Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you:
No adverts like this in the forums anymore.
Times and dates in your local timezone.
Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance.
Email notifications for threads you want to watch closely.
Being a part of the oldest wargaming community on the net.
If you are already a member then feel free to login now.
Mad Doc Grotsnik wrote: As someone utterly ignorant of the physics behind why we can't exceed the speed of light, I think Just Tony has an interesting point.
I'm a complete layman to this with nothing more advanced than GCSE Physics, but my understanding based on what has been explained to me is that whilst in very basic theory all you'd have to do is point a spaceship at an area of empty space and just keep accelerating, the faster it's going the more energy would be required to accelerate it further up to the point that it'd take more energy than could ever be available in total to push it over the light barrier.
(Having said all that, I now sit back and wait for someone better qualified (Which means practically anyone ) to tell me I've got that completely wrong!)
This message was edited 1 time. Last update was at 2018/04/05 15:15:43
simonr1978 wrote: I'm a complete layman to this with nothing more advanced than GCSE Physics, but my understanding based on what has been explained to me is that whilst in very basic theory all you'd have to do is point a spaceship at an area of empty space and just keep accelerating, the faster it's going the more energy would be required to accelerate it further up to the point that it'd take more energy than could ever be available in total to push it over the light barrier.
Not just more energy than exists in total, literally infinite energy. It's not a question of "we can't find enough fuel" that could be solved by more efficient engines or whatever, it is impossible to accelerate to the speed of light.
There is no such thing as a hobby without politics. "Leave politics at the door" is itself a political statement, an endorsement of the status quo and an attempt to silence dissenting voices.
simonr1978 wrote: I'm a complete layman to this with nothing more advanced than GCSE Physics, but my understanding based on what has been explained to me is that whilst in very basic theory all you'd have to do is point a spaceship at an area of empty space and just keep accelerating, the faster it's going the more energy would be required to accelerate it further up to the point that it'd take more energy than could ever be available in total to push it over the light barrier.
Not just more energy than exists in total, literally infinite energy.
I nearly put that but wasn't 100% confident, thanks Peregrine.
Just Tony wrote: That's pretty much it in a nutshell. Some people can't get past the speed of light as the hard stop. I'm not old enough to remember when the speed of sound was the unattainable speed, but I've read and watched enough on it to realize that the consensus was wrong the second Chuck Yeager broke that barrier.
That is not a valid comparison at all. The speed of sound was a barrier for manned aircraft, not a hard barrier in general. A simple rifle bullet could exceed the speed of sound easily, and there was no question about that. The barrier factor was in two parts: propeller-driven aircraft can not get enough power to go that fast (the prop tips start breaking the sound barrier and suffer crippling efficiency losses), and that current structural designs were not able to sustain the aerodynamic forces. Controls locked up and required more than human strength to operate, and catastrophic structural failure followed soon after. Everyone knew that the barrier would likely be broken at some point, once the engineering challenges were overcome, Yeager (flying a plane developed by a well-funded research program) just got there first.
The speed of light, on the other hand, is an absolute limit. It requires infinite energy to accelerate to the speed of light, no matter how you design your spacecraft. This is a consequence of relativity, and the governing equations have been well proven by observation and theory. It's possible that we're wrong about everything, but it's incredibly unlikely and any alternative theory would somehow have to explain our observations that currently follow the equations for relativity. There's just no credible reason to suspect that we're wrong on this.
This message was edited 1 time. Last update was at 2018/04/05 15:58:04
There is no such thing as a hobby without politics. "Leave politics at the door" is itself a political statement, an endorsement of the status quo and an attempt to silence dissenting voices.
Just Tony wrote: That's pretty much it in a nutshell. Some people can't get past the speed of light as the hard stop. I'm not old enough to remember when the speed of sound was the unattainable speed, but I've read and watched enough on it to realize that the consensus was wrong the second Chuck Yeager broke that barrier.
That is not a valid comparison at all. The speed of sound was a barrier for manned aircraft, not a hard barrier in general. A simple rifle bullet could exceed the speed of sound easily, and there was no question about that. The barrier factor was in two parts: propeller-driven aircraft can not get enough power to go that fast (the prop tips start breaking the sound barrier and suffer crippling efficiency losses), and that current structural designs were not able to sustain the aerodynamic forces. Controls locked up and required more than human strength to operate, and catastrophic structural failure followed soon after. Everyone knew that the barrier would likely be broken at some point, once the engineering challenges were overcome, Yeager (flying a plane developed by a well-funded research program) just got there first.
The speed of light, on the other hand, is an absolute limit. It requires infinite energy to accelerate to the speed of light, no matter how you design your spacecraft. This is a consequence of relativity, and the governing equations have been well proven by observation and theory. It's possible that we're wrong about everything, but it's incredibly unlikely and any alternative theory would somehow have to explain our observations that currently follow the equations for relativity. There's just no credible reason to suspect that we're wrong on this.
Not yet. The great thing about science is that we keep discovering new things, so our current understanding of physics and the speed of light will undoubtedly develop further. As of our current understanding, the speed of light is a hard barrier. Traveling at the speed of light is impossible, going faster even more. But who knows what new theories will be developed in the next 50-100 years, let alone the next 1000? Maybe, some day in the far future we might even find a way to actually travel at light speed. But if such a day ever comes, it is still a long, long way into the future.
Just Tony wrote: That's pretty much it in a nutshell. Some people can't get past the speed of light as the hard stop. I'm not old enough to remember when the speed of sound was the unattainable speed, but I've read and watched enough on it to realize that the consensus was wrong the second Chuck Yeager broke that barrier.
That is not a valid comparison at all. The speed of sound was a barrier for manned aircraft, not a hard barrier in general. A simple rifle bullet could exceed the speed of sound easily, and there was no question about that. The barrier factor was in two parts: propeller-driven aircraft can not get enough power to go that fast (the prop tips start breaking the sound barrier and suffer crippling efficiency losses), and that current structural designs were not able to sustain the aerodynamic forces. Controls locked up and required more than human strength to operate, and catastrophic structural failure followed soon after. Everyone knew that the barrier would likely be broken at some point, once the engineering challenges were overcome, Yeager (flying a plane developed by a well-funded research program) just got there first.
The speed of light, on the other hand, is an absolute limit. It requires infinite energy to accelerate to the speed of light, no matter how you design your spacecraft. This is a consequence of relativity, and the governing equations have been well proven by observation and theory. It's possible that we're wrong about everything, but it's incredibly unlikely and any alternative theory would somehow have to explain our observations that currently follow the equations for relativity. There's just no credible reason to suspect that we're wrong on this.
Not yet. The great thing about science is that we keep discovering new things, so our current understanding of physics and the speed of light will undoubtedly develop further. As of our current understanding, the speed of light is a hard barrier. Traveling at the speed of light is impossible, going faster even more. But who knows what new theories will be developed in the next 50-100 years, let alone the next 1000? Maybe, some day in the far future we might even find a way to actually travel at light speed. But if such a day ever comes, it is still a long, long way into the future.
Any new theory has to account for the observations validated by previous theories. If the speed of light is not a universal absolute, special relativity doesn't work and nor does [i]causality[i] itself.
If you can travel faster than light then you can observe an event happening, then travel to that event and arrive prior to the event occurring and prevent it from ever happening from the reference frame of a different observer. This violates one of special relativity's fundamental and testable foundations, that all reference frames are equally valid and the laws of physics are the same in all reference frames.
This message was edited 1 time. Last update was at 2018/04/05 17:18:46
The Laws of Thermodynamics:
1) You cannot win. 2) You cannot break even. 3) You cannot stop playing the game.
Colonel Flagg wrote:You think you're real smart. But you're not smart; you're dumb. Very dumb. But you've met your match in me.
If you can travel faster than light then you can observe an event happening, then travel to that event and arrive prior to the event occurring and prevent it from ever happening from the reference frame of a different observer. This violates one of special relativity's fundamental and testable foundations, that all reference frames are equally valid and the laws of physics are the same in all reference frames.
I may be being dim here but can you explain this to me in an "Idiot's Guide" way? The closer you can get to a kind of "See Spot run" level of understanding for my benefit the better.
If you have seen an event happening then being able to travel faster than the speed of light surely wouldn't mean you could effectively travel upstream and arrive back in time because you're starting from a point already after that light has reached your position. I can see how it would enable you to outpace that light and prevent someone further away from seeing that event, but I can't grasp how that would inherently allow to backwards time travel to a point before it occurred.
Pacific wrote: What I find quite interesting at the moment is that you have literally the biggest fodder for conspiracy theories ever, with an investigation into collusion between aspects of the White House and Russia and the prospect that the country is being influenced/coerced by a foreign power, and the quarters from which the theories usually spring is completely ignoring it.
Exactly.
I've had a conversation exactly like this with my sister. She's been a conspiracy nut for years, JFK was her gateway drug, but she's dabbled in all kinds of stuff, not cryptozoology but all the various government conspiracy stuff. So she's argued some 9/11 truther nonsense, and more recently pizzagate and Seth Rich stuff. And yet, she absolutely rejects any notion of Trump/Russia, she rejects the one conspiracy theory that's been taken seriously by people in positions to know if something should be taken seriously. The one that's produced indictments and guilty pleas is the one she doesn't give the time of day. If she's pressed on the issue, she'll start on some stuff about the deep state and the whole thing being a Clinton set up, somehow, it's really weird.
It's given me a bit more insight in to what is actually going with conspiracy believers. Not enough to, you know, make a coherent explanation for what's happening, or suggest a method for bringing people out of this crazy or anything useful like that, but still I understand a little more after seeing that part of my sister's approach. Thing is, I think as well as a natural tendency to believe an exciting story, and a desire to be part of select group who are in the know about the world's secrets, there's also a strong counter-cultural factor at play. That last one explains why conspiracy nuts would reject the one conspiracy that the FBI takes seriously. It also explains why the conspiracy nuts tends to broadly shift against the flow of politics, why it tends to have a drift left or right in opposition to who's in power at that point in time.
Automatically Appended Next Post:
Just Tony wrote: What I'm saying is that we are in our infancy with understanding the plausibility of photodynamics. Think about magnets for a second. At one time we knew that lodestone stuck to iron. That's it. Now, since we've advanced, not only do we know WHY that happens, we can measure magnetic fields, and even PRODUCE magnetic fields. My argument is that our current understanding of the speed of light and any possibility of exceeding it is as backwater as pre-electricity humans and magnetism. We already have a device that is breaking Newtonian law that NASA is supposed to be testing in zero gravity (blanking on the name of the drive, but it's the one with the weird copper cone...) so we're nowhere NEAR the complete understanding of that part of physics to say "never".
Sure, never say never. But also appreciate this is an idea way beyond anything we've ever managed before. We didn't know why magnets worked, but we could observe it happening. Another common comparison is to manned flight which some had thought impossible, but we had seen stuff fly - we might not have known if we could achieve the engineering capability needed for flight, but we knew flight was possible. The same is true for your example of breaking the sound barrier - we had seen plenty of stuff move faster than the speed of sound, we just didn't know if we could get a manned plane to do it.
In comparison, literally nothing we have ever observed has ever been capable of exceeding the speed of light. We do not have even a proposed mechanism that could make it happen.
That doesn't mean we are destined to never figure out a way to do it or bypass it, but we should we appreciative of it being a challenge way beyond anything else we've ever attempted.
This message was edited 3 times. Last update was at 2018/04/06 03:21:05
“We may observe that the government in a civilized country is much more expensive than in a barbarous one; and when we say that one government is more expensive than another, it is the same as if we said that that one country is farther advanced in improvement than another. To say that the government is expensive and the people not oppressed is to say that the people are rich.”
Adam Smith, who must have been some kind of leftie or something.
Pacific wrote: What I find quite interesting at the moment is that you have literally the biggest fodder for conspiracy theories ever, with an investigation into collusion between aspects of the White House and Russia and the prospect that the country is being influenced/coerced by a foreign power, and the quarters from which the theories usually spring is completely ignoring it.
Exactly.
I've had a conversation exactly like this with my sister. She's been a conspiracy nut for years, JFK was her gateway drug, but she's dabbled in all kinds of stuff, not cryptozoology but all the various government conspiracy stuff. So she's argued some 9/11 truther nonsense, and more recently pizzagate and Seth Rich stuff. And yet, she absolutely rejects any notion of Trump/Russia, she rejects the one conspiracy theory that's been taken seriously by people in positions to know if something should be taken seriously. The one that's produced indictments and guilty pleas is the one she doesn't give the time of day. If she's pressed on the issue, she'll start on some stuff about the deep state and the whole thing being a Clinton set up, somehow, it's really weird.
It's given me a bit more insight in to what is actually going with conspiracy believers. Not enough to, you know, make a coherent explanation for what's happening, or suggest a method for bringing people out of this crazy or anything useful like that, but still I understand a little more after seeing that part of my sister's approach. Thing is, I think as well as a natural tendency to believe an exciting story, and a desire to be part of select group who are in the know about the world's secrets, there's also a strong counter-cultural factor at play. That last one explains why conspiracy nuts would reject the one conspiracy that the FBI takes seriously. It also explains why the conspiracy nuts tends to broadly shift against the flow of politics, why it tends to have a drift left or right in opposition to who's in power at that point in time.
Automatically Appended Next Post:
Just Tony wrote: What I'm saying is that we are in our infancy with understanding the plausibility of photodynamics. Think about magnets for a second. At one time we knew that lodestone stuck to iron. That's it. Now, since we've advanced, not only do we know WHY that happens, we can measure magnetic fields, and even PRODUCE magnetic fields. My argument is that our current understanding of the speed of light and any possibility of exceeding it is as backwater as pre-electricity humans and magnetism. We already have a device that is breaking Newtonian law that NASA is supposed to be testing in zero gravity (blanking on the name of the drive, but it's the one with the weird copper cone...) so we're nowhere NEAR the complete understanding of that part of physics to say "never".
Sure, never say never. But also appreciate this is an idea way beyond anything we've ever managed before. We didn't know why magnets worked, but we could observe it happening. Another common comparison is to manned flight which some had thought impossible, but we had seen stuff fly - we might not have known if we could achieve the engineering capability needed for flight, but we knew flight was possible. The same is true for your example of breaking the sound barrier - we had seen plenty of stuff move faster than the speed of sound, we just didn't know if we could get a manned plane to do it.
In comparison, literally nothing we have ever observed has ever been capable of exceeding the speed of light. We do not have even a proposed mechanism that could make it happen.
That doesn't mean we are destined to never figure out a way to do it or bypass it, but we should we appreciative of it being a challenge way beyond anything else we've ever attempted.
The crux of this that I want to point out is OUR understanding. OUR. The conspiracy theory (maybe, maybe not) of extraterrestrial life visiting the planet (repeatedly, some would say) depends on how those extraterrestrials can understand and manipulate FTL travel. Not us. The reason so many people dismiss the idea is the pure ego of the human race. We couldn't possibly accept that somewhere in the universe there's someone better than us.
Just Tony wrote: The crux of this that I want to point out is OUR understanding. OUR. The conspiracy theory (maybe, maybe not) of extraterrestrial life visiting the planet (repeatedly, some would say) depends on how those extraterrestrials can understand and manipulate FTL travel. Not us. The reason so many people dismiss the idea is the pure ego of the human race. We couldn't possibly accept that somewhere in the universe there's someone better than us.
Having a bigger brain doesn't change the basic laws of the universe. There isn't a point of cleverness where gravity just stops being a thing. It's the same for the speed of light. No matter how clever we might imagine an alien creature to be, the speed of light remains a hard, universal constant.
The issue is fundamentally nothing to do with any level of cleverness. It is about the speed of light being a universal constant.
Now we can make up fun ideas about wormholes and warp drives and other stuff, or dream of an alien species that thought of some other way to get around this idea and maybe one of those ideas might end up being true.
But what we can't do is say 'oh humans in the past overcome engineering challenges that were thought impossible, therefore we should expect that it is also possible to overcome the basic laws of the galaxy'. They're just not the same thing.
“We may observe that the government in a civilized country is much more expensive than in a barbarous one; and when we say that one government is more expensive than another, it is the same as if we said that that one country is farther advanced in improvement than another. To say that the government is expensive and the people not oppressed is to say that the people are rich.”
Adam Smith, who must have been some kind of leftie or something.
2018/04/06 06:20:33
Subject: Re:Conspiracy Theories: What's your take?
Waiting for my shill money from Spiral Arm Studios
Pretty much the only way that its possible to exceed the speed of light without violating the laws of physics is to "cheat" by bending space in some fashion(Star Trek Warp Drives), or moving into another dimension through one hole and out another hole back into this dimension(wormholes, 40k Warp Travel, Star Wars Hyperdrives). Such that from your perspective you don't exceed the speed of light, and thus need infinite energy, yet from the perspective of the rest of the universe you appear to be exceeding the speed of light.
I don't think aliens have visited this planet, i don't think Aliens exist period. But if and when humans do develop "FTL" technology, it will be one of the above methods. We'll learn to bend space or travel to adjacent dimensions to side-step vast distances, because any other method as far as we know is impossible for traveling between stars in a timely fashion.
Alien conspiracy theories most likely arose from civilians seeing military prototypes being tested and not understanding what they were. Then the government possibly engaged in feeding the conspiracy theories a little to act as a smoke screen for the actual projects that were witnessed.
This message was edited 1 time. Last update was at 2018/04/06 06:22:59
Self-proclaimed evil Cat-person. Dues Ex Felines
Cato Sicarius, after force feeding Captain Ventris a copy of the Codex Astartes for having the audacity to play Deathwatch, chokes to death on his own D-baggery after finding Calgar assembling his new Eldar army.
When it comes to aliens (and with no intention to berate or belittle fellow posters), I've always felt it supremely arrogant to believe we're the only intelligent life in the galaxy, let alone the universe.
Now. Are they visiting earth? Probably not. Will we ever come across each other? Well, possibly. But not for a long time I'd imagine.
Fed up of Scalpers? But still want your Exclusives? Why not join us?
Mad Doc Grotsnik wrote: When it comes to aliens (and with no intention to berate or belittle fellow posters), I've always felt it supremely arrogant to believe we're the only intelligent life in the galaxy, let alone the universe.
Now. Are they visiting earth? Probably not. Will we ever come across each other? Well, possibly. But not for a long time I'd imagine.
It's not arrogance, it statistics. The Universe is so large the odds of there being no other life (intelligent or otherwise) is so extraordinarily low, that the concept of us being alone is utterly absurd. Now visiting Earth? Unlikely and to be frank, if aliens had that sort of technology, why would they even bother coming down here? We'd probably be more like a neat scientific observation. Something to be looked at, but never interacted with.
Mad Doc Grotsnik wrote: When it comes to aliens (and with no intention to berate or belittle fellow posters), I've always felt it supremely arrogant to believe we're the only intelligent life in the galaxy, let alone the universe.
Now. Are they visiting earth? Probably not. Will we ever come across each other? Well, possibly. But not for a long time I'd imagine.
It's not arrogance, it statistics. The Universe is so large the odds of there being no other life (intelligent or otherwise) is so extraordinarily low, that the concept of us being alone is utterly absurd. Now visiting Earth? Unlikely and to be frank, if aliens had that sort of technology, why would they even bother coming down here? We'd probably be more like a neat scientific observation. Something to be looked at, but never interacted with.
Well, we can apply a little human spirit to that....
If we have the technology and found relatively primitive life, what would our natural curiosity dictate?
And remember, our innate curiosity and wanderlust is a major factor in how we came even this far. We didn't just explore our world (many migratory species do this), but sought to understand how it works. The rest comes from that.
Fed up of Scalpers? But still want your Exclusives? Why not join us?
If we have the technology and found relatively primitive life, what would our natural curiosity dictate?
Put them in a zoo! Exploit their world for minerals! Cheap labour!
Breed them for meat. That's humanity's main interaction with animals.
Nah. Our first and most important connection to animals was when we began domesticating wolves into dogs. Still exploitation, but much more subtle and mutually beneficial than meat farms.
Playing by the odds, not only would there be alien life in our galaxy, but there should be some millions or billions of years older than life on Earth. Intelligent life with a million year head start over us might have very different ideas about the desirability of FTL travel, what is interesting about Earth (if anything), and how to satisfy their curiosity. Who can even imagine what ideologies might come into play or the economics of interstellar cattle mutilation or sapient abduction tourism?
Mad Doc Grotsnik wrote: When it comes to aliens (and with no intention to berate or belittle fellow posters), I've always felt it supremely arrogant to believe we're the only intelligent life in the galaxy, let alone the universe.
Now. Are they visiting earth? Probably not. Will we ever come across each other? Well, possibly. But not for a long time I'd imagine.
It's not arrogance, it statistics. The Universe is so large the odds of there being no other life (intelligent or otherwise) is so extraordinarily low, that the concept of us being alone is utterly absurd. Now visiting Earth? Unlikely and to be frank, if aliens had that sort of technology, why would they even bother coming down here? We'd probably be more like a neat scientific observation. Something to be looked at, but never interacted with.
I had an interesting thought on the Fermi paradox the other day; our assumption on detecting alien civilisations is based on them using high power wide band broadcasts, but barely a century into having that technology we’re already abandoning it in favour of localised low power networks and narrow band directional transmissions, as there far more efficient and flexible (e.g. streaming instead of broadcasts). Which suggests that the time for which an advanced civilisation is detectable could be incredibly short.
Zed wrote: *All statements reflect my opinion at this moment. if some sort of pretty new model gets released (or if I change my mind at random) I reserve the right to jump on any bandwagon at will.
2018/04/06 19:27:55
Subject: Re:Conspiracy Theories: What's your take?
If you can travel faster than light then you can observe an event happening, then travel to that event and arrive prior to the event occurring and prevent it from ever happening from the reference frame of a different observer. This violates one of special relativity's fundamental and testable foundations, that all reference frames are equally valid and the laws of physics are the same in all reference frames.
I may be being dim here but can you explain this to me in an "Idiot's Guide" way? The closer you can get to a kind of "See Spot run" level of understanding for my benefit the better.
If you have seen an event happening then being able to travel faster than the speed of light surely wouldn't mean you could effectively travel upstream and arrive back in time because you're starting from a point already after that light has reached your position. I can see how it would enable you to outpace that light and prevent someone further away from seeing that event, but I can't grasp how that would inherently allow to backwards time travel to a point before it occurred.
I'll stick this in a spoiler so I don't subject people to special relativity unless they want to be
Spoiler:
It comes down to how distance in spacetime is measured. Special Relativity showed us that the distance we travel through space depends on the reference frame of an observer and that the same goes for time. However the distance we travel through combined spacetime is the same for all observers. Spacetime distance is what is called an invariant, which means that no matter the frame of reference it will always be the same.
Distance in Minkowski spacetime (so we're ignoring general relativity effects) is calculated using the equation (s)^2 = (ct)^2 - (x)^2 - (y)^2 - (z)^2 where the s^2 represents spacetime distance, c is an arbitrary universal constant velocity which allows us to have a value for time in the same units as space, t is the observed time of travel, and x, y and z are the observed spacial travel. So different observers can measure different values of t, x, y and z but when they put them into that equation, they will all get the same value of s. We should also look at spacetime diagrams and the
Now, we know that distance travelled in space is equal to velocity (v) multiplied by time (t), so we can replace the spacial distances with vt. We can also pick a reference frame where all the motion is in one direction, eliminating the other two spacial components.
So now we have (s)^2 = (ct)^2 - (vt)^2. Lets say that our spaceship can travel at twice the speed of our arbitrary universal velocity (v=2c). this gives us (s)^2 = (ct)^2 - (2ct)^2. Lets expand out those brackets, resulting in s^2 = (ct)^2 - 4(ct)^2 = -3(ct)^2. Oh dear, our spacetime distance is negative. This means we have moved backwards in spacetime from our starting point from the reference frame of every observer. This means we have moved into our own past. If we wanted we could travel far enough and kill our own grandfather before we were born, which is clearly a violation of causality (the cause of an event must happen before the effect, in the kill your own grandfather scenario we can have the effect, grandfather killed by grandchild, happen before the cause, grandson is born and develops time machine). So this arbitrary velocity we picked must also be a cosmic speed limit in order to prevent time travel to the past, which creates paradoxes.
For another example, we start on earth in a rocket which travels at less than our arbitrary velocity. Our friend pushes a big red button and launches us on our way to the space station Chronos orbiting Alpha Centauri. When we get there we write a note and hand it over to a delivery service which puts it on a rocket which travels faster than our cosmic speed limit. As that ship is travelling backwards in spacetime, it can reach earth before we left and hand over our note to our friend, who reads it and doesn't push the big red button.
At this point we haven't specified that the arbitrary velocity we've been using is the speed of light, but that literally falls out on its own if we create a simple experiment to get some numbers and then compare the results to the outcome of the light clock thought experiment.
So lets do that. We're sitting on a train travelling at velocity v in the x direction, as observed by our friend sitting on a hill. We sit on this train for a time t, as measured by our watch, before getting off. From our reference frame of inside the train, we can perfectly validly say that we aren't moving, the rest of the universe is. So in our reference frame the spacial distance is zero and the time was t, so our spacetime distance is s^2 = (ct)^2.
Our friend on the hill thinks that he's stationary and the train is moving and he times our journey with his watch, giving our journey time of T. So his measurement of our spacetime distance is s^2 = (cT)^2 - (vT)^2. As spacetime distance is invariant these two measurements must be equal to each other. Setting them equal and doing some rearranging nets us T = ct / sqrt(c^2 - v^2) which we can further tinker with to get T = t / sqrt(1 - (v/c)^2).
Let's say y = 1/sqrt(1 - (v/c)^2), giving us a nice and pretty T = yt. This came directly out of spacetime distance with an arbitrary value for c.
At this point lets switch over to our Einstein light clock thought experiment. In this example we have a clock that operates by bouncing a photon vertically between two plates.. We are again sitting on our train, travelling at velocity v, but this time we're timing our journey using our cool light clock. Our friend is again sitting on his hill, and he is also looking at the light clock.
Einstein's special relativity came from two postulates, the first being that the speed of light is constant in all reference frames and the second being that there is no universal at-rest reference frame from which you can measure all motion relative to. The first comes from Maxwells field equations which, when combining the electric and magnetic field equations, produced an equation for an electromagnetic wave with a velocity independent of motion of reference frame, i.e light. The latter disallows a means of measuring absolute motion (i.e being able to say you are moving without having to specify what you are moving relative to) and was supported by the results of the Michelson-Morley experiment when they failed to detect the luminiferous aether, which would have been a universal reference frame.
From our point of view on the train, the photon just goes up and down. Like how when you're on a moving (but not accelerating) vehicle, if you throw an object up into the air it comes straight back down into your hand rather than ending up hitting the back wall. From the point of view of our friend, however, the light is not travelling straight up and down, but rather at an angle as it has to hit the plate which has moved slightly from when it left the other plate, as seen here: So, from the point of view of our friend, the clock is taking longer for each tick compared to your measurements as the light is having to travel further but cannot travel faster to compensate as the speed of light is constant. Doing some pythagoras and rearranging, you once again end up with the time measured by your friend (T) being equal to the time measured by you on the train (t) multiplied by our factor y, but this time the c in that factor is not arbitrary but has to be the speed of light.
Now, at this point some people try to argue against the light clock experiment by saying it can't be used as the light clock is a fabrication just to make the maths easier. So now we're going to have you sit be a very intelligent chameleon with knowledge of special relativity and have one eye on the light clock and one eye on a normal clock. If the discrepancies in the two observed times are due to the unreal nature of the light clock, then the times measured by the light clock and the normal clock should be different. But they won't be. Time dilation (which is what this thought experiment leads us to) has been observed in countless particle accelerator experiments.
So, since we reached the same solution from both the Minkowski spacetime equation and the light clock thought experiment, it is very fair to assume that the arbitrary velocity c we used in the Minkowski equation must be the speed of light and therefore if we were to travel faster than light we'd end up travelling into the past.
Phew, nice bit of relativity recap for me, was fun. Hopefully it went some way to answering your question.
This message was edited 3 times. Last update was at 2018/04/06 19:30:27
The Laws of Thermodynamics:
1) You cannot win. 2) You cannot break even. 3) You cannot stop playing the game.
Colonel Flagg wrote:You think you're real smart. But you're not smart; you're dumb. Very dumb. But you've met your match in me.
If we have the technology and found relatively primitive life, what would our natural curiosity dictate?
Put them in a zoo! Exploit their world for minerals! Cheap labour!
Breed them for meat. That's humanity's main interaction with animals.
Nah. Our first and most important connection to animals was when we began domesticating wolves into dogs. Still exploitation, but much more subtle and mutually beneficial than meat farms.
In the US, a very dog-friendly country, there are about 90 million dogs, but about 9 billion chicken are slaughtered each year. On a global scale, dogs (and other pets) are a tiny fraction of animals raised by humans.
If you are only interested in quantity and not quality of the relationship. Humans interact as minimally as possible for consumption purposes with chickens. Humans interact with dogs in a multitude of ways for a myriad reasons. In the context of "why would aliens interact with humans", clearly "to eat them" is the least likely or interesting answer.
I'll stick this in a spoiler so I don't subject people to special relativity unless they want to be
Spoiler:
It comes down to how distance in spacetime is measured. Special Relativity showed us that the distance we travel through space depends on the reference frame of an observer and that the same goes for time. However the distance we travel through combined spacetime is the same for all observers. Spacetime distance is what is called an invariant, which means that no matter the frame of reference it will always be the same.
Distance in Minkowski spacetime (so we're ignoring general relativity effects) is calculated using the equation (s)^2 = (ct)^2 - (x)^2 - (y)^2 - (z)^2 where the s^2 represents spacetime distance, c is an arbitrary universal constant velocity which allows us to have a value for time in the same units as space, t is the observed time of travel, and x, y and z are the observed spacial travel. So different observers can measure different values of t, x, y and z but when they put them into that equation, they will all get the same value of s.
We should also look at spacetime diagrams and the
Now, we know that distance travelled in space is equal to velocity (v) multiplied by time (t), so we can replace the spacial distances with vt. We can also pick a reference frame where all the motion is in one direction, eliminating the other two spacial components.
So now we have (s)^2 = (ct)^2 - (vt)^2. Lets say that our spaceship can travel at twice the speed of our arbitrary universal velocity (v=2c). this gives us (s)^2 = (ct)^2 - (2ct)^2. Lets expand out those brackets, resulting in s^2 = (ct)^2 - 4(ct)^2 = -3(ct)^2. Oh dear, our spacetime distance is negative. This means we have moved backwards in spacetime from our starting point from the reference frame of every observer. This means we have moved into our own past. If we wanted we could travel far enough and kill our own grandfather before we were born, which is clearly a violation of causality (the cause of an event must happen before the effect, in the kill your own grandfather scenario we can have the effect, grandfather killed by grandchild, happen before the cause, grandson is born and develops time machine). So this arbitrary velocity we picked must also be a cosmic speed limit in order to prevent time travel to the past, which creates paradoxes.
For another example, we start on earth in a rocket which travels at less than our arbitrary velocity. Our friend pushes a big red button and launches us on our way to the space station Chronos orbiting Alpha Centauri. When we get there we write a note and hand it over to a delivery service which puts it on a rocket which travels faster than our cosmic speed limit. As that ship is travelling backwards in spacetime, it can reach earth before we left and hand over our note to our friend, who reads it and doesn't push the big red button.
At this point we haven't specified that the arbitrary velocity we've been using is the speed of light, but that literally falls out on its own if we create a simple experiment to get some numbers and then compare the results to the outcome of the light clock thought experiment.
So lets do that. We're sitting on a train travelling at velocity v in the x direction, as observed by our friend sitting on a hill. We sit on this train for a time t, as measured by our watch, before getting off. From our reference frame of inside the train, we can perfectly validly say that we aren't moving, the rest of the universe is. So in our reference frame the spacial distance is zero and the time was t, so our spacetime distance is s^2 = (ct)^2.
Our friend on the hill thinks that he's stationary and the train is moving and he times our journey with his watch, giving our journey time of T. So his measurement of our spacetime distance is s^2 = (cT)^2 - (vT)^2. As spacetime distance is invariant these two measurements must be equal to each other. Setting them equal and doing some rearranging nets us T = ct / sqrt(c^2 - v^2) which we can further tinker with to get T = t / sqrt(1 - (v/c)^2).
Let's say y = 1/sqrt(1 - (v/c)^2), giving us a nice and pretty T = yt. This came directly out of spacetime distance with an arbitrary value for c.
At this point lets switch over to our Einstein light clock thought experiment. In this example we have a clock that operates by bouncing a photon vertically between two plates.. We are again sitting on our train, travelling at velocity v, but this time we're timing our journey using our cool light clock. Our friend is again sitting on his hill, and he is also looking at the light clock.
Einstein's special relativity came from two postulates, the first being that the speed of light is constant in all reference frames and the second being that there is no universal at-rest reference frame from which you can measure all motion relative to. The first comes from Maxwells field equations which, when combining the electric and magnetic field equations, produced an equation for an electromagnetic wave with a velocity independent of motion of reference frame, i.e light. The latter disallows a means of measuring absolute motion (i.e being able to say you are moving without having to specify what you are moving relative to) and was supported by the results of the Michelson-Morley experiment when they failed to detect the luminiferous aether, which would have been a universal reference frame.
From our point of view on the train, the photon just goes up and down. Like how when you're on a moving (but not accelerating) vehicle, if you throw an object up into the air it comes straight back down into your hand rather than ending up hitting the back wall. From the point of view of our friend, however, the light is not travelling straight up and down, but rather at an angle as it has to hit the plate which has moved slightly from when it left the other plate, as seen here:
So, from the point of view of our friend, the clock is taking longer for each tick compared to your measurements as the light is having to travel further but cannot travel faster to compensate as the speed of light is constant.
Doing some pythagoras and rearranging, you once again end up with the time measured by your friend (T) being equal to the time measured by you on the train (t) multiplied by our factor y, but this time the c in that factor is not arbitrary but has to be the speed of light.
Now, at this point some people try to argue against the light clock experiment by saying it can't be used as the light clock is a fabrication just to make the maths easier. So now we're going to have you sit be a very intelligent chameleon with knowledge of special relativity and have one eye on the light clock and one eye on a normal clock. If the discrepancies in the two observed times are due to the unreal nature of the light clock, then the times measured by the light clock and the normal clock should be different. But they won't be. Time dilation (which is what this thought experiment leads us to) has been observed in countless particle accelerator experiments.
So, since we reached the same solution from both the Minkowski spacetime equation and the light clock thought experiment, it is very fair to assume that the arbitrary velocity c we used in the Minkowski equation must be the speed of light and therefore if we were to travel faster than light we'd end up travelling into the past.
Phew, nice bit of relativity recap for me, was fun. Hopefully it went some way to answering your question.
Thanks for the time you spent on that, it's helped a bit. The mathematics involved I'll admit is a bit beyond me but I'm more than happy to trust you on that!
It's been appreciated.
2018/04/08 01:15:07
Subject: Re:Conspiracy Theories: What's your take?
Supreme UFO Commander Brart: Okay guys, this is our thirty second exercise in this forgotten backwater, so I hope everyone knows what to do.
General Assembly: *Affirmative murmer*
Grazt: Hee hee hee!
Brart: Nargle, you're on Cattle Mutilation duty again.
Nargle: Cattle mutilation? Again? Can't somebody else do it this time?
Brart: No one else on this team has your experience in Cattle Mutilation.
Nargle: That's because no one else ever gets stuck with Cattle Mutilation!
Brart: Be that as it may, you're still the one with the experience, so the job falls to you.
Brart: Next, Grazt...
Grazt: Hee hee hee!
Brart: Grazt, you are officially off Anal Probe duty.
Grazt: Off?! But
Brart: Grazt, we do not need more paternity issues over 'accidentally' impregnating these Earthlings.
Grazt: There's no proof it was me! The Earthling could have been inseminated by one of its own kind!
Brart: Grazt... Human males do not normally get pregnant.
Grazt: Oh.
Brart: Barney...
Barney: Yo!
Brart: Barney, you are in charge of making sure there are plenty of weather balloons and St. Elmo's fire in the area.
Barney: Baaaalllloooons! Brart: Yes Barney, balloons. They're all yours.
Brart: Now, everyone, let's move out!
End of Suppressed Recording
The Auld Grump
This message was edited 1 time. Last update was at 2018/04/08 01:17:34
Kilkrazy wrote:When I was a young boy all my wargames were narratively based because I played with my toy soldiers and vehicles without the use of any rules.
The reason I bought rules and became a real wargamer was because I wanted a properly thought out structure to govern the action instead of just making things up as I went along.
If we have the technology and found relatively primitive life, what would our natural curiosity dictate?
And remember, our innate curiosity and wanderlust is a major factor in how we came even this far. We didn't just explore our world (many migratory species do this), but sought to understand how it works. The rest comes from that.
Yeah, I find the argument that alien species would leave us alone out of disinterest extremely unconvincing. While we can't assume other species would be the same as us, at the same time we are the only intelligent species we know of and we're defined by our curiosity, particularly of other life. Hell, we speculate endlessly about the mere possibility of meeting alien life, if we ever find it we're very unlikely to just leave it alone. As such, while we can't assume other species will be as curious as us, assuming the exact opposite seems particularly wrong headed.
The reason I find reported alien sightings particularly unconvincing is that from an alien point of view they make absolutely no sense. First we have to accept the aliens travel this far but don't actually want to talk to us, this is an assumption but not an implausible one, so we'll work with it. But if the aliens just want to observe us, you'd think they'd do that as best they could without being seen by us. At which point we have to note that according to the theory behind ufos, the alien's method for observing us involves flying down to a height where they are visible to the human eye and then buzzing around doing impossible aerodynamics with all their ship lights turned on. It's fething stupid, to be perfectly honest. It requires us to believe that aliens can travel faster than the speed of light but have nothing to match our satellite imaging.
This message was edited 1 time. Last update was at 2018/04/09 07:16:58
“We may observe that the government in a civilized country is much more expensive than in a barbarous one; and when we say that one government is more expensive than another, it is the same as if we said that that one country is farther advanced in improvement than another. To say that the government is expensive and the people not oppressed is to say that the people are rich.”
Adam Smith, who must have been some kind of leftie or something.
One aspect of UFO's rarely mentioned is that over time the appearance of possible 'alien craft' has changed in accordance with mankind's level of technological sophistication. In the 19th century UFO's appeared as slow moving and balloon-like. Later, hovering saucers became prevalent, and later still triangles and other shapes that moved at higher and higher speeds became the norm.
Why would aliens change their appearance for our sake?
2018/04/09 14:32:42
Subject: Re:Conspiracy Theories: What's your take?
Aliens just don't understand our way of life, so they ignore us...
"They're made out of meat."
"Meat?"
"Meat. They're made out of meat."
"Meat?"
"There's no doubt about it. We picked up several from different parts of the planet, took them aboard our recon vessels, and probed them all the way through. They're completely meat."
"That's impossible. What about the radio signals? The messages to the stars?"
"They use the radio waves to talk, but the signals don't come from them. The signals come from machines."
"So who made the machines? That's who we want to contact."
"They made the machines. That's what I'm trying to tell you. Meat made the machines."
"That's ridiculous. How can meat make a machine? You're asking me to believe in sentient meat."
"I'm not asking you, I'm telling you. These creatures are the only sentient race in that sector and they're made out of meat."
"Maybe they're like the orfolei. You know, a carbon-based intelligence that goes through a meat stage."
"Nope. They're born meat and they die meat. We studied them for several of their life spans, which didn't take long. Do you have any idea what's the life span of meat?"
"Spare me. Okay, maybe they're only part meat. You know, like the weddilei. A meat head with an electron plasma brain inside."
"Nope. We thought of that, since they do have meat heads, like the weddilei. But I told you, we probed them. They're meat all the way through."
"No brain?"
"Oh, there's a brain all right. It's just that the brain is made out of meat! That's what I've been trying to tell you."
"So ... what does the thinking?"
"You're not understanding, are you? You're refusing to deal with what I'm telling you. The brain does the thinking. The meat."
"Thinking meat! You're asking me to believe in thinking meat!"
"Yes, thinking meat! Conscious meat! Loving meat. Dreaming meat. The meat is the whole deal! Are you beginning to get the picture or do I have to start all over?"
"Omigod. You're serious then. They're made out of meat."
"Thank you. Finally. Yes. They are indeed made out of meat. And they've been trying to get in touch with us for almost a hundred of their years."
"Omigod. So what does this meat have in mind?"
"First it wants to talk to us. Then I imagine it wants to explore the Universe, contact other sentiences, swap ideas and information. The usual."
"We're supposed to talk to meat."
"That's the idea. That's the message they're sending out by radio. 'Hello. Anyone out there. Anybody home.' That sort of thing."
"They actually do talk, then. They use words, ideas, concepts?"
"Oh, yes. Except they do it with meat."
"I thought you just told me they used radio."
"They do, but what do you think is on the radio? Meat sounds. You know how when you slap or flap meat, it makes a noise? They talk by flapping their meat at each other. They can even sing by squirting air through their meat."
"Omigod. Singing meat. This is altogether too much. So what do you advise?"
"Officially or unofficially?"
"Both."
"Officially, we are required to contact, welcome and log in any and all sentient races or multibeings in this quadrant of the Universe, without prejudice, fear or favor. Unofficially, I advise that we erase the records and forget the whole thing."
"I was hoping you would say that."
"It seems harsh, but there is a limit. Do we really want to make contact with meat?"
"I agree one hundred percent. What's there to say? 'Hello, meat. How's it going?' But will this work? How many planets are we dealing with here?"
"Just one. They can travel to other planets in special meat containers, but they can't live on them. And being meat, they can only travel through C space. Which limits them to the speed of light and makes the possibility of their ever making contact pretty slim. Infinitesimal, in fact."
"So we just pretend there's no one home in the Universe."
"That's it."
"Cruel. But you said it yourself, who wants to meet meat? And the ones who have been aboard our vessels, the ones you probed? You're sure they won't remember?"
"They'll be considered crackpots if they do. We went into their heads and smoothed out their meat so that we're just a dream to them."
"A dream to meat! How strangely appropriate, that we should be meat's dream."
"And we marked the entire sector unoccupied."
"Good. Agreed, officially and unofficially. Case closed. Any others? Anyone interesting on that side of the galaxy?"
"Yes, a rather shy but sweet hydrogen core cluster intelligence in a class nine star in G445 zone. Was in contact two galactic rotations ago, wants to be friendly again."
"They always come around."
"And why not? Imagine how unbearably, how unutterably cold the Universe would be if one were all alone ..."
Sebster, I think you are assuming all the aliens would be of uniform purpose, capability and, for lack of a better word, professionalism. Why assume they are the opposite of humanity in that regard?
amanita wrote: One aspect of UFO's rarely mentioned is that over time the appearance of possible 'alien craft' has changed in accordance with mankind's level of technological sophistication. In the 19th century UFO's appeared as slow moving and balloon-like. Later, hovering saucers became prevalent, and later still triangles and other shapes that moved at higher and higher speeds became the norm.
Why would aliens change their appearance for our sake?
That's simply not true. Cigar shaped craft, disks and balls of light have been recorded all through the history of UFO sightings. If you look at ancient accounts of objects in the sky, you see similar varieties of shapes. However, people have always recorded events in accord with their understanding of the universe. Shields in the sky? Airships? Hovering saucers? Soundless triangles? It seems like people rationalize what they see using what they already know, and popular culture fixates on the particular shape of craft most interesting or easily grasped at the time. Whether these are alien ships or mundane weather phenomena, they have always defied one simple description.
This message was edited 1 time. Last update was at 2018/04/09 15:59:05
) to tell me I've got that completely wrong!)
