Question: In earth years, what is the period of revolution for the planet that seemed to defy the gravitational laws of the progenitor of the fundamental laws of motion?

<P0-S0> the concept of inertia can be further generalized to explain the tendency of objects to continue in many different forms of constant motion, even those that are not strictly constant velocity. <P0-S1> the rotational inertia of planet earth is what fixes the constancy of the length of a day and the length of a year. <P0-S2> albert einstein extended the principle of inertia further when he explained that reference frames subject to constant acceleration, such as those free-falling toward a gravitating object, were physically equivalent to inertial reference frames. <P0-S3> this is why, for example, astronauts experience weightlessness when in free-fall orbit around the earth, and why newton's laws of motion are more easily discernible in such environments. <P0-S4> if an astronaut places an object with mass in mid-air next to himself, it will remain stationary with respect to the astronaut due to its inertia. <P0-S5> this is the same thing that would occur if the astronaut and the object were in intergalactic space with no net force of gravity acting on their shared reference frame. <P0-S6> this principle of equivalence was one of the foundational underpinnings for the development of the general theory of relativity. <SEP> <P1-S0> Newton's laws of motion are three physical laws that, together, laid the foundation for classical mechanics. <P1-S1> They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. <P1-S2> More precisely, the first law defines the force qualitatively, the second law offers a quantitative measure of the force, and the third asserts that a single isolated force does n't exist. <P1-S3> These three laws have been expressed in several ways, over nearly three centuries, and can be summarised as follows: <SEP> <P2-S0> the basis for the modern understanding of orbits was first formulated by johannes kepler whose results are summarised in his three laws of planetary motion. <P2-S1> first, he found that the orbits of the planets in our solar system are elliptical, not circular (or epicyclic), as had previously been believed, and that the sun is not located at the center of the orbits, but rather at one focus. <P2-S2> second, he found that the orbital speed of each planet is not constant, as had previously been thought, but rather that the speed depends on the planet's distance from the sun. <P2-S3> third, kepler found a universal relationship between the orbital properties of all the planets orbiting the sun. <P2-S4> for the planets, the cubes of their distances from the sun are proportional to the squares of their orbital periods. <P2-S5> jupiter and venus, for example, are respectively about 5.2 and 0.723 au distant from the sun, their orbital periods respectively about 11.86 and 0.615 years. <P2-S6> the proportionality is seen by the fact that the ratio for jupiter, 5.2 / 11.86, is practically equal to that for venus, 0.723 / 0.615, in accord with the relationship. <P2-S7> idealised orbits meeting these rules are known as kepler orbits. <SEP> <P3-S0> It was only the orbit of the planet Mercury that Newton's Law of Gravitation seemed not to fully explain. <P3-S1> Some astrophysicists predicted the existence of another planet (Vulcan) that would explain the discrepancies; however, despite some early indications, no such planet could be found. <P3-S2> When Albert Einstein formulated his theory of general relativity (GR) he turned his attention to the problem of Mercury's orbit and found that his theory added a correction, which could account for the discrepancy. <P3-S3> This was the first time that Newton's Theory of Gravity had been shown to be less correct than an alternative. <SEP> <P4-S0> Mercury is the smallest and innermost planet in the Solar System. <P4-S1> Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System. <P4-S2> It is named after the Roman deity Mercury, the messenger to the gods.