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I had to explain why there were no real UFOs today using the whole time-space thing as evidence, and I realized that I have no idea how to explain time space except for "over there is in a different time as over here. Moving through space is like moving through time , kinda. Other stars are in a way different time as we are, but not really, just in a different time space thing" |
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Jun 17, 2015 09:42
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| # ? May 2, 2024 17:12 |
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nonazis posted:I had to explain why there were no real UFOs today using the whole time-space thing as evidence, and I realized that I have no idea how to explain time space except for "over there is in a different time as over here. Moving through space is like moving through time , kinda. Other stars are in a way different time as we are, but not really, just in a different time space thing" brilliant, submit this post to Physical Review Letters |
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Jun 17, 2015 13:20
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If nothing can go faster than the speed of light (and nothing with mass can go at the speed of light) how could light be unable to reach any part of the universe? How is there an "unobservable" universe.
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Jun 17, 2015 14:34
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unwantedplatypus posted:If nothing can go faster than the speed of light (and nothing with mass can go at the speed of light) how could light be unable to reach any part of the universe? How is there an "unobservable" universe. its really big. that and red shift |
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Jun 17, 2015 14:36
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Basically there's a distance where light emitted at the very beginning of the universe would just now be reaching us. light from beyond there hasn't reached us yet so it's beyond the observable universe |
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Jun 17, 2015 14:42
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I'm talking about the parts of the universe that will never be visible to us. Supposedly, there are parts of the universe that are moving faster than the speed of light relative to us in a direction points away from us.
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Jun 17, 2015 18:34
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Bwee posted:I am going to goldmine this when you are done regardless of the contest let me know when you want it goldmined security_drone
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Jun 17, 2015 18:46
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Cumt posted:let me know when you want it goldmined security_drone Thanks! I'm actually working on a video for nonazis to try to demonstrate Minkowski diagrams as a method of explaining spacetime / more intuitively understanding Lorentz transformations in spacetime, so maybe after that would be great. |
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Jun 17, 2015 19:03
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im now listening to a short history of nearly everything by bill bryson while i run and its really interesting but does anyone know how outdated the science is? it's over a decade old
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Jun 17, 2015 19:12
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I'd say it's outdated by about a decade then |
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Jun 17, 2015 19:16
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Bwee posted:im now listening to a short history of nearly everything by bill bryson while i run and its really interesting but does anyone know how outdated the science is? it's over a decade old It's still largely accurate as much of what its talking about is history and paradigm shifts. It approaches almost everything in it in broad strokes that make it easy to look up or find more information on any given topic. There's a few factual errors: http://errata.wikidot.com/0767908171 But it's one hell of an entertaining book, marvelously written and I recommend it to everybody. Obviously, we've refined our estimate of the age of the universe and confirmed the Higgs boson, but I can't think of any theory or concept illustrated in it that has been flat out proven wrong (besides the relatively minor mistakes in it). But I haven't read the book in 10 years so I could be way off. |
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Jun 17, 2015 19:47
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unwantedplatypus posted:If nothing can go faster than the speed of light (and nothing with mass can go at the speed of light) how could light be unable to reach any part of the universe? How is there an "unobservable" universe. unwantedplatypus posted:I'm talking about the parts of the universe that will never be visible to us. Supposedly, there are parts of the universe that are moving faster than the speed of light relative to us in a direction points away from us. This is a very insightful question. You're like the forum's own version of Charles Misner, who brought up a fundamental part of this problem in the 60s. It's definitely a glaring problem when you look at the facts. The universe is 13.817±0.048 billion years old, and the oldest light we can see is just a little younger than that, and we can't see any further back than the recombination epoch. So given those facts, you'd think that we wouldn't ever see any new light from across that 'horizon'.  The first problem is partially solved by expansion of the universe actually accelerating. While no matter is moving at superluminal speeds, the universe itself is expanding at an increasing rate, causing it to appear like galaxies are accelerating away from us in the very distant cosmos as covered previously in this thread. The redshifted light from the galaxies will slowly decrease the energy of light approaching us until the object is superluminal to us, and then it'll disappear. This might seem counterintuitive, but think of the universe expanding like a balloon you are inflating instead of like an explosion filled with things. The galaxies are sitting on the balloon, and the ballon is expanding, speeding up and adding more air as it goes. (The actual topology is flat as far as we can observe, but the metaphor is still apt). Just like the balloon, no galaxy is at the 'center' of the universe: Each has their own space as the universe itself expands and no location is any more central than any other location. The existence of black holes confirms that distortions in space and time can outpace light. This still didn't solve the homogeneous, isotropic nature of the universe though. There were already objects unable to communicate with each other that somehow shared properties that they would have had to interact with each other in order to share (like the distribution of matter in the galaxy, the temperature of the cosmic microwave background, etc). So it seemed pretty obvious that the universe was a good deal larger than it immediately made sense for it to be. The explanation isn't fully hammered out yet but there's two contenders. Most people lean toward the concept of inflation. Inflation was a very brief but very potent period in the early formation of the universe.  The inflation is believed to have increased the volume of the universe by 10^78. This meant the primordial contents of the universe would be much more thinly distributed throughout an enormous area. The universe went from a microscopically small point (about 1 planck width) at an unbelievably enormous temperature, to about the size of a grapefruit. (Doesn't sound like a lot but yeah, 10^78 as much volume.) This expansion took place faster than light, but no radiation (and the entire universe was just radiation at that point) ever travelled faster than light. The resultant drop in temperature formed a kind of soup of primordial particles, diffuse but still hot and high energy. This theory is the one most supported by observational details at the moment, but it's still not particularly strong. It shares a lot of similarities with dark energy as I described earlier, but a far more powerful force brought about by some scalar influencer only apparent at the incredibly high temperatures and energies of the big bang. The action of the accelerating expansion itself is interesting because it's described as an inverse Schwarzschild metric, so it's sort of like the cosmological horizon (the observable universe) is a reverse event horizon, and objects exponentially accelerating away eventually cross that inverted event horizon the other way and become inaccessible to the observer within one 'observable' universe. Basically it boils down to, 'this is how the universe looks, and it doesn't make sense with what expansion would be predicted just based off elapsed time. Obviously, we can't yet replicate the conditions found in the big bang in any accelerator ever built by many, many orders of magnitude, though each accelerator adding additional energy puts us closer and closer to those primordial physics. They look at the consequences of the universe and the evidence of the big bang. The evidence for the big bang is strong, but the flatness, the isotropic nature, and the lack of certain predicted electronuclear-force derived configurations of matter anywhere suggests it's incomplete, they conclude there must have been a period of inflation: when could it have taken place and what would be the consequences?' and they think they've narrowed it down but there's still a lot of questions, and in them probably an explanation for dark energy and the unexpected realities of the universe's current expansion. joke_explainer fucked around with this message at 22:40 on Jun 17, 2015 |
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Jun 17, 2015 22:37
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Wrapping my head around these concepts isn't the easiest thing but it's fun. I understand (vaguely) how certain parts of the universe could be unobservable now but you would think eventually the entire universe would become observable as light finally manages to travel the distance between any two distant galaxies. Essentially if you accept... A: light is the fastest thing in the universe B: The velocity of an object emitting light does no affect the relative velocity of that light Then light should be able to go from any one point in the universe to any other point given enough time. Therefore eventually the observable universe would encompass the entire universe. However, from what I've read from other sources it doesn't sound like this is the case. Instead it sounds like, barring FTL wackiness, some sections of the universe will be eternally unobservable. ---------------- |
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Jun 18, 2015 00:14
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unwantedplatypus posted:Wrapping my head around these concepts isn't the easiest thing but it's fun. To answer these questions, I couldn't find any gif or video that just precisely explained what I wanted to so I had to make a video to explain the first part. Well, I actually first made a 150 meg gif, then a 4 meg gif that looks ridiculously compressed, then I gave up and just uploaded it to youtube. Click the image to view the video. Or click here: https://www.youtube.com/watch?v=PU76IhZG3uM  The second part is more complicated. See, time isn't a thing when you are a photon. There's no such thing as proper time. A photon's creation to any arbitrary amount of travel takes no time from the reference frame of the photon. So, when you have light traveling through space, and it's losing energy like described in the video, and its destination is accelerating faster and faster away, eventually you get to a point where the light has less energy than the cosmic microwave background radiation. Essentially at that point we will have no visible galaxies closer than 13.82 billion years away (+ how ever many billions upon billions of years to reach that point). Since the cosmic microwave background will wash out anything weaker than it, nothing can be seen. Even further still, the light disappears entirely. It's effectively behind an event horizon created by the expansion of the universe, if you want to put it that way. Light can never escape the faster-than-light expansion from that light to us as the universe continues to blow itself apart. The Doppler effect doesn't affect the speed of the light, but it does affect the wavelength. Decreasing energy continuously means there's less and less light until there's statistically zero and eventually actually zero past those barriers. As to whether or not there are already large sections of the universe that will forever be unobservable, that largely depends on the final size of the universe which we don't know for sure. We just think it is unfathomably vaster than the current observable universe. If that's true, then yes, there will be big parts of the universe we will never even have a chance to see, and then large parts we can see but only for a little while. (Few 100 billion billion billion billion billion billion years or whatever). joke_explainer fucked around with this message at 07:10 on Jun 19, 2015 |
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Jun 19, 2015 06:50
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Probably important to note there's three kinds of redshift: Cosmological redshift as that video describes, which is due to the expansion of space and is a wavelength increase to the amount space expanded as light traveled through it Doppler redshift is dependent on the emission of light and the vector of the motion toward the observer. It's not 'true' redshift in that it is different depending on where and at what speeds it is measured. Gravitational redshift is the result of gravity's effect on light. Energy is decreased coming out of a gravity well and increased going down it, corresponding with redshift from escaping gravity and blueshift from going toward it. This is 'true' redshift, in that the light would appear redshifted to any observer. The video depicts cosmological redshift. |
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Jun 19, 2015 07:32
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Getting back on topic. I think the Great Filter idea is really rather interesting. We really only have data up to the "Tool using animals with big brains" step. For every step after that we only have one data point or no data at all. The fact we exist only tells us that advanced civilization is possible, not the likelihood of it developing. IMO the biggest hurdle, at least on Earth, seems to be the development of language. Language is extremely versatile and can be used to describe pretty much any idea or concept, no matter how advanced. We already have tool-using animals that are (relatively) intelligent. Chimps and ravens, for example, are genetically unrelated yet are able to make and use tools. This suggests, perhaps, that the prerequisites to evolve intelligence are not so rare. Anyway, neither ravens nor chimps have developed any form of versatile system of communication that we might call a language. So knowledge of only very simple tools is able to be passed on from individual to individual and generation to generation, and anything as abstract as an "idea"? Forget about it. If a chimp figures out a way to make a good club, that knowledge is probably dying with him. So it seems like the prerequisites to forming an intelligence or society or whatever are 1) Adequate EQ 2) Ability to use tools 3) Ability to distribute advanced information between individuals (i.e. a language) What point am I trying to make? Well language is primarily a social function and it requires a lot of brainpower to create and use, so a society will only form between groups of interdependent, intelligent individuals. So just thinking right now of potential evolutionary pathways that fulfill the conditions for a language (ie, capable of intelligence and live socially): Hive insects Pack hunters Herd Animals And we have a few animals that already fit that description. So I think the "filter" in this case is probably the acquisition of the ability to communicate. Note: I may very well be very wrong. The only authority I have backing me up in this is google and my own navel gazing. Take this with a grain of salt. ---------------- |
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Jun 19, 2015 19:51
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unwantedplatypus posted:I'm talking about the parts of the universe that will never be visible to us. Supposedly, there are parts of the universe that are moving faster than the speed of light relative to us in a direction points away from us. Tebulot posted:I also recall reading an article that proved by way of game theory that the most intelligent decision to make when confronted with alien communication is to just sit down and shut up and pretend we don't exist What, now that we've invented the holodeck and replicator while the galactic civilization has merged consciousness with the ether and transcended mortality we can surely negotiate or beat them if they happen to find us? Surely we should meet them when we're apes compared to them rather than when we're ants compared to them. |
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Jun 20, 2015 22:34
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Those hidden tribes in the Amazon are just gonna get shot by illegal loggers or something |
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Jun 20, 2015 22:36
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If those tribes are so cool why didn't they invent guns and shoot the loggers?
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Jun 20, 2015 22:37
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drilldo gets it |
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Jun 20, 2015 22:39
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drilldo squirt posted:If those tribes are so cool why didn't they invent guns and shoot the loggers?
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Jun 20, 2015 22:48
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I spent 4 hours making that redshift video... How could I make it more approachable or something? Is the typing animated text too slow or something? I had it just show block text at first but it seemed harder to follow what it was supposed to be showing. |
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Jun 20, 2015 22:54
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If it wasnt for Zephram Cochran, humans would've been subjugated by klingons centuries from now and no one would've noticed |
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Jun 20, 2015 22:55
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joke_explainer posted:I spent 4 hours making that redshift video... How could I make it more approachable or something? Is the typing animated text too slow or something? I had it just show block text at first but it seemed harder to follow what it was supposed to be showing. add sound
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Jun 20, 2015 23:01
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joke_explainer posted:As to whether or not there are already large sections of the universe that will forever be unobservable, that largely depends on the final size of the universe which we don't know for sure. Well... the already redshifted light wouldn't un-redshift, but the new light sent by distant objects would reach us. Come to think of it, we might get a mighty fine cosmic background radiation tan, too. |
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Jun 20, 2015 23:08
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or if it starts to contract- I don't really know what the latest thought on the possibility of that is though
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Jun 20, 2015 23:21
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well, since we don't know what's making the universe expand and we don't know what's making galaxies accelerate away from us (aka dark energy), I don't see why it couldn't start contracting for no particular reason e. I bet it's another of Q's little games |
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Jun 20, 2015 23:28
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DeepQantas posted:Surely if there's a "final size" at all (universe stops expanding) then both the theoretically invisible light and the practically invisible light would become visible again? The expansion of the universe is accelerating. Eventually the expansion between the galaxies will outpace the speed of light: The distance between us will be growing by more than 299 792 458 meters per second. So light starts to lag behind, and will never ever catch up. As it continues to get redshifted, there's less and less light occupying more and more area. If diluted one drop of something in a gigantic vessel of water, and keep diluting and keep diluting, eventually the amount of the drop becomes statistically zero. That happens to light too. It's kind of annoying because in the distant, distant future, intelligent life will not be able to discover anything that we have about the origin of the universe. The cosmic microwave background will be gone, and all evidence of other galaxies will be gone too. The only logical conclusion then is that the universe is static, which will be wrong. gently caress. marry. t-rex posted:or if it starts to contract- It would contract if inflation was not involved, but it probably was, and now all of the observational evidence suggests things are so far apart as to no longer be causally linked. All our observations show the universe is flinging itself apart more and more rapidly every second. DeepQantas posted:well, since we don't know what's making the universe expand and we don't know what's making galaxies accelerate away from us (aka dark energy), I don't see why it couldn't start contracting for no particular reason It's tempting to imagine the laws of the universe might change arbitrarily, but these measurements are consistent across a lot of different methods of observing and many different fields. Things don't seem to change much. Though, one alternate explanation for the 'inflation' effects is models proposing the speed of light is variable, which is kind of interesting. But that's a huge can of worms I doubt I could adequately cover... |
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Jun 20, 2015 23:40
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well there's the massive inflation period after the big bang so the speed of the expansion has already changed seemingly arbitrarily. that is to say... who knows how or why? |
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Jun 20, 2015 23:56
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DeepQantas posted:well there's the massive inflation period after the big bang so the speed of the expansion has already changed seemingly arbitrarily. that is to say... who knows how or why? Inflation would be hardly arbitrary. It would necessitate a very specific set of circumstances. It also took place in billionths of a microsecond, where the universe went from smaller than an atom to the size of a grapefruit, where all future matter in the universe was a cloud of energy within that tiny sphere, predating even the forces the would lead to light. We'd see more evidence for the changing of physical properties in the intervening billions of years if they were likely to change, but no matter what direction we look (or how far back in time), things seem roughly isotropic, which is one of the big problems which led to theorizing inflation in the first place. joke_explainer fucked around with this message at 03:06 on Jun 21, 2015 |
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Jun 21, 2015 01:18
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big bung |
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Jun 21, 2015 02:16
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mycophobia posted:big bung Yeah ok I can't top that. Go ahead and goldmine it Cumt the minkowski demo is too complicated to shoehorn in here. |
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Jun 21, 2015 04:04
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| # ? May 2, 2024 17:12 |
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Great thread |
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Jun 21, 2015 04:26
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