This article is a list of notable unsolved problems in

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

. Problems may be theoretical or experimental. Theoretical problems result from inability of current

theories A theory is a systematic and rational form of abstract thinking about a phenomenon, or the conclusions derived from such thinking. It involves contemplative and logical reasoning, often supported by processes such as observation, experimentation, ...

to explain observed phenomena or experimental results. Experimental problems result from inability to test or investigate a proposed theory. Other problems involve unique events or occurrences that have not repeated themselves with unclear causes.

Planetary astronomy

The Solar System

* Orbiting bodies and rotation: ** Are there any non-dwarf

planets beyond Neptune Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and continued at the start of the 20th with Percival Lowell's ...

? ** Why do extreme trans-Neptunian objects have elongated orbits? ** The rotation rate of

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

: *** Why does the magnetosphere of Saturn rotate at a rate close to that at which the planet's clouds rotate? *** What is the rotation rate of Saturn's deep interior? * Satellite

geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...

: ** What is the origin of the chain of high mountains that closely follows the equator of Saturn's moon,

Iapetus In Greek mythology, Iapetus (; ; ), also Japetus, is a Titan, the son of Uranus and Gaia and father of Atlas, Prometheus, Epimetheus, and Menoetius. He was also called the father of Buphagus and Anchiale in other sources. Iapetus was linked ...

? *** Are the mountains the remnant of hot and fast-rotating young Iapetus? *** Are the mountains the result of material (either from the rings of Saturn or its ring) that over time collected upon the surface?

Extra-solar

* How common are

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

-like planetary systems? Some observed planetary systems contain

Super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...

s and

Hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...

s that orbit very close to their stars. Systems with Jupiter-like planets in Jupiter-like orbits appear to be rare. There are several possibilities as to why Jupiter-like orbits are rare, including that data is lacking or the grand tack hypothesis. * How do Jupiter-mass Binary Objects form?

Stellar astronomy and astrophysics

Solar cycle The Solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a periodic 11-year change in the Sun's activity measured in terms of Modern Maximum, variations in the number of observed sunspots on the Sun ...

: ** How does the Sun generate its periodically reversing large-scale magnetic field? ** How do other Sol-like stars generate their magnetic fields, and what are the similarities and differences between stellar activity cycles and that of the Sun? ** What caused the Maunder Minimum and other grand minima, and how does the solar cycle recover from a minimum state? * Coronal heating problem: ** Why is the Sun's

corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus or disease responsible for the COVID-19 ...

so much hotter than the Sun's surface? ** Why is the

magnetic reconnection Magnetic reconnection is a physical process occurring in electrically conducting Plasma (physics), plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle accelerati ...

effect many orders of magnitude faster than predicted by standard models? *

Space weather Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ion ...

prediction: ** How does the Sun produce strong southward-pointing magnetic fields in solar

coronal mass ejections A coronal mass ejection (CME) is a significant ejection of plasma mass from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understanding ...

that lead to

geomagnetic storms A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere that is driven by interactions between the magnetosphere and large-scale transient plasma and magnetic field structures that originate ...

? How can we predict

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

and geomagnetic super-storms? * What is the origin of the stellar mass spectrum? That is, why do astronomers observe the same distribution of stellar masses—the

initial mass function In astronomy, the initial mass function (IMF) is an empirical function that describes the initial distribution of masses for a population of stars during star formation. IMF not only describes the formation and evolution of individual stars, it a ...

—apparently regardless of the initial conditions? *

Supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

: What is the mechanism by which an implosion of a dying star becomes an explosion? *

p-nuclei p-nuclei (''p'' stands for proton-rich) are certain proton-rich, naturally occurring isotopes of some elements between selenium and mercury inclusive which cannot be produced in either the s- or the r-process. Definition The classical, gro ...

: What astrophysical process is responsible for the

nucleogenesis Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...

of these rare isotopes? *

Fast radio burst In radio astronomy, a fast radio burst (FRB) is a transient radio wave of length ranging from a fraction of a millisecond, for an ultra-fast radio burst, to 3 seconds, caused by a high-energy astrophysical process as yet not understood. Astronome ...

s (FRBs): What causes these transient radio pulses from distant galaxies, lasting a few milliseconds each? Why do some FRBs repeat at unpredictable intervals but many others do not? Several models have been proposed but no one theory has become widely accepted. * The Oh-My-God particle and other

ultra-high-energy cosmic ray In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray part ...

s: What physical processes create cosmic rays whose energy exceeds the GZK cutoff? * Nature of

KIC 8462852 Tabby's Star (designated as KIC 8462852 in the Kepler Input Catalog and also known by the names Boyajian's Star and WTF (Where'sTheFlux?) Star, is a binary star in the constellation Cygnus approximately from Earth. The system is compo ...

, commonly known as Tabby's Star: What is the origin of the unusual

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

changes of this star? * What are the source and origin of the IBEX ribbon?

Galactic astronomy and astrophysics

* Galaxy rotation problem: Is

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

(solely) responsible for differences in observed and theoretical speed of stars revolving around the center of galaxies? * Age-metallicity relation in the Galactic disk: Is there a universal age-metallicity relation (AMR) in the Galactic disk (both "thin" and "thick" parts of the disk)? In the local (primarily thin) disk of the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

, there appears to be no evidence of a strong AMR. A sample of 229 nearby "thick" disk stars has been used to investigate the existence of an age-metallicity relation in the Galactic thick disk and indicates that there is an age-metallicity relation present in the thick disk. Stellar ages from

asteroseismology Asteroseismology is the study of oscillations in stars. Stars have many Resonance, resonant modes and frequencies, and the path of sound waves passing through a star depends on the local speed of sound, which in turn depends on local temperature a ...

confirm the lack of any strong age-metallicity relation in the Galactic disc. * Ultraluminous X-ray sources (ULXs): What powers X-ray sources that are not associated with

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

but exceed the

Eddington limit The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The stat ...

of a

neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...

stellar black hole A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be ...

? Are they due to

intermediate-mass black hole An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range of one hundred to one hundred thousand (102–105) solar masses: significantly higher than stellar black holes but lower than the hundred thousand to more than ...

s? Some ULXs are periodic, suggesting non-isotropic emission from a neutron star. Does this apply to all ULXs? How could such a system form and remain stable? * What is the origin of the

Galactic Center GeV excess The Galactic Center GeV Excess (GCE) is an unexpected surplus of gamma-ray radiation in the center of the Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance ...

? Is it due to the annihilation of dark matter particles or a new population of millisecond pulsars? * The infrared/TeV crisis: Lack of attenuation of very energetic gamma rays from extragalactic sources.

Black holes

* Gravitational singularities: Does

general relativity General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...

break down in the interior of a

black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...

due to

quantum effects Quantum mechanics is the fundamental physical theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is the foundation of a ...

, torsion, or other phenomena? *

No-hair theorem The no-hair theorem states that all stationary black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three independent ''externally'' observabl ...

: ** Do black holes have an internal structure? If so, how might the internal structure be probed? *

Supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical ...

s: ** What is the origin of the

M–sigma relation The M–sigma (or ''M''–''σ'') relation is an empirical correlation between the stellar velocity dispersion ''σ'' of a galaxy bulge and the mass M of the supermassive black hole at its center. The ''M''–''σ'' relation was first present ...

between supermassive black hole mass and galaxy velocity dispersion? * The formation of high-redshift

quasar A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...

s: ** How do the most distant

s grow their

supermassive black holes A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical o ...

up to 10¹⁰ solar masses so early in the history of the universe (with redshift greater than 6 to 7)? * Black hole information paradox and black hole radiation: ** Do black holes produce thermal radiation, as expected on theoretical grounds? *** If so—meaning black holes can evaporate away—what happens to the information stored in them? This appears to be an issue because the unitarity of quantum mechanics does not allow for the destruction of information. Does the radiation stop at some point for black hole remnants? * Firewalls: Do firewalls exist around black holes?Originally published
in Quanta, December 21, 2012. * Final parsec problem: Supermassive black holes appear to have merged, and what appears to be a pair in this intermediate range has been observed, in PKS 1302–102. However, theory predicts that when supermassive black holes reach a separation of about one parsec, it may take billions of years to orbit closely enough to merge—greater than the age of the universe. * Naked singularity: Is the

cosmic censorship hypothesis The weak and the strong cosmic censorship hypotheses are two mathematical conjectures about the structure of gravitational singularities arising in general relativity. Singularities that arise in the solutions of Einstein's equations are typical ...

correct? Does a naked singularity exist?

Cosmology

Cosmological principle In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equa ...

: ** Is the universe homogeneous and isotropic at sufficiently large scales, as claimed by the

cosmological principle In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equa ...

and assumed by all models that use the Friedmann–Lemaître–Robertson–Walker (FLRW) metric, including the current version of the ΛCDM model, or is the universe

inhomogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

anisotropic Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ver ...

? ** Is the CMB dipole purely kinematic, or does it signal

anisotropy Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ve ...

of the universe, resulting in the breakdown of the FLRW metric and the cosmological principle? ** Is the

Hubble tension Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther a galaxy is from the Earth, the faste ...

evidence that the cosmological principle is false? ** If the cosmological principle is correct, is the FLRW metric the correct metric describing the universe? ** Are the observations interpreted as the accelerating expansion of the universe correctly interpreted, or are they instead evidence that the

is false? ** Copernican principle: Are cosmological observations made from Earth representative of observations from the other positions in the universe? *

Dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

: ** What is the identity and composition of dark matter? ** Is dark matter a

particle In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...

? If so, is it a

WIMP WiMP is a music streaming service available on mobile devices, tablets, network players and computers. WiMP, standing for "Wireless Music Player," was a music streaming service that emphasized high-quality audio. WiMP offered music and podcast ...

, an

axion An axion () is a hypothetical elementary particle originally theorized in 1978 independently by Frank Wilczek and Steven Weinberg as the Goldstone boson of Peccei–Quinn theory, which had been proposed in 1977 to solve the strong CP problem ...

, the lightest

superpartner In particle physics, a superpartner (also sparticle) is a class of hypothetical elementary particles predicted by supersymmetry, which, among other applications, is one of the well-studied ways to extend the Standard Model of high-energy physics. ...

(LSP), or something else? ** Do the phenomena attributed to dark matter point to an extension of gravity instead of some other type of matter? *

Dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...

: ** What causes the observed accelerating expansion of the universe (the de Sitter phase)? ** Are the observations showing the accelerating expansion of the universe correctly interpreted, or are they evidence that the

is false? ** Why is the energy density of the dark energy component of the same magnitude as the density of matter at present when the two evolve quite differently over time? Could this observation be a coincidence of

timing Timing is the tracking or planning of the spacing of events in time. It may refer to: * Timekeeping, the process of measuring the passage of time * Synchronization, controlling the timing of a process relative to another process * Time metrolo ...

? ** Is dark energy a pure cosmological constant or are models of quintessence such as phantom energy applicable? ** Do early dark energy models resolve the

? *

Baryon asymmetry In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and an ...

: Why is there far more

matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...

than

antimatter In modern physics, antimatter is defined as matter composed of the antiparticles (or "partners") of the corresponding subatomic particle, particles in "ordinary" matter, and can be thought of as matter with reversed charge and parity, or go ...

in the

observable universe The observable universe is a Ball (mathematics), spherical region of the universe consisting of all matter that can be observation, observed from Earth; the electromagnetic radiation from these astronomical object, objects has had time to reach t ...

? *

Cosmological constant problem In cosmology, the cosmological constant problem or vacuum catastrophe is the substantial disagreement between the observed values of vacuum energy density (the small value of the cosmological constant) and the much larger theoretical value of ...

: ** Why does the

zero-point energy Zero-point energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly Quantum fluctuation, fluctuate in their lowest energy state as described by the Heisen ...

of the

vacuum A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...

not cause a large

cosmological constant In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), alternatively called Einstein's cosmological constant, is a coefficient that Albert Einstein initially added to his field equations of general rel ...

? *

Size Size in general is the Magnitude (mathematics), magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to three geometrical measures: length, area, or volume. Length can be generalized ...

and

shape of the universe In physical cosmology, the shape of the universe refers to both its local and global geometry. Local geometry is defined primarily by its curvature, while the global geometry is characterised by its topology (which itself is constrained by curv ...

: ** The diameter of the

is approximately 93 billion light-years; what is the size of the whole universe? Is it infinite? ** What is the 3-

manifold In mathematics, a manifold is a topological space that locally resembles Euclidean space near each point. More precisely, an n-dimensional manifold, or ''n-manifold'' for short, is a topological space with the property that each point has a N ...

of comoving space, i.e. of a comoving spatial section of the universe, informally called the "shape" of the universe? *** Neither the curvature nor the topology is presently known, though the curvature is known to be "close" to zero on observable scales. The

cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower ...

hypothesis suggests that the shape of the universe may be unmeasurable. Since 2003,

Jean-Pierre Luminet Jean-Pierre Luminet (born 3 June 1951) is a French astrophysicist, specializing in black holes and cosmology. He is an emeritus research director at the CNRS ( Centre national de la recherche scientifique). Luminet is a member of the Laboratoir ...

, et al., and other groups have suggested that the shape of the universe may be the Poincaré dodecahedral space. Is the shape unmeasurable, the Poincaré space, or another 3-manifold? *

Cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower ...

: ** Is the theory of cosmic inflation in the very early universe correct? If so, what are the details of this epoch? ** What is the hypothetical

scalar field In mathematics and physics, a scalar field is a function associating a single number to each point in a region of space – possibly physical space. The scalar may either be a pure mathematical number ( dimensionless) or a scalar physical ...

that gave rise to this cosmic inflation? ** If inflation happened at a single point, is it self-sustaining through inflation of quantum-mechanical fluctuations and thus ongoing in some extremely distant place? * Horizon problem: ** Why is the distant universe so homogeneous when the

Big Bang theory The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including the ...

seems to predict larger measurable anisotropies of the night sky than those observed? *** Cosmological

inflation In economics, inflation is an increase in the average price of goods and services in terms of money. This increase is measured using a price index, typically a consumer price index (CPI). When the general price level rises, each unit of curre ...

is generally accepted as the solution, but are other possible explanations such as a variable speed of light more appropriate? *

: If ΛCDM is correct, why are measurements of the Hubble constant failing to converge? *

Axis of evil The phrase "axis of evil" was first used by U.S. president George W. Bush and originally referred to Iran, Ba'athist Iraq, and North Korea. It was used in Bush's State of the Union address on January 29, 2002, less than five months after the ...

: Some large features of the microwave sky at distances of over 13 billion light-years appear to be aligned with both the motion and orientation of the

. Is this due to systematic errors in processing, contamination of results by local effects, or an unexplained violation of the Copernican principle? * Why is there something rather than nothing? Origin and fate of the universe: ** How did the conditions for anything to exist arise? ** Is there potentially an infinite amount of unknown astronomical phenomena throughout our entire universe? ** Is the universe heading toward a Big Freeze, a

Big Rip In physical cosmology, the Big Rip is a hypothetical cosmological model concerning the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, and even spacetime itself, is p ...

, a

Big Crunch The Big Crunch is a hypothetical scenario for the ultimate fate of the universe, in which the expansion of the universe eventually reverses and the universe recollapses, ultimately causing the cosmic scale factor to reach absolute zero, an eve ...

, or a

Big Bounce The Big Bounce hypothesis is a cosmological model for the origin of the known universe. It was originally suggested as a phase of the ''cyclic model'' or ''oscillatory universe'' interpretation of the Big Bang, where the first cosmological event ...

, or is it part of an infinitely recurring

cyclic model A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 ...

? *

Multiverse The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describ ...

: ** Is there a

multiverse The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describ ...

and is such a concept relevant? Are such ideas scientifically-testable or will they forever remain in the realm of

pseudoscience Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method. Pseudoscience is often characterized by contradictory, exaggerated or unfalsifiable cl ...

? Are such

metaphysical Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of h ...

questions interpretable in the fields of cosmology, astronomy, physics, or any other

scientific Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

discipline? ** Are metaphysical approaches such as the

anthropic principle In cosmology, the anthropic principle, also known as the observation selection effect, is the proposition that the range of possible observations that could be made about the universe is limited by the fact that observations are only possible in ...

necessary to explain unsolved questions such as the

cosmological constant problem In cosmology, the cosmological constant problem or vacuum catastrophe is the substantial disagreement between the observed values of vacuum energy density (the small value of the cosmological constant) and the much larger theoretical value of ...

Extraterrestrial life

* Is there other life in the Universe? Especially: ** Is there other intelligent life? ** Is there potentially an infinite amount of extraterrestrial genera throughout our universe? If so, what is the explanation for the

Fermi paradox The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. Those affirming the paradox generally conclude that if the conditions required ...

? * Nature of

Wow! signal The Wow! signal was a strong narrowband radio signal detected 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 appeare ...

: ** Was this singular event a result of any extraterrestrial phenomenon? If so, what was its origin?

References

{{DEFAULTSORT:Unsolved problems in astronomy Astronomy-related lists

Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...