How did the British keep the fact that they broke the Enigma code secret? |
- How did the British keep the fact that they broke the Enigma code secret?
- How do engineers prevent the thrust chamber on a large rocket from melting?
- Why do cosmologists hypothesize the existence of unobservable matter or force(s) to fit standard model predictions instead of assuming that the standard model is, like classical mechanics, incomplete?
- Big Bang: What evidence do we have for what happened "behind the wall", before what we can observe?
- Why do flames coming out of a rocket engine get narrower?
- What is the difference in the lifespan of nuclear waste from Uranium vs Thorium?
- Does the refractive index of water change as its acidity changes?
- If energy can't be created or destroyed, then why do electrons continue spinning around the nucleus for billions of years?
- Is calculating for computers as easy with large numbers as it is for small numbers?
- How does the curved shape of a chopper's blade cause an increase in the speed of air passing above the blade than below it?
- How does one interpret phonon dispersion relations?
- Would it be a good idea to diversify a newborn child's microbiome as much as possible?
- How do fish know where home is? Do they have a set place in the ocean they always come back to?
- Was the Boston Tea Party bad for the environment?
- What exactly happens at the triple point of water?
- How do we know a certain sample size of humans is large enough?
- What causes the atmospheric phenomenon known as glory?
- When scientists studying a certain species of migrating birds, how do they count or estimate the number of the birds?
- How do astronauts stay grounded in space?
- When an animal has died, they start to bloat due to bacteria in it producing gases. What prevents this from happening in a living animal?
- Does a water/ethanol mixture in a pressure cooker release relatively more ethanol with steam release? Is the maximum pressure reduced?
- How long after eating something do our bodies gain weight?
- Are Nuclides and Isotopes the same thing?
- What's the difference between a neutrino and anti neutrino?
| How did the British keep the fact that they broke the Enigma code secret? Posted: 03 Nov 2019 05:42 PM PST What statistical formula's did the British and Allied forces use, if any, to decide to take action based on the German deciphered information? This might get into game theory or statistics, but how could they be sure that the Germans would not 'get wise' and switch their code? How often could they change their behavior before it became suspicious? P.S. I'm a new redditor and got on the site for askscience, so thanks and keep up the good work! [link] [comments]  |
| How do engineers prevent the thrust chamber on a large rocket from melting? Posted: 03 Nov 2019 06:49 AM PST Rocket exhaust is hot enough to melt steel and many other materials. How is the thrust chamber of a rocket able to sustain this temperature for such long durations? [link] [comments]  |
| Posted: 04 Nov 2019 03:41 AM PST It seems as though popular explanations of concepts like dark matter and dark energy come in the form of "the best mathematical model we currently have to fit a set of observations, such as the cosmic background radiation and the apparent acceleration of inflation, imply that there must be far more matter and more energy than the matter and energy that we can observe, so we hypothesize the existence of various forms of dark matter and dark energy." This kind of explanation seems baffling. I would think that if a model doesn't account for all of the observations, such as both CBR and acceleration and the observed amount of matter and energy in the universe, then the most obvious hypothesis would not be that there must be matter and energy we can't observe, but that the mathematical model must be inaccurate. In other fields, if a model doesn't account for observations using methods that were themselves used to construct the model, it is far more natural to think that this would tend to suggest that the model is wrong or incomplete rather than that the observations are wrong or incomplete. There seems to be an implied rejoinder: the Standard Model of the universe is really accurate at mathematically formulating many observations and predicting many observations that were subsequently confirmed, and there is so far no better model, so we have reason to think that unobservable things implied by it actually exist unless someone can propose an even better mathematical model. This also seems baffling: why would the assumption be that reality conforms to a single consistent mathematical formulation discoverable by us or any mathematical formulation at all? Ordinarily we would think that math can represent idealized versions of the physical world but would not insist that the physical world conform itself to a mathematical model. For example, if we imagine handling a cylindrical container full of water, which we empty into vessel on the scale, if the weight of the of the water is less than that which would be predicted according to the interior measurements of the container and the cylinder volume equation, no one would think to look for 'light liquid,' they would just assume that the vessel wasn't a perfect cylinder, wasn't completely full of water, or for some other reason the equation they were using did not match the reality of the objects they were measuring. So this is puzzling to me. It is also sufficiently obvious a question that I assume physicists have a coherent answer to it which I just haven't heard (I also haven't this question posed, but I'm not a physicist so it wouldn't necessarily come up). Could someone provide that answer or set of answers? Thank you. [link] [comments]  |
| Big Bang: What evidence do we have for what happened "behind the wall", before what we can observe? Posted: 04 Nov 2019 06:00 AM PST I understand that observing increased density further back in time, together with redshift of light, make up a valid foundation for the theory of expansion of the (visible) universe. However, we cannot see all the way back. As I understand it, it isn't even theoretically possible to obeserve anything from when our universe was to dense for light to propagate (exist?). We do in effect have a "wall" at the edge of the universe we cannot see through, and thus cannot observe all the way back, even with better technology. So why do we interpolate the observed expansion of the observable universe all the way back to a point? Could it not be that it existed in some other larger states? Bonus question. Not mandatory:): Do the main theories of big bang translate in any way over to the rest of the universe, outside the observable one? Could it be that other parts had size to them while our neighboorhood was infinitesimal? [link] [comments]  |
| Why do flames coming out of a rocket engine get narrower? Posted: 03 Nov 2019 07:52 AM PST Reference: https://i.redd.it/irpgqmm41hw31.png The flames coming out of the rocket engine are clearly getting narrower as they move farther out. It's this effect due to fluid mechanics (Bernoulli's law?) or is it due to plasma dynamics (something counterintuitive happening because of moving free charges in the plasma)? A combination? Or something different? [link] [comments]  |
| What is the difference in the lifespan of nuclear waste from Uranium vs Thorium? Posted: 03 Nov 2019 05:46 PM PST I often see that nuclear waste has long lifespans, and this is a major drawback from nuclear energy. Is this true for both Uranium and Thorium? [link] [comments]  |
| Does the refractive index of water change as its acidity changes? Posted: 04 Nov 2019 04:31 AM PST |
| Posted: 04 Nov 2019 01:43 AM PST I've been taught in school that energy can't be created or destroyed, only transformed. That brought up a question. How is it possible that electrons continue to spin for really long periods of time? Where is that energy coming from? [link] [comments]  |
| Is calculating for computers as easy with large numbers as it is for small numbers? Posted: 04 Nov 2019 03:59 AM PST |
| Posted: 03 Nov 2019 08:15 PM PST About airfoils, it's said that a wing's top is curved and its bottom is flat. Since its top is curved, air on top of a wing moves faster than air on bottom. This relates to Bernoulli's Principle. I have never been able to understand this fact about airfoils, or to be more precise, I could never...errr... visualize it? How does an increase in surface area (i.e. curved rotor blades) cause an increase in speed of air passing over it? I understand that this speed increase causes a pressure decrease due to Bernoulli's principle, but why exactly does the speed increase? [link] [comments]  |
| How does one interpret phonon dispersion relations? Posted: 03 Nov 2019 03:14 PM PST I am having trouble understanding this concept. The frequency ω is plotted against the wave vector k, but how do I actually read it? Do I search for a frequency and look which modes are "(co)existing" at that frequency? Or do I pick a wave vector (a direction) and look which frequencies are allowed for these values of k? I can probably read it both ways, but where is cause and effect exactly? Here's what I know: Let's assume a 2D case with a simple Brillouin Zone Γ-X-Y-Γ. The sections of the dispersion relation correspond to values of k, where Γ denotes the point where k is very small and the wavelength λ is very large. Traveling along the x-axis is basically like traversing the edges of the Brillouin Zone, covering all possible directions of the wave vector.
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| Would it be a good idea to diversify a newborn child's microbiome as much as possible? Posted: 03 Nov 2019 07:42 PM PST When a new child is born, im to understand that both parents should hold the child with their bare chest or at least get good skin to skin contact as to populate their microbiome with the parents bacteria and such. Would it be a wise idea to have another two or three people who exhibit good health get in there just for the diversity it would offer? In particular, people who are not related to the parents, seeing as a parent or sibling of the parents would have a very similar biome. Thanks for your help! [link] [comments]  |
| How do fish know where home is? Do they have a set place in the ocean they always come back to? Posted: 03 Nov 2019 07:12 AM PST How do fish navigate the oceans, and how do they not get lost along their way? Do they have a place in the ocean they would call home and always come back to? [link] [comments]  |
| Was the Boston Tea Party bad for the environment? Posted: 03 Nov 2019 08:24 PM PST Based on a brief conversation held tonight. I know that tea was shipped as solid blocks in wooden boxes, at least for long distance travel. It's also my understanding that it was a HUGE shipment, like potentially years worth of tea. Finally, I know that tea is also slightly acidic, so altogether, I think there must have been some effect on the local marine flora and fauna. I know this has a lot of moving parts, so any bits of help would be greatly appreciated. [link] [comments]  |
| What exactly happens at the triple point of water? Posted: 04 Nov 2019 12:04 AM PST Whenever I try to learn more about the triple point of water, I often read that its a combination of pressure and temperature where a substance coexists as all 3 phases. But, I never understood what exactly happens at this triple point and why water changes between solid liquid and gas. I've only found this video (https://www.youtube.com/watch?v=MP6MVLWuNZQ) which sort of explains the coexistence of all 3 phases. Not that there is anything wrong with the video, but where can I find other explanations like this which may be more detailed and elaborate? [link] [comments]  |
| How do we know a certain sample size of humans is large enough? Posted: 03 Nov 2019 04:09 PM PST How do scientists or researchers determine the sample size needed for a reliable study? I've seen posts with n=49 and can't see how that small sample size could be considered large enough to produce an accurate cross section of society. [link] [comments]  |
| What causes the atmospheric phenomenon known as glory? Posted: 03 Nov 2019 12:05 PM PST |
| Posted: 03 Nov 2019 06:00 PM PST What is the method that they usually use, thank you [link] [comments]  |
| How do astronauts stay grounded in space? Posted: 03 Nov 2019 09:48 AM PST Since low earth orbit is charged with plasma, what's keeping astronauts protected from a charge differential in their environment to keep them from getting electrocuted? [link] [comments]  |
| Posted: 03 Nov 2019 10:19 AM PST How does the body make sure that the bacteria can't start digesting the intestine from the inside out when we're still alive? [link] [comments]  |
| Posted: 02 Nov 2019 10:33 PM PDT This discussion gave rise to the question how a reasonable mixture of ethanol and water (say 1:9) would behave if cooked in a pressure cooker. While ethanol boils at a lower temperature than water, a pressure cooker usually reaches a much higher temperature than both liquids' boiling point. On the other hand, ethanol has a higher vapour pressure, so it should reduce the maximum temperature that can be achieved before the valve opens. How would the mixture behave? Would it release mostly ethanol? Is there maybe an easy formula/rule of thumb with which the composition and release temperature of an (initial) ethanol/water mixture can be predicted (given a certain maximum pressure)? edit: Sigh, I misspoke in the title, it should read "Is the maximum temperature reduced?" [link] [comments]  |
| How long after eating something do our bodies gain weight? Posted: 03 Nov 2019 02:16 PM PST If I had a stable diet which never changed and a stable work and exercise plan which help me maintain my body size, the I go on a 3 day binge, eating fatty fried food, drinking loads of sugary drinks and alcohol, I refuse to leave my couch and spend the rest of my time sleeping and snacking(day around Christmas), then I go right back to my normal routine. When would I expect to see the fat start to appear on my body? I recently indulged for a few days then went back to work and felt completely bloated and uncomfortable, and a more polite coworker said I looked fatter. So just 48 hours later my body had noticeably changed. Is there a finite way of knowing how fast our bodies turn excess fat and calories into fat on our bodies, or is it a bit too vague to tell without testing a person. [link] [comments]  |
| Are Nuclides and Isotopes the same thing? Posted: 03 Nov 2019 06:51 PM PST |
| What's the difference between a neutrino and anti neutrino? Posted: 03 Nov 2019 12:45 PM PST I know quarks and antiquarks, electrons and positrons have opposite charges. What makes neutrinos antimatter self distinguishable? [link] [comments]  |
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