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Hubble's law, also known as the Hubble–Lemaître law, [ 1 ] is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving away. For this purpose, the recessional velocity of a galaxy is typically determined by ...
where F is the gravitational force acting between two objects, m 1 and m 2 are the masses of the objects, r is the distance between the centers of their masses, and G is the gravitational constant. The first test of Newton's law of gravitation between masses in the laboratory was the Cavendish experiment conducted by the British scientist Henry ...
Zeno's paradoxes are a series of philosophical arguments presented by the ancient Greek philosopher Zeno of Elea (c. 490–430 BC), [ 1 ][ 2 ] primarily known through the works of Plato, Aristotle, and later commentators like Simplicius of Cilicia. [ 2 ] Zeno devised these paradoxes to support his teacher Parmenides 's philosophy of monism ...
t. e. In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler absent the third law in 1609 and fully in 1619, describe the orbits of planets around the Sun. These laws replaced circular orbits and epicycles in the heliocentric theory of Nicolaus Copernicus with elliptical orbits and explained how planetary velocities vary.
e. In standard cosmology, comoving distance and proper distance (or physical distance) are two closely related distance measures used by cosmologists to define distances between objects. Comoving distance factors out the expansion of the universe, giving a distance that does not change in time due to the expansion of space (though this may ...
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs) to Earth.
v. t. e. The two-body problem in general relativity (or relativistic two-body problem) is the determination of the motion and gravitational field of two bodies as described by the field equations of general relativity. Solving the Kepler problem is essential to calculate the bending of light by gravity and the motion of a planet orbiting its sun.
When the visual and absolute magnitudes are known, the distance to the star can be calculated. The stars lie at a distance of 2.52 × 10 ^ 6 ± 0.14 × 10 ^ 6 ly (1.594 × 10 11 ± 8.9 × 10 9 AU) and the whole Andromeda Galaxy at about 2.5 × 10 ^ 6 ly (1.6 × 10 11 AU). [6]