I am working on a solar water heater, and I am trying to figure out this geometry problem. I know a parabola is the most efficient movable shape to collect the sun's energy, but what is the most efficient fixed shape? It will clearly change with date and lattitude, but given an average day, what shape focus the most energy onto a heating tube? [more inside]
So there's a powerline outside my bedroom window, and I thought, huh. Turns out I'm sleeping with my head in a 6mG AC magnetic field. Help me use physics to stop caring. [more inside]
Where can I buy a glass capillary tube so narrow such that I can see the maximum capillary rise for water? [more inside]
Please recommend an alegbra/trig-based physics textbook to supplement the free textbook used in my college physics class. [more inside]
I'm currently in the first year of a PhD program in physics. Right now I am just taking classes. My school does not have a qualifying exam, and there's not much I need to do outside of my classwork. However, I don't want to live from homework to homework -- so I'd like to set aside some extra time for textbook-reading and problem-solving. Have you done this? Tell me about your experience. [more inside]
Why do things look darker when they're wet?
How much physical force is required to play an Anglo concertina? More specifically: if I'm recovering from surgery and not allowed to lift anything heavier than a milk jug, will playing a concertina be kosher or not?
I have recently gotten rejection letters from all of the PhD programs to which I applied for the coming fall. Now I'm back to square one and I think I need to figure out what's wrong with my approach so far. Basically I want the hive mind to tell me exactly what steps it thinks I should take to find the right school and make my application competitive. Can you help? [more inside]
Conventional hard drives are magnetic media, so why is it if you disassemble one and stick a magnet to a platter, you don't feel any magnetic attraction at all? I can understand feeling a very weak level of attraction, but it feels like sticking a magnet to a piece of plastic or wood.
When installing a container garden, does the distribution of weight matter for the safety of the deck it's sitting on? [more inside]
Where can I learn about the physics of spaceflight if I don't know calculus? What books, movies, video games, websites, etc., would you recommend? [more inside]
Spouse has been using an electric eel for the past few days and is curious about the physics of how the snake travels through the pipe. He doesn't understand how the machine pushes the snake in to the pipe or how the snake travels through the pipe. We are having a hard time finding good search terms for this. It's easy to find information on how to use a machine auger, but not easy to know what to look up to understand the physics behind it. Does it have to do with springs? How things coil?
I picked up the first edition of Halliday & Resnick's Physics from my local bookshop. My goal is to work through it (along with a calculus text) for fun and profit. Will I be missing out on anything important by using the original 1960's text, rather than one of the more recent ones (now titled Fundamentals of Physics)?
At the same instant, The three year old fan drops the autographed ball Sandy gave him before the game from the same exact height that Sandy released his pitch. Which one will hit the ground first? [more inside]
Having a brainfart about bare optical fiber that is really bothering me. Tried to google this and while I think the answer is yes my google-fu is failing in a big way. [more inside]
I'm looking for books that either explain concepts in physics or encourage an interest in physics topics that are likely to be accessible and interesting for ~13 year old girls who are keen on science. What are the contemporary equivalents of "A Brief History of Time" and "Einstein's Dreams" for kids today? Related fields are welcome. [more inside]
What would happen to earth if we suddenly had 10% less water? The mass of the planet would change, so would our orbit? Would weather and seasons change? Would it affect tides and the moon? At what point would we begin to suffer? Is it 10% or 20% or 50%? [more inside]
Are there any good videos of "floating" grand jetés on YouTube (or other online streaming video sites)? [more inside]
Why is it that in the morning that a car parked overnight in the garage has no condensation on it but a car parked outside in the driveway is covered with dew? The garage in question is completely open on one end since it's an old horse barn with no doors. I would think the atmosphere in the garage (relative humidity and temp) would be virtually identical to the outside.
What are the best resources for a crash course in Calculus and Physics? [more inside]
I'm currently in the very very early research stages of making a career change and I'm starting to think that I sold myself short in regards to my education. I have a Bachelor of Arts in History and, well, I've really been struggling to find "my place" in the career world for the last 5 years. I'm starting to think I sold myself short by not pursuing more math/science related careers. Is it too late for me to maybe find a career in STEM I would enjoy? [more inside]
It makes sense that things being very hot take a long time to cool off, it makes sense that some materials don't get too hot and others hold heat for a very long time, but how is it possible that some material can both get extremely hot while also cooling off very quickly? [more inside]
Asking for a friend: I am currently a postdoc who researches black holes, but I'm interested in changing fields. In particular, I'd like to do something in climate science. How can I go about this? [more inside]
I sometimes make iced coffee by placing a glass mason jar filled with ice into my single serve coffee maker and letting it brew / fill with hot coffee. I include a metal spoon inside the jar to act as a kind of heat sink and prevent the glass from breaking due to thermal stress. But should I bother? Does that spoon actually do anything?
According to my understanding of how noise-cancelling headphones work, the headphones detect low-frequency ambient noise levels near my ears, and emit a frequency which cancels out the ambient noise, so that instead I hear silence in place of the noise. Although I can't hear these noise-cancelling frequencies, I'm wondering whether they might be having a cumulative negative effect on my hearing. Is it only audible frequencies that have the potential to harm? Or can prolonged exposure to inaudible frequencies have a detrimental physical effect?
I'm an (older) grad student doing research in applied physics. I've ticked all my class requirements but have a shortlist of subjects I feel would be useful to my research and my career. I've translated these into a list of reputable, recommended textbooks to read. I've started reading those, usually in the evenings after all daily tasks are complete, and I enjoy it very much - but does anyone have tips to maximize the payoff of those reading hours? [more inside]
So, imagine we have a 100 meter tall tower, a 100 kg weight, and a rocket. Consider the following two, very similar scenarios... [more inside]
Hi everyone, My younger sister is 12, very smart, and has expressed interest in becoming a scientist. She loves physics and astronomy, especially, but she may have some untapped interest in other scientific fields as well. [more inside]
Career-advise me! Fellow mefites who enjoy both the humanities and the sciences: which did you pick for your career, and why? Or: were you able to somehow combine the two? Bonus points if you have experience with the medical field. [more inside]
I have a physics question, but my googling hasn't been able to provide anything satisfactory tonight. It's about cosmological models of creation in which NO initial conditions whatsoever are assumed. [more inside]
Where can I find royalty free photography and art for science fiction and space? Things like black holes, worm holes, spaceships, and futuristic technology? I'm looking for something with a Weyland Industries vibe to it.
Neal Stephenson's new novel, Seveneves, starts with the moon breaking up into seven pieces (spoilers for the first 50 pages of the book inside). [more inside]
So I have a few years to kill and I'd like to spend them fully understanding what physicists and mathematicians know about time. I'm not looking for any sort of summary, I want to understand the math from the bottom up. I once caught my father going through the Annus Mirabilis papers with a red pen; that's the sort of proficiency I have in mind. [more inside]
I need help evaluating different career paths as I plan a move to Rhode Island; I have a PhD in physics. What careers should I be looking into and what skills should I develop to have a very good chance of landing a job in under a year? [more inside]
After seeing Furious 7 this weekend, a physics question came up about weight and leverage. Spoilers and such below the break. [more inside]
I got accepted to two PhD programs in physics, one at Clemson University, and the other at Ohio University. I have one week to make my decision and I'm frankly terrified of making the wrong one. I don't really know how either school is seen in terms of what a degree from either one would mean for my future career. I know that neither is particularly well known or prestigious (at least I'd never heard of them before I applied). So, can anyone, especially anyone who knows the ins and outs of grad school, and particularly anyone who has attended either (or both!) help me make my decision? [more inside]
Earlier today I was warming up a test tube in chem lab by placing its bottom in a warm stream of water from a faucet and I noticed something peculiar; the stream of water seemed to capture the test tube and hold it in place. [more inside]
Another question from the "things my 9-year-old asked me and Google can't find" file: what would happen if you tried to hit a major league fastball with a tennis racket? Would the ball rip through the strings? Or would you actually be able to hit the ball back with distance? Would you hurt yourself?
I am looking for a resource that lists probability distributions and their common real-world applications. For example, I'd expect to see: Lognormal - daily returns in the stock market. Poisson - failure rates for mechanical equipment, ... [more inside]
What happens if your group exceeds the weight limit on a slide at the water park? [more inside]
If you dove into an 11ft pool of baby oil, would you be able to push yourself to the surface or would you drown? AKA what allows us to float? [more inside]
Many sites say that the largest known prime is "2^57,885,161 − 1, a number with 17,425,170 digits." Given this and well known research about the density of primes, I think it's at least possible to estimate the number of primes between 1 and 2^57,885,161 − 1. But I don't know how to do this myself. I really want the answer to this one (the order of magnitude at least), but I've got lots of these, and I'd ideally like more cool ones. :) [more inside]
I have a B.Sc in computer science and have one year of experience English using my CELTA qualification. Looking around, I see a lot of requests for people with North American B.Sc's to teach Math/Physics/CS in Asia. I'm trying to decide whether to go and start teaching, or whether it is better to get a state teaching qualification (2yr) in the Netherlands first... [more inside]
I'm sure you've all seen the quite obvious and silly "gravity will fail" hoax. It got me wondering...if all the planets, stars, asteroids, comets, black holes, etc (basically all known physical matter) were to somehow align on one side of the planet would the cumulative gravity exceed Earth's? I asked my dad (a doctor of nuclear chemistry) and he was stumped. Exclude dark matter for these purposes.
How do I calculate the radiation energy that a surface / object receives at distance d from a light source of power W watts? I'm familiar, in theory, with the inverse square law but need help thinking about how to apply it. [more inside]
I have been invited to dinner at the home of Russian emigre's who are both physicists. I work administratively at a medical school. The context of the dinner is that the couple are clients of my partner, who is an artist. Other than Putin jokes, or asking them to explain string theory, does anybody have any suggestions for conversation starters that won't make me seem like I failed my "physics for poets" class in undergrad? [more inside]
Quantum physicists of MeFi: I want to know all the quantum mechanics I need to know to understand quantum computing. I am mathematically literate and willing to learn more math, but I want to minimize my need to study physical phenomena or experimental results. [more inside]
I have a hose that can put out water at 60 litres per second (16 gallons per second) and I want to know if this hose can roughly replicate a wind speed of 275 kilometres per hour (170mph). We will put an object right in front of the hose - so there will be little pressure fall-off from the hose. Is this conversion measurement at all possible? I don't mind if the answer is a little approxiamate.
I need help thinking of cool ways to spend $30k or more for high school physics equipment! If you're a physics teacher, or had a great physics teacher in high school (or college), tell me what equipment makes for inspiring and effective physics education. [more inside]
My co-authors and I recently got a paper accepted to a major scientific journal. If we can provide a striking illustration, I think we have a decent chance to make the cover. That would be really cool and might be worth paying an external illustrator for. I never commissioned any artwork before, so I have questions about how to proceed. [more inside]