Featured Science Threads - Page 3

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: Math Challenge - August 2020
functional analysis, operator theory, topology, measure theory, calculus
Authors: Math_QED (MQ), Infrared (IR), Wrobel (WR), fresh_42 (FR).
Featured Thread: Difference between Physics and Mathematics
Our forums are full of physics and mathematics. One cannot talk about the former without getting into calculations and mathematics sooner or later: Hilbert spaces, differential operators and linear algebra all over the place. Students of both faculties have normally a similar motivation, foundation and interests in both - more or less...
Featured Thread: Face shield bleach disinfection
Face shield or respirators are getting to be as common as masks in public. What kind of bleach in basin can theoretically kill the covid-19 virus? What should be the concentration of bleach and now does it kill it?
Featured Thread: Starting to Learn Python: Development Tools and Environments
There is a dizzying array of editors and IDE's out there. What is a good option to get started? I've never programmed (or done anything technical) on Windows. Is there any general advice about using the Windows environment for programming? I don't want to get into installing Linux at this stage. Do I need to be able to find my way around the Windows O/S, or does an IDE make that unnecessary?
Featured Thread: Twin paradox explained for laymen
As a layman I also have conceptual difficulties with the twin paradox. It would allow me to move on if some one could quickly answer the rather obvious question: would there be any time dilation if the earth was removed entirely from the thought experiment so that the twins are in a symmetrical relationship of inertia or relative motion. I cannot see how there could be but would then have to look to gravity to explain it.
Featured Thread: Using Far-UVC Light To Kill Airborne Human Coronaviruses
This paper was published in Nature, and it presented a rather fascinating result if it is true. The researcher used far-UVC light (222 nm wavelength) to kill the viruses in airborne aerosol with a claim based on the current guidelines that far-UVC is not as harmful as UVA and UVB.
Featured Thread: LHCb discovers a new tetraquark state
In a recent paper submitted by the LHCb collaboration at arXiv, they have reported a tetraquark state composed of charm quarks and antiquarks. The statistical significance of the data is more than 5σ...
Featured Thread: Math Challenge - July 2020
Functional Analysis, Topology, Differential Geometry, Analysis, Physics
Authors: Math_QED (MQ), Infrared (IR), Wrobel (WR), fresh_42 (FR).
Featured Thread: Meaning of quark mass
What is the meaning of the mass assigned to an individual quark?
A hydrogen atom is less massive than the sum of an unbound proton and an unbound electron. If I add energy to the atom the system becomes more massive, and when I add enough then I have an unbound electron and proton, each of which has the usual mass...
Featured Thread: Dark matter experiment XENON1T sees an excess at low energies
XENON1T sees an excess of events at low energies that doesn't have a good explanation at the moment.
Featured Thread: A Competitor to the Drake Equation
A alternative to the Drake Equation for thinking about how likely intelligent life on other planets has been recently published. The Astrobiological Copernican Weak and Strong Limits for Intelligent Life proposes a different way to think about the possibility of intelligent life other places than earth.
Featured Thread: PF has donated to support black STEM organizations
In honor of Juneteenth , PF has donated $50 to Black Girls Code and $50 to The National Society of Black Engineers. See what you can do today and beyond to further the support for african-americans in STEM!
Featured Thread: Differential Forms or Tensors for Theoretical Physics Today
There are a few different textbooks out there on differential geometry geared towards physics applications and also theoretical physics books which use a geometric approach. Yet they use different approaches sometimes. What are the advantages of one over the other? Do theoretical physicists today tend to prefer one over the other and is it field specific?
Featured Thread: Math Challenge - June 2020
Normed, Banach and Hilbert spaces, topology, geometry, linear algebra, integration, flux.
Authors: Math_QED (MQ), Infrared (IR), Wrobel (WR), fresh_42 (FR).
Featured Thread: Elevators and airflow
Elevators are a problem in this post COVID world. It is impossible to maintain social distancing while also meeting the passengers-per-hour needs of the building. Skyscrapers without efficient elevators are not practical.
Featured Thread: SpaceX Crew Dragon Launch Try #2 3:22PM EST
Watch history unfold on Saturday, May 30, as NASA and SpaceX launch astronauts Robert Behnken and Douglas Hurley to the International Space Station. Here we go again! Set for 3:22PM EST. Lots of analysis in this live video already!
Featured Thread: Project Loon, Stratospheric balloon
Project Loon is a network of stratospheric balloons designed to bring Internet connectivity to rural and remote communities worldwide. There is one being tracked, between Reunion and Mauritius in the Indian Ocean. Another one over Equador, 6 over Peru, 1 over Puerto Rico, 3 over Kenya and 1 near the Seychelles.
Featured Thread: Crew Dragon Demo-2: Launch at 4:15PM EST
It doesn't happen every day decade that people are being launched to orbit in a new spacecraft. The last time it happened was 2003 (Shenzhou), and the last time before that was the Space Shuttle in 1981. The next time will be in 12 hours, if the weather stays good. And for the first time it is a private spacecraft. Going to orbit is no longer the exclusive domain of governments. You can call SpaceX if you want a ride (and have maybe 100 million dollars).
Featured Thread: Math Challenge - May 2020
Test your skills in this month's math challenge thread! Topological spaces and metrics, integrals, abstract algebra (groups and rings), heat equation, geometry .
Featured Thread: Almost Plausible Solar Takeover Plan
I'm normally among those who think that renewable advocates lack realism when they advocate 100% wind+solar grid. This article is the first I've seen that comes close to being plausible. I do doubt the article's numbers for storage and for wind, but the basic idea of massively overbuilding solar is in the right direction...
Featured Thread: What Have Educators Learned About Distance Learning?
The cumulative experience with distance learning must have soared in the past 2 months.
  • What has been learned?
  • What works? What doesn't work?
  • Are there new distance learning methods or strategies for the coming fall term?
Featured Thread: T2K sees ~3 sigma evidence for neutrino CP violation
Previous measurements already hinted at this, now we have a relatively strong single measurement. CP violation is linked to matter/antimatter asymmetries. They are small for quarks, but it looks like they are larger in the neutrino sector. The measurement favors the maximal CP violation that was still within the range set by other parameters. DUNE will measure this parameter more precisely in the future.
Featured Thread: Why do boats have a pointy bow?
A (displacement) boat hull has a design goal of making as little water resistance as possible with the required volume for load carrying capability. To achieve this the hull is given the shape similar to a vertical symetrical airfoil. But as the leading edge of a boat (it's bow) seems to be made as sharp as possible, the leading edge of airfoils are round. Why aren't boats bow round as the airfoil?
Featured Thread: Physics Challenge April 2020
Can solve solve one of these 3 physics challenge problems? This is an experiment if we could establish a little physics competition. Topics include, Classical Physics, Special Relativity Theory
Featured Thread: Clarification of accelerator physics terminology
I have been reading some papers on accelerator physics recently, especially those on the LHC and the upcoming FCC-hh. As a beginner, I am not supposed to know everything, but there are a few terms that I feel I have to know in order to penetrate further into this field...
Featured Thread: How can I measure the terrestrial tide on my place?
How can I measure the terrestrial tide on my place? Since i don't have a MEMS gravimeter or a laser spectometer what will be the simplest method to measure the local earth tide variations?
Featured Thread: Math Challenge - April 2020
Calculus (Polynomials, Series and Functions), Differential Equations, Operators, Normal Distribution, Number Theory (Authors: Infrared - IR; QuantumQuest - QQ; fresh_42 - FR)
Featured Thread: Can dx be negative?
This is more of a "housekeeping" question (i.e. it's not particularly interesting), though I haven't studied much in the way of infinitesimals so apologies in advance for my lack of rigour! As far as I'm aware, an infinitesimal can be thought of as a small change in some quantity. Changes can be either positive or negative, so subsequently it also seems reasonable for ##dx## to potentially represent a negative change...
Featured Thread: Can large Black Holes ever spaghettify? (and more)
So Alice and Bob are hanging out near a really large black hole. It's quiet. Nothing has entered the BH is a while. Alice tosses Bob in and then waits long enough for him to collide with the singularity. Of course, Bob is keeping time differently than Alice - so I rather doubt that the time period Alice calculates for Bob to reach the "center" has any real meaning to Bob. But Alice's real goal is to enter the BH herself and to never seen Bob again...
Featured Thread: Innovations to help COVID-19 treatment efforts
I didn't see a thread so far in the Medical forum that addressed the specific innovations that are being worked on to help combat this pandemic, so I thought I'd start this thread. One such innovation may be using plasma from Pts who have recovered from the virus to help treat new Pts. I don't know much about that, so hopefully Bill or Jim or others can comment...
Featured Thread: Why is rolling easier than sliding?
I learned that rolling involves the coefficient of static friction unlike sliding that involves the coefficient of kinetic friction. It's known that the coefficient of static friction is always higher than the coefficient of kinetic friction. This should result in rolling to be more difficult than sliding as it involves higher frictional force, which is not the case in real life...
Featured Thread: Math Challenge - March 2020 (Part II)
This is an extra round of questions, because the ones in part I had been solved so fast. However, we still have some easy ones here. They are from calculus, abstract algebra, algebraic geometry, and topology. (Authors: Infrared- IR; fresh_42 - FR)
Featured Thread: Quickly Transitioning to Teaching Online Due to COVID-19
There's a good chance that the spread of the COVID-19 virus will cause colleges and universities to suspend on-ground class meetings. I know that UC Berkeley and UCLA have already done so to some degree, and the schools I teach at have suggested instructors prepare the possibility by getting ready to teach courses online...
Featured Thread: What makes the current coronavirus different than others?
An interview on NPR with virologists discussed the reasons that this current viral pandemic is different than others in the past. Key differences were: - Ability of make new viruses - apparently 1000 times more prolific than flu...
Featured Thread: Tidal effect of Sun on Earth
It's well known that the tidal effect of the Moon on the Earth causes the Earth's rotation to slow down and the radius of the Moon's orbit to increase over time. However, the Sun also exerts a tidal effect on the Earth, which should also contribute to slowing down the Earth's spin. This raises two questions...
Featured Thread: Students Engaged In Active Learning Think They Learn Less
My classes are a blend of both. My students had to do a pre-lecture in which they had to read up something or watch a video, followed by a short quiz based on the material that was presented. When to come to class, I give them a "traditional lecture", but heavy on (i) clicker questions and discussions, (ii) in-class problem solving where they work in groups to solve problems, and (iii) in cases where we have "labs", the experimental work is often incorporated within the lecture as they are observing the result...
Featured Thread: Math Challenge - March 2020
We have a variety of areas this month: calculus, trigonometry, topology, algebra (geometry, linear, abstract), so I hope you all will find an interesting one. Authors: QQ (QunatumQuest), IR (Infrared), FR (fresh_42)
Featured Thread: Debris found in fuel tanks of 70% of inspected 737 Max jets
Yes, that 737 Max. News. It's unclear if these airplanes were supposed to be delivered to customers already if the 737 Max wouldn't be grounded for other reasons, but foreign objects in more than half of the inspected planes is certainly nothing customers want to see. There are 350 more aircraft waiting they have to check.
Featured Thread: E=mc^2 before Einstein
A short historical paper gives evidence that Einstein was not the first who discovered E=mc2E=mc2. "The mass-energy relation E=mc2 has a dual origin, one grounded in the postulate of the existence of an aether made of "ultramondane particules" moving in space at the speed of light, c; the other, a consequence, first deduced by Henri Poincare, of John Poynting's electromagnetic Theorem."
Featured Thread: Ptolemaic Model of Solar System
Why did the Ptolemaic model coupled the motion of Venus to the sun? You notice that the center of the smaller orbit of Venus is always in line with the sun. Anyone knows why those folks back then forced it to move this way? There must be a reason why they thought Venus was always very close to the sun and can't move too far away from it.
Featured Thread: FFT scaling vs analytical FT
How does the scaling of the numerical output of a forward FFT compare to the mathematical definition of the Fourier transform?
Featured Thread: Proper barograph linkage settings for maximum pen displacement?
What would the settings be for both the linkage and the screw so that the smallest change in the aneroid disc causes the largest change in the movement of the recording chart pen? Currently, I have the screw screwed all the way into the axle up to the lock nut and I am utilizing the last hole in the linkage.
Featured Thread: Math Challenge - February 2020
A lot of calculus questions this month, but a bit (linear and abstract) algebra, too. The functional analysis question is a bit tricky.
Featured Thread: Amateur microscope mostly for children
When I was a child I used to have a microscope. I don't remember the maximum zoom it could do. Nowadays when I look up for amateur microscopes on the web, they seem to go up to either 1000x or 2000x. Do you think it's enough to get some fun by looking at bugs and cells of onions for example? The use would not be for research, only to have fun. Is there any recommendations you could provide?
Featured Thread: An observer passing the event horizon of a black hole
I am not particularly well aquainted with GR and my questions are concerning the often mentioned statement that an observer that passes the event horizon won't notice it. But is this really correct? I have recently thought about different scenarios and I have three particular ones below that I would like others to consider...
Featured Thread: LIGO+Virgo saw something unknown
Not much is known so far. It was a very short burst seen by all three detectors, with a false alarm rate of 1 per 25 years - a good chance this is something real. The burst was 14 milliseconds long and the fitted central frequency is 65 Hz, which means they had just about a single cycle in the signal. Expect more updates in the following days.
Featured Thread: Math Challenge - January 2020
Topics include Useful Equations And Inequalities, Calculus, Functional Analysis, Small Groups
Featured Thread: Betelgeuse unusual dimming, ready to supernova?
The red giant, and semi-regular variable, Betelgeuse is the dimmest seen in years, prompting some speculation that the star is about to explode.
Featured Thread: Innovative Scientific Uses of GPS
New ways to use GPS for scientific purposes. Feel an earthquake, Monitor a volcano, Probe the snow, Sense a sinking, Analyze the atmosphere. What are some that you can come up with?
Featured Thread: See the first precise pulsar surface map
Using NICER data, scientists have obtained the first precise and dependable measurements of both a pulsar’s size and its mass, as well as the first-ever map of hot spots on its surface.