What is the function of alkaloids in living organisms?
Why does aging occur?
What is the exact evolutionary history of flowers?
How do cells determine what size to grow to before dividing?
How does general anaesthetic actually work?
What is the origin of the preponderance of specific enantiomers in biochemical systems?
How can we move so controllably, even though the motor nerve impulses seem haphazard and unpredictable?
Why is there a high diversity of phytoplankton, which seems to violate the competitive exclusion principle?
What are the quantitative properties of immune responses? What are the basic building blocks of immune system networks and what roles are played by stochasticity?
What is the biological function of sleep? Why do we dream? What are the underlying brain mechanisms? What is its relation to anaesthesia?
How do genes govern our body, withstanding different external pressures and internal stochasticity?
Is Feynmanium the last chemical element that can physically exist? That is, what are the chemical consequences of having an element with an atomic number above 137, whose 1s electrons must travel faster than the speed of light?
What is the mechanism that causes certain materials to exhibit superconductivity at temperatures much higher than around 25 kelvin? Is it possible to make a material that is a superconductor at room temperature?
What is the nature of the glass transition between a fluid or regular solid and a glassy phase? What are the physical processes giving rise to the general properties of glasses and the glass transition?
Why does the electron emission in the absence of light increase as the temperature of a photomultiplier is decreased?
What causes the emission of short bursts of light from imploding bubbles in a liquid when excited by sound?
Is topological order stable at non-zero temperature? Equivalently, is it possible to have three-dimensional self-correcting quantum memory?
How do we rigorously prove the existence of Bose–Einstein condensates for general interacting systems?
Can the nematic to smectic (A) phase transition in liquid crystal states be characterized as a universal phase transition?
What is the nature of semiconductor nanocrystals? What is the cause of the nonparabolicity of the energy-size dependence for the lowest optical absorption transition of quantum dots?
What is the lowest possible worst-case time complexity of Shellsort with a deterministic, fixed gap sequence?
What is the capacity of the very simple access scheme used by ALOHAnet, which helps mediate usage of an internet channel?
How are infants able to learn language? (Nature versus nurture arguments: Psychological nativism, i.e., the language ability is somehow “hardwired” in the human brain versus “tabula rasa” or blank slate, i.e., language is acquired due to brain’s interaction with environment.)
How does the Sun generate its periodically reversing large-scale magnetic field? How do other solar-like stars generate their magnetic fields, and what are the similarities and differences between stellar activity cycles and that of the Sun?
What explains solar wind, the turbulence in solar flares, coronal mass ejections, and magnetospheric substorms?
Why is the Sun’s corona (atmosphere layer) so much hotter than the Sun’s surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models?
What is responsible for the numerous interstellar absorption lines detected in astronomical spectra? Are they molecular in origin, and if so which molecules are responsible for them and how do they form?
What is the origin of the M-sigma relation between supermassive black hole mass and galaxy velocity dispersion?
How did the most distant quasars grow their supermassive black holes up to 109 solar masses so early in the history of the Universe?
Why does the number of objects in the Solar System’s Kuiper belt fall off rapidly and unexpectedly beyond a radius of 50 astronomical units (the so-called “Kuiper cliff”)?
Is dark matter responsible for differences in observed and theoretical speed of stars revolving around the centre of galaxies, or is it something else?
What is the exact mechanism by which an implosion of a dying star becomes an explosion?
Why is it that some cosmic rays appear to possess energies that are impossibly high, given that there are no sufficiently energetic cosmic ray sources near the Earth?
What is the origin of magnetar magnetic field?
Is the Universe at very large scales anisotropic, making the cosmological principle an invalid assumption?
Is there a universal age–metallicity relation (AMR) in the Galactic disk (both “thin” and “thick” parts of the disk)?
Why is there a discrepancy between the amount of lithium-7 predicted to be produced in Big Bang nucleosynthesis and the amount observed in very old stars?
What mechanism causes those particles to initially have energies high enough for Fermi acceleration to work on them?
What are the transient radio pulses, which only last a few milliseconds from emission regions thought to be no larger than a few hundred kilometres, and estimated to occur several hundred times a day?
Is it possible to make a theoretical model to describe the statistics of a turbulent flow (in particular, its internal structures)?
What are the full existence and smoothness properties of the solutions to the Navier–Stokes equations, which describe the motion of viscous fluid substances?
What is the smallest area of a shape that can cover every unit-length curve in the plane (Moser’s worm problem)?
What is the largest area of a shape that can be maneuvered through a unit-width L-shaped corridor (moving sofa problem)?
Is the Mandelbrot set locally connected?
How can we detect and correct for systematic errors, especially in sciences where random errors are large?
How far can the number of integer points in a circle centered at the origin be from the area of the circle (Gauss circle problem)?
Is π a normal number? Are its digits “random”?
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?
Why is there far more matter than antimatter in the observable universe?
What is the identity of dark matter?
Are there extra dimensions?
Why are there three generations of quarks and leptons?
Is there a theory that can explain the masses of particular quarks and leptons in particular generations from first principles?
What is the mass of neutrinos?
What is the origin of the M-sigma relation between supermassive black hole mass and galaxy velocity dispersion?
How did the most distant quasars grow their supermassive black holes up to 109 solar masses so early in the history of the Universe?
What is the exact mechanism by which an implosion of a dying star becomes an explosion?
Why is it that some cosmic rays appear to possess energies that are impossibly high, 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?
Why is the observed energy of satellites flying by Earth sometimes different by a minute amount from the value predicted by theory?
Are there Population III stars?
Why is there is discrepancy between the amount of lithium-7 predicted to be produced in Big Bang nucleosynthesis and the amount observed in very old stars?
Why did the universe have such low entropy in the past?
Do black holes produce thermal radiation?
Are there exceptions to the principle of causality?
Is there a single possible past?
Is the present moment physically distinct from the past and future or is it merely an emergent property of consciousness?
Why does time have a direction?
How does the quantum description of reality give rise to the reality we perceive?
What constitutes a “measurement” which causes the wave function to collapse into a definite state?
Do “fundamental physical constants” vary over time?
What is the minimum number of dimensionless physical constants from which all other dimensionless physical constants can be derived?
Are dimensionful physical constants necessary at all?
[New geoscience problems as of May 2022]
How abundant are radiogenic elements in the interior?
What controls the dynamics of storm tracks?
What are the mechanisms that cause oscillations in equatorial climate (such as the El Nino Southern Oscillation or the Quasi-Biennial Oscillation )?
What are skyquakes?
What causes Hessdalen lights?
How are granite magma chambers emplaced in the crust?
What are the structures and locations of the magmatic systems that might cause supervolcanoes?
What is the precise nature of chemical heterogeneity associated with the Gutenberg discontinuity?
What are the light alloying elements in the Earth’s outer core and how are they distributed?
Wilson Lin - Personal Website 