Origin of the genetic code
Cells translate genetic sequences into proteins. How did a code and the machinery that reads it arise together?
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Origin of viruses
Viruses have remarkably different genomes and structures. Did their major lineages emerge independently, and from what ancestors?
Flowering plant origins
Fossils and DNA offer different timelines for the earliest living flowering-plant lineages. Why do their estimated beginnings still disagree?
Biological homochirality
Life predominantly builds proteins and nucleic acids from particular mirror-image forms. How did those molecular preferences become established?
Circadian temperature compensation
Most chemical reactions change speed with temperature. A plant’s daily clock can keep nearly the same rhythm. How do its components cooperate to do that?
Human X-chromosome inactivation
Developing cells can silence much of one X chromosome. How do human embryos establish which copy becomes inactive?
Escape from X-chromosome inactivation
An inactive X chromosome is not completely silent. Why do some genes escape, and why does that vary between tissues and cells?
Sound–touch synesthesia
For some people, sounds consistently evoke localized touch sensations. What creates that unusually strong link between hearing and touch?
Developmental stuttering
Stuttering often begins while speech is developing, and many children later recover. What explains its onset and different developmental paths?
Neutrino mass ordering
Neutrinos have three mass states. Which is heavier: the close pair or the third state?
Leptonic CP violation
Do neutrinos and antineutrinos change flavour differently in a way that violates charge–parity symmetry?
Neutron lifetime puzzle
Proton-counting beam measurements and stored-neutron measurements give incompatible neutron lifetimes.
QCD critical point
Does hot, baryon-rich nuclear matter have a critical endpoint where the character of its phase transition changes?
Neutron-star equation of state
How does pressure depend on density inside a cold neutron star?
r-process sites
Which events supplied the rapid neutron-capture elements found throughout our Galaxy?
Type Ia supernova progenitors
Which white-dwarf systems produce the different Type Ia supernovae?
Supermassive black-hole seeds
What initial black holes grew into the massive objects seen in the early Universe?
Origin of cosmic magnetic fields
Where did the seed magnetic fields amplified into cosmic magnetism come from?
Ionizing photon escape during reionization
How many ionizing photons escaped early galaxies and reached intergalactic hydrogen?
Solar dynamo
Where and how does the Sun regenerate the magnetic field underlying its activity cycle?
Diffuse astrophysical neutrino sources
Which populations produce the diffuse high-energy neutrino flux measured by IceCube?
Cuprate pairing mechanism
What microscopic interaction produces superconducting electron pairs across the cuprate phase diagram?
Hole-doped cuprate pseudogap
Why do hole-doped cuprates lose low-energy electronic states before superconductivity appears?
Charge order in kagome superconductors
Why does charge order break symmetry differently across the AV3Sb5 kagome superconductor family?