It has been suggested that this article be merged into Unsolved problems in physics. (Discuss) Proposed since June 2009. |
There are a variety of problems in astronomy regarding the universe. Some of them are:
- Baryon asymmetry
- Why is there far more matter than antimatter in the observable universe?
- Dark matter
- What is dark matter?[1] Is it related to supersymmetry? Do the phenomena attributed to dark matter point not to some form of matter but actually to an extension of gravity?
- Electroweak symmetry breaking
- What is the mechanism responsible for breaking the electroweak gauge symmetry, giving mass to the W and Z bosons? Is it the simple Higgs mechanism of the Standard Model,[2] or does nature make use of strong dynamics in breaking electroweak symmetry, as proposed by Technicolor?
- Entropy (arrow of time)
- Why did the universe have such low entropy in the past, resulting in the distinction between past and future and the second law of thermodynamics?[3]
- Neutrino mass
- What is the mechanism responsible for generating neutrino masses? Is the neutrino its own antiparticle? Or could it be an antiparticle that simply cannot join and annihilate with a normal particle because of its irregular state?
- Inertial mass/gravitational mass ratio of elementary particles
- According to the equivalence principle of general relativity, the ratio of inertial mass to gravitational mass of all elementary particles is the same. However, there is no experimental confirmation for many particles. In particular, we do not know what the weight of a macroscopic lump of antimatter of known mass would be.
- Proton spin crisis
- As initially measured by the European Muon Collaboration, the three main ("valence") quarks of the proton account for about 12% of its total spin. Can the gluons that bind the quarks together, as well as the "sea" of quark pairs that are continually being created and annihilating, properly account for the rest of it?**
- Quantum chromodynamics (QCD) in the non-perturbative regime
- The equations of QCD remain unsolved at energy scales relevant for describing atomic nuclei, and only mainly numerical approaches seem to begin to give answers at this limit. How does QCD give rise to the physics of nuclei and nuclear constituents?
- Shape of the Universe
- What is the 3-manifold 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 hypothesis suggests that the shape of the Universe may be unmeasurable, but since 2003, Jean-Pierre Luminet et al. and other groups have suggested that the shape of the Universe may be the Poincaré dodecahedral space. Is the shape unmeasurable, or is it the Poincaré space, or is it another 3-manifold?
- Strong CP problem and axions
- Why is the strong nuclear interaction invariant to parity and charge conjugation? Is Peccei-Quinn theory the solution to this problem?
- Accretion disc jets
- Why do the accretion discs surrounding certain astronomical objects, such as the nuclei of active galaxies, emit relativistic jets along their polar axes? Why are there Quasi-Periodic Oscillations in many accretion discs? Why does the period of these oscillations scale as the inverse of the mass of the central object? Why are there sometimes overtones, and why do these appear at different frequency ratios in different objects?
- Corona heating problem
- Why is the Sun's Corona (atmosphere layer) so much hotter than the Sun's surface?****
- Extraterrestrial life
- Is there life outside of Earth? There have been many claimed pieces of evidence of its existence, but none of them are widely accepted.
- Gamma ray bursts (short duration)
- How do these short-duration high-intensity bursts originate?[4]
- Observational anomalies
- Hipparcos anomaly: How far away are the Pleiades, exactly?**
- Pioneer anomaly[1]: What causes the apparent residual sunward acceleration of the Pioneer spacecraft?[5][6] ****
- Flyby anomaly: Why is the observed energy of satellites flying by earth different by a minute amount from the value predicted by theory?****
- Galaxy rotation problem: Is dark matter responsible for differences in observed and theoretical speed of stars revolving around the center of galaxies, or is it something else?
- Supernovae: What is the exact mechanism by which an implosion of a dying star becomes an explosion?
- Ultra-high-energy cosmic ray[1]
- Why is it that some cosmic rays appear to possess energies that are impossibly high (the so called Oh-My-God particle), given that there are no sufficiently energetic cosmic ray sources near the Earth? Why is it that (apparently) some cosmic rays emitted by distant sources have energies above the Greisen-Zatsepin-Kuzmin limit?[7][8]
See also
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References
- ^ a b c 13 things that do not make sense newscientistspace, 19 March 2005, Michael Brooks
- ^ Open Questions, Particle Physics, item 6
- ^ Open Questions item 4
- ^ Open Questions, Cosmology and Astrophysics, item 11
- ^ Open Questions, Particle Physics, item 13
- ^ newscientistspace item 8
- ^ Open Questions, Cosmology and Astrophysics, item 12
- ^ newscientistspace item 3