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: 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...
Featured Thread: Black hole mass coupled to expansion source of dark energy?
A recent article proposes observed black hole growth in ellipticals being coupled to expansion, and sourcing dark energy. Observational evidence for cosmological coupling of black holes and its implications for an astrophysical source of dark energy..
Featured Thread: Chess fundamentally harder to "effectively" solve than Go?
Typically, the converse is claimed - Go is harder to solve than chess for (among other reasons) simple combinatorics. But for a perfect knowledge player to play effectively against "near-perfect players" I think the reverse may be true...
Featured Thread: Why unitary evolution?
Why is the fundamental evolution of systems postulated to be unitary rather than a more general CPTP map? The usual justification for why the evolution of physical systems is unitary in quantum mechanics involves arguments like "probabilities must sum to 1" or similar arguments that apply equally to any CPTP map. I'm just curious what justifications people here would use for selecting out unitary evolution in particular...
Featured Thread: Staff and Member Appreciation
Did you know we're entering Physics Forums' 22nd year!? Incredible and it keeps getting better and better! We welcomed the MHB community a few months ago and Insight authors published 26 Insights this year! Physics Forums is nothing without the amazing support from you, our members. You make the community.
Featured Thread: Big announcement made fusion energy
The US Department of Energy is set to reveal a “major scientific breakthrough” this week after scientists were reportedly able to produce a fusion reaction that created a net energy gain for the first time.
Featured Thread: How can you tell the spin of a particle by looking at the Lagrangian?
It is extremely mysterious to me how to tell that one Lagrangian should govern one spin as opposed to another. The only thing that sticks out to me at all here are the gamma matrices, which act on spinors. However, a similar term is also present in the Dirac equation, so this can't be the full story. How does the "spin content" drop out...
Featured Thread: Are we living in the matrix? No.
David Tong gives an interesting talk about the lattice chiral fermion problem here. Abstract: Are we living in the matrix? No. Obviously not. It's a daft question. But, buried underneath this daft question is an extremely interesting one: is it possible to simulate the known laws of physics on a computer...
Featured Thread: Most commonly misspelled science and math words
I'm looking for a list of commonly misspelled engineering, science, and math words. What do you see often? Using the list we generate maybe I can clean up Physics Forums along the way.
Featured Thread: Group like operations that are not associative
Is there any example of an operation that fails the associativity test, but meets the other two tests? I'll refer to this hypothetical entity as an almost-group for the purposes of this post lacking any knowledge of a better name. While my specific motivation is in Lie groups, an example of such an operation that is a finite almost-group but not associative would be helpful.
Featured Thread: Extending Newton's laws -- Is the concept of force still defined?
It is argued that the correct interpretation of Newton's 2nd Law for one body of mass m reads "The dynamics (i.e. vector sum of all external forces acting on the body = "all its interactions") dictates the kinetics (i.e. time derivative of the momentum vector = "motion")", under the assumption that the body's mass will not change during the action of the external forces and after that. Now let us assume that the effect of the external forces is to dictate the motion of the body by making it lose mass, i.e. we step out of Newton's 2nd law's assumptions.
Featured Thread: Sabine Hossenfelder on the search for new particles
In private, many physicists admit they do not believe the particles they are paid to search for exist – they do it because their colleagues are doing it. Note: Please read what she is talking about before commenting.
Featured Thread: Artemis 1 going to the Moon: News and Reactions
For the first time in 50 years, a crew capsule is sent towards the Moon again. The Flight Readiness Review (FRR) for Artemis 1 concluded - the rocket is on track for a launch on August 29, 12:33 UTC (08:33 local time) or in the two hours afterward. Backup launch windows are daily from September 2 to September 6.
Featured Thread: Introducing Math Problem of the Week
One of the best things to migrate over from MHB is their Problem of the Week program. Let me introduce the POTW director anemone! anemone had been running the POTW at MHB for 8 years and we're very glad to have her continue the great program here. I'll let her say hi and tell you what to expect!
Featured Thread: What is the correct way of measuring remaining battery capacity?
I was searching for a way to measure the remaining charge of a battery using Arduino. Most (almost all) of the tutorials are simply measuring the battery voltage using the ADC on the Arduino. Is there any better method of measuring the remaining battery capacity that does not use the voltage at the terminals as a reference? (The solution does not have to use an Arduino.)
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