Featured Science Threads - Page 12

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: Beam-powered propulsion - keeping the beam focused
I've often read that beam-powered propulsion is the only basic interstellar propulsion concept without physics problems. To me, that doesn't seem far from the truth. However, for a long time I've felt that the biggest obstacle to overcome is the beam divergence problem. Most of the concepts I've read about use a single laser...
Featured Thread: Lightning discharge's effect on rain fall velocity?
I know that rain is charged and the lightening is a discharge, and both are relative to the ground, I think, but I don't know the relative polarities... is there some way that the charged rain drops are being momentarily attracted upwards by the lightening or its regional effects? Could it be that the metal car itself is altering its charge and somehow repelling the rain charges for a moment?
Featured Thread: Major breakthroughs of medicine in the last 20 years?
We hear so often of the great advances of medicine. Every day one reads of breakthroughs in research in the news. But then I never hear of it again. I'm not a doctor or biologist, but am wondering what are the important discoveries ***and which had practical applications*** of the last 20 years?
Featured Thread: The state of carbon in stars
A popular video I just watched described Fred Hoyle's discovery that the elements of the universe are created in stars. Key to his theorizing was the prediction that fusion would produce of a new state of carbon that had never been observed and which theory predicted would be unstable. Hoyle believed that under the physical conditions present in stars this form of carbon could exist. What was this new type of carbon?
Featured Thread: Blowing between two objects -- Why is the pressure low?
This is the problem: A person blows through a straw between two empty soda cans. Do the cans move closer together or away from each other? Explain why they move the way they do. Partial answer: The cans will move closer together. Given that information, we can conclude that the air pressure in the region between the soda cans must be lower than normal...
Featured Thread: China Boldly Goes ...
Here is an interesting item I would like to share. It seems that China has drastically pushed the boundaries of power transmission grid operations. They boldly go where no man has gone before...
Featured Thread: I Learned C, Now What?
So I'm about to be done with my first class in programming where we learned C programming. Unfortunately, I don't actually know what you can do with it. All of our programs in my class have involved us programming and running everything using Visual Studios, not developing standalone executables or something...
Featured Thread: SQM vs Pilot Waves - Potential issue with Pilot Waves?
For whatever reason, pilot waves have been mentioned quite a lot recently, and so I decided to take a closer look at it. I've seen many people claim that it makes the same predictions as standard quantum mechanics (Schrodinger equation, etc.), but I was pointed to this paper which seems to show that there is actually an issue with the predictions of the pilot wave theory...
Featured Thread: Are memories made of this or that?
When I look at a scene and then later recall that scene, I am accessing a memory of that scene. But what is it that is stored in memory for me to access? Is it the sensory input or is it the constructed visual experience?That is, do we construct the recalled visual scene in the same way that we construct the original experience (from neural representations of the raw sensory input), or do we recall the constructed scene?
Featured Thread: Erik Verlinde's new view on dark matter
"Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon..."
Featured Thread: Evidence of Light-by-light scattering by ATLAS
For centuries, scientists argued whether light was waves or particles. Light scattering with other light would favor the particle concept. Today we know both models are wrong, but quantum electrodynamics also predicts this scattering - just with an incredibly tiny rate, so it has never been observed before. Lead-lead collisions at the LHC allow a search for it...
Featured Thread: Advance of Technology; 1818 to 2318...
This article from 1820 covers many advances in technology; Slavery; Prosthetic limbs; Voyage to the Moon denial; Mammoth power; Newton's Principia; Airconditioning; Recorded voice; Whale power, and Energy from underground...
Featured Thread: H-theorem in quantum information theory
"Remarkable progress of quantum information theory (QIT) allowed to formulate mathematical theorems for conditions that data-transmitting or data-processing occurs with a non-negative entropy gain. However, relation of these results formulated in terms of entropy gain in quantum channels to temporal evolution of real physical systems is not thoroughly understood..."
Featured Thread: Can you solve this geometry problem for nine year olds?
I was in a primary school class room the other day and the teacher asked me for help with this geometry problem, that he had set for his class as an extension challenge, but then realised he couldn't do.
The known angles are marked in degrees. We have to find the angle x. I spent five minutes trying to do it on the board...
Featured Thread: Physics From Symmetry
Superb, utterly superb. Got my copy this morning. QM is developed from symmetry, the only thing not derived is the Born Rule. QM is simply group theory applied to a complex field just as mechanics is group theory applied to particles. Very very highly recommended.
Featured Thread: Submit your interview questions for Dr. James Gates
Met theoretical physicist James Gates at the WAPT meeting tonight. He said he'd be interested in doing an Insight Interview. Let's get some good questions rolling! Here are some links if you are not familiar with his history and work...
Featured Thread: Math texts that make you fall in love all over again
I often see textbook recommendations here that about rigour and depth of coverage. Serious books for serious people! This question is different. I'm looking textbooks that inspire a love for mathematics. And I want to come at it from two different angles...
Featured Thread: What software do you use in your field of study?
In the spirit of "It's fun to make lists", tell the forum what software you use in your field of study - with emphasis on what programs you use, rather than what general purpose computer languages you use. How much of your software is used because its a favorite of a particular department at a particular university?
Featured Thread: How many of your students actually read the course syllabus?
Is Anybody Reading the Syllabus? To Find Out, Some Professors Bury Hidden Gems (Chronicle of Higher Education). I never used the Easter-egg trick myself, but if I had a nickel for every time I answered a question about something that was in the syllabus (e.g. "How much does this test count towards the final grade?") I could have retired years ago.
Featured Thread: Nobel laureate perspective on the history, status and future of GR
This paper offers a Nobel laureate perspective on the history, status and future of GR in the astrophysical regime..., General Relativity and Cosmology: Unsolved Questions and Future Directions.
Featured Thread: RIP Physicist Deborah Jin
It is with great sadness that the woman who I thought would eventually win the Nobel Prize in Physics, Deborah Jin, has passed away this past Sept. 15, after a battle with cancer. This one will truly hurt. She was in the prime of her life and her career. The Nobel Committee missed a tremendous opportunity to award a deserving physicist of her prize.
Featured Thread: The 2016 Nobel prize in physics
Congrats to three British physicists working at US universities who have won the Nobel Prize in Physics for revealing the secrets of exotic matter. Thoughts?
Featured Thread: Micromass' big October challenge!
Time for the October challenge! This time a lot of people sent me suggestions for challenges. I wish to thank them a lot! If you think of a good challenge that could be included here, don't hesitate to send me!
Featured Thread: What's the feasibility of space mining companies?
Recently, I've been reading about those space mining companies (like Deep Space Mining and Planetary Resources), and from an amateur point of view, I thought that the overall idea was pretty interesting. But what's the feasibility of such a project? Are there any chances that we could develop this technology within the next decade or so?
Featured Thread: How would dark matter aggregate?
My only source of information on dark matter is popular science texts, like New Scientist. One thing that is never explained is how it gets to aggregate around galaxies. Lacking the ability to shed energy by radiation, it seems it should just fly straight past and through, never even getting trapped into an orbit. I can think of two possible explanations, neither very convincing...
Featured Thread: Is Desert Ever a Good Thing?
Cutting down rain forest causes desert, and this is viewed as an upset to the world's climate. What I'm wondering is whether any and all desert is basically bad, or whether some amount of desert somehow contributes to the health of the planet. In other words, if we exclude the man made deserts from consideration, would the natural deserts that exist be considered to have a positive effect on the earth...
Featured Thread: Biggest Science or Math Pet Peeve
Could be a common wrong definition or an ineffient way to solve a certain equation. I don't know, what in science and math bugs you? Educators should fill this thread! :D
Featured Thread: What will be the next big revolution?
Some say block-chain economies, some say driver-less cars and some say clean energy. What do you think?
Featured Thread: GAIA - 1 billion stars and counting
The GAIA telescope has been mapping stars in the Milky Way with unprecedented quality and quantities. It has been assembling the most detailed 3D map ever made of our Milky Way galaxy and has currently mapped over 1 billion stars. There are already hints that the Milky Way may be shaped differently from what we thought...
Featured Thread: Risk Index for Shared Components
In an earlier thread, Science Vulnerability to Bugs, I mentioned the case "Faulty image analysis software may invalidate 40,000 fMRI studies". In another recent case (can't find the link), an author decided to un-license his public domain contribution and withdrew it from publicly shared libraries, which broke very many products dependent on it.
Featured Thread: SpaceX Needs Us!
As already posted on PF, and you have likely seen in the news, a SpaceX rocket exploded, September 1, 2016. Elon Musk is reaching out for help in finding out how it happened. I already have my idea of what might have happened, but I want to let everyone else look for themselves to see if they can deduce anything. Some of the smart people at PF might be able to see something that the...
Featured Thread: Murray Gell-Mann on Entanglement
In this video Murray Gell-Mann discuses Quantum Mechanics and at 11:42 he discuses entanglement. At 14:45 he makes the following statement: "People say loosely, crudely, wrongly that when you measure one of the photons it does something to the other one. It doesn't." Do most physicists working in this field agree with the above statement?
Featured Thread: Relating integral expressions for Euler's constant
Thus is something you don't see in every textbook. A not so complicated method to relate integrals and limits involving Euler's constant.
Featured Thread: Micromass' big September challenge!
September, schools restart, summer ends, but a new challenge is here:
RULES:
1) In order for a solution to count, a full derivation or proof must be given. Answers with no proof will be ignored....
Featured Thread: Patchwork viruses in animals
Scientists found a virus that is made out of 4 to 5 separate components - it infects mosquitoes, and they have to catch at least four of those components to get infected, the smallest, fifth component is optional. For plants and fungi, similar viruses were known before, but (at least according to the study) this is the first example in animals studied in detail. I have never heard of those things before and I thought it would be interesting to share that.
Featured Thread: Fitting circles inside other circles
I'm working on the following fun problem. I have a circle of a given radius, R0. (Green circle in the image). I want to be able to supply a radius of the first circle that is to fit into this large circle. Lets say R1 is 0.75 * R0. Following this I find the best position of R2 (to maximize its radius), is on top of the smaller circle. This is the largest circle that can fit inside the green circle without...
Featured Thread: Redesigning Mathematics Curriculum
I've had a pretty poor experience going through the standardized education system in California, and now that I'm in college, I'm really fed up with how mathematics is taught (even at the college level). With this said, I thought it would be fun for me to redesign the entire math education curriculum from scratch exactly the way I would want it to be. I think this might be a fun general discussion about how math is taught in the US...
Featured Thread: Imagining a Higgsless Universe
I would like to imagine how would physics look in a Universe governed by Standard model, sans Higgs. IOW: how would the unbroken SU(2)*U(1) be different from our usual broken one? There is no "usual" electromagnetism in such a Universe. Instead, there are two new forces, SU(2) weak isospin and U(1) weak hypercharge. (I'll be skipping word "weak" from now on)...
Featured Thread: Describe your work like you're a 6 year old
Life as a scientist sounds way more fun when you describe it like you're a six year old.
"I can read things some people can't read so I read them and then write them again only now those people can read it." Now's your turn.
Featured Thread: A terrestrial, temperate planet around Proxima Centauri
Published today in Nature: "At a distance of 1.295 parsecs1, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun’s closest stellar neighbor and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun2 and a mass of about 12 per cent of the mass of the Sun."...
Featured Thread: How is it that mathematics describes reality so well?
Humans created that tool, that language, that consists of axioms and their implications. Mathematics does a good job of communicating the behavior of physical phenomena. How is it that mathematics and the physical reality agree with each other ?
Featured Thread: "Space and Stuff"
Due to the constant never ending supply of "cool stuff" happening in Aerospace these days I'm creating this thread to consolidate posts every time something new comes along. Please feel free to add random information if its relevant. So to start things off here is the SpaceX Dragon launch coming up shortly, I'll be following up afterwards to see how it all goes.
Featured Thread: Quantum mechanics is random in nature?
I heard from many sources that quantum mechanics is purely random in nature. Has this been demonstrated? Phenomena like the wave function collapse are considered 'purely random'. If we can establish that collapse is random, we have to base that on the property of being statistical in its nature, right?
Featured Thread: Amplification of RNA by an RNA polymerase ribozyme
As far as I understand, it is a big step towards replicating RNA systems. They found an RNA enzyme that can synthesize longer RNA molecules, and fully replicate shorter RNA molecules - completely without proteins. It cannot replicate itself (or its corresponding RNA), that would be another huge step.
Featured Thread: Micromass' big August challenge!
August is already well underway, so time for some nice challenges! This thread contains both challenges for high schoolers and college freshmen, and for more advanced people. Also some previously unsolved challenges are omitted.
Featured Thread: The Perseids are coming!
The Perseid meteor shower will be at it's peak next Friday (August 12)! They'll be seen best in the Northern Hemisphere and mid-southern latitudes around 1:00 am. Anybody going to go out and see them? :smile:

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