11 Terrifying Problems That Physics Still Can't Solve

Summary

The video presents 11 unresolved problems, moving from familiar everyday effects to questions about the universe’s origins and the long-term fate of matter. In each case, observations and experiments exist, but scientists do not yet agree on a complete explanation.

1. Why rubbing materials creates static electricity A sweater’s crackle and the shock from a doorknob are examples of contact electrification. Metals can be explained by electrons moving between them, but insulating materials such as wool, plastic, and glass are less straightforward. Electrons, ions, and tiny fragments of material may all transfer charge. Experiments find complex patches of positive and negative charge on the same surface. A 2025 study found that repeatedly touching identical silicone blocks could give them a repeatable charging order, apparently influenced by tiny changes to surface roughness and contact history. The mechanism remains unresolved, with practical implications for industrial safety and devices that generate electricity from motion.

2. Why ice is slippery The traditional idea that body weight melts ice by pressure is insufficient, especially at very low temperatures. Frictional heating can help explain sliding, but not why a foot may slip as soon as it touches the ice. Research points to a disordered, partly liquid-like surface layer; weakly bonded surface molecules; and possibly electric interactions between the ice and the material sliding over it. Measurements have also found that the thin film at the interface may be much thicker and more viscous than ordinary water. Different mechanisms may matter under different conditions, but no account has won general agreement.

3. Whether hot water can freeze faster than cold water The Mpemba effect is the reported observation that initially hotter water can sometimes freeze before cooler water. Results depend on what counts as “freezing” and on variables such as evaporation, convection, dissolved gases, container contact, and supercooling. Carefully controlled tests have failed to find a general effect in ordinary water, while other experiments have demonstrated related “hotter cools faster” behavior in microscopic systems and quantum setups. The broader phenomenon is real in some systems; its status in a kitchen freezer remains disputed.

4. What glass is as a state of matter Glass behaves mechanically like a solid, but its atoms lack the orderly repeating structure of a crystal. As a liquid cools, it gradually becomes extremely viscous rather than freezing at one sharp temperature. Its properties retain a memory of how it cooled. Scientists disagree over whether a deeply cooled liquid has a hidden transition to an ideal glass or simply becomes slower and more rigid without such a transition. The “old windows flow downward” story is a myth: their unevenness comes from how they were made and installed.

5. Whether liquid water has two forms Water has many unusual properties, including ice floating, a density maximum near 4°C, and strong changes in behavior as it is supercooled. One proposal is that, at sufficiently low temperatures, water separates into two liquid forms: a dense, disordered liquid and a less-dense, more open one. Their proposed critical point lies in “no man’s land,” where liquid water freezes too quickly for conventional study. X-ray laser experiments have reported evidence consistent with two liquid forms and, in 2026, with a critical point nearby. The evidence is promising but not conclusive, and some researchers argue that water’s anomalies do not require a second liquid.

6. What ball lightning is Witnesses have reported glowing spheres appearing during storms, but accounts vary and the phenomenon is difficult to reproduce. In 2012, instruments in China recorded a luminous event following a lightning strike; its spectrum showed light from elements found in local soil. This supports a theory in which lightning vaporizes soil material that later glows as it cools and reacts with air. However, that idea does not explain every report, such as apparent balls inside aircraft or buildings. Other proposals include microwave energy, plasma, and visual effects caused by lightning stimulating the brain.

7. How lightning begins Scientists understand much about lightning’s development after a leader channel forms, and how collisions between ice particles help separate charge in storm clouds. The puzzle is how the first discharge starts: measured electric fields in clouds appear too weak to break down air according to standard calculations. Proposed explanations include cosmic-ray electrons triggering runaway avalanches and pointed ice crystals concentrating the electric field. Observations have identified fast positive breakdown and fine structures in lightning channels, but have not yet revealed what triggers the first discharge.

8. How long quantum tunneling takes Quantum particles can sometimes cross barriers they lack the energy to climb. Tunneling explains phenomena including radioactive decay and the Sun’s nuclear fusion. Yet there is no universally accepted definition of how long a particle spends inside a barrier. An “attoclock” experiment found a delay consistent with zero, while an experiment using ultracold rubidium atoms and a Larmor clock measured a nonzero time in the barrier. The results may reflect different definitions of tunneling time; scientists have not agreed on how to reconcile them.

9. Why neutron-lifetime experiments disagree Free neutrons decay into protons, electrons, and antineutrinos. Beam experiments infer the lifetime by counting decay protons; bottle experiments measure how many neutrons survive confinement. The best results described in the video differ by about 10 seconds, beyond their stated experimental uncertainties. The discrepancy could arise from an unrecognized systematic error, or possibly from an unusual decay channel that one method would miss. A proposed dark-matter decay explanation has been substantially constrained but not entirely eliminated. The lifetime matters both for testing particle physics and for predicting the amount of helium made in the early universe.

10. Why ancient stars contain less lithium than predicted Big Bang nucleosynthesis successfully predicts the abundance of hydrogen, helium, and deuterium, but predicts roughly three to four times more lithium than is observed in old stars. Possible explanations include lithium being destroyed inside stars, errors in nuclear-reaction calculations, or unknown physics in the early universe. Evidence that stars can deplete lithium exists, but it has not clearly explained the observed pattern. A lithium measurement in gas outside stars has been reported to be consistent with the Big Bang prediction, but that evidence is not decisive.

11. Whether protons—and therefore matter—eventually decay Some grand unified theories predict that protons can decay, which would mean ordinary matter is not permanent. Large underground detectors have searched for proton-decay signals but have not observed one. The simplest theories have been ruled out, while more complex versions remain possible. The current experimental limits imply a proton lifetime vastly longer than the age of the universe. Future experiments, including Hyper-Kamiokande and DUNE, are intended to search further. Whether matter lasts forever remains unknown.

Research Methods and Approaches Featured

• Surface charging: Compare rubbing and contact between materials; map charge patterns with fine probes; test how humidity, surface texture, and repeated contact affect the outcome.
• Ice friction: Combine friction measurements, spectroscopy, molecular simulations, and sensitive probes of the thin interface between ice and another surface.
• Freezing and cooling: Control starting temperatures and container conditions; distinguish cooling to 0°C from the onset of crystallization; test related effects in colloids and trapped ions.
• Glass: Compare competing theoretical models with laboratory-made ultrastable glasses and naturally aged materials such as amber.
• Supercooled water: Cool tiny droplets rapidly, use laser pulses to create brief liquid states, and probe them with ultrafast X-ray scattering.
• Ball lightning and lightning initiation: Record storms with cameras, spectrographs, radio instruments, balloons, aircraft, and radio-telescope arrays.
• Tunneling: Infer timing using laser-based attoclocks or spin rotation in a Larmor clock.
• Neutron lifetime: Compare decay-product counting in a beam with survivor counting in a bottle trap; develop additional beam, bottle, and space-based measurements.
• Early-universe elements: Compare nucleosynthesis predictions with measurements of primordial gas and old stars; measure relevant nuclear reactions in laboratories.
• Proton decay: Use large, shielded underground water detectors to search for characteristic light patterns from a decay.

Researchers and Sources Featured

Names are given in the forms most readily identifiable from the subtitles; some names and technical terms appear to have been garbled by automatic transcription.

• Static electricity: Thales; William Gilbert; Otto von Guericke; Stephen Gray; Charles du Fay; Benjamin Franklin; Johan Carl Wilcke; Bartosz Grzybowski and colleagues (Northwestern University, 2011); Juan Carlos Sabato and Scott Waitukaitis (Institute of Science and Technology Austria, 2025); Zhong Lin Wang and colleagues (Georgia Institute of Technology). Sources mentioned include Science, Nature, and the 2025 IST Austria study on self-organization in a triboelectric series.
• Ice slipperiness: Michael Faraday; James and William Thomson (Lord Kelvin); Frank Philip Bowden; T. P. Hughes; Robert Rosenberg; Bart Weber; Daniel Bonn; Mischa Bonn; Martin Müser; Akaf Atila; Sergey Sukhomlinov. Sources mentioned include The Journal of Physical Chemistry Letters, Physical Review Letters, and institutional work from the University of Amsterdam, the Max Planck Institute for Polymer Research, and Saarland University.
• Mpemba effect: Aristotle; Francis Bacon; René Descartes; Erasto Mpemba; Denis Osborne; George Kell; Nicola Bregović; Henry Burridge; Paul Linden; Oren Raz and collaborators; Antonella? (name unclear in subtitles); Avinash Kumar; John Bechhoefer; researchers at Innsbruck. Sources mentioned include Physics Education, American Journal of Physics, Scientific Reports, Proceedings of the National Academy of Sciences, Nature, and Physical Review Letters.
• Glass: Philip Anderson; Walter Kauzmann; Gerald Adam; Julian Gibbs; Theodore Kirkpatrick; D. Thirumalai; Peter Wolynes; Giorgio Parisi; David Chandler; Juan Garrahan; Edgar Zanotto; Jing Xiao; Cindy Simon; Gregory McKenna; Mark Ediger; Thomas Parnell; John Mainstone. Sources mentioned include Science and Nature Communications, as well as the University of Queensland pitch-drop experiment and the Trinity College Dublin pitch-drop experiment.
• Water’s possible second liquid: Martin Chaplin; Robin Speedy; Austin Angell; Osamu Mishima; Peter Poole; Francesco Sciortino; Ulrich Essmann; Eugene Stanley; David Liu; David Chandler; Pablo Debenedetti; Jeremy Palmer; Anders Nilsson; Kyung Hwan Kim; Fivos Perakis. Sources mentioned include Nature and Science, Stockholm University, and experiments at the European X-ray laser facility and South Korea’s PAL-XFEL facility.
• Ball lightning: Mark Stenhoff; Nikola Tesla; Georg Wilhelm Richmann; John Abrahamson; James Dinniss; Gerson Paiva and colleagues; Eli Jerby; Vladimir Dikhtyar; Pyotr Kapitsa; Yusuf Peer; Alexander Kendl; the Chinese research team from Northwest Normal University, whose individual names are unclear in the subtitles. Sources mentioned include Nature and Physical Review Letters, including the 2012 Chinese plateau observation and its 2014 spectrum analysis.
• Lightning initiation: Benjamin Franklin; Thomas-François Dalibard; Basil Schonland; Charles Boys; Tsutomu Takahashi; Thomas Marshall; C. T. R. Wilson; Alexander Gurevich; Gennady Milikh; Robert Roussel-Dupré; Gerald Fishman; Joseph Dwyer; Walter Petersen; William Rison; Brian Hare. Sources mentioned include Nature Communications, Nature, NASA’s BATSE and Fermi missions, and the LOFAR radio telescope.
• Quantum tunneling time: George Gamow; Ronald Gurney; Edward Condon; Hans Geiger; John Mitchell Nuttall; Robert Atkinson; Fritz Houtermans; Loy McColl; Thomas Hartman; A. B. Baz; Ursula Keller; Igor Litvinyuk; Alexandra Landsman; Lisa Torlina; Aephraim Steinberg; Ramon Ramos; David Spierings; Isabel Racicot; Paul Kwiat; Raymond Chiao. The subtitles also mention 2025 Nobel Prize recipients John Clarke, Michel Devoret, and John Martinis. Sources include Nature and Nature Physics.
• Neutron lifetime: James Chadwick; Arthur Snell; John Robson; Andrew Yue and colleagues (NIST); Francisco Gonzalez and the UCNτ collaboration; Bartosz Fornal; Benjamin Grinstein; Xiaoen Tang; Jack Wilson and colleagues. Sources and facilities include NIST, Los Alamos National Laboratory, the UCNτ experiment, the BL3 beam project, J-PARC, Physical Review Letters, and NASA’s MESSENGER spacecraft.
• Cosmological lithium problem: Steven Weinberg; Ralph Alpher; George Gamow; Ryan Cooke; Max Pettini; Monique and François Spite; Andreas Korn; Lorenzo Sbordone; Brian Fields; Keith Olive; Maxim Pospelov; Joseph Pradler; Christopher Howk; Nicolas Lehner; Brian Fields; Grant Matthews; Hubert Reeves; William Fowler; Fred Hoyle; Akito Tajitsu. Sources mentioned include Nature, WMAP and Planck, the Subaru Telescope, and CERN nuclear-reaction measurements.
• Proton decay: Ugo Amaldi; Wim de Boer; Hermann Fürstenau; Andrei Sakharov; Jogesh Pati; Abdus Salam; Howard Georgi; Sheldon Glashow; Maurice Goldhaber; Frederick Reines; Clyde Cowan; Masatoshi Koshiba; Takaaki Kajita; Arthur McDonald; Freeman Dyson; Fred Adams; Greg Laughlin. Sources and experiments include LEP at CERN, IMB, Kamiokande, Super-Kamiokande, KATRIN, Hyper-Kamiokande, DUNE, and Physical Review Letters.