Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: mjn.mixael on September 11, 2010, 02:23:45 pm
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Because you all complained about the box.. it now moves a Herc.
I roll my eyes at you all. :rolleyes: :lol:
Crane Test (http://vimeo.com/14835382)
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For your next miracle, have it move an Orion.
It will be meta-lifting.
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For your next miracle, have it move an Orion.
It will be meta-lifting.
Since space is relative, from a certain point of view, the Hercules is stationary and it is the Orion that is moving.
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Not exactly, read about twins paradox to find out why.
Basically, it depends on which one is moving "relative to the universe", pilot in Herc experiences acceleration and time dilation (although small), while Orion does not.
(I know that it's not the best nor the most sciencific explaination, but it should be enough here).
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Not exactly, read about twins paradox to find out why.
Basically, it depends on which one is moving "relative to the universe", pilot in Herc experiences acceleration and time dilation (although small), while Orion does not.
(I know that it's not the best nor the most sciencific explaination, but it should be enough here).
Wrong. If you construct a reference frame with the herc as an immovable object, then it's the rest of the universe that moves. Very simple operation, mathematically speaking.
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Give a Herc a lever long enough and a fulcrum to rest it on, and it could move the universe.
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Not exactly, read about twins paradox to find out why.
Basically, it depends on which one is moving "relative to the universe", pilot in Herc experiences acceleration and time dilation (although small), while Orion does not.
(I know that it's not the best nor the most sciencific explaination, but it should be enough here).
Wrong. If you construct a reference frame with the herc as an immovable object, then it's the rest of the universe that moves. Very simple operation, mathematically speaking.
Really? I'm not sure Dragon is incorrect. Acceleration is key here.
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Then we could try relative to the mass centre. Because they are in space, the common centre of mass of the Herc and the Orion has to remain the same except if they give or receive energy. So, by moving the Herc to the left, to keep the centre of mass in the same place the Orion will move to the right, even if very very little.
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Not exactly, read about twins paradox to find out why.
Basically, it depends on which one is moving "relative to the universe", pilot in Herc experiences acceleration and time dilation (although small), while Orion does not.
(I know that it's not the best nor the most sciencific explaination, but it should be enough here).
Wrong. If you construct a reference frame with the herc as an immovable object, then it's the rest of the universe that moves. Very simple operation, mathematically speaking.
Really? I'm not sure Dragon is incorrect. Acceleration is key here.
Dragon is incorrect. It's important to remember that there is no 'relative to the universe' - only the relative acceleration profiles between the ships matter.
- Note that gravity and acceleration are the same thing as well, so passing very close to a massive object also works for time dilation. Various theorists have constructed time machines using General Relativity.
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Time machines that can only go one way I bet.
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Not exactly, read about twins paradox to find out why.
Basically, it depends on which one is moving "relative to the universe", pilot in Herc experiences acceleration and time dilation (although small), while Orion does not.
(I know that it's not the best nor the most sciencific explaination, but it should be enough here).
Wrong. If you construct a reference frame with the herc as an immovable object, then it's the rest of the universe that moves. Very simple operation, mathematically speaking.
Really? I'm not sure Dragon is incorrect. Acceleration is key here.
Dragon is incorrect. It's important to remember that there is no 'relative to the universe' - only the relative acceleration profiles between the ships matter.
- Note that gravity and acceleration are the same thing as well, so passing very close to a massive object also works for time dilation. Various theorists have constructed time machines using General Relativity.
I'm profoundly aware of all that (you're quoting basic tenets of GR here), but I believe that there may be no reference frame in which the Herc remains stationary even to itself. I could be wrong.
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dragon is right, time dilation applies to objects that can "feel" acceleration. but i'm not sure how that's relevant to the initial point. you CAN have a reference frame in which the orion moves and the herc does not.
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dragon is right, time dilation applies to objects that can "feel" acceleration. but i'm not sure how that's relevant to the initial point. you CAN have a reference frame in which the orion moves and the herc does not.
Are you sure? I'm not denying it, but I don't immediately see an IRF where that's true.
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dragon is right, time dilation applies to objects that can "feel" acceleration. but i'm not sure how that's relevant to the initial point. you CAN have a reference frame in which the orion moves and the herc does not.
Are you sure? I'm not denying it, but I don't immediately see an IRF where that's true.
Im not really sure how GR works but, what about the center of mass of the herc?
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Because you all complained about the box.. it now moves a Herc.
I roll my eyes at you all. :rolleyes: :lol:
Crane Test (http://vimeo.com/14835382)
Vimeo doesn't work on my phone. . . .
You suck. :p
On a different note, my girlfriend also sucks ;7
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dragon is right, time dilation applies to objects that can "feel" acceleration. but i'm not sure how that's relevant to the initial point. you CAN have a reference frame in which the orion moves and the herc does not.
Are you sure? I'm not denying it, but I don't immediately see an IRF where that's true.
Im not really sure how GR works but, what about the center of mass of the herc?
It could not qualify as an IRF as it undergoes translational acceleration, but my GR is not good enough to say much past that.
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yeah, i'm sure of that, but like everyone else it seems, that's about the limit of my relativity :P
someone mentioned the twin paradox. that is explained by this effect: one twin stays on earth while the other flies away and back for some amount of time at .9c or something like that. in each one's reference frame, the other was traveling at .9c. so which one has aged less? the one that flew away and back, because he had to accelerate to .9c. he was the one that was "really" moving.
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yeah, i'm sure of that, but like everyone else it seems, that's about the limit of my relativity :P
someone mentioned the twin paradox. that is explained by this effect: one twin stays on earth while the other flies away and back for some amount of time at .9c or something like that. in each one's reference frame, the other was traveling at .9c. so which one has aged less? the one that flew away and back, because he had to accelerate to .9c. he was the one that was "really" moving.
I thought that was because he flew back, as in, if the twin on earth was to go off and get his brother after he had reached the end of his travels, it would be the earth twin that aged less. but since it was the twin that went off into space and later came to earth, it was he who aged less.
sorry if im not making myself clear.
and again, I don't really know much about advanced physics, much less this theoretical stuff, so I am probably wrong.
I bet herra will come along and tell us how it all really is soon enough.
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The resolution lies in the definition of an inertial reference frame vs. non-inertial reference frame.
There is no frame from which the Herc can be seen as stationary that is itself not undergoing acceleration. Any observer in such a frame would feel fictitious forces due to said acceleration. Thus the frame is said to be non-inertial.
Therefore all the weird stuff like the Twin Paradox applies to the Herc, but not the ship containing the Herc.
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When he was far away from Earth and turned back, he was not in an inertial reference frame. He moved through various IRFs to this effect:
Before he turned back, he perceived his twin as aging slower.
After he turned back, he still perceives this.
Before he turned back, (He leaves Earth from his perspective) and (He leaves Earth from his twin's perspective) were simultaneous events.
After he turned back, they are not. This is because of the relativistic definition of simultaneity.
After he turns back, he is in an inertial reference frame such that t=0 for him is t=x for his twin, a nonzero number.
His twin perceives his journey to take, say, 8 years, while the twin aged 10 years.
He perceives his journey to take 8 years, which means that from his point of view, his twin should have aged 6.4 years. However, after he turned around, his brother's clock has started at 3.6 years in his new IRF- so his twin has ultimately aged 10 years.
Note that nowhere here have I used the concept of a "universal" IRF to which either one is compared. It's the acceleration that changes the starting point in the IRF.
Now, this raises the question of why the IRF did not significantly change in the initial and final accelerations- that is, when the traveler took off and landed on Earth. The answer again has to do with simultaneity, which has to do with both the IRFs of the two events and their proximity. Two events that occur at the same place will always be simultaneous.
For further reading (http://en.wikipedia.org/wiki/Relativity_of_simultaneity). Thanks to Battuta for explaining this originally and linking to some very helpful material in the FTL thread.
Although honestly I don't see how this discussion arose at all since neither a crane or a Herc is capable of withstanding the kind of acceleration that would be required to attain relativistic velocity inside an Orion hangar. :wtf:
[EDIT] Ninja'd by watsisname, who is also correct about the IRFs.
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I am a tachyon. :D
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The resolution lies in the definition of an inertial reference frame vs. non-inertial reference frame.
There is no frame from which the Herc can be seen as stationary that is itself not undergoing acceleration. Any observer in such a frame would feel fictitious forces due to said acceleration. Thus the frame is said to be non-inertial.
Therefore all the weird stuff like the Twin Paradox applies to the Herc, but not the ship containing the Herc.
Yeah, this is my understanding.
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Twin paradox is only a paradox because it presents a situation where special relativity does not work.
Special relativity can only be applied when everything moves at constant velocity. As soon as accelerations come into play, it means that the accelerating observer is no longer contained to the same inertial frame.
And before you ask, even though constant velocities are relative, accelerations are absolute (although the amount of acceleration is relative - if you accelerated at 9,80665 m s^-2 for infinite time, you would feel the same acceleration for the whole time but static observers would note that your velocity approaces c and acceleration approaches zero).
Rest assured though that when the crane moves Herc, both the Orion and Herc experience accelerations (conservation of momentum, shift of common centre of gravity and all that) but due to Orion's immensely larger mass, it can in almost all practical applications of physics be considered as static object while the Herc moves within the inertial coordinates fixed at the Orion. Errors using this method would likely be about the same order as (Herc's mass)/(Orion's mass) which I would estimate at, say, something close to 10^-9 magnitude just from the top of my head. Or even less.
..actually, what the heck.
/me goes check the mass values from the model files
From sparky_fs2.vp:
Retail HercI: mass 302.460114 units
Retail Orion: mass 1646203.000000 units
...which results as about 2x10^-5
Which is actually a lot more than I would have expected, to be honest, but still very, very much.
It means that if Herc moves a metre, Orion moves about 20 micrometres to opposing direction. Not exactly an observable amount in most situations.
Plus I don't know if these units of mass make any sense whatsoever. Which actually brought up an interesting topic in irc - are the mass and MOI values of ships preserved comparative to retail values in MediaVP's? :nervous:
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Twin paradox is only a paradox because it presents a situation where special relativity does not work.
Incorrect, to my knowledge. The twin paradox can be resolved entirely inside SR.
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Twin paradox is only a paradox because it presents a situation where special relativity does not work.
Incorrect, to my knowledge. The twin paradox can be resolved entirely inside SR.
Yes, it is, as long as you assume that all changes of velocity are instantaneous and then handle each phase of the trip as an idealized component.
What I meant is that it's only a "paradox" when people look at it assuming that same stuff that applies to constant-speed inertial frames applies into switched inertial frames. My wording was poor; what I should have said is that the simplest example of Special Relativity does not apply to more complex situations (where velocity is NOT a constant).
And properly solving it still requires handling accelerations which are synonymous to gravity fields in General Relativity so, you probably would end up needing to use GR anyway if you wanted anything but idealized solutions.
The simplest way to un-paradox the twin paradox is to make both twins emit EM pulses at standard intervals and calculate the amount of pulses that both twins receive from the other, taking pulse travel time into account...
That said...
/me sees Newton and Einstein and raises Schrödinger and Dirac
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(http://imgs.xkcd.com/comics/centrifugal_force.png)
That should clear things up. :p
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Rest assured though that when the crane moves Herc, both the Orion and Herc experience accelerations (conservation of momentum, shift of common centre of gravity and all that) but due to Orion's immensely larger mass, it can in almost all practical applications of physics be considered as static object while the Herc moves within the inertial coordinates fixed at the Orion. [etc]
Haha, that's a good point -- I don't think any of us had thought of that. :P
Edit: On the note of xkcd discussing physics, I always loved this one, too:
http://xkcd.com/669/ :lol:
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...which results as about 2x10^-5
Which is actually a lot more than I would have expected, to be honest, but still very, very much.
If you assume the mass ratio to be somewhat similar to that between a Nimitz carrier and one of its fighter complement, this makes some sense. A Nimitz class CVN displaces about 100,000 tonnes, while the loaded mass of one of its F/A-18 fighter complement is about 17 tonnes (10 tonnes empty), for a ratio of about 1E-4, an order of magnitude greater than that between Herc and Orion. Of course, the Orion is a much, much larger ship than a Nimitz, to the tune of being almost ten times as long, and something like three to five times wider as well as "taller," while a Herc isn't all that much larger than the Hornet, IIRC. Assuming a similar density between the Orion and the Nimitz, I get that an Orion is about 100-250 times more massive than a Nimitz, while a Herc might conceivably be several times heavier than a Hornet or similar modern fighter.
* Herra Tohtori sees Newton and Einstein and raises Schrödinger and Dirac
What the hell does QM have to do with all this? :p
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Well, in case we have to solve the interactions of a very small Herc and a very small Orion... :p
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Newton wins, he is the deadliest son of a ***** in Space, after all ;)