Featured Science Threads - Page 5

Previously most measurements using electrons favored a larger value while measurements with muons found a smaller value for the radius. Now a second electron measurement measured a result that agrees with the muon-based measurements...

Water found on potentially habitable exoplanet. "Astronomers have for the first time discovered water in the atmosphere of a planet orbiting within the habitable zone of a distant star." - from the BBC

Highly respected journals and books are the authorities in science. But they can be challenged by arguments based on other facts. The latter are also taken from highly respected journals and books. Thus one cannot dispense with the authorities....

What happens to research when a leading researcher passes away? A new study looked at this in the Life Sciences . The study observed that when a leading expert in a field died there was a significant increase in publications by new researchers (with new ideas?). it was also determined that those researchers who were coauthors with the expert had a dramatic decrease in their publications...

We are often asked for solution manuals of various textbooks. Unfortunately we can't answer those requests, as they are either not existent, from questionable sources, or breach the copyright law. There is no other way than to contact the author or publisher in these cases. The situation, however, is different for our own exercises. I will therefore upload solutions to math challenge questions from the past in this thread...

I'm happy to announce that the entire collection of (3043) photos taken of Richard Feynman giving his famous 1961-64 introductory physics lectures at Caltech (including his blackboards - original source material for the book, The Feynman Lectures on Physics [FLP]) have been posted in deep-zoomable format, along with a modified "FLP Notes Viewer" application (now renamed, "FLP Image Viewer") suitable for perusing them...

Topics: ring of functions, arithmetic-geometric mean, geometry, Hilbert space, quaternions, prime, convergence, curve, gauge transformation

It is now possible to obtain almost complete information of important aspects of embryonic development. This includes location and movement of all cells in a embryo as well as which genes are active in each cell. Important information in any attempt to understand ow embryos make adult forms...

A number of posters have asserted that Quantum Field Theory (QFT) provides a better description of quantum entanglement than the non-relativistic Quantum Mechanics. Yet I don't see QFT references in experimental papers on entanglement. Why not?

Why is p^4 not hermitian for hydrogen states with l=0 when p^2 is?
Doesn't this contradict the following theorem?

The product of two hermitian matrices, A and B, is hermitian if and only if they commute, AB=BA.

Found August 14. LIGO/Virgo estimate 99.8% chance that it is such a collision and only 0.2% chance that one of the objects is in the "mass gap": Between 3 and 5 solar masses, heavier than known neutron stars but lighter than known black holes. The chance for every other type of event is negligible. This is certainly something new and will keep astronomers busy for months...

Radiation has been released following a Russian rocket explosion at the Nyonoksa naval ballistic missile test site. Could a short burst of radiation be released if there was no critical nuclear reaction?

Interesting article ...... NEW SOURCE OF SPACE RADIATION: Astronauts are surrounded by danger: hard vacuum, solar flares, cosmic rays. Researchers from UCLA have just added a new item to the list. Earth itself...

"Previous machine-learning studies found that the acoustic signals detected from an earthquake fault can be used to predict when the next earthquake will occur," Ke Gao, a computational geophysicist at Los Alamos National Laboratory..."

I get the basics of green screening. The processing software recognizes a small range of green and can substitute a different image where it occurs. Here's what I don't get: if a subject is standing in front of a green screen, they will have reflections of green...

Interesting paper on the arXiv today. The authors claim that there is observational evidence that we live in a region with slightly lower density than the universe average, just by chance. Taking this into account can explain as much as 5.5% of the discrepancy in the Hubble constant between the local measurements and the CMB measurement. If you shift the local measurements to lower values by 5.5% (about 3.8 km/sec/Mpc), then the discrepancy is within the experimental errors...

1. - 2. posed and moderated by QuantumQuest
3. - 8. posed and moderated by Math_QED
9. - 10. posed and moderated by fresh_42
Keywords: calculus, abstract algebra, measure theory, mechanics, dynamical systems

The rare discovery is the second-fastest pair ever discovered, whipping around each other at speeds reaching hundreds of kilometers per second. The two white dwarf stars complete an orbit around each other every seven minutes. It's also known as an eclipsing binary system because one of the stars repeatedly crosses in front of the other...

Suppose we want to create a device that faithfully simulates some aspect of Nature. To do so, we need to know enough about the working of this aspect so that we know how to build the simulation. Being able to create a detailed blueprint for a perfect simulation means that we understood this aspect. Not being able to do this implies lack of understanding...

Quantum theory is widely thought to be a theory of the fundamental microscopic constituents of matter. It is supposed to tell us something about how matter behaves at the fundamental microscopic level, from which the classical macroscopic behavior should somehow emerge...

Perhaps the most dramatic moment of Apollo 11's mission to the moon was when the Eagle began its final descent to the lunar surface and the Apollo Guidance Computer became overloaded. Few were more nervous than the young computer programmer who had written the code for the landing...

The wording of the definition of the meter has apparently changed recently. I'm wondering about the motivation for the change. The current definition is...

The collaboration with the questionable acronym improved their measurement with a joint analysis of the whole dataset of six gravitationally lensed quasars. Measurements based on supernovae (measuring the Hubble constant "now") and measurements based on the cosmic microwave background (needing an extrapolation to get the current value) have been in disagreement for a while now...

It is with profound sadness that I must report that we've learned legendary PF brother @jim hardy passed away earlier this week. Jim was loved by countless members here and was an incredible positive force for the community and all our outside readers...

1. - 4. posed and moderated by QuantumQuest
5. - 8. posed and moderated by Math_QED
9.+10. posed and moderated by fresh_42

keywords: calculus, polynomials, trigonometry, diagonalizability, projective linear spaces, finite vector spaces, Brownian motion, Galois groups, matrix decomposition, Hilbert spaces

Yesterday afternoon I heard (and so did every bird in the district) a very loud, low frequency, double boom which was very vigorous and I suspected all sorts of things but then I thought "double boom!!" and (engaging smartarse mode) I informed my wife that it was only a sonic boom. I was later proved right...

Article with data showing immunizations save more than they hurt. Vaccines are one of the great benefits of biology has bestowed upon humanity, in that they have saved many lives and greatly reduced suffering...

Back in 1896, acetaldehyde phenylhydrazone (APH) kept melting at two very different temperatures. A batch he produced on Monday might melt at 65 °C, while a batch on Thursday would melt at 100 °C. Here's why...

Just interested in what may be achieved by putting a man/men on the moon again.

Quantum Jumps are predicted using microwave monitoring. Weird. "Yale researchers have figured out how to catch and save Schrödinger's famous cat, the symbol of quantum superposition and unpredictability, by anticipating its jumps and acting in real time to save it from proverbial doom." - physorg

Test your skills on 15 math challenges! We have a prize this month donated by one of our most valued members, and that's what the points are for. The first who achieves 6 points, will win a Gold Membership!

"Whether earthquakes of different sizes are distinguishable early in their rupture process is a subject of debate. Studies have shown that the frequency content of radiated seismic energy in the first seconds of earthquakes scales with magnitude, implying determinism "

611 pages of notes Richard Feynman made in 1961-64 to plan and prepare lectures for Caltech's two-year introductory physics course, later known as The Feynman Lectures on Physics, have been posted in deep-zoomable format at The Feynman Lecture Website.

Wolfram made what I would call a gigantic move: they released the Wolfram Engine for Developers - for zero cost! The idea of the Engine is primarily that you can call and run Wolfram Language commands from lots of different sources. I predict this will greatly enhance usage of the Wolfram Language and Mathematica, as it has always been so amazingly expensive, particularly for commercial users...

"When the launch of NASA's Orbiting Carbon Observatory and Glory missions failed in 2009 and 2011, the agency said it was because their launch vehicle malfunctioned. The clamshell structure (called fairing) encapsulating the satellites as they traveled aboard Orbital ATK's Taurus XL rocket failed to separate on command. Now, a NASA Launch Services Program (LSP) investigation has revealed that the malfunction was caused by faulty aluminum materials."

Many ways to approach the Riemann Hypothesis have been proposed during the past 150 years, but none of them have led to conquering the most famous open problem in mathematics. A new paper in the Proceedings of the National Academy of Sciences (PNAS) suggests that one of these old approaches is more practical than previously realized...

I have an OCR A level "physics A" student, and we're working through past papers. Time and time again, we've come across questions which are astonishingly ambiguous and answer schemes which are in my view, astonishingly picky or just plane bizarre. I've taken some of these to OCR but got no progress...

All organism on earth use a genetic code consisting of 64 three-letter codons to encode the 20 amino acids found in proteins. Scientists in the field of synthetic biology have long sought to expand the genetic code to allow encoding of more than 20 natural amino acids found in most organisms...

"Theories of human behavior suggest that people’s decisions to join a group and their subsequent behavior are influenced by perceptions of what is socially normative. In online discussions, where unruly, harassing behavior is common, displaying community rules could reduce concerns about harassment..."

Fast, reliable high-bandwidth internet everywhere in the world - that is the promise of the upcoming satellite constellations. To get a good bandwidth with many customers this needs many satellites; to get a good latency they have to be in low Earth orbit (LEO)...

I came across a reputedly true bit of Cold War spy stuff in a book "Farewell: the greatest spy story of the twentieth century" by Sergei Kostin. It's about a KGB defector, Colonel Vladmir Vetrov who blew the structure of the KGB to the French. As a result, the US sowed the seeds of a spoof about US development of a Gamma Ray Laser to the Russians. He's mentioned in Wikipedia so it's not just fiction. What could be the basis which made them think that Nuclear transitions could be used in a laser type reaction?

Bacteriophages, viruses that infect bacteria, have long interested scientists as a potential therapy for bacterial infections. Today, in the journal Nature Medicine, scientists report the first clinical use of genetically-engineered bacteriophages to treat an antibiotic-resistant bacterial infection nodules...

I have used Laplace transform during my EE studies to solve differential equations and in control system analysis, but we were taught that as a tool kit to make the math easier. The physical meaning was never explained. I know basic time and frequency domain concepts (thanks to Fourier series), but I am having a hard time understanding the physical reality of the Laplace transform...

The 6th Annual International Academy of Astronautics Conference on Planetary Defense ended this past Friday. I watched about half of the presentations. I have little astronomy background but was interested in what was being done about NEO detection, characterization effects and mitigation of potential hazardous asteroids...

Some of the question will probably require to look up or ask about some definitions or formulas on the internet, which shouldn't be a problem nowadays. It is part of our new world. They might look harder than they are. Topics include: Chevalley Eilenberg Complexes, Buildings, Measure Theory, Linear Operator, Affine Variety and more!

"Riess observed 70 Cepheid stars — stars that pulse at a well-observed rate — calculated their distance and rate, and then compared them with a certain type of supernovae that are used as measuring sticks. It took about two years for the Hubble telescope to make these measurements, but eventually Riess calculated an expansion rate of 74." - APnews | Thoughts on this finding? Does it really require new physics to explain?

"The local residents took the substance to be volcanic lava, which, however, later turned out to be rocks. The rocks had melted after coming in contact with a high tension power cable of the state electricity distribution company that had fallen to the ground."

While SpaceX tested the engines of a Crew Dragon capsule something went wrong. A lot of smoke was released, no one was harmed. Unfortunately that is the end of official statements already. It was planned to do an in-flight abort test of Crew Dragon in June or July and a crewed flight (first crewed US spaceflight since the retirement of the Space Shuttle) not earlier than August, but this timeline is now obsolete....

In the course of my career, (in the years 1986-1990), on two occasions I discussed with two very intelligent physics PhD.'s a problem that surfaces in regards to interference patterns. The first PhD. knew very little Optics and (around the year 1986) was asking me, "how can you possibly get an interference pattern? Are you telling me...

Earth and Titan are the only objects in the Solar System with stable liquids on its surface. Earth has water oceans, lakes, rivers and rain, Titan has methane/ethane oceans, lakes, rivers and rain. Earth has seasons, and so does Titan. They are just much longer as Saturn's orbital period is 29.5 years...