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Physics Forums Featured Threads
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Math Challenge - February 2019
Time for our new winter challenge! This time our challenge has also two Computer Science related questions and a separate section with five High School math problems. Enjoy! -
Are no chemical elements truly stable?
I recently learned that Bismuth is actually radioactive with its longest lived isotope having a half-life of about 20 quintillion years. As a very basic question, what determines whether an element/isotope will be radioactive? Is there something special about certain isotopes that makes them stable? Are no elements truly stable, but just have half-lives too long to accurately measure? -
Who would win a perfect game of chess?
While chess hasn't been solved yet, other games have. For example, I know that in in some games, like connect four, if both players play perfectly, the player who goes first will always win. On the other hand, some games, like tic tac toe, a perfect game will result in a draw; in fact, I recently found out that this is true for checkers as well. What I'm wondering though, is if it's possible to predict which scenario a perfect game... -
Anti-Cancer Virus Treatment
This Science News article reports that researchers using a modified adenovirus (that normally causes mild respiratory infections) that only grows in retinoblastoma tumor cells, researchers were able to improve upon (but apparently not cure) the results of cancer drugs in rabbits and mice. Trials in children (where most cases occur) are beginning... -
Astro Image Stacking (optimize DSS image stacking and post processing)
I created this thread because every online resource I have examined to date has been largely worthless- either totally over-engineered complexity or superficial garbage (can you tell I am irritated?). The problem is simple: optimize DSS image stacking and post processing based on quantitative image data. The essential metrics are 1) signal-to-noise ratio and 2) dynamic range... -
Summary of Frauchiger-Renner
Since there seems to be a bit of confusion on this, I thought I'd just post a brief summary. Just some terminology: Superobserver: Somebody who measures another observer, i.e capable of resolving the complete quantum state of another observer and performing measurements on it. Hyperobserver: Like a Superobserver, but also capable of using a unitary evolution to reverse... -
Best Engineering in the Past 100 years
We commonly see lists of "best science" both here on PF and elsewhere. I think it is time for a little friendly rivalry from the engineering side. I arbitrarily chose 100 years as the period. The wheel and Roman aqueducts were great engineering but not much fun for us to talk about because we don't know much about the engineers... -
Math Challenge - January
Rules: a) 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. b) 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... -
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... -
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... -
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... -
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... -
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. -
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... -
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!
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