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To expand on this, light can only travel at light speed because photons don't have mass and infinity times zero is still zero.
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Dec 10, 2019 22:09
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DrSunshine posted:It comes from special relativity, and comes out as a consequence of the mass-energy equivalence - E=mc^2. Without getting into the math of it, accelerating requires energy, and energy is the same as mass. It only becomes relevant as you approach the speed of light, but essentially it becomes exponentially more and more energy-intensive to accelerate something the closer and closer you get to light speed, because the faster you go, the more massive you are because the more energy you have. This means that you would require infinite energy to accelerate to light speed. Thank you for not calling me a moron.  I might just not be smart enough to get it. I don't think I understand the terms. Let's say we're shooting a dime at FTL and have, somehow, created an accelerating device that is only the weight of another dime that we've attached to it. I don't want to use the term "magic", but lets say the second dime can harness the energy of a sun or whatever. Why would the acceleration just stop? Like we could get to 99.9% of light speed, but not light speed, because...?
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Dec 10, 2019 22:14
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You would infinitely accelerate but your rate of acceleration would exponentially decrease as you approach the speed of light (as it will take more energy to accelerate the same amount the faster you are going) so you will never get there.
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Dec 10, 2019 22:18
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1glitch0 posted:Thank you for not calling me a moron. Only things without mass can actually reach the speed of light. Photons, the packet of energy that we know as light, does not have any mass. Things without mass can only travel at the speed of light. As soon as something has mass, it cannot ever reach light speed. It can get really close, but the closer it gets, the more massive it is, which then requires more energy to make it go faster. watch this and see if it sheds some massless packets of energy onto the situation https://www.youtube.com/watch?v=msVuCEs8Ydo
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Dec 10, 2019 22:45
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1glitch0 posted:Thank you for not calling me a moron. the way i've heard it explain is that as you approach the speed of light, you actually begin to accumulate mass when energy is further applied. So all that happens is the dime is going to gain mass as you apply more energy to it. E=mc^2 is a constant, not an equation (or something like that). so because c = sqrt(E/m), as energy increases, so must mass.
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Dec 10, 2019 23:23
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1glitch0 posted:Thank you for not calling me a moron. It's like you're on a treadmill that continually gets faster and faster, no matter how hard you try, no matter how hard you run. Or-- Let's say I'm running, and I look up ahead, and I only have a mile left. But somehow, God is interfering with me. As soon as I reach the halfway mark, God doubles the amount of distance left. I speed up, and reach it again. God multiplies the distance left by 4. I try to speed up, but every time I reach the halfway mark, God doubles the distance again, and again and again. By the third time, God multiplies it by 8, then 16, then 32, then 64 and so on. It's plain to see that I will never, ever, ever reach the end because as long as I move forward, God is always doubling the distance left to run faster than I can move. EDIT: With your dime, say it is moving 99.9% of light speed. Fair enough! It's moving very fast. But if you want to move it at 99.99% light speed, say that costs 1 Tiberium. Great! Now it's moving that much faster. But if you want to go from 99.99%, it costs 100 Tiberium. To go to 99.999%, it costs 10,000 Tiberium. To get to 99.9999% it costs 10000000 Tiberium! You can expend all the Tiberium you want, but you'll never get to 100% because you would need to expend an infinite amount of Tiberium to get there. DrSunshine fucked around with this message at 00:09 on Dec 11, 2019 |
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Dec 10, 2019 23:57
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Everything in the universe moves at the speed of light. You're only allowed to change direction. You can be moving through time and moving through space, but you can't move at the speed of light through space and also move forward through time. We spend our lives moving more or less at the speed of light in the timeward direction.
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Dec 11, 2019 00:14
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Arglebargle III posted:Everything in the universe moves at the speed of light. This is not correct at all. Arglebargle III posted:You're only allowed to change direction. No Arglebargle III posted:You can be moving through time and moving through space, but you can't move at the speed of light through space and also move forward through time. Also No. Time and space are not separate things. Spacetime is one thing. nothing can truly be stationary, ever, because you are always moving in one way or another. Arglebargle III posted:but you can't move at the speed of light through space and also move forward through time. Close. Only massless particles can travel at the speed of light, and they experience no spacetime between source and destination. It's not just time that is zeroed out, but space as well.
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Dec 11, 2019 00:24
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A lot of people with physics degrees get this wrong or express this wrong at least. The speed of light is not the maximum speed in the universe. This is a really important point for understanding special relativity. The speed of light is the only speed in the universe. The universe is not a space that has the magical property that nothing can go faster than c. The universe is a spacetime that has the property that everything in it moves at c. Science youtube channels are exactly the place where you'll get the first, wrong answer reinforced so really do go read a book though. I recommend Why Does E=MC2 by Brian Cox and Jeff Forshaw. Arglebargle III fucked around with this message at 01:06 on Dec 11, 2019 |
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Dec 11, 2019 00:54
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Arglebargle III posted:A lot of people with physics degrees get this wrong or express this wrong at least. You just expressed it entirely wrong yourself, so do you have a YouTube channel i can throw under the bus? PBS spacetime is not a Chanel that gets it wrong as far as my limited understanding goes.
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Dec 11, 2019 01:12
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Feh to all of that. You may think you get this. You may think you comprehend it, even that you comprehend it well. I know I did. What did I need the math for? I got the concept. Plus, I suck at math. Turns out, when I needed to go deeper, I had to learn the math. As I said, I suck at math, so it was hard. But I loving did it. And you know what? I didn't know it without the math. I didn't understand it. I thought I comprehended it, but what I had comprehended was empty. The math helped me really understand. It made the concept sing. It was worth the effort. Forget analogies. If you want to really know how it works, dedicate yourself to learning the math. Otherwise, you're cheating yourself. Maybe you're fine with that, but I know I wasn't.
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Dec 11, 2019 01:26
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This thread really wants me to start a youtube channel.
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Dec 11, 2019 01:27
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1glitch0 posted:Thank you for not calling me a moron. (Don't want to get into a whole thing about the actual mathematics, just saying if you want to get the gist, imagine that.)
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Dec 11, 2019 01:54
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Arglebargle III posted:A lot of people with physics degrees get this wrong or express this wrong at least.
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Dec 11, 2019 02:02
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Owlofcreamcheese posted:FTL itself isn't specifically in to the past time travel. It is, though. FTL = Time Travel, there's no grand limit on this. If you can travel at FTL speeds, you can engage in time travel. Owlofcreamcheese posted:It just allows time travel by moving between referance frames. If you do that, you are time travelling. If you move at FTL speeds away from the Earth, then return at FTL speeds, you can arrive an arbitrary amount of time before you left, i.e. time travel into the past. Owlofcreamcheese posted:Which like, I guess if you are doing something so weird and it messes up causality that would suck but consequences being weird if you take them to the edges doesn't mean they can't happen. Any time you move at FTL speeds you are breaking causality. I come back to Atomic Rocket because they did write-ups on this with useful diagrams for grasping the causality violations that FTL anything causes. Project Rho posted:However, faster-than-light communication (which includes travel) breaks something very fundamental about physics, something that is often ignored by sci-fi, and difficult for non-physicists to understand. If you allow faster-than-light (FTL), then you break causality: you are allowing time-travel. One pithy way of saying this is:
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Dec 11, 2019 02:14
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ashpanash posted:Feh to all of that. I know enough of the math to know that i don't know enough math to have a true understanding. However, there's nothing wrong with starting at a conceptual level and parsing what you can. That's one nice thing about some science channels, they make some of the high level math accessible.
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Dec 11, 2019 03:31
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I thought infinity times zero is undefined?
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Dec 11, 2019 03:35
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Arglebargle III posted:I thought infinity times zero is undefined? it depends on what infinity
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Dec 11, 2019 03:59
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LtStorm posted:It is, though. FTL = Time Travel, there's no grand limit on this. If you can travel at FTL speeds, you can engage in time travel. theres no such thing as global causality in GR though. The space-time of General Relativity is a Pseudo-Riemannian Manifold. That means that while it isn't necessarily flat, you can always take a small enough region of space that locally it behaves just like Minkowski space. This is why any principle that applies in Special Relativity globally must apply to General Relativity locally. Speed of light is a global limit in SR, but a local one in GR. Causality is globally enforced in SR, but only locally in GR. And so on. We have fields that satisfy certain conditions locally, which gives you local causality. But global structure is determined by the Lagrangian and boundary conditions. In the big picture, there isn't a cause-and-effect, because the entire structure is already predetermined. If you have a flat space-time, you can use the local causality to build up a causal timeline, which is basically what we're doing. But having exceptions to that simply isn't a contradiction. PawParole fucked around with this message at 13:41 on Dec 11, 2019 |
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Dec 11, 2019 13:33
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ashpanash posted:From what I remember, the EMDrive guy didn't have an argument either, he just built this thing and measured some thrust from it. When he attempted to explain it in some way, he had to resort to weird, utterly nonsensical poo poo like 'bouncing off pilot waves' in order to explain how it worked. Basically, yeah. Also conservation of momentum is a prrtty big deal, Noether's theorem (a badass math lady btw) means it is mathematical fact in spacetime. You really need crazy speculative quantum poo poo to be true to even begin to break it. A misshaped microwave ain't gonna cut it.
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Dec 11, 2019 13:55
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Libluini posted:I think the Einstein-Rosen Bridge isn't possible at all, at least I've read on Wikipedia/Scientific American that an Einstein-Rosen Bridge is defined as a wormhole between a black hole and a white hole and since we never found evidence for white holes, they probably don't exist. Do wormholes between two black holes have their own term to describe them, or are people just calling them Einstein-Rosen Bridges anyway? So properly explaining this would require me to get into math and drawing spacetime diagrams that I did enough of for life, but the short of it is an ER bridge is what happens when you describe a black hole in a certain coordinate system. Since GR is invariant under choice of coordinates, this is valid. Except now you can extend the coordinates beyond what a BH is, and get an object on the other side, basically kinda like assuming you can be a negative distance away from a black hole. That's a white hole. We can guess at it's properties if it were to exist, but the question is if this is simply a mathematical curiosity or something that is physically meaningful. An ER bridge is then changing the coordinates in spacetime and picking a path in those coordinates that allows you to cross from one to the other, and is why it's often considered the most viable type of wormhole. quote:On the galaxies without dark matter thing, I believe I've read something about that on Scientific American, too. Wasn't there a controversy about how the observations of seemingly dark matter-less galaxies were interpreted or were the new papers after that and about something even newer? There was controversy - very rightly, even if borne out of the niche I have mentioned - but these are new findings. I'm on mobile so can't really easily chuck in the links but you should be able to find those two papers if you search in google. quote:But at least I would hold back before judging this new development. I've read Sabine Hossenfelder describing how the diphoton-thing went down and I was embarrassed by proxy by all the time that was wasted by what was essentially, just white noise in the LHC-data. Sure, there have been some absolute clunkers in particle physics. Pentaquark was another thing. That said, standard of proof in physics is really high generally. In medicine/sociology, most research findings are false due to high p value, p hacking, and most hypotheses are false which means false positives far outweigh the correct positives. We should of course reserve some judgment, but it is far from only proof, just the latest in line. quote:For all we know, we may already have found some Dyson sphere-like constructions. Some of the systems near us behave oddly, with something dimming the light in regular patterns. All the conventional explanations for the observations so far (dust clouds, really dense Oort clouds, etc.) have certainly been plausible, but non of them cover all aspects of the observations perfectly. There's always something missing were astronomers have to shrug and wait for better data. My personal bet is 5% chance of at least one of them being aliens.
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Dec 11, 2019 14:15
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ashpanash posted:Feh to all of that. This is 100 percent accurate.
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Dec 11, 2019 14:21
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PawParole posted:theres no such thing as global causality in GR though. The space-time of General Relativity is a Pseudo-Riemannian Manifold. That means that while it isn't necessarily flat, you can always take a small enough region of space that locally it behaves just like Minkowski space. This is why any principle that applies in Special Relativity globally must apply to General Relativity locally. Speed of light is a global limit in SR, but a local one in GR. Causality is globally enforced in SR, but only locally in GR. And so on. While this is true, a closed timelike curve in GR is a very iffy subject. They are probably possible since a Kerr spacetime contains them, and in the exterior it is a physical solution that we don't have a reason to doubt for the interior outside the singularity. Very disconcerting, but cosmic censorship saves us here. Of course censorship is a philosophical argument, and you can invent more audacious arguments how a CTC could work outside of an event horizon. Those are real murky waters to tread. E; sorry for post spam but there were lots of things I wanted to respond to and it would be tricky to do in one post on mobile. dex_sda fucked around with this message at 14:33 on Dec 11, 2019 |
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Dec 11, 2019 14:30
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Thank christ that the last several posts have been actually and genuinely interesting physics and math discussions. I feel like I'm getting a sneak peak into the cutting edge. One of the older posts that was, "Sometimes physics actually has a certain simplicity/elegance to it" was also deeply fascinating.
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Dec 11, 2019 14:45
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LtStorm posted:Any time you move at FTL speeds you are breaking causality. What if you do though? "Then would be really weird and bad!" is a reason to not want something to be possible, not a protection that it isn't possible. It'd be really hosed up if causality was just a local condition but like, "it'd be really hosed up! No I mean, like really hosed up! can you imagine? gently caress, that would be way too hosed up" isn't a reason something can't be.
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Dec 11, 2019 15:06
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There's also for example some theories that maybe wormholes have some kind of self-correcting measure to prevent causality breaking down.
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Dec 11, 2019 15:22
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Raenir Salazar posted:There's also for example some theories that maybe wormholes have some kind of self-correcting measure to prevent causality breaking down. Yeah, that's the handwavy stuff I alluded to. It's got holes (tautological in nature for one thing), though some arguments we hold as likely true also do, so real iffy to talk about, and very metaphysical.
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Dec 11, 2019 15:43
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Owlofcreamcheese posted:What if you do though? "Then would be really weird and bad!" is a reason to not want something to be possible, not a protection that it isn't possible. It'd be really hosed up if causality was just a local condition but like, "it'd be really hosed up! No I mean, like really hosed up! can you imagine? gently caress, that would be way too hosed up" isn't a reason something can't be. Bu you can't have cause precede effect! All of our current physics is based on this premise, and physics explains the universe with unbelievable accuracy and precision: "The Standard Model can make predictions that match experiments to one part in 10 billion." General Relativity has been measured fantastically accurately as well. Our confidence in physics is based on how well it explains the observations we make, so if you throw out causality, you'd have to supply evidence that beats out the current models of physics with greater accuracy and better predictive power than anything we have right now. EDIT: Look at this cool picture of a gravitational lens, captured by the Hubble Space Telescope. Wow!
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Dec 11, 2019 17:04
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We have like an even better camera being put up at one of the Lagrange points right?
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Dec 11, 2019 17:07
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Raenir Salazar posted:We have like an even better camera being put up at one of the Lagrange points right?  Yes it's definitely launching in 20
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Dec 11, 2019 17:25
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eXXon posted:
gently caress I hope JWST makes it up eventually. The latest news was that the sun shield deployment passed some tests. https://www.nasa.gov/feature/goddard/2019/nasa-s-james-webb-space-telescope-clears-critical-sunshield-deployment-testing With the luck we've had so far, it's going to blow on one of Musk's rockets halfway to L1.
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Dec 11, 2019 17:42
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ashpanash posted:From what I remember, the EMDrive guy didn't have an argument either, he just built this thing and measured some thrust from it. When he attempted to explain it in some way, he had to resort to weird, utterly nonsensical poo poo like 'bouncing off pilot waves' in order to explain how it worked. No he has an argument. It is on his website. It isn’t grossly wrong—there is some subtle flaw in his argument that I’m not getting.
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Dec 11, 2019 22:14
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i reckon theres aliens. if they're so smart we can't even comprehend it then it stands to reason we just aren't smart enough to figure out what to look for or where. our grasp of physics and whatnot is just too primitive. sort of like how ants don't really comprehend what a human is.
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Dec 11, 2019 22:17
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Owlofcreamcheese posted:What if you do though? "Then would be really weird and bad!" is a reason to not want something to be possible, not a protection that it isn't possible. It'd be really hosed up if causality was just a local condition but like, "it'd be really hosed up! No I mean, like really hosed up! can you imagine? gently caress, that would be way too hosed up" isn't a reason something can't be. oocc I don't think you appreciate the magnitude of a statement like "causality isn't true"
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Dec 11, 2019 22:20
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A big flaming stink posted:oocc I don't think you appreciate the magnitude of a statement like "causality isn't true" I've only got a very shaky grasp on things but my understanding of if "causality isn't true" would mean things 'just happen'. Surely we'd see more unicorns?
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Dec 11, 2019 22:25
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Owlofcreamcheese posted:What if you do though? "Then would be really weird and bad!" is a reason to not want something to be possible, not a protection that it isn't possible. It'd be really hosed up if causality was just a local condition but like, "it'd be really hosed up! No I mean, like really hosed up! can you imagine? gently caress, that would be way too hosed up" isn't a reason something can't be. This: A big flaming stink posted:oocc I don't think you appreciate the magnitude of a statement like "causality isn't true" If a post is made in a forum and no one is there to read it, does it still exist? Who knows! But for a post to have been made, someone has to make it. Posts don't just appear fully formed out of nowhere. Calling causality into question also casts into debate lots of things we can see and verify, like posts.
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Dec 11, 2019 23:23
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Trainee PornStar posted:I've only got a very shaky grasp on things but my understanding of if "causality isn't true" would mean things 'just happen'. i mean, everything we understand is predicated on logic, and logic is predicated on causality. if causality is not true, then we literally know nothing. the fact that everything we have observed up to this time appears to follow causality just means that our observations are also worthless. like, imagine if every time you observed anything you would have to give equal consideration to hume's problem of induction. at that point solipsism becomes a valid interpretation of reality. A big flaming stink fucked around with this message at 23:33 on Dec 11, 2019 |
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Dec 11, 2019 23:29
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It's also possible that actual FTL travel or tachyon technology requires updating the equations we use for Lorentz transformations between reference frames or time dilation, or the tachyons themselves don't travel in straight lines through time or some such exotic physics so reference frames don't end up with negative time factors. Obviously if faster-than-light phenomena exist, there are physics about them that we don't currently understand. If the physics laws we know about allowed FTL properties, we'd already have figured out how they work.
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Dec 12, 2019 01:43
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Infinite Karma posted:It's also possible that actual FTL travel or tachyon technology requires updating the equations we use for Lorentz transformations between reference frames or time dilation, or the tachyons themselves don't travel in straight lines through time or some such exotic physics so reference frames don't end up with negative time factors. im not sure if this works. Even if we can "cheat" with regards to distance, etc, that still would allow information to propagate at faster than the speed of light which, again, renders causality on shaky grounds.
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Dec 12, 2019 01:58
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http://www.projectrho.com/public_html/rocket/fasterlight.php#exultant posted:Time was slippery. The way Pirius understood it, it was only the speed of light that imposed causal sequences on events.
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Dec 12, 2019 02:10
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