Strong Exponential Time Hypothesis
As satisfiability clauses become longer, does the best worst-case running-time exponent approach exhaustive search?
Explore all problems.
QMA versus QCMA
Does a quantum computer gain verification power when its certificate can be a quantum state rather than a classical string?
VP versus VNP
Can every polynomial described as a sum of efficiently computable terms itself be computed by a small arithmetic circuit?
Jupiter’s interior
Juno’s measurements suggest that Jupiter’s core blends gradually into its hydrogen-rich surroundings. How large is this region, what is it made of, and how did it form?
Earth’s core composition
Earth’s core is mostly iron and nickel, but these alone do not explain its measured properties. Which lighter elements are mixed in, and how are they distributed?
Solar modelling problem
Measurements of the Sun’s composition and interior do not all agree with standard solar models. Which changes would make the different lines of evidence fit together?
Venus’s climate history
Venus and Earth began as similar rocky planets. Did Venus ever have oceans, or did its water remain steam and escape before oceans could form?
Moon formation
A giant impact is the leading explanation for the Moon’s origin. Its exact sequence must account for the Moon’s composition, orbit and relationship to Earth.
Early Mars climate
Ancient Martian rocks and landforms record liquid water under a fainter Sun. What climate sustained it, and how persistent were those wet conditions?
Uranus’s internal heat
Uranus does release heat from its interior, despite older claims that it does not. How does its interior lose heat and produce the seasonal energy budget we observe?
Glass transition
A cooling liquid can become enormously slower without developing a crystal’s obvious order. What microscopic change explains its transition into a glass?
Primordial lithium problem
Old, metal-poor stars contain less lithium than standard early-universe calculations predict. Did the stars destroy it, or is something missing from the calculation or inference?
Core-collapse supernova mechanism
The collapse of a massive star can launch an explosion. Which stars explode, and can models predict the explosion and remnant from the star’s pre-collapse structure?
Diffuse interstellar bands
Starlight passing through interstellar gas picks up many absorption bands. Some have known molecular carriers, but most still lack a secure identification.
Planetesimal formation
Planetary systems start with small solid grains. How do these become gravitationally bound bodies before collisions or inward drift remove them?
Onset of plate tectonics
Earth’s moving plates are well established today. How and when did its early surface develop the connected system of recycling and motion we recognize as plate tectonics?
Large low shear velocity provinces
Two enormous regions near the bottom of Earth’s mantle slow seismic waves. What mixtures of heat and material create them, and how have they changed through time?
Aerosol–cloud interactions
Airborne particles change how clouds form and reflect sunlight. How much cooling do those changes produce, across different clouds and weather conditions?
Perovskite solar module durability
Perovskite solar cells can be highly efficient. Can full modules keep that performance through decades of outdoor light, heat, moisture and partial shading?
Electrochemical ammonia synthesis
Electricity can convert nitrogen into ammonia in the laboratory. Can a process sustain useful production rates with low total energy use and long-lived reactors?
Thermal PFAS mineralization
Heating can remove PFAS from waste without fully destroying it. How can thermal treatment prevent incomplete breakdown products and escaping fluorinated vapours?
Electrochemical direct air capture
Electrochemical cells can capture carbon dioxide from air. Can larger stacks sustain that performance while purifying the gas and keeping airflow resistance manageable?
Electrochemical lithium extraction from geothermal brines
Electrochemical cells can selectively recover lithium from geothermal-like brines. Can industrially made electrodes keep that performance during prolonged exposure to hot, impurity-rich feeds?
Animal magnetoreception
Many animals use Earth’s magnetic field to orient themselves. How does that weak field become a signal their nervous systems can use?