rare Earth argues that complex life cannot exist on large gaseous planets like Jupiter and Saturn (top row) or Uranus and Neptune (top middle) or smaller planets such as Mars and Mercury.
The Great American Interchange on Earth, approximately 3.5 to 3 Ma, an example of species competition, resulting from continental plate interaction
An artist's rendering of the structure of Earth's magnetic field-magnetosphere that protects Earth's life from solar radiation. 1) Bow shock. 2) Magnetosheath. 3) Magnetopause. 4) Magnetosphere. 5) Northern tail lobe. 6) Southern tail lobe. 7) Plasmasphere.
Tide pools resulting from the tidal interactions of the Moon are said to have promoted the evolution of complex life.
Triangular prism ovair. The layers of the atmosphere are drawn to precise scale. Objects within them, such as the weather balloon are not. It is designed to be displaced at its native resolution (430×700px) or higher. It will render incorrectly (things start disappearing) below that.