The usual approach to detecting dark matter is to search for particles with a specific range of masses. The hope is that even if we see nothing, we'll at least know more about what dark matter is not.
Physicists at Fermilab have now released the first data from a different type of detector, one that looks for dark matter over a much wider range at lower sensitivity.
Result: still no dark matter, but a larger swathe of parameter space ruled out.
#OTD in 1905. Albert Einstein completes his doctoral thesis at the University of Zurich.
Titled "Eine neue Bestimmung der Moleküldimensionen", he calculated the size of sugar molecules in solution and from this a value for the Avogadro constant. It is related to his work on Brownian motion, published in the same year, and supported the atomic hypothesis, which was still controversial among leading physicists at the time.
J. J. Thomson of the Cavendish Laboratory announces his discovery of the electron as a subatomic particle, over 1,800 times smaller than a proton (in the atomic nucleus), at a lecture at the Royal Institution in London.
Thomson showed that cathode rays were composed of previously unknown negatively charged particles (now called electrons), which he calculated must have bodies much smaller than atoms and a very large charge-to-mass ratio.
Why the physics of particles might be on the verge of a revolution, how black holes evaporate, and when relativity inspires young minds. It’s “Phreaky Physics,” on Big Picture Science.
French mathematician and physicist Henri Poincaré was born #OTD in 1854.
He is considered one of the founders of the field of topology. He was among the first to present the Lorentz transformations, part of the groundwork for Albert Einstein’s theory of special relativity. Poincaré also studied the behavior of planetary orbits and contributed to the three-body problem in celestial mechanics, exploring the stability and motion of celestial bodies.
New publication: "Climate of a cave laboratory representative for rock art caves in the Vézère area (south-west France)"
Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of paint... #Physics#SocialSciencehttps://doi.org/10.5038/1827-806X.52.2.2442
The problem of free will raises all kinds of questions. What does it mean to make a decision, and what does it mean to say that our actions are determined? What are laws of nature? What are causes? What sorts of things are we, when viewed through the lenses of physics, and how do we fit into the natural order? Ismael provides a deeply informed account of what physics tells us about ourselves.
American mathematical physicist J. Willard Gibbs died #OTD in 1903.
Gibbs' most celebrated contributions were in the field of thermodynamics, particularly concerning the phase rule, chemical potential, and Gibbs free energy—a concept named after him. The Gibbs free energy is particularly critical in predicting the direction of chemical reactions and phase changes. His book, "Elementary Principles in Statistical Mechanics," laid the foundation for modern statistical mechanics.
This video explores a fascinating #science#physics phenomenon: the pressure of a liquid and a gas within a sealed container (in a gravity environment) depends on where the gas is located! The explaination is so counter-intuitive.
“The moment you put people into big institutions the goal shifts from knowledge discovery to moneymaking.” —Sabine Hossenfelder, My dream died, and now I'm here
Could the planetary system in "3 Body Problem" — a system where the stars are so close in their orbits that their motion becomes random — exist? Peter Watson, emeritus professor of physics at Carleton University, writes for @TheConversationUS about chaotic systems and how stochastic problems are like drunk people trying to get around. "You cannot predict where the next step will take him, but you can say that he will eventually reach the door." Article contains spoilers for Netflix's "3 Body Problem."
German physicist Arnold Sommerfeld died #OTD in 1951.
In 1916, he introduced the idea of elliptical orbits for electrons, and he also introduced additional quantum numbers which included the azimuthal quantum number and magnetic quantum number. He also introduced a dimensionless physical constant known as the fine-structure constant. This constant characterizes the strength of the electromagnetic interaction between elementary charged particles.
Here is a curious finding from our statistical analysis https://arxiv.org/abs/2403.16217 :
A #Feynmangraph is a graphical short hand notation for a complicated integral that computes the probability for scattering processes in #quantum field theory.
An electrical circuit can also be described as a graph. What happens if we interpret the Feynman graph as an #electrical network, where each edge is a 1 Ohm resistor? We can then compute the resistance between any pair of vertices and collect all these values in a "resistance matrix", as shown below. The average of all these resistances is called "Kirchhoff index". Now it turns out that this average resistance is correlated fairly strongly with the Feynman integral of that graph: A graph with large contribution to quantum scattering amplitudes on average also has a large electrical resistance. Isn't that a nice connection between two seemingly distinct branches of theoretical #physics ?
French mathematician and physicist Siméon-Denis Poisson died #OTD in 1840.
He is known for his significant contributions to mathematical physics, particularly in the fields of mechanics, probability theory, and electricity. He made crucial advancements in understanding the behavior of fluids & the mathematical treatment of physical phenomena. Some of his most notable contributions include: Poisson distribution, potential theory, fluid mechanics, electromagnetism.
Swedish astronomer, physicist, and mathematician Anders Celsius died #OTD in 1744.
In 1742, Celsius introduced the temperature scale that bears his name. His original scale was actually the reverse of what we use today: it set the boiling point of water at 0 degrees & the freezing point at 100 degrees. However, shortly after his death, the scale was reversed by Carl Linnaeus, resulting in the 0 degrees for freezing & 100 degrees for boiling that we are familiar with.