Fictional planets of the Solar System 40 Eridani A. Counter-Earth was a hypothetical planet sharing an orbit with Earth, but on the opposite side of the Sun (hence Earth and Counter-Earth would always be invisible to each other). The idea of a counter-Earth has never been a serious scientific hypothesis in modern times. Phaëton is a name given to a supposed planet existing in the past between the orbits of Mars and Jupiter, which no longer exists, having become the Solar System's asteroid belt. Proposed not long after the discovery of multiple asteroids at the beginning of the 19th century, the idea that the asteroids were
Entropic gravity surface area would be given by: From algebraic substitution of these into the above relations, one derives from first principles Newton's law of universal gravitation: Entropic gravity, as proposed by Verlinde in his original article, reproduces the Einstein field equations and, in a Newtonian approximation, a 1/r potential for gravitational forces. Since its results do not differ from Newtonian gravity except in regions of extremely small gravitational fields, testing the theory with earth-based laboratory experiments doesn’t appear feasible. Spacecraft-based experiments performed at Lagrangian points within our solar system would be expensive and challenging. Even so, entropic gravity in its current