In the Dust of This Planet: Horror of Philosophy

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Between Mars and Jupiter lies the asteroid belt. Asteroids are minor planets, and according to NASA there are approximately between 1.1 and 1.9 million asteroids in the main asteroid belt larger than 0.6 miles (1 km) in diameter and millions more smaller asteroids. Approximately 4.5 billion years ago a dark cloud of gas and dust began to collapse. As it shrank, the cloud flattened into a swirling disk known as a solar nebula, according to NASA Science. Darklife: Negation, Nothingness, and the Will-to-Life in Schopenhauer," Parrhesia no. 12 (2011), p. 3. The Earth's Moon is thought to have formed as a result of a single, large head-on collision. [91] [92]

At this point in its evolution, the Sun is thought to have been a T Tauri star. [25] Studies of T Tauri stars show that they are often accompanied by discs of pre-planetary matter with masses of 0.001–0.1 M ☉. [26] These discs extend to several hundred AU—the Hubble Space Telescope has observed protoplanetary discs of up to 1000AU in diameter in star-forming regions such as the Orion Nebula [27]—and are rather cool, reaching a surface temperature of only about 1,000K (730°C; 1,340°F) at their hottest. [28] Astronomers continue to come up empty in their search for Planet 9. A recent 2022 sky survey using the 6-meter Atacama Cosmology Telescope (ACT) in Chile found thousands of tentative candidate sources but none could be confirmed. The evolution of moon systems is driven by tidal forces. A moon will raise a tidal bulge in the object it orbits (the primary) due to the differential gravitational force across diameter of the primary. If a moon is revolving in the same direction as the planet's rotation and the planet is rotating faster than the orbital period of the moon, the bulge will constantly be pulled ahead of the moon. In this situation, angular momentum is transferred from the rotation of the primary to the revolution of the satellite. The moon gains energy and gradually spirals outward, while the primary rotates more slowly over time.

At the end of the planetary formation epoch, the inner Solar System was populated by 50–100 Moon-to- Mars-sized protoplanets. [49] [50] Further growth was possible only because these bodies collided and merged, which took less than 100million years. These objects would have gravitationally interacted with one another, tugging at each other's orbits until they collided, growing larger until the four terrestrial planets we know today took shape. [35] One such giant collision is thought to have formed the Moon (see Moons below), while another removed the outer envelope of the young Mercury. [51]

Over the course of the Solar System's evolution, comets were ejected out of the inner Solar System by the gravity of the giant planets and sent thousands of AU outward to form the Oort cloud, a spherical outer swarm of cometary nuclei at the farthest extent of the Sun's gravitational pull. Eventually, after about 800 million years, the gravitational disruption caused by galactic tides, passing stars and giant molecular clouds began to deplete the cloud, sending comets into the inner Solar System. [81] The evolution of the outer Solar System also appears to have been influenced by space weathering from the solar wind, micrometeorites, and the neutral components of the interstellar medium. [82] This model, known as the nebular hypothesis, was first developed in the 18th century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Its subsequent development has interwoven a variety of scientific disciplines including astronomy, chemistry, geology, physics, and planetary science. Since the dawn of the Space Age in the 1950s and the discovery of exoplanets in the 1990s, the model has been both challenged and refined to account for new observations. But that restrictive definition helped isolate what should and should not be considered a planet — a problem that arose as astronomers discovered more and more planet-like objects in the solar system. Pluto was among the bodies that didn't make the cut and was re-classified as a dwarf planet. About 99.9% of the material fell into the middle of the cloud and became the Sun. Once the centre became hot and dense enough it triggered nuclear fusion. Then visible light flooded the solar system for the first time. Main article: Late Heavy Bombardment Meteor Crater in Arizona. Created 50,000 years ago by an impactor about 50 metres (160ft) across, it shows that the accretion of the Solar System is not over.Moons of solid Solar System bodies have been created by both collisions and capture. Mars's two small moons, Deimos and Phobos, are thought to be captured asteroids. [90] That is the 1 million Euro question. We are currently just exploring what processes drive the formation and evolution of other solar systems, and what we can learn from this about our own solar systems (and Earth’s!) history. We think that many other stars have exoplanets around them but probably not all of them. In average, studies found there to be about 1 to 2 exoplanet per star — but that is an average! Some stars may have 8, others may have none. What is (and isn't) a planet? T Tauri stars like the young Sun have far stronger stellar winds than more stable, older stars. Uranus and Neptune are thought to have formed after Jupiter and Saturn did, when the strong solar wind had blown away much of the disc material. As a result, those planets accumulated little hydrogen and helium—not more than 1 M Earth each. Uranus and Neptune are sometimes referred to as failed cores. [43] The main problem with formation theories for these planets is the timescale of their formation. At the current locations it would have taken millions of years for their cores to accrete. [42] This means that Uranus and Neptune may have formed closer to the Sun—near or even between Jupiter and Saturn—and later migrated or were ejected outward (see Planetary migration below). [43] [44] Motion in the planetesimal era was not all inward toward the Sun; the Stardust sample return from Comet Wild 2 has suggested that materials from the early formation of the Solar System migrated from the warmer inner Solar System to the region of the Kuiper belt. [45] Explore the solar system in greater detail with these interactive resources from NASA. Discover the wonders of the solar system with this educational material from ESA. See where the planets are in their current orbit of the sun with this interactive orrery from NASA. Bibliography The Age of Catastrophe, Books.fr/Cairn.info (October 2020) and the journal Collapse (Urbanomic Publications).