| Why is the gravitational constant, a value that is fundemental to so many fields of science, only know to within 4 significant digits? What about this figure is so intrinsically difficult to measure? Posted: 30 Dec 2018 06:17 AM PST According to the wikipedia page, the gravitational constant is " known with some certainty to within four significant digits". What is it that prevents us from getting a more accurate calculation of this value? submitted by /u/Math-Code-Love [link] [comments] |
| Why do fluorescent and phosphorescent materials emit photons of lower energy than they absorbed? Posted: 30 Dec 2018 05:58 AM PST Intuitively, that makes sense. But if an electron absorbs a photon by being excited into a higher-energy orbital, and it emits a photon by "falling" down to its original orbital, should it not then emit a photon with the same amount of energy as the one absorbed? Mechanistically, where in the process is the energy lost? submitted by /u/Roswalpg [link] [comments] |
| How do Einstein-Rosen bridges help us reconcile the AMPS black hole complementary paradox? Posted: 30 Dec 2018 01:06 AM PST I hope my title is sufficient. Its hard to sum all this up in one question. I've been watching a bunch of Leonard Susskind lectures on YouTube. The questions I have come up in several of the videos, but this one seems to have all the elements that I'm confused by: https://www.youtube.com/watch?v=OBPpRqxY8Uw 1) At the 17 minute mark, he starts talking about entanglement of space in a vacuum (https://youtu.be/OBPpRqxY8Uw?t=1028). He draws a vertical line to represent a divide between two adjacent areas of space. He then draws little circles on the left and right side ("cells") and talks about how the circle on the left is entangled with the circle on the right. Later at minute 21, he starts talking about how the entanglement holds space together. Ok, so the entanglement is holding the left cell to the right cell... but what is holding the left cell to the cell below it or above it? It feels like we have a bunch of chain links, and we keep making little groupings of two. But we aren't forming a fabric of any sort.... just a bunch of tiny chains of length 2. Wouldn't we need more connections? If we allow for 2 connections per link, we could form a long chain. We still don't really have a fabric. For a 2D fabric, it seems like we'd need at least 3 connections per cell. But wouldn't that violate the monogamy of entanglement? Or does that only apply to entangled particles? (Actually, that principal is what is chaffing at me in all of these questions.) 2) A theme throughout the whole video is an attempt to reconcile the paradox that comes from the AMPS thought experiment. Specifically, it is to address the problem when we create entangled particles, feed one particle to black hole A and one to black hole B, and then consider what is happening at the event horizon of either black hole. If we consider a particle inside the event horizon but at the edge, then it should be entangled with a particle just outside the event horizon. But that particle is already entangled with a particle in the other black hole. Hence the paradox. His solution is to say that it isn't actually three particles, but two. And he uses an Einstein-Rosen bridge to reconcile how we seemingly have 1 particle in two different places. But what I can't understand is that we fed both of our original entangled particles to the black holes. So they both went past the event horizon. Yet we have one entangled particle outside the event horizon. How did it get out? Presumably it never went in, but we specifically built our two black holes from these particles. The starting premise of our thought experiment is that they are both inside the event horizon. 3) Why do we treat the two black holes as if they are one giant entangled particle? This seems to be problematic if we change the way we build our black holes. We start as normal creating entangled particles and putting one into black hole A and the other into black hole B. But now lets create more pairs, putting one into black hole B and the other into a new black hole: C. Ignoring the question of what is happening at the event horizon and just considering the entangled particles in each black hole, this situation seems fine as long as you consider each pair of particles individually. You have a bunch of tiny Einstein-Rosen bridges between each entangled pair. But if we consider the black holes as a whole and try to build a large Einstein-Rosen bridge, we run into that pesky monogamy of entanglement problem again. I should mention that while I'm an enthusiast, I'm a novice. I understand only the most basic of the math behind all of this. If you've made it this far, thank you for sticking with me. And if you have input, thank you for your help! submitted by /u/ibn4n [link] [comments] |
| Does the buildup of massive cities (NYC, Dubai, etc.) impact the wobble / axis of Earth in any discernible way? Posted: 30 Dec 2018 07:23 AM PST |
| Whats the difference between cAMP and the IP3-DAG pathway? Posted: 30 Dec 2018 03:15 AM PST I'm actually confused. I know that both are G protein coupled receptor pathways. This is my understanding: Activation of the Gs protein causes activation of adenyl cyclase, which causes cAMP levels in the cell to increase, which caused calcium influx. Activation of another Gs protein causes activation of the phospholipase pathway and caused IP3-DAG, which causes calcium influx. Is my understanding correct? submitted by /u/HouhoinKyoma [link] [comments] |
| Is the percentage of people born with Autism higher than it used to be? Posted: 29 Dec 2018 07:39 PM PST It seems like you hear about people being born with Autism more and more. Is there of an actual increase in the percentage of people being born with autism, or do you just hear about it more because of increased population size, social media/discussion, improved diagnosis criteria, higher quality of medical care, decreased childhood mortality rates, etc.? If there has been an increase, do we know the reason(s)? I guess this could be asked about any condition. Just curious about Autism. Not sure what to flair this, so sorry if it's incorrectly flaired. submitted by /u/Ballistic_Turtle [link] [comments] |
| How do climate scientists isolate human activity from other factors that may contribute to climate change? Posted: 29 Dec 2018 04:50 PM PST |
| Is there good reason that the many worlds interpretation of quantum mechanics is so popular? Posted: 29 Dec 2018 04:40 PM PST The underlying issue I'm having is that science is terrific at not giving anything value without evidence, but I hear about the many worlds interpretation of quantum mechanics all the time. So I'm wondering first, is there some conceivable method of testing this someday that I'm not aware of? I get that it's only an interpretation, and could explain what we see in a way, but I worry that this interpretation is just a lot of fun and that's what's making it popular. Second, let's assume we could devise some experiment, and it turned out that everything that could happen indeed does, what could we do with this knowledge? Or maybe that's not even possible to speculate about. submitted by /u/squeth [link] [comments] |
| How does the current extinction rate compare to previous mass extinction events? Posted: 29 Dec 2018 08:49 PM PST |
| How does the eye actually turn photons into signals in our brain? What's the physical process that allows that to happen? Posted: 29 Dec 2018 10:18 AM PST |
| What about rabies makes it to where a blood test cannot determine if an animal or person is infected? Posted: 29 Dec 2018 09:42 AM PST |
| Can you convert a 2D movie to 3D? Posted: 29 Dec 2018 07:02 PM PST I just saw The Polar Express in 3D and was surprised that such an old movie would be animated with 3D in mind. Is there some kind of process to convert 2D footage into 3D? submitted by /u/Legate_Invictus [link] [comments] |
| With the Flu vaccine only able to target a few strains and subject to mutation during production, is there a reason why anti-virals such as oseltamivir (Tamiflu) are not used as an option for annual flu preventative? Posted: 29 Dec 2018 01:14 PM PST |
| Why does coming into contact with a dangerous substance like di-methyl-mercury kill you? Posted: 29 Dec 2018 01:45 PM PST |
| How is the charge of an electron measured as accurately as it is? Posted: 29 Dec 2018 09:56 AM PST I roughly understand how the milikan oil drop experiment showed how electric charge was quantized, but how was the experiment able to differentiate such small amounts of charge? How has the measurement of the elementary charge improved since then? submitted by /u/yesireallyamthatdumb [link] [comments] |
| What is the genetic origin of a “house cat?” Posted: 29 Dec 2018 07:00 AM PST Domesticated dogs are genetically identical to grey wolves. What kind of feline do domesticated cats come from? submitted by /u/Elmerthe3rd [link] [comments] |
| Do chickens or other birds have unique “voices”? Posted: 29 Dec 2018 06:53 AM PST |
| How do we develop nonstandard mapping motor skills, such as when moving a computer mouse to rotate in a pan-based 3d FPS game, and how does this differ from standard mapping? Posted: 29 Dec 2018 04:59 AM PST I'm not sure if the question makes sense... But if you imagine playing an FPS game and how you are rotating in a 3d, pan-based environment to aim the reticle (which I understand to be nonstandard mapping?) - what happens in the brain? My second question would be: is the brain activity different from the same scenario but instead the cursor orientation happens in a 2d environment such as your desktop? And the third question: are these visuomotor skills developed differently from "normal" visuomotor skills where you grab an object in real life or shoot a real gun at a target? submitted by /u/CHADLETKING [link] [comments] |
| If space time / the universe is actually curved, is there evidence that the furthest galaxies we can see are not actually our own galaxy or that we are simply looking back on ourselves? Posted: 29 Dec 2018 12:00 PM PST I've often heard that we need to think of ourselves as residing on the surface of a balloon that is expanding ever outward and that the universe is not actually a straight line. So if what we peer out at the universe in what we perceive is a straight line, how do we know that at some point that light hasn't come full circle and that we aren't actually looking at our own galactic neighborhood? Would we even be able to recognize the Milky Way from so far away and among trillions of others? On a related note, we say that distance galaxies are expanding away from us at rates that defy our current understanding of the universe. Would this not make since if we are expanding away while also observing ourselves expand away from across the cosmos? It seems to me that the rate and/or red shifting would increase proportional to the distance if this were the case, similar to what we are actually observing. What am I missing that would otherwise suggest that this is not actually how the universe works? submitted by /u/ColoradoPrime [link] [comments] |
