| Photons have no mass but are affected by gravity. Do photons themselves affect gravity, e.g. could one make a black hole solely from photons? Posted: 17 Dec 2015 05:49 AM PST Experiments have shown that photons are affected by gravity. E.g. if you look at the edge of the moon the light of the stars behind is bent slightly by its gravity. Or in black holes light is bent so hard that it cannot leave the event horizon. Now that poses the question if light itself affects gravity. I mean it has energy and it interacts with gravity. But its particles are massless. If I were to convert all mass of a black hole into energy and the energy into photons, what would happen in regards to gravity? Would it stay the same or would it simply disappear letting the photons out of their prison? submitted by InterstellarGlue [link] [113 comments] |
| If photons have no mass, how can a laser beam bore a hole through something? Wouldn't the equation E=MC^2 resolve to 0=0? Posted: 16 Dec 2015 12:31 PM PST I keep reading in some replies in AskScience that photons have no mass. I assumed laser beams were composed of photons, but wasn't sure if that was ALL they were composed of. So I searched the Internet and found this article: https://www.rp-photonics.com/photons.html which doesn't (for me) clarify an answer. I know I must be missing something in my understanding, because if lasers are composed only of photons with no mass, then using Einstein's equation E=MC2 would result in the Mass being 0 and the resulting equation being 0=0, where the Energy would also be 0. So, how can a laser light beam composed of "massless photons" produce energy to bore a hole through a substance? EDIT: WOW! Thanks for all the answers. I learned several new things today, one of them being what I "already knew" was an incomplete understanding of the knowledge I had. submitted by FalconAF [link] [737 comments] |
| When humans smell something "bad", does that stem from social conditioning, or is it our body's natural response to said smell? Posted: 17 Dec 2015 08:54 AM PST For instance, garbage. We're told all our lives that garbage is gross, don't dig through garbage, ect. Does it smell bad to us because of our aversion, or is this something our body does naturally? submitted by xsp4rrow [link] [12 comments] |
| What are the psychoactive effects of an adenosine receptor agonist? Posted: 17 Dec 2015 07:44 AM PST Given that caffeine works through it's antagonism of adenosine receptors, and that this can temporarily prevent drowsiness, would an agonist have the reverse effect and promote sleepiness? I have had a search of journal literature and can't seem to find a study investigating the psychoactive effects of an agonist. Common sense brings me to think an agonist may have potential as a safer treatment of insomnia than Benzodiazepines, given the less crucial role of the adenosine system to neurological functioning compared with the GABA system, but this is quite obvious so I am assuming there is some sort of reason why it isn't? submitted by JoeLivUni [link] [2 comments] |
| Would it be more efficient to send rockets into space from Earth's axis? Posted: 17 Dec 2015 06:53 AM PST So, since we spin on an Axis, would it not be more efficient to fire up a rocket from the north/south axis rather than where we do it in Florida/Texas? It would seem logical that given the centripetal force, that the atmosphere would even be thinner?? allowing for less force/distance to reach space? submitted by TheRemixedLife [link] [7 comments] |
| What is electrical energy? Posted: 17 Dec 2015 04:33 AM PST In a circuit electrons are flowing through a wire from the negative pole to the positive pole. In this process they transfer a certain amount of energy to whatever consumes the energy in this circuit. My teacher pictures this energy as backpacks worn by the electrons, which are full before the energy is consumed and then emptied by the consumer after which the electrons move on to the positive pole of the battery. I would like to know what this energy actually is. Thanks in advance! submitted by Maegor1 [link] [4 comments] |
| How do rockets apparently break e = 1/2 * m *v^2? Posted: 17 Dec 2015 02:23 AM PST The energy of a moving body is e = 1/2 * m * v2, so you must supply increasing amounts of energy for a constant acceleration. (e.g. it takes more energy to go from 10->20 m/s than from 0->10 m/s). However, a rocket has no (or many) frames of reference so a increase of 10 m/s must require the same amount of energy whether going form 0->10 m/s or 100->110 m/s. What explains this apparent contradiction? submitted by PixiePooper [link] [24 comments] |
| If black holes are infinitely dense. How can they have different sizes? Posted: 16 Dec 2015 12:18 PM PST I've heard that black holes have 0 volume and that they are infinitely dense. What exactly does this mean? I know there is something I'm not getting because I've heard that black hole the size of a peanut would have as much mass as the earth. This wouldn't be true if all black holes had 0 volume. submitted by ThePinkAdmiral [link] [100 comments] |
| Is there a limit to how acidic (or basic) something can be? Posted: 15 Dec 2015 10:10 PM PST |
| If a point is translated a unit either up, down, left, or right, determined randomly, in a two dimensional cartesian plane every second for an infinite amount of seconds, what position would it approach as the amount of seconds approaches infinity? Posted: 16 Dec 2015 06:40 PM PST I envision the origin (assuming it starts at the origin) to be the most likely destination for the point after n iterations. However, I doubt that if I carried out this experiment 1000, 10,000, or 1,000,000 times that the point would fall anywhere close to the origin. Is there even an answer to this question? submitted by stir_fry [link] [13 comments] |
| If a photon does not experience time, how does it exist? Posted: 17 Dec 2015 03:07 AM PST A photon moves at the speed of light. An object moving at the speed of light does not experience any passage of time. So basically, the photon (from it's relative view) ends up at it's destination at the same time it was created. How is that logically possible? How can it literally be created at Time X and absorbed at Time X? submitted by EternalNY1 [link] [7 comments] |
| Did we always know that electricity was a physical phenomenon? If not, when did we find out? Posted: 16 Dec 2015 08:32 PM PST |
| Let's say a space ship flies past Earth at close to the speed of light. From the ship's perspective, the Earth is the one traveling at near light-speed. If all motion is relative, how does one determine which of them experiences time dilation? Posted: 17 Dec 2015 09:24 AM PST |
| In which direction is spacetime "curved"? Posted: 17 Dec 2015 05:24 AM PST I've spent years trying to get my head around General Relativity, and I've never been satisfied with any explanation for how gravity is caused by the "curvature" of spacetime. I think I finally figured out where the roadblock is! I refer back to the classic example of a very massive object "weighing down" the fabric of spacetime, causing any planet passing by to follow the curvature rather than continue in a straight line. As demonstrated in this gif. This seemingly intuitive explanation, to me, makes no sense at all. We're told that spacetime consists of 4 dimensions: x, y, z, and t. However, this gif acts as if the planet is rolling around in a cereal bowl, which is being pulled "down" by a gravity-like force (otherwise, an approaching planet's path would dip slightly into the curvature then continue straight). My question is, which way is "down" supposed to be? The gif suggests that "down" is perpendicular to the direction of travel of the planet. Sorry, that just doesn't do it for me. What happens when another planet comes flying in from some random direction, how does it interact with this curvature in spacetime? For that planet, is the spacetime around the star curved in a different direction? It seems that every time I try to look up an explanation to all this, I'm just told, "this is how it is, isn't that fascinating?". Nobody actually goes into detail about why it's like that or how we came to that conclusion. Hopefully my question has made sense, please enlighten me! Thanks in advance! submitted by FearTheHump [link] [3 comments] |
| When formatting a hard drive, why is overwriting it 7 times considered to be more secure than just filling it with zeroes? Posted: 17 Dec 2015 01:34 AM PST I know that simply formatting a hard drive does not actually erase any of the contents on disk, but what data could possibly be recovered if the formatted drive gets overwritten once with all zeroes? submitted by nitro8t [link] [3 comments] |
| Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science Posted: 16 Dec 2015 07:02 AM PST Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Physics, Astronomy, Earth and Planetary Science Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Asking Questions: Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Answering Questions: Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience. If you would like to become a member of the AskScience panel, please refer to the information provided here. Past AskAnythingWednesday posts can be found here. Ask away! submitted by AutoModerator [link] [58 comments] |
| Which way does the gravity pull at the exact center of a large object? Posted: 16 Dec 2015 06:15 AM PST Hypothetically, if the exact center of the earth or the sun was cool enough to not burn us alive and we travel there. We dig ourselves a little room with the exact center of the room being the exact center of the earth. My question is, which direction would gravity pull us? Would we be pulled towards the nearest wall comparable to the centrifugal force of the spinning carnival ride? Would we float around in the room since the gravity from all the mass of the earth is pulling us in every direction instead of down? submitted by royalrush05 [link] [69 comments] |
| What is the difference between a brain when its sexually aroused and when it's not? Could we replicate this to synthesise aphrodisiacs? Posted: 16 Dec 2015 09:44 AM PST |
| What causes elements to form into all the different rocks and gems we find on Earth? Posted: 16 Dec 2015 07:38 PM PST Is it simply different materials found in the ground, or is there more to it than this? I saw the giant jade stone on the front page and now I'm super curious about what makes them all form differently. submitted by cajunflavoredbob [link] [4 comments] |
| Do we get more sensitive to low frequency sounds as we reach middle age? Posted: 17 Dec 2015 04:52 AM PST |
| How do we guarantee an object in space is a certain distance (light-years) away? Posted: 16 Dec 2015 05:22 PM PST After reading the news about the new earth-like planet, how do we guarantee the distance to an object like that? Is it not possible that after travelling a light-year it could be a lot closer? submitted by Cov3rt [link] [12 comments] |
| What makes outer space so ill-fitting for microbial life, compared to other extreme conditions on earth where a select few species has been shown to thrive? Posted: 16 Dec 2015 06:54 PM PST |
| How do alkaline metals and hydrogen ions stimulate our taste buds for things to taste salty? Posted: 17 Dec 2015 04:20 AM PST |
| How do the police trace phone calls and do you really need to stall the criminal on the phone to complete the trace? Posted: 16 Dec 2015 07:31 PM PST |
| Shouldn't propellers be on the bow of a ship not the stern? Posted: 16 Dec 2015 10:05 PM PST Aircraft typically have the propellers on the front. The ones that don't tend to be loud because of the dirty air. There is also a loss of efficiency. Why doesn't the engineering translate to ships as well? submitted by Flyheading010 [link] [4 comments] |
