Featured Science Threads - Page 1

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?

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...

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...

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...

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...

Ramsey numbers, Einstein Tiles, and 3 Arithmetic Progressions Covering:
- New Ramsey number bounds
- Aperiodic tiling discovery of an Einstein tile
- Three Arithmetic Progressions

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...

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...

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...

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?

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...

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)...

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...

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?

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.

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!

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...

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?

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...

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...

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...

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.

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...

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?

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!

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!

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.

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...

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?

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?

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...

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..

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...

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...

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.

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.

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...

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...

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.

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.

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.

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.

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.

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!

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.)

Given already high-precision experimental data about hadrons with light quarks, the main barrier to determining u, d, and s quark masses is doing the QCD calculations. But, are the new experiments that could be done that would advance the measurement of these masses?

It is said that some physicists doubted the existence of atoms in 1900 until Einstein proved their existence a few years later. Did Mendeleev's creation of the periodic table in the 1870s already prove the reality of atoms by giving the known elements atomic masses?

I try to clarify some misunderstandings about the general structure of relativistic QFT. Particularly the important defining property of "locality".

My question is, as is with normal colour and fluorescence the effect stops immediately the light is switched off. Why does the effect linger with Glow in the dark? Why are the emissions so much slower not instant the moment the light is switched off?