Topic: Astronomy

You are looking at all articles with the topic "Astronomy". We found 66 matches.

Hint: To view all topics, click here. Too see the most popular topics, click here instead.

๐Ÿ”— Timeline of the far future

๐Ÿ”— Physics ๐Ÿ”— Lists ๐Ÿ”— Statistics ๐Ÿ”— Astronomy ๐Ÿ”— Time ๐Ÿ”— Futures studies ๐Ÿ”— Geology ๐Ÿ”— Extinction ๐Ÿ”— Solar System ๐Ÿ”— Astronomy/Solar System

While the future can never be predicted with absolute certainty, present understanding in various scientific fields allows for the prediction of some far-future events, if only in the broadest outline. These fields include astrophysics, which has revealed how planets and stars form, interact, and die; particle physics, which has revealed how matter behaves at the smallest scales; evolutionary biology, which predicts how life will evolve over time; and plate tectonics, which shows how continents shift over millennia.

All projections of the future of Earth, the Solar System, and the universe must account for the second law of thermodynamics, which states that entropy, or a loss of the energy available to do work, must rise over time. Stars will eventually exhaust their supply of hydrogen fuel and burn out. Close encounters between astronomical objects gravitationally fling planets from their star systems, and star systems from galaxies.

Physicists expect that matter itself will eventually come under the influence of radioactive decay, as even the most stable materials break apart into subatomic particles. Current data suggest that the universe has a flat geometry (or very close to flat), and thus will not collapse in on itself after a finite time, and the infinite future allows for the occurrence of a number of massively improbable events, such as the formation of Boltzmann brains.

The timelines displayed here cover events from the beginning of the 11th millennium to the furthest reaches of future time. A number of alternative future events are listed to account for questions still unresolved, such as whether humans will become extinct, whether protons decay, and whether the Earth survives when the Sun expands to become a red giant.

Discussed on

๐Ÿ”— Sweden Solar System

๐Ÿ”— Astronomy ๐Ÿ”— Sweden ๐Ÿ”— Solar System ๐Ÿ”— Astronomy/Solar System

The Sweden Solar System is the world's largest permanent scale model of the Solar System. The Sun is represented by the Ericsson Globe in Stockholm, the largest hemispherical building in the world. The inner planets can also be found in Stockholm but the outer planets are situated northward in other cities along the Baltic Sea. The system was started by Nils Brenning and Gรถsta Gahm and is on the scale of 1:20 million.

Discussed on

๐Ÿ”— The โ€œOh-My-God Particleโ€

๐Ÿ”— Physics ๐Ÿ”— Astronomy

The Oh-My-God particle was the highest-energy cosmic ray detected at the time (15 October 1991) by the Fly's Eye detector in Dugway Proving Ground, Utah, US. Its energy was estimated as (3.2ยฑ0.9)ร—1020ย eV, or 51ย J. This is 20 million times more energetic than the highest energy measured in electromagnetic radiation emitted by an extragalactic object and 1020 (100 quintillion) times the photon energy of visible light, equivalent to a 142-gram (5ย oz) baseball travelling at about 26ย m/s (94ย km/h; 58ย mph). Although higher energy cosmic rays have been detected since then, this particle's energy was unexpected, and called into question theories of that era about the origin and propagation of cosmic rays.

Assuming it was a proton, this particle traveled at 99.99999999999999999999951% of the speed of light, its Lorentz factor was 3.2ร—1011 and its rapidity was 27.1. At this speed, if a photon were travelling with the particle, it would take over 215,000 years for the photon to gain a 1ย cm lead as seen in Earth's reference frame.

The energy of this particle is some 40 million times that of the highest energy protons that have been produced in any terrestrial particle accelerator. However, only a small fraction of this energy would be available for an interaction with a proton or neutron on Earth, with most of the energy remaining in the form of kinetic energy of the products of the interaction. The effective energy available for such a collision is โˆš2Emc2, where E is the particle's energy and mc2 is the mass energy of the proton. For the Oh-My-God particle, this gives 7.5ร—1014ย eV, roughly 60 times the collision energy of the Large Hadron Collider.

While the particle's energy was higher than anything achieved in terrestrial accelerators, it was still about 40 million times lower than the Planck energy. Particles of such energy would be required in order to explore the Planck scale. A proton with that much energy would travel 1.665ร—1015 times closer to the speed of light than the Oh-My-God particle. As viewed from Earth it would take about 3.579ร—1020ย years, or 2.59ร—1010 times the current age of the universe, for a photon to gain a 1 cm lead over a Planck energy proton as observed in Earth's reference frame.

Since the first observation, at least 72 similar (energy > 5.7ร—1019ย eV) events have been recorded, confirming the phenomenon. These ultra-high-energy cosmic ray particles are very rare; the energy of most cosmic ray particles is between 10ย MeV and 10ย GeV. More recent studies using the Telescope Array have suggested a source for the particles within a 20-degree radius "warm spot" in the direction of the constellation Ursa Major.

Discussed on

๐Ÿ”— Cecilia Payne-Gaposchkin

๐Ÿ”— Biography ๐Ÿ”— Women scientists ๐Ÿ”— Biography/science and academia ๐Ÿ”— Women's History ๐Ÿ”— Astronomy ๐Ÿ”— Smithsonian Institution Archives

Cecilia Helena Payne-Gaposchkin (nรฉe Payne; (1900-05-10)May 10, 1900 โ€“ (1979-12-07)December 7, 1979) was a British-born American astronomer and astrophysicist who proposed in her 1925 doctoral thesis that stars were composed primarily of hydrogen and helium. Her groundbreaking conclusion was initially rejected because it contradicted the scientific wisdom of the time, which held that there were no significant elemental differences between the Sun and Earth. Independent observations eventually proved she was actually correct

Discussed on

๐Ÿ”— Solar storm of 1859

๐Ÿ”— Telecommunications ๐Ÿ”— Meteorology ๐Ÿ”— Astronomy ๐Ÿ”— Solar System

The solar storm of 1859 (also known as the Carrington Event) was a powerful geomagnetic storm during solar cycle 10 (1855โ€“1867). A solar coronal mass ejection (CME) hit Earth's magnetosphere and induced the largest geomagnetic storm on record, September 1โ€“2, 1859. The associated "white light flare" in the solar photosphere was observed and recorded by British astronomers Richard C. Carrington (1826โ€“1875) and Richard Hodgson (1804โ€“1872). The storm caused strong auroral displays and wrought havoc with telegraph systems. The now-standard unique IAU identifier for this flare is SOL1859-09-01.

A solar storm of this magnitude occurring today would cause widespread electrical disruptions, blackouts and damage due to extended outages of the electrical grid. The solar storm of 2012 was of similar magnitude, but it passed Earth's orbit without striking the planet, missing by nine days.

Discussed on

๐Ÿ”— Wow signal

๐Ÿ”— History ๐Ÿ”— Physics ๐Ÿ”— Telecommunications ๐Ÿ”— Skepticism ๐Ÿ”— Astronomy ๐Ÿ”— History of Science ๐Ÿ”— Physics/History ๐Ÿ”— Paranormal

The Wow! signal was a strong narrowband radio signal received on August 15, 1977, by Ohio State University's Big Ear radio telescope in the United States, then used to support the search for extraterrestrial intelligence. The signal appeared to come from the direction of the constellation Sagittarius and bore the expected hallmarks of extraterrestrial origin.

Astronomer Jerry R. Ehman discovered the anomaly a few days later while reviewing the recorded data. He was so impressed by the result that he circled the reading on the computer printout, "6EQUJ5", and wrote the comment "Wow!" on its side, leading to the event's widely used name.

The entire signal sequence lasted for the full 72-second window during which Big Ear was able to observe it, but has not been detected since, despite several subsequent attempts by Ehman and others. Many hypotheses have been advanced on the origin of the emission, including natural and human-made sources, but none of them adequately explains the signal.

Although the Wow! signal had no detectable modulationโ€”a technique used to transmit information over radio wavesโ€”it remains the strongest candidate for an alien radio transmission ever detected.

Discussed on

๐Ÿ”— Entropic Gravity

๐Ÿ”— Physics ๐Ÿ”— Astronomy

Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic forceโ€”a force with macro-scale homogeneity but which is subject to quantum-level disorderโ€”and not a fundamental interaction. The theory, based on string theory, black hole physics, and quantum information theory, describes gravity as an emergent phenomenon that springs from the quantum entanglement of small bits of spacetime information. As such, entropic gravity is said to abide by the second law of thermodynamics under which the entropy of a physical system tends to increase over time.

At its simplest, the theory holds that when gravity becomes vanishingly weakโ€”levels seen only at interstellar distancesโ€”it diverges from its classically understood nature and its strength begins to decay linearly with distance from a mass.

Entropic gravity provides the underlying framework to explain Modified Newtonian Dynamics, or MOND, which holds that at a gravitational acceleration threshold of approximately 1.2ร—10โˆ’10ย m/s2, gravitational strength begins to vary inversely (linearly) with distance from a mass rather than the normal inverse-square law of the distance. This is an exceedingly low threshold, measuring only 12ย trillionths gravity's strength at earth's surface; an object dropped from a height of one meter would fall for 36 hours were earth's gravity this weak. It is also 3,000 times less than exists at the point where Voyager 1 crossed our solar system's heliopause and entered interstellar space.

The theory claims to be consistent with both the macro-level observations of Newtonian gravity as well as Einstein's theory of general relativity and its gravitational distortion of spacetime. Importantly, the theory also explains (without invoking the existence of dark matter and its accompanying math featuring new free parameters that are tweaked to obtain the desired outcome) why galactic rotation curves differ from the profile expected with visible matter.

The theory of entropic gravity posits that what has been interpreted as unobserved dark matter is the product of quantum effects that can be regarded as a form of positive dark energy that lifts the vacuum energy of space from its ground state value. A central tenet of the theory is that the positive dark energy leads to a thermal-volume law contribution to entropy that overtakes the area law of anti-de Sitter space precisely at the cosmological horizon.

The theory has been controversial within the physics community but has sparked research and experiments to test its validity.

Discussed on

๐Ÿ”— SN 1006

๐Ÿ”— Physics ๐Ÿ”— China ๐Ÿ”— Astronomy ๐Ÿ”— History of Science ๐Ÿ”— Astronomy/Astronomical objects ๐Ÿ”— Arab world

SN 1006 was a supernova that is likely the brightest observed stellar event in recorded history, reaching an estimated โˆ’7.5 visual magnitude, and exceeding roughly sixteen times the brightness of Venus. Appearing between April 30 and May 1, 1006 AD in the constellation of Lupus, this "guest star" was described by observers across the modern day countries of China, Japan, Iraq, Egypt, and the continent of Europe, and possibly recorded in North American petroglyphs. Some reports state it was clearly visible in the daytime. Modern astronomers now consider its distance from Earth to be about 7,200 light-years.

Discussed on

๐Ÿ”— Wanggongchang Explosion

๐Ÿ”— Military history ๐Ÿ”— Disaster management ๐Ÿ”— Death ๐Ÿ”— China/Chinese history ๐Ÿ”— China ๐Ÿ”— Astronomy ๐Ÿ”— Geology ๐Ÿ”— Military history/Asian military history ๐Ÿ”— Geology/Meteorites ๐Ÿ”— Military history/Chinese military history ๐Ÿ”— Explosives ๐Ÿ”— Astronomy/Solar System

The Wanggongchang Explosion (Chinese: ็Ž‹ๆญๅป ๅคง็ˆ†็‚ธ), also known as the Great Tianqi Explosion (ๅคฉๅ•Ÿๅคง็ˆ†็‚ธ), Wanggongchang Calamity (็Ž‹ๆญๅป ไน‹่ฎŠ) or Beijing Explosive Incident in Late Ming (ๆ™šๆ˜ŽๅŒ—ไบฌ็ˆ†็‚ธไบ‹ไปถ), was an unexplained catastrophic explosion that occurred on May 30 of the Chinese calendar in 1626 AD during the late reign of Tianqi Emperor, at the heavily populated Ming China capital Beijing, and had reportedly killed around 20,000 people. The nature of the explosion is still unclear to this day, as it is estimated to have released energy equivalent to about 10-20 kiloton of TNT, similar to that of the Hiroshima bombing.

Discussed on