Featured Science Threads - Page 7

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: 2018 PF Award Ceremony
Happy New Year! It's been another incredible 365 days spent on PF! Congrats to all who were nominated as it's a true honor. It should be remembered each voting list could easily have been ten times as long. We have an amazing core of members here at PF. A member may have won more than one category, but can be awarded for just one...
Featured Thread: Thank You PF Mentors!
PF owes much of it's success because of our tireless volunteer Mentor crew. In 2018 they dealt with well over 3000 reports! Some take 5 minutes and some take days to handle. But community policing is just one of dozens of hats they wear. I am always proud to learn about a Mentor taking extra patient time to explain a science concept, forum issue or question in private that literally takes days. These situations are not rare...
Featured Thread: Using the thermosyphon effect for a floor water heating system
I've moved to a "new" house - built about 350-400 years ago. Firewood in a stove kind of works for heating a few rooms, but not the full house. So far it seems like the grid power tends to die about twice a month. Temperatures is expected to reach -25C (-13F) for the coldest couple of weeks every winter. Hence I need some kind of backup power and heat source...
Featured Thread: CLIC (CERN accelerator) proposal
CLIC is a proposed accelerator, potentially at CERN, that would collide electrons and positrons at energies far above what previous colliders achieved. Its overall energy would still be below the LHC but (unlike at the LHC) all the collision energy is available for the creation of new particles - it would combine the approximate energy reach of the LHC with the cleanliness of elementary particle collisions...
Featured Thread: RIP PF Member Morbius
Rest in Peace, Dr. Gregory Greenman, aka @Morbius. Underneath the occasional curmudgeon-like exterior, Morbius was a gentleman and a scholar and a PF friend. I was wondering why we had not heard from him for a few years so I began looking and, alas, sadly, I came across a January 2015 obituary for him.
Featured Thread: Thank You PF Members! + PF Member Award Voting!
Another year has passed and another year I am so thankful to our community. It's an example for the rest of the world how an open community full of members with different backgrounds, genders, language, age, educational background, jobs etc etc can come together in peace, fun and production to learn and explore quality math and science topics...
Featured Thread: Math Equation Christmas Tree and Graph
Ok math and science brains, it's time to get creative and festive! Using LaTeX or on a graph can you build an amazing christmas tree or holiday/winter scene using math equations? DESMOS is a great tool to use. Post your equation set and photo and maybe you'll get gold membership!
Featured Thread: Vote for the Breakthrough of the Year
Science Magazine is holding its annual vote for the people's choice for Breakthrough of the Year, which will accompany the editors' own choice. Voting is open until Dec 5, after which they will narrow the field to the top for choices for a second round of voting.
Featured Thread: Solar Cycle #25 is upon us
Over the last 2 weeks I have noted the first sunspots of the new solar cycle 25. How do I know they are spots of the new cycle ? Because they are higher latitude and opposite magnetic polarity. Before I show an image, a little history and science. Over the many observed solar cycles, a feature of the sunspots and the 11 year cycle...
Featured Thread: Math Challenges - November 2018
Rules: In order for a solution to count, a full derivation or proof must be given. Answers with no proof will be ignored. Solutions will be posted around 15th of the following month. It is fine to use nontrivial results without proof as long as you cite them and as long as it is "common knowledge to all mathematicians". Whether the latter is satisfied will be decided on a case-by-case basis...
Featured Thread: Gradient vector without a metric
Is it possible to introduce the concept of a gradient vector on a manifold without a metric?
Featured Thread: Inconsistency versus lack of knowledge
In traditional logic, a system is inconsistent if it can lead to a contradiction. Furthermore, if the inconsistency is non-explosive (not all consequences follow from the contradiction), then the system is para-consistent.
Both definitions fail to distinguish between the following two real-world scenarios...
Featured Thread: Measurement of Earth's Mass - with Neutrinos
At very high energies Earth absorbs a relevant fraction of neutrinos passing through it. Experiments receive more of these neutrinos from above than from below and the difference depends on the mass of Earth. So why not measure it?

Neutrino tomography of Earth

The uncertainty is very large, of course. While the result is very close to the number from gravitational measurements they have a 25% measurement uncertainty. Larger datasets and KM3NeT will help reducing the uncertainty. While unlikely, Earth might have accumulated something dark matter like - it would appear in gravitational measurements but not necessarily in neutrino absorption data.

Apart from the overall mass they also measure the density in different regions of the interior of Earth and confirm that the core has a higher density than the surrounding material. Again no surprise (seismic measurements have measured this long ago) but a nice confirmation, and with a lot of potential for future improvements.
Featured Thread: How does light split into colors?
Today I came home to find very discrete lines of colored light on my living room floor. Can anyone help me to explain this phenomena? I am familiar with dispersion but am wondering how the combination of glass and blinds is creating this effect. When I rotate the shutters as you can see from the pictures, the colors changed...
Featured Thread: Recharge an RV battery by hand cranking a generator
If you've seen breaking bad you probably already know what I'm asking. In this episode I'm watching, they are hand cranking the generator to recharge the battery. They are moving nowhere near as fast as the motor would have spun it. My dad had a hand crank device that was, more or less, a toy. So I'm sure they were producing some electricity...
Featured Thread: How can quarks exist if they are confined?
According to nonperturbative QCD, quarks and gluons don't exist and in nonperturbative QED with two spinors (e.g. proton and electron) hydrogen isn't composed of a proton and an electron.
Featured Thread: Exotic Bicycle Designs and Engineering
Every so often we get requests for engineering projects to work on. One common theme that I've seen is Kickstarter / Indiegogo campaigns for novelty bicycles to solve that last mile problem in urban transportation...
Featured Thread: Gaia parallaxes might reduce tension for Hubble constant
In the last years a discrepancy between two methods to measure the Hubble constant appeared. Measurements based on redshift and the cosmic distance ladder produced results of about 73 km/(s*Mpc) while measurements based on the cosmic microwave background lead to results of about 68 km/(s*Mpc). While not completely outside the uncertainties the difference was still curious...
Featured Thread: Structure of Matter in Quantum Field Theory
This is a topic I've mentioned a few times before. Essentially the structure of matter in quantum gauge field theories is unclear to me. I have no clear question here, just some initial discussion points. So at the first level, it seems a particle based view of quantum field theory is difficult to maintain. In brief on the Hilbert Spaces of interacting field theories there is no well-defined number operator ##N##...
Featured Thread: Soyuz launch failure with crew on board (crew is fine)
A Soyuz flight that was supposed to launch two astronauts to the ISS had a booster failure (half an hour before this post). The Soyuz capsule separated from the rocket and landed, the crew is fine. Rescue teams got to them quickly. While they had to endure higher g-forces than usual they seem to be in a good condition.
Featured Thread: Can anyone learn advanced math?
I often ask myself if anyone can learn math to an advanced level? I think that every healthy person can get very good at math. The only condition is that the person is interested in math. Of course, to get on the level of a Field-Medal winner you have to be blessed a little bit. But I think you can reach and understand a lot just by working out hard. What do you guys think? Can anyone learn math to a high level?
Featured Thread: Black holes squishing Earth
Scares of the CERN accelerator creating a black hole that swallows Earth are in the news once again. I know it is not possible for an accelerator to produce such a black hole in practice. But surely it's impossible even in principle. Surely, a particle accelerator creating a tiny black hole that could grow to swallow the Earth would violate the law of conservation of energy...
Featured Thread: Math Challenge - October 2018
Summer is coming and brings .... Oops, time for a change! Fall (Spring) is here and what's better than to solve some tricky problems on a long dark evening (with the power of returning vitality all around).
Featured Thread: LHCb Discovers Two New Particles
"The LHCb collaboration has found two never-before-seen particles, as well as hints of another new particle, in high-energy proton collisions at the Large Hadron Collider (LHC). Future studies of the properties of these new particles will shed light on the strong force that binds subatomic particles called quarks together." - LHC
Featured Thread: Has the Riemann hypothesis been proven?
I have heard through the grapevine that the Riemann hypothesis has been proven. What I read was this is a claim made by none other than Sir Atiyah himself and that he is planning to give a talk next week. So *if* the statement is true that it is a claim made by Atiyah, then it is of course an extremely serious and probably correct solution...
Featured Thread: Nobel Prize 2018 Announcements
The Nobel Prize winners of 2018 will be announced during the first week of October, starting with the Nobel Prize in Physiology or Medicine on Monday October 1. As most of us are biased towards physics: The physics prize will be announced Tuesday October 2 @ 11.45 (Stockholm time - CEST) at the earliest.
Featured Thread: Hardy's approach to quantum gravity and QM interpretation
Work in quantum foundations is partly considered important because of the hope that the way we think about QM may point to a road to quantum gravity. Lucien Hardy, who is well-known in quantum foundations for his reformulation of QM in terms of five "reasonable" axioms, is one of the people who try to make this really tangible...
Featured Thread: The Rise of Incentivized Competitions for Humanity
The recent rise of incentivized competitions for humanity has prompted me to create this thread, to tell PFers what's out there and to share my meager experienced in "almost" entering one. The largest and arguably most influential one has been the XPRIZE organization which finds sponsors and puts out many competitions to solve some of our worst problems. Its a competitive game with many teams worldwide...
Featured Thread: Is a trip Alpha Centuri system feasible?
Can the journey be completed within the lifetime of a human adult? Assuming we have got around little problems like having an adequate form of propulsion, shielding from radiation, and avoiding deadly collisions with milligram sized dust particles. Let's say our engines can provide constant acceleration then deceleration at 1g.
Featured Thread: Does the Principle of Least Action Have a Physical Meaning?
I have found that some people say “yes, definitely”, and other days “no, definitely not”. Those who say “no” seem to regard PLA as merely a neat way of packaging the equations. Those who say “yes” seem to regard PLA as somehow fundamental. Is there a consensus among physicists that I am unaware of? If not, why not? What could the physical meaning of PLA even be?
Featured Thread: Swampland conjecture
The swampland conjecture is currently a very hot topic. Can someone explain, in simple terms, what exactly the swampland idea is? In particular, the conjecture states that the string landscape is surrounded by an even larger swampland of consistent-looking semiclassical effective field theories, which are actually inconsistent. What exactly does it mean that an effective theory is inconsistent?
Featured Thread: Intermediate Math Challenge - September 2018
Summer is coming and brings a new basic math challenge! Enjoy! For more advanced problems you can check our other basic level math challenge thread!
Featured Thread: Basic Math Challenge - September 2018
Summer is coming and brings a new basic math challenge! Enjoy! For more advanced problems you can check our other intermediate level math challenge thread!
Featured Thread: Double blind peer review winners and losers
Double blind peer review is a process in which not only the author does not know the name of the reviewer (which is the standard practice), but also the reviewer does not know the name of the author (which is not a standard practice). What would happen if the scientific community suddenly decided to shift to the double blind review process? Who would be the winners? Who would be the losers?
Featured Thread: Analyzing the game of tennis
I am trying to analyze the game of tennis. I started very simply by analyzing just the ground strokes, ignoring the serve, and calculating the odds of winning a single point given the odds of returning each ground stroke. I got a surprising (to me) result showing that the player to goes first always has a lower probability of winning the point than the opponent...
Featured Thread: Cellphone Distraction in Classroom Can Lead to Lower Grades
This is something many of us instructors have to deal with, something that was never an issue when I was still in college. Students now come to class equipped with notebook laptop, tablets, and of course, the ubiquitous cellphones. Different instructors have different policy on the use of the electronics, ranging from an outright ban, to "I don't care if you use these during class session as long as you don't distract...
Featured Thread: The 2018 Fields Medal has been awarded...
The 2018 Fields Medal has been awarded to: Caucher Birkar, Alessio Figalli, Peter Scholze, Akshay Venkatesh. More inside...
Featured Thread: How much time should I study?
I'm having trouble in studying. I am studying full time from Monday to Monday but I just cannot get focused all the time, I realized that more than half of the time I'm sleepy or struggling to maintain my focus. I'm doing my degree in physics and I feel like I need to study full time, but I just can't do it, what should I do?
Featured Thread: Genoa Bridge Collapse - Engineering Perspectives
The dramatic collapse of a bridge in Italy with many fatalities has been the big item of news all over Europe. I just wonder if the qualified people here can throw any light not on the specifics which would be hard for them to know, but in general...
Featured Thread: Basic Math Challenge - August 2018
Summer is coming and brings a new basic math challenge! Enjoy! For more advanced problems you can check our other intermediate level math challenge thread!
Featured Thread: Intermediate Math Challenge - August 2018
Summer is coming and brings a new intermediate math challenge! Enjoy! If you find the problems difficult to solve don't be disappointed! Just check our other basic level math challenge thread!
Featured Thread: Sabine Hossenfelder and Beauty in Physics
From the Vice article: "Who doesn’t like a pretty idea? Physicists certainly do. In the foundations of physics, it has become accepted practice to prefer hypotheses that are aesthetically pleasing. Physicists believe that their motivations don’t matter because hypotheses, after all, must be tested. But most of their beautiful ideas are hard or impossible to test. And whenever an experiment comes back empty-handed..."
Featured Thread: Happy RNA Day!
Today (AUG 1) is RNA Day, an international celebration of one of the most versatile biomolecules in existence. What are some areas of RNA research that excite you most? Some of the most intriguing areas of current research to me (with example links for further reading)...
Featured Thread: How is physics knowledge used in everyday life?
What I am struggling to come to grips with is how knowing physics, the topics typically taught in a high school intro course, can be useful in everyday life. I am not looking for everyday examples of physics concepts. I mean real actual examples of using Newton’s laws or momentum in real life purposefully. Can you think of a time when you actually used your physics knowledge in everyday life?
Featured Thread: What makes a problem computationally NP?
As the title says, what makes a decision problem NP complex? Is it application of the definition (as in: solvable in polynomial time by a non-deterministic Turing machine)? Also, if P does not equal NP, does it mean that NP problems can only be solved in O(exp(n)) time/steps?
Featured Thread: Easy ways you can support Physics Forums
We are all members of an amazing community of science and math passionate people from all over the globe. However, "amazing" doesn't just happen over night or by itself. "Amazing" happens when members take pride and responsibility for the health of the community...
Featured Thread: Basic Math Challenge - July 2018
Summer is coming and brings a new basic math challenge! Enjoy! For more advanced problems you can check our other intermediate level math challenge thread!
Featured Thread: Intermediate Math Challenge - July 2018
Summer is coming and brings a new intermediate math challenge! Enjoy! If you find the problems difficult to solve don't be disappointed! Just check our other basic level math challenge thread!
Featured Thread: What are the frontiers of cosmology research?
I have completed post grad in Physics and in the transition phase between post grad and Ph.D. I am interested in cosmology and also completed a post grad course on Astrophysics and Cosmology. Can anyone enlighten me about what are the current debates and active topics of research going on in Cosmology?
Featured Thread: No metastable type IIB de Sitter vacua
Take note of today's Obied-Ooguri-Spodyneiko-Vafa 18. Curious situation: After it had influenced much the development of the string theory community’s attention and almost all of its public media perception since 2003, after what must be thousands of followup publications, the argument of KKLT 03 for a large finite number of metastable de Sitter spacetime vacua of type IIB string theory...

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