Featured Science Threads - Page 1

Below is a curated list of some of the most interesting and highest quality science news and discussions on Physics Forums. News and discussions are added weekly. Also check the Hot Threads page for discussions choosen algorithmically.
Featured Thread: Question about Rutherford experiment: Which of these could not be concluded?
In the early 20th century, scattering experiments were carried out by directing high-speed alpha particles at thin metal foils. Which of the following could not be concluded from these experiments?
A. Most of the atoms are empty spaces.
B. The nucleus of the atom is positively charged.
C. There is a concentration of charge in the atom.
D. There is a concentration of mass in the atom.
Featured Thread: Sources to study basic logic for precocious 10-year old?
I am advising the mother of a precocious 10-year-old who studies on his own and already has some rudimentary algebra skills. I am not tutoring the child, just giving some recommendations. One aspect that seems inadequately represented among resources on the Internet or books that she could order are books on basic logic...
Featured Thread: Looking for Axions in Neutron Stars
Axions are hypothetical particles that have never been detected. However, it is theorized that they may be found near spinning Neutron stars. These elementary particles are purely hypothetical. If we did manage to find them, though, we could solve some of the biggest problems in the cosmos, including the identity of at least one kind of dark matter...
Featured Thread: New Developments In The Search For Planet X
New tighter parameters for where a hypothetical Planet X that influences the dynamics of trans-Neptunian objects is and how big it has to be if it exists, have been released as a pre-print. There are some hints from the orbits of known objects in the solar system that there might be a Planet X out there that has not been discovered. A recent study by Siraj et al. (the link is to a pre-print of the paper), analyzes a bigger data set (orbits of 51 objects v. 11 in previous studies) to work out where this Planet X should be based upon these hints. It concludes that...
Featured Thread: Redshifts of nearby galaxies
We have had a number of threads lately on the redshifts of Local Group galaxies. Replies have focused on how these are not cosmological in origin. This is of course true, But there is something more basic. These redshifts are measured from Earth, not the center of the Milky Way. The Earth is in motion with respect to the galaxy as a whole and Galaxy X can be moving towards Earth but away from the galaxy as a whole or vice versa...
Featured Thread: CERN Experiment NA62 observes rare Kaon decay mode
Geneva, 25 September 2024. At a seminar at CERN this week, the NA62 collaboration reported the unequivocal confirmation of the ultra-rare decay of a positively charged kaon into a positively charged pion and a neutrino–antineutrino pair. Experiments including NA62 have previously measured and seen evidence of this process. However, this is the first time it has been measured with a statistical significance of five standard deviations, crossing the threshold traditionally required to claim a discovery in particle physics...
Featured Thread: Car stalls during idle after battery replacement, then fine after two days
How or why is it that replacing a dead car battery with a new one would allow the car to stall while the engine idling for 1 or 2 days, and then no further stalling after that? This makes no sense. Typical modern car by a well-known foreign manufacturer. Fuel-injected, in case that is important.
Featured Thread: Wow! signal could be from interstellar hydrogen clouds
A new paper proposes cold interstellar hydrogen clouds as a source of a bright radio signal seen in 1977. Normally these clouds are quiet, but they can get excited and start emitting radio waves by some nearby source of radiation. This new paper has found several more signals...
Featured Thread: Incandescent bulbs in teaching
Incandescent light bulbs were soft-banned in the EU in 2016 and last year in the US. If you go to any store selling bulbs, all of them are LED, which makes sense both from many perspectives. We are soon going to face a generation of students who have never in their life seen an incandescent bulb. Meanwhile, they are typically used as examples in many physics classrooms...
Featured Thread: Optimizing Exposure Times: Balancing Efficiency and Image Quality
To summarize, data I acquired when imaging a particular target shows that I can retain 75% of my images for stacking at 10s exposure times, but only 50% of the images taken with 15s exposures. The difference is entirely due to tracking error and no, I am not going to get an autotracker...
Featured Thread: Rock on Mars possibly indicating Life
NASA people are excited about a new (old actually) rock that their rover Perseverance found a few days ago.
Featured Thread: Researchers calculate how much faster time passes on the Moon
A team of physicists with NASA's Jet Propulsion Laboratory at the California Institute of Technology has calculated more precisely how much faster time passes on the moon than on the Earth...
Featured Thread: Dam Failures and Infrastructure Damage in a Changing Environment
Extreme weather events associated with a changing climate are producing more frequent flooding events in various parts of the US and world in general. Infrastructure designed for a cooler environment is now at risk...
Featured Thread: Parallelizing N-Queens
A colleague has a parallel algorithm problem. There is a similar, more familiar problem that also uses backtracking, so let's discuss that. The problem is called n-queens. You have an nxn chessboard and the goal is to place n queens on them so that no queen attacks another: no two queens are on the same row, the same column, or the same diagonal.
Featured Thread: How 'Messy' are Fusion Reaction Chains in Stars?
How 'Messy' are Fusion Reaction Chains in Stars? When looking up stellar nucleosynthesis and the various reactions that occur inside stars, I often see very straightforward reaction chains, such as this one for the Silicon burning process (isotope numbers and such left out)...
Featured Thread: Documenting the setup of my new telescope
This thread is for documenting the setup of my new telescope. It's not completely new, I'll be using some peripherals from the old telescope, such as the camera, filter wheel, off-axis guider (OAG), mini PC, focuser, etc. But the optical tube assembly (OTA), mount and tripod are new...
Featured Thread: What's the point of a thesis?
I will play devil's advocate to some extent. I'm looking from the outside in and won't have the same insight as some of you PhDs...If a research paper is around 20-30 pages tops, what's the point of spending all that time to write up a 100, 200, 500-page PhD thesis...
Featured Thread: Dark energy might not be constant after all
The Dark Energy Spectroscopic Instrument (DESI) will measure the effect of dark energy on the expansion of the universe. It will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3D map spanning the nearby universe to 11 billion light years...
Featured Thread: Things to try while Eclipse Watching
We can:
0) watch the eclipse unfold with our ISO approved eclipse glasses
1) listen for insects chirping as they think night has fallen
2) make a pinhole camera from a shoe box
3) wear red and green clothing to see how our perception changes in the twilight of the eclipse (to witness the Purkinje Effect)
Featured Thread: Eye protection while watching a total solar eclipse
I got myself some glasses for the upcoming solar eclipse, but they are very dark! They work fine for looking at the Sun in all its glory, but I suspect I won't be able to see anything of interest during the eclipse. Does anyone have experience filtering out the harmful UV while still being able to see something during the eclipse?
Featured Thread: Alaska Airlines is grounding its 737 MAX-9 fleet
Alaska Airlines is grounding its 737 MAX-9 fleet for checks after a door plug failed mid-flight on January 5th during flight AS-1282 from Portland, Oregon, to Ontario, California. The incident, involving an aircraft with 171 passengers and 6 crew, occurred at 16,000 feet, causing part of the cabin wall to blow out...
Featured Thread: Iron core barely boosting field strength
My setup will consist of four coils positioned horizontally around a microscope objective, and one underneath, such that the coils opposite each other will create a homogenous field in the center, with a downward gradient from the lower magnet. distance between opposite coils will be approximately 3 inches, so that's why I believed an iron core would be needed to achieve 15mT at the center...
Featured Thread: New Salt Cooled Nuclear Reactor Approved by NRC
For the first time in 50 years, a non-water-cooled nuclear reactor has received approval from the NRC It will be a nonpower pilot plant to be built in Oak Ridge Tennessee...
Featured Thread: The changing physics curriculum in 1961
Phillip Morse (of Morse and Feshbach) wrote this preface for the preliminary* edition of his book Thermal Physics. It has some interesting comments about curriculum reform...
Featured Thread: Major Math Discoveries in 2023
Ramsey numbers, Einstein Tiles, and 3 Arithmetic Progressions Covering:
- New Ramsey number bounds
- Aperiodic tiling discovery of an Einstein tile
- Three Arithmetic Progressions
Featured Thread: Correspondence between areal radius differences and proper distances
Differences in Schwarzschild r coordinate (areal radius) generally don't have any simple relation to reasonable distance definitions. This thread establishes a limited sense in which they do: Locally, near any event in the fully extended Schwarzschild geometry, distance measured along the spacelike radial geodesic orthogonal to a colocated free faller is simply radial coordinate difference...
Featured Thread: The infinite sequence of the digits of pi
Is there a way to prove if the 0s (or 1s 2s or 3s or ... or 9s) that are present in the infinite sequence of digits of pi in the decimal system are finite or infinite? If they are infinite they are countable infinite or uncountable infinite? My intuition tells me that they are countable infinite but cant find a way to prove it...
Featured Thread: The Emergence of Space-time in String Theory
In that book strings were part of normal space-time plus for consistency some extra dimensions. Spin 2 particles naturally emerged and so did GR. I didn't think anything of it at the time (pun intended), but I recently saw a discussion about what time is with Michio Kaku on the panel. He claimed that the concept of time emerged from String Theory. Others poo-pooed it saying how can you have vibrating strings without time. Michio kept silent, but I thought there must be something to it for him to say it...
Featured Thread: Where are the black holes?
A simple calculation suggests there should be many black holes relatively nearby. Why don't we detect them? Where should the nearest black hole be?
Featured Thread: How non-conscious can an Observer be and cause wave function collapse?
Can a mere broken sensor, or not-wired-up sensor, or results never looked at "Consciously" by anyone, still cause "consciously indisputable" wave function collapse...
Featured Thread: Dude! Where's my wormhole?
Confusion about the location of the wormhole in a conformal diagram of the Schwarzschild black hole. Recently I was brushing up my knowledge of black holes with (among others) Zee's "Einstein gravity in a Nutshell" and encountered the analytical continuation of the Schwarzschild black hole in the famous Kruskal-Szekeres coordinates (Zee: chapter VII.2)...
Featured Thread: Black Holes in Curved Spacetime
Do Black Holes form in Curved Spacetime? What is and is not known about this?
We've been talking in another thread about supermassive black holes. That has me thinking about really, really big BH's - so large that the spacetime curvature and evolution of the universe matters. Let's start by defining the density of a black hole as its mass divided by the volume enclosed by its event horizon...
Featured Thread: Supermassive black hole, surface gravity and tidal forces
A light black hole has stronger surface gravity and tidal forces just outside the horizon than a supermassive black hole. Why can't light nevertheless escape just inside the horizon of the supermassive black hole?
Featured Thread: Which science communicator do you find to maintain the most accuracy?
Who do you rate as the most accurate in communicating science, in particular physics? Was watching a Sean Carroll video and his answers to some questions seemed to run counter to the norm.
Featured Thread: Math Challenge Thread (October 2023)
The Math challenge threads have returned!

Rules:
1. You may use google to look for anything except the actual problems themselves (or very close relatives).
2. Do not cite theorems that trivialize the problem you're solving.
3. Do not solve problems that are way below your level. Some problems may be intended for high school or early university level students. If a problem looks way too easy for you, leave it for someone else :)
4. Have fun!
Featured Thread: Number systems in science
A couple of weeks ago we had an interesting thread where a tangent developed discussing whether real-valued measurements were possible. I would like to generalize that discussion a bit in this one and discuss all scientific purposes, not just measurements...
Featured Thread: Light Heavy and Semiheavy Water Equilibrium
If I start with a mix of half H2O and half D2O, when it equilibrates it will be half HDO, a quarter H2O, and a quarter D2O. My question is "how long does this take?". Ballpark is fine - microseconds? Days? Centuries?
Featured Thread: Measuring the W mass
A few months ago, there was a discussion on the W mass. It unfortunately degenerated with posters attacking the honesty of the researchers. A pity, because we never got into the issues involved in making a sub-100 ppm measurement. The first problem is that the decay is W to lepton + neutrino...
Featured Thread: Remark on centrifugal force in Heino Falcke's black hole book
A question about how to interpret a remark on centrifugal force in a popular science book. Currently, I'm reading the Dutch translation of Heino Falcke's "Light in the Darkness: black holes, the universe and us" as a preparation on a course on black hole I'm giving later this year. In part 1 it contains a remark about space telescopes, and the author imagines us to travel with the orbiting telescope...
Featured Thread: Unlocking the Secrets of Prof. Verschure's Rosetta Stones
I purchased a collection of thin sections that I believe comprise the research materials of Prof. Rob Verschure, who at the time was faculty at the Geological Institute in Amsterdam. What changed this purchase from eccentric (although, at $2 per sample, also very affordable) to something more elevated is that Prof. Verschure published his findings on many of these samples...
Featured Thread: The Latest Higgs Boson Mass Measurement
The world average Higgs boson mass is now about 125.27 GeV and is less uncertain than it used to be. The current Particle Data Group global average measurement for the Higgs boson mass is 125.25 ± 0.17 GeV.
Featured Thread: How feasible is home radio astronomy?
Is a homemade radio telescope realistic? There seems to be a confluence of multiple technologies that makes the situation better than when I was a wee lad: software-defined radio (SDR), the easy availability of satellite dishes, surveillance drives, and fast CPUs...
Featured Thread: Lines of stars that we see in the sky
Many stars are parts of star clusters. The parts of many of those clusters actually lie within the same region and the evidence for this is their common chemical fingerprints. How likely is it that a particular 'line of stars' would appear a line from other frames?
Featured Thread: Math Challenge - July 2023
Welcome to this month's math challenge thread!
Rules:
1. You may use google to look for anything except the actual problems themselves (or very close relatives).
2. Do not cite theorems that trivialize the problem you're solving.
3. Have fun!
Featured Thread: Math Challenge - June 2023
Welcome to the reinstatement of the monthly math challenge threads!
1. You may use google to look for anything except the actual problems themselves (or very close relatives).
2. Do not cite theorems that trivialize the problem you're solving.
3. Have fun!
Featured Thread: Saturn has 145 moons!
Astronomers have discovered 62 new moons orbiting the ringed planet Saturn, bringing the total to 145 Moons, with 121 irregular moons and 24 regular moons.
Featured Thread: What Are Infinitesimals?
When I learned calculus, the intuitive idea of infinitesimal was used. These are numbers so small that, for all practical purposes (say 1/trillion to the power of a trillion) can be taken as zero but are not. That way, when defining the derivative, you do not run into 0/0, but when required, you can neglect them as being zero for all practical purposes...
Featured Thread: AI, do you fear it?
I think that a lot of people fear AI because we fear what it may reflect about our very own worst nature, such as our tendency throughout history to try and exterminate each other.
But what if AI thinks nothing like us, or is superior to our beastial nature?
Do you fear AI and what you do think truly sentient self-autonomous robots will think like when they arrive?
Featured Thread: Quantum analog of Boltzmann entropy?
In classical statistical physics, entropy can be defined either as Boltzmann entropy or Gibbs entropy. In quantum statistical physics we have von Neumann entropy, which is a quantum analog of Gibbs entropy. Is there a quantum analog of Boltzmann entropy?
Featured Thread: How do I become a mathematician?
I’m currently a senior in high school. All of my applications are finished and I am now in the waiting zone. At the same time, I started to wonder what my future will be and frankly I was quite inspired by the discussion in 2006 about what it takes to become a mathematician...

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