Featured Science Threads - Page 11

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: Penrose' Chess problem
"This chess problem - originally drawn by Sir Roger Penrose - has been devised to defeat an artificially intelligent (AI) computer but be solvable for humans. The Penrose Institute scientists are inviting readers to workout how white can win, or force a stalemate and then share their reasoning."
Featured Thread: Using big data to identify astronomocal data bias
I've been following, albeit loosely, the use of big data to refine astronomical data. It has been frequently noted that astronomy is an excellent test ground for big data approaches. I'm led to wonder what kind of results have been achieved to date and how effective are these methods for detecting bias in data sets such as foreground contamination? Can it be used to test the parameter space of assumptions applied to data sets?
Featured Thread: Happy Earth Day 2017!
Time to think about what you can personally do to be a good steward of our home Earth. What activities are you doing today? I will pick up trash I find in my community during my dog walk. I will also be planting some flowers. Oh and patching some holes in my lawn with white clover. It's good for the bees!
Featured Thread: Math Challenge by Andrewkirk #1
A triangle has vertices ##A##, ##B## and ##C##. Mark points ##A',B',C'## on edges ##\overline{BC},\overline{CA},\overline{AB}## respectively so that each is one third of the way along the edge, as shown in the diagram. The lines ##\overline{AA'},\overline{BB'},\overline{CC'}## intersect at points ##A'',B'',C''## and form a triangle inside triangle ##ABC##...
Featured Thread: b -> s µµ decays: Current status and updates next week
Something curious is going on with these decays. LHCb gives a seminar talk Tuesday next week, a livestream will be available. I'll summarize the current status here. I tried to keep most at the advanced (I)-level, but I don't think that always worked. (B)-level summary: We might have found signs of new unexpected physical effects, but the situation is still unclear...
Featured Thread: Concordance cosmology paper
What do people think of this paper? If I understand correctly, they are saying that the need for Λ disappears if we do N-body simulations that properly take account of GR. I think they are saying that past simulations have used Newtonian approximations that don't properly account for density fluctuations. Can this be? If true, it seems like a major advance. Comments?
Featured Thread: Entanglement Entropy - Part 1: Quantum Mechanics
Quantum Mechanics(QM) is one of the greatest intellectual achievements in human history. Not only because it describes the world at the microscopic level and in turn provides us with the technological advancement that we enjoy today, but also because it shows us how little we know about the world we’ve been living in for so long....
Featured Thread: Relativity using the Bondi k-Calculus
In the early 1960s, Hermann Bondi advocated a presentation of special relativity (called the k-calculus [which involves no calculus–just simple algebra]) that is advertised to be a “simple logical extension of well-known Newtonian ideas, without any of its mathematical trappings.”
Featured Thread: Impossibility to have fever
I'd like to know if it's physiologically possible for a human being to be unable to have fever. A related person to me claims that he has never experienced fever in his life, even during influenza, pneumonia and other infections. Is there any similar case of immunodeficiency registered in the medical literature?
Featured Thread: Interpretation of the photoelectric effect
The photoelectric effect is usually presented as an example disproving classical electromagnetism as viable model for interaction of light with matter and as evidence of quantization of energy in the electromagnetic field, i.e. the existence of photons. I would like to discuss a thought based on non-relativistic quantum mechanics w/o and relation to Planck, Einstein etc. showing - imho - why this is not so straightforward.
Featured Thread: Inflation, horizon-problem and thermal equilibrium
In this paper the following arguments are given why the horizon problem is a fake problem. It raised by me the following question: Why is it assumed in the formulation of the horizon problem that the observed thermal equilibrium from the CMB has to be explained by thermalization right after t=0?
Featured Thread: So You Want to Be a Physicist: 22 Part Guide
One of the most frequent questions we get is the process and background of being a physics major. Often, we have students asking what are the requirements of obtaining a physics degree, and what can one do with such accomplishments. I am hoping that, in a series of postings on this topic, we get to go over and demystify the whole process of what one can expect...
Featured Thread: Cancer causes: circa 67% are Replication error
"Most textbooks attribute cancer-causing mutations to two major sources: inherited and environmental factors. A recent study highlighted the prominent role in cancer of replicative (R) mutations that arise from a third source: unavoidable errors associated with DNA replication."
Featured Thread: Tiny Tweak in Teaching Basic Circuits
I'm sure we have all seen the frequent questions from students who don't understand the difference between potential and voltage in a circuit. They seem to think that zero voltage has physical significance. Even using the phrase "voltage drop" is not sufficient, because they say, "What happens when it drops to zero," leading to the concept that voltage is a consumable...
Featured Thread: Why does formation of snow flakes not violate entropy law?
Snow flakes are highly structured, they form from water vapor which has very little structure. I must be misunderstanding entropy, my interpretation of it is that isolated system must evolve into more chaotic less structured states, which is not what happens with snow flakes. Can someone explain?
Featured Thread: LHCb observes 5 new particles (excited hadrons)
Plain old standard model baryons, but 5 at the same time, and with crystal clear peaks in the decay to ##\Xi_c^+ K^-##. Each peak in the figure is a particle never seen before, and the significances of those peaks are about 20 sigma (10 sigma for the 5th one). A broad 6th state might hide around 3200 MeV...
Featured Thread: Math Challenge by Erland #1
A rectangle is divided into a finite number of sub-rectangles. The sides of the sub-rectangles are all parallel to sides of the large rectangle. Each sub-rectangle has at least one side with integer length. Prove that the large rectangle also has at least one side with integer length.
Featured Thread: Fish becoming land-dwellers today
And we can watch different related species at different steps in the transition. In this case, the reason is not the availability of food, but the lower number of predators on land. "At low tide, blennies are commonly found swimming in rock pools around the edges of the island. But when high tide moves in, they climb up to dry land and shuffle around the rocks until the tide retreats. The researchers found that this is most likely..."
Featured Thread: Specifications for elephant-resistant steel poles
I have camera traps out on the African bush, that are monitoring the responses of leopards to artificial scents. The cameras are in steel boxes to protect them from elephants, the boxes are bolted to brackets 150 mm long and the brackets are bolted to steel poles at a height of either 500 or 700 mm above ground level. The poles are 40 x 40 mm mild steel angle, either 2mm or 3mm thickness...
Featured Thread: Math Challenge by QuantumQuest #1
CHALLENGE:
Prove that if ##P(x), Q(x), R(x)## and ##S(x)## are all polynomials such that ##P(x^{5}) + xQ(x^{5}) + x^{2}R(x^{5}) = (x^{4} + x^{3} + x^{2} + x + 1)S(x)##, ##x - 1## is factor of ##P(x)##.
Featured Thread: What is the Quantum of Sound in Gases and Air
It is usually referred to as Phonons for sound waves in solid. But, where it gets confusing, is in gases and air. Some still call it Phonons, others say, Phonons can only be used in solid states. So what is the Quantum of Sound in Gases/Air?
Featured Thread: Math Challenge by Charles Link #1
Beginning with a cube with each side of length 1", drill a 1" diameter hole all the way through in each of the 3 perpendicular directions. Find the remaining volume.
Featured Thread: Why is Hilbert not the last universalist?
It is often said that Poincare was the last universalist, i.e. the last mathematician who understood more-or-less all mathematics of his time. But Hilbert's knowledge of math was also quite universal, and he came slightly after Poincare. So why was Hilbert not the last universalist? What branch of math he didn't understood sufficiently well to deserve this title?
Featured Thread: Is the US abandoning its position as a science superpower?
"China is aggressively attempting to displace the US as the world's scientific superpower, and the US is aggressively attempting to abandon it's scientific superpower status, while Europe seems all but recovered from WWII. ....". I was wondering how the rest of you on PF feels on this regard.
Featured Thread: Can modern physics be understood qualitatively?
I'm curious on just how much modern physics can be understood qualitatively, without equations. I know that people can understand F=ma with just words. For example, the acceleration an object experiences is directly proportional to overall force pushing or pulling on the object. The more force the more acceleration and vice versa. Of course, this ignores the fact that its a differential equation...
Featured Thread: Are there really 4 fundamental math operations?
It's strange to me that multiplication and division are considered fundamental operations.
It makes sense for me that addition is a fundamental operation but multiplication is just like a function or algorithm that takes several numbers and apply additions. This is true even for multiplication with real number.
Featured Thread: Do patents inhibit development in the technology?
What do I mean by inhibit, you know taking patent or taking permission to use its license takes some time and money and if we think in large scale, today, almost every company spends lots of time to protect their tech. My point is maybe all these things slows the improvement in technology. I think if everything were free to use things would get faster in terms of tech...
Featured Thread: Is Reverse Engineering Ethical?
Suppose that there are 2 companies. One of them is yours and other company publishes a product which can affect your situation in marketplace.Is it ethical to buy the product and resolve it by reverse engineering to get an idea to counterattack? It's not about producing similar technology but getting an idea to help you to think differently.
Featured Thread: Can a space vessel generate its own photon wind?
In a nutshell, does Newton's "action = -reaction" law apply to massless particles? If a spaceship directs a condensed light beam on its own heat-resistant photon sail, what would happen?
Featured Thread: Problem with science today and the war on reason
"The "scicomm" effect may be a contributing factor to people being less willing to accept science, but I don't think it's completely at fault. I think you have to go deeper and look at phenomena like confirmation bias. A reasonable person who is willing to be swayed by the balance of evidence will consider details behind scicomm statements." - Choppy
Featured Thread: NASA press conference: Exoplanets around TRAPPIST-1
Yes, 7 planets around TRAPPIST-1, all about Earth-sized with quite precise radius estimates from transits, and approximate mass measurements from transit timing variation. 3 are too hot for liquid water (b,c,d), 3 of them in the habitable zone (e,f,g), 1 (h) is too cold. The three planets seen before were the innermost two and the outermost one, so all potentially habitable planets are new. Probably tidally locked (all?).
Featured Thread: A possible solution to the cosmic lithium problem
This paper; Non-extensive Statistics Solution to the Cosmological Lithium Problem, offers a plausible solution to the cosmic lithium problem that has baffled astrophysics, and BBN aficionados, for decades. Unlike prior efforts, it does not invoke any BTSM particles or new physics, just a twist on statistical modeling which looks entirely reasonable...
Featured Thread: Top 3 brighest planets as seen from other planets
I'd have to think Jupiter from Mars would be the brightest but after that it's hard to say. Any guesses?
Featured Thread: Is the multiverse fake physics?
Woit over at his blog "not even wrong" considers string theory based multiverse to be fake physics. Is string theory based multiverse fake physics?
Featured Thread: Four 4s puzzle
Say you've got four 4s -- 4, 4, 4, 4 -- and you're allowed to place any normal math symbols around them. How many different numbers can you make? It's best to think of a number and then try to make it.
Featured Thread: Increased demand for STEM in next 4 years?
Supposing immigration is heavily restricted in the future will there be an increased demand for home-grown US STEM in the next 4-8 years? How will these new rules impact the job market for US citizens? What sectors do you think will experience the biggest surge in demand?
Featured Thread: Metallic hydrogen created in the lab
"Producing metallic hydrogen has been a great challenge to condensed matter physics. Metallic hydrogen may be a room temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures..."
Featured Thread: A, T, C, G: Add X and Y (DNA bases)
All natural life uses the same four bases in its DNA: A paired with T and C paired with G. Scientists worked on adding more bases. Just putting them into DNA is not hard, the challenging part is to keep them there: They should not get removed/replaced during reproduction. This has now been achieved...
Featured Thread: On the Heisenberg uncertainty relation
Are there fundamental limits on the accuracy for measuring both position ##q## at time ##t## and momentum ##p## at time ##t+\Delta t##, with tiny ##\Delta t##? If yes, why? If no, why can't one then measure (in principle) both ##q## and ##p## arbitrarily well at the same time ##p## (which is not allowed by Heisenberg's uncertainty relation), by taking ##\Delta t## sufficiently small and noting that any measurement takes time?
Featured Thread: What menial mental task do you struggle with?
We're all pretty smart people on this forum, but what little things does your mind, for whatever reason, just never want to learn? For me, it's the stupid trig functions. I can't just put angles and numbers on a triangle and solve anything. I have to tell myself "SOH CAH TOA." Every time...
Featured Thread: What does the American educational system (K-12) teach well?
One of the things I read and hear about is how poorly the American educational system teach math or science. I would like to pose the opposite question: what does the American educational system (K-12) teach well? What, to your knowledge or experience, do students graduating from the American educational system in general come away knowing best?
Featured Thread: New Findings about the Evolution of Complex Cellular Life
Humans, other animals, plants, fungi and almost all other forms of complex, multi-cellular life are known as eukaryotes. How eukaryotes evolved from simpler prokaryotic organisms is a major question in evolutionary biology. The current view is that eukaryotes evolved from the fusion between a bacterium (which would eventually become the mitochondrion) and an archaeal host through a process called endosymbiosis.
Featured Thread: Why colonize Mars and not the Moon?
I watched the 6-episode series called Mars this week. Elon Musk kept emphasizing that humans must spread out to at least one other planet to ensure human survival in the event of some extinction event on Earth. Wouldn't colonization of the Moon achieve the same purpose? Seems like that would be a more viable option.
Featured Thread: Rethinking the Earth's core
The missing element mystery in the earths core may have been solved. Lead researcher Eiji Ohtani from the University of Tokyo told BBC News: "We believe that silicon is a major element - about 5% [of the Earth's inner core] by weight could be silicon dissolved into the iron-nickel alloys."
Featured Thread: Stream channels as a indication of fault movement
I was zooming around the NE region of the South Island of New Zealand in Google Earth today and discovered a classic example of offset stream channels across a major fault, the Awatere Fault. The Awatere Fault which is one of the major faults that the Alpine fault splinters into in the upper South Island. It's companions are the Wairau Fault...
Featured Thread: Stephen Weinberg on Understanding Quantum Mechanics
"The development of quantum mechanics in the first decades of the twentieth century came as a shock to many physicists. Today, despite the great successes of quantum mechanics, arguments continue about its meaning, and its future."
Featured Thread: New Organ (mesentery) found!
"Researchers have classified a brand-new organ inside our bodies, one that's been hiding in plain sight in our digestive system this whole time. Although we now know about the structure of this new organ, its function is still poorly understood, and studying it could be the key to better understanding and treatment of abdominal and digestive disease."
Featured Thread: Vacuum or pressure to move spaghetti through a hole
I can create a small vacuum in my mouth to move that "string" of spagetti into my mouth. I know it is possible, but I do not understand how spaghetti is possible to suck in if the shape is even and round like a "piston". I have learned that pressure is acting angular to any surface. With the spaghetti, that surface will cause the pressure to act 90° to it, and (in my thoughts) not be able to create a force...
Featured Thread: Nobel Prize Winning Molecular Machines
The Nobel prize in chemistry for 2016 has been awarded "for the design and synthesis of molecular machines." These are fascinating constructions made up of just a few molecules, so they are the smallest machines possible. It is far from trivial to get these things working, especially since thermal noise is important at that scale (although in some cases, thermal noise can be rectified and serve as a source of energy)...
Featured Thread: How do you answer "So what's the practical application....?"
The situation of course is that I tell somebody that I am studying math, and if I mention some specifics, like mention Topology or Algebra, (which I have to sort of explain is not "college algebra"), or whatever. Then comes the question "So what's this used for in..you know, real life?" As I see it there are two extremes to answer this question...

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