The Frontier

An academic paper concludes a quantum attack on Bitcoin mining using Grover's algorithm would require energy roughly equal to 3% of the sun's output, making it physically unfeasible.

The Michelson-Morley experiment (1887) did not prove the ether nonexistent. It only falsified certain ether theories, like the existence of an ether wind. Michelson continued to believe in the ether until his death in the 1920s.

Nielsen argues that falsification in science is far more complicated than naive models suggest. The Michelson-Morley result didn't induce special relativity; it merely ruled out some ether models while others remained viable.

Lorentz derived the mathematical transformations that form the basis of special relativity before Einstein, but interpreted them as physical effects of moving through the ether. His theory was experimentally indistinguishable from Einstein's until later tests like muon decay experiments in the 1940s.

Poincaré understood key postulates of special relativity but clung to a dynamical explanation for length contraction, which Nielsen suggests shows how deep expertise can sometimes obstruct fundamental conceptual shifts.

Sean Carroll speculates that an interest in physics can offer an escape from a fraught world, like other forms of relaxation, by engaging the brain on less consequential problems.

Carroll identifies two genuine unsolved problems for the many-worlds interpretation: the probability problem and the structure problem of how classical subsystems emerge from Hilbert space.

Carroll dismisses common critiques of many-worlds, like ontological extravagance or energy requirements, as non-problems with understood answers.

Carroll argues world-tubes and classical descriptions in physics are valid frameworks for their purposes, and updating them to quantum field theory isn't necessary as poetic naturalism respects different levels of description.

Carroll states the preferred basis problem in quantum mechanics is solved by decoherence, which picks out pointer states robust to environmental monitoring that coincide with states having definite spatial positions.

Carroll explains the JWST's narrow field of view is for studying faint, distant objects like early galaxies, while the Nancy Grace Roman Telescope's wide field is for surveying large-scale structure and transient events like supernovae.

Carroll states loop quantum gravity's strength is its natural attempt to quantize GR with new variables, but its major weakness is offering no mechanism to cure high-energy infinities or unify with matter fields, unlike string theory.

Carroll explains the Schrödinger equation was initially successful because it correctly solved for the discrete energy spectra of atoms like hydrogen, answering the central physics problem of the 1920s.

Carroll clarifies that light cannot escape a black hole because the event horizon recedes at light speed; as an electromagnetic wave, light's propagation speed is fixed by Maxwell's equations, making escape impossible.

Carroll argues a finite-dimensional Hilbert space for a de Sitter patch leads to Boltzmann brain recurrences, but an infinite-dimensional Hilbert space for the whole universe allows the state to settle quiescently and avoid them.

Carroll explains to relativity students that standing on Earth feels a force because the surface prevents free-fall, accelerating you at 1g away from your geodesic trajectory, though he wouldn't phrase it as the ground accelerating outward.

Carroll clarifies that the double-slit experiment with electrons does require shielding from decoherence (like air molecules or light) just as quantum computers do, contradicting simplistic textbook descriptions.

Carroll speculates complex life is likely impossible in a conformal field theory because such scale-free theories lack the definite size parameters essential for bounded, information-processing organisms.

David Friedberg says the moon's low gravity and lack of atmosphere make it cheaper to ship manufactured goods to Earth than via terrestrial methods.