The physics of space battle

if youre talking about retro-causality, then it probably isn't within a many-worlds framework (it could be though, but that's some messed up physics)...

I suppose "block universe theory" is more comforting than the multi-verse theory, if you think on it a little.

It is somewhat horrifying to consider the idea of an iterating branch of time for every decision you didn't make, for every microsecond that you maintained your sanity, there might be an alternate branch in time where you snapped psychotic and randomly destroyed everything you loved, with an infinite array of other branches concerning the order, ferocity, or longevity or your rage before someone ultimately dealt with you.

Within the infinite to the power of infinity iterations of the multi-verse theory, there is at least one iteration at any given moment per human where that human, for no particular reason, embarks on a successful endeavor to destroy the human race.

the-anger wrote:skimmed that briefly, work - coffee = bad reading... delayed choice quantum eraser experiment?

re quantum mechanics, entanglement and so on, this link explains a lot in a way that most should be able to follow even without a good grasp on quantum mechanics - http://www.ipod.org.uk/reality/

so... interference with a part of an entangled pair breaks the entanglement?

ill copy the snippets that explain why entanglement cant be used for FTL information transmission...

To sum up, Einstein believed the following: There was no "spooky action-at-a-distance" which apparently violated Special Relativity (i.e., there was locality). Objects had definite reality, properties independent of observation.

However, the violation of Bell's Inequality reveals that the reverse is true

There is a strange connection between particles which instantaneously informs the undisturbed particle of the type of measurement just carried out on its [entangled] partner (however Special Relativity is not violated because no information can be transmitted using this method).

bell's inequality is quite amusing too...

say you have any 3 sets A, B and C. these could be the set of yellow things, the set of triangular things, anything really, so long as they have absolutely nothing to do with one another (eg, the set of fowls and the set of birds are known to be related and wouldn't apply here)...

the inequality states that the number of things that fit into A but not into B, together with the number of things that fit into B but not into C, must be at least as big as the number of things that fit into A but not C.

the inequality is true for all non-quantum objects, and has been proven to be broken by quantum objects. the reason for this is because for quantum objects they are correlated (if you read more into it, the 'belonging-to-a-set' means any measurable property, and the quantum object is a superposition of the wavefunctions of the properties rather than a particle in any sense); this is in essence the uncertainty principle at work saying that you cant simultaneously determine and collapse 2 properties of a quantum object if they are correlated.

the main problem isn't engines. isn't capacitance. it's heat dissipation.

think about it.

I had a curious thought.

ok so... if there is "spooky action at a distance" there is absolutely a way to transfer information.. you just have to figure out how to break the rules; and I thought of one possible way, maybe.

Observation seems to be key, but, what has to make the observation? Humans, certainly, but do animals count? do machines?

Would it be possible to a machine to monitor such a particle, not it's current status, but to see when it's partner has been observed? thus triggering an alert when it is observed?

This method of communication would require a huge bank of entangled particles for a distinctly finite amount of communication, but it would still be possible.

Even the slightest possibility allows a window for innovation, techniques and methods we never considered.

less than 2 hundred years ago, the fastest form of long distance communication was by various couriers of solid copy. (carrier pigeons ect.) and no one even considered that electricity or radio waves (both known quantities in universities even then) might hold the keys to sending messages that could decide the fate of civilization.

rather than saying no, ill elaborate...

'spooky action at a distance' is a descriptive term and not one that defines any such action necessarily in any way.

no information is 'transferred' because once entangled you can no longer consider the particles as separate entities - they are 2 sides to the same coin for some correlated properties.

taking this coin analogy further... if you observe one side of the coin, you can conclude what the other side must then be. but there is no way you could use this information at all - you cannot force the outcome in either side (you cannot flip a coin with the result pre-determined, and physics doesnt cheat), the best you could do is transmit your knowledge to the other observer, which of course, is bound by the speed of light.

a more correct description of the situation is: if you were to entangle two particles by spin (ie, up/down spin), then their spin becomes correlated. you have absolutely no way of guessing which result you will get on the first measurement of either particle, and you cannot set up the entanglement process to yield a specific result for a specific observer. even if you could track which particle goes where, wavefunction collapse is a probabilistic process where the outcome cannot be determined without actually collapsing it (but you can know what outcomes are possible ahead of time).

so you cannot:
1. set up the entanglement so that you end up with a specific result for a specific observer
2. predict what the first observation will be for either observer (even if you somehow know which particle went where).

the result for both observers is random, and you cannot use the 'if one side is X the other must be Y' reasoning because you would have to transmit that information FTL too, creating a circular problem...

"Would it be possible to a machine to monitor such a particle, not it's current status, but to see when it's partner has been observed? thus triggering an alert when it is observed?"

nope. the simple answer is the machine would itself be composed of particles, or any measurement method would interact with the particle in order to absorb information / energy from it in any way at all - if it does not interact with it then the particle may as well not exist for the purposes of 'measurement' / 'observation'.

to check on a particle you have to observe it. if you observe it you will collapse the wavefunction, always yielding a 'particle has been observed' result. any attempt to get around this will not work lol... you can only 'read' the resulting state from a particle or it's entangled partners destructively (as in, destroying any superpositioned states the system had).

so then you might ask how we know that an uncollapsed wavefunction exists at all, or how quantum computers are supposed to work? statistics. only the statistics of many many many repetitions of the same experiments has given us some definite confirmation, each measurement collapsing / measuring / observing the particle and confining it to a single possible state in the process.

as for quantum computations, these are done in isolation (from all sources of interference, heat, EM, other particles, etc) and then the result inspected afterwards (which for most q.computations will be a collapsed state anyway).

I don't remember his name, but a particle researcher currently nominated for a Nobel prize was able to measure the effects of a particle on itself (while it had been co-locating immediately prior to observation), thereby supporting many of the theories of quantum mechanics.

the-anger wrote:

so you cannot:
1. set up the entanglement so that you end up with a specific result for a specific observer
2. predict what the first observation will be for either observer (even if you somehow know which particle went where).

I was able to follow most of your post, but ultimately you are not addressing my proposal, and these two points in particular are way left field.

My thought was to find a way to monitor for wave function collapse, thus telling you that the partner had been observed. It may indeed not be possible to do this, but without this capacity, how are we doing any experiments in the first place?

the-anger wrote: as for quantum computations, these are done in isolation (from all sources of interference, heat, EM, other particles, etc) and then the result inspected afterwards (which for most q.computations will be a collapsed state anyway).

so if it's inspected in a collapsed state, and all you have are correlations, the idea that either a or b could be either a or b (schrodinger's cat) is really just philosophy.

To sum up, Einstein believed the following: There was no "spooky action-at-a-distance" which apparently violated Special Relativity (i.e., there was locality). Objects had definite reality, properties independent of observation.

However, the violation of Bell's Inequality reveals that the reverse is true

There is a strange connection between particles which instantaneously informs the undisturbed particle of the type of measurement just carried out on its [entangled] partner (however Special Relativity is not violated because no information can be transmitted using this method).

This is what i'm going off of. The closing statement, that no information can be "transmitted" seems to be in contradiction to the rest of the statement, or possibly betrays a lack of vision.

I was not however, able to find anything to articulate on "a violation of bell's inequality"; can you shed light on that specifically?

If there is a way to tell that a particle is informed that a measurment, or type of measurement, has been applied to it's partner at some time previously, you can then use that itself to communicate. Granted each pair of particles can only be used once & likely communicates only in one, predetermined direction, granted the form of communication i'm proposing would require huge quantities of these particles, likely sequestered seperately and used in specific sequence, so that even the simplest communication might be required to occur on a schedule and at monumental (easily prohibitive) cost, it's still communicating a binary message faster than the speed of light.

It's far from the flexibility we're accustomed to, that does not make it "impossible."

as far as monitoring wavefunction collapse, it just cannot be done. if you are monitoring it and are able to obtain a reading on it, how would you determine if it is a collapsed state or not if measuring it guarantees that you're looking at a collapsed (single) result? ie, can you distinguish between measuring a collapsed wavefunction, compared to measuring a wavefunction that collapsed because you measured it?

to me it seems that it can't be done, because in order to obtain a reading of it in any form you would have to collapse it. even a multi-valued reading can't be done, because any attempt to observe it would always yield a distinct, random result by definition.

experiments are done in repetition, with data collected and studied for correlations. each result will have been a reading of a collapsed state. we can't observe an uncollapsed wavefunction, but we can do the next best thing... since wavefunctions can be thought of as a probability density function, it stands to reason that the distribution of multiple results of measurement of the same prepared quantum state (and their statistical analysis) would be enough to reconstruct what the wavefunction would look like.

Kackling Kobold wrote:

To sum up, Einstein believed the following: There was no "spooky action-at-a-distance" which apparently violated Special Relativity (i.e., there was locality). Objects had definite reality, properties independent of observation.

However, the violation of Bell's Inequality reveals that the reverse is true

There is a strange connection between particles which instantaneously informs the undisturbed particle of the type of measurement just carried out on its [entangled] partner (however Special Relativity is not violated because no information can be transmitted using this method).

This is what i'm going off of. The closing statement, that no information can be "transmitted" seems to be in contradiction to the rest of the statement, or possibly betrays a lack of vision.

I was not however, able to find anything to articulate on "a violation of bell's inequality"; can you shed light on that specifically?

If there is a way to tell that a particle is informed that a measurment, or type of measurement, has been applied to it's partner at some time previously, you can then use that itself to communicate. Granted each pair of particles can only be used once & likely communicates only in one, predetermined direction, granted the form of communication i'm proposing would require huge quantities of these particles, likely sequestered seperately and used in specific sequence, so that even the simplest communication might be required to occur on a schedule and at monumental (easily prohibitive) cost, it's still communicating a binary message faster than the speed of light.

It's far from the flexibility we're accustomed to, that does not make it "impossible."

it isn't my place to say what is and isn't possible lol, its just a matter of fact with this sort of thing...

it is impossible to tell if a wavefunction collapsed yet or not because you would have to 'inspect' it somehow. the way in which you inspect it must interact with it in some way in order to probe it, but at the same time not perturb it in any way - a logically paradoxical requirement if wavefunctions are (and they are) descriptions of waves of some sort.

re bell's inequality...

recall the probability relation that shows 2 random variables as independent.
P(A|B) = P(A)
reads: the probability of A, given that B has occurred, is just as likely as if B had not occurred at all.
this proves P(B) is irrelevant to calculating P(A) at any given time, if that relation holds true.

Bell's Inequality is, crudely put, a test of whether some variables or outcomes are related to one another, showing whether or not knowing the value of any of the variables will reveal anything about the others.

pick 3 totally unrelated conditions / true-false tests that you can quiz some object on. call them A,B and C. make them so it is impossible for the answer to, in any way, bias the answer to the others.
next, run the tests for many objects, recording the answers for each object asked.

from the results, create 3 different tally's for the number of objects that answered yes / true for some combination of tests:

#1 = N(A and not B)
#2 = N(B and not C)
#3 = N(A and not C)

the order the questions were asked is irrelevant, actually... you could even swap B for A, or C for B. the inequality is: #1 + #2 >= #3.

if that inequality is broken in any way, it means that the answer to one test must say something about the answer to another test. this so far has only been broken within quantum mechanics, by simply saying that entanglement IS a correlation that, ordinarily, 2 separate measurements of two particles at a distance should not influence one another... but they do...

but the laws of probability make bell's inequality patently false; sure it may be true on average, but every example i've seen fails to account for the possibility of a fluke; the one in a million or more chance that a sampling placed in "#1"s place comes out with a value of zero.

One in a million times is entirely too often for absolutes.

Maybe i'm not understanding it.


As for monitoring wave function collapse, if they can't somehow tell that there was a collapse, or indeed that the particle was ever "behaving as a wave" at some point previously, in what way is quantum entanglement more than a philosophy?

It's odd that I understood this in the past, perhaps incorrectly, but the more anyone tries to "clarify," the less this sounds like a valid theory, and more like navel contemplation.

Let me try an object example (layman terms work for me); I have two paperclips in my desk, one red one blue. If my dog got into my desk and ate one, I don't know for sure if it's the red one or the blue one she ate until i observe either one of the paperclips. All this is pretty straight forward, and centers around what i may or may not have observed.

Quantum theory would say that these two paperclips are both simultaneously red and blue until one of them is observed, at which point both of their colors become fixed regardless of how far apart they are.

Einstein says no; they were each separately red and blue, you just hadn't looked yet.

I'm starting to agree with Einstein here.

I'm also unsure of how bells inequality relates to the color of paperclips in this scenario.

ok, going with your paperclips, the experiment is a little more complex than that.

start with two white paperclips, enclosed in individual air-tight sachets. imagine then a machine, that without anyone seeing, will open the sachets and drench both of the paperclips with a special kind of paint mixture before sealing them again. for simplicity's sake lets say that no spills happen, both paperclips receive an equal amount of paint, and a separate canister of paint is used up completely each time in the process.

since this paint is a quantum property (like spin) it must follow some rules. for one, lets say this paint comes in a white mixture, but dries either red or blue when exposed to air. furthermore, the net total of red paint and blue paint must be conserved - if you create more red paint you must create more blue paint somewhere, and likewise when destroying it.

so now we have paperclips containing a quantum property that when measured will take on one of two allowed states. before we go into what happens when they are entangled, lets change the experiment slightly and say that each paperclip was painted with a separate canister of paint and only half the canister was needed on either. ill come back to why that is in a bit...

so far, no entanglement happens because the paperclips have not yet interacted with each other in any way. either one of them could be blue or red, and both could be blue or red - their color is independent of one another's because they are not entangled, and their color's origin are unrelated.

if we now open one of the sachets and expose the paperclip to air, we will see that it takes on a single color, either red or blue (we have no way of knowing yet which result to expect). if we open the second one, it will do the same and will take on either red or blue at random (not entangled). if you were to examine the outcomes of the experiment, your data after 100 times should approach:
R,R = 25
B,R = 25
R,B = 25
B,B = 25

each time you are measuring one paperclip first before measuring the other.

in probability terms, this could be predicted like so:
Pr(R) = Pr(B) = 50%
Pr(R and B) = Pr(R)Pr(B) = 25%
Pr(R and R) = Pr(R)Pr(R) = 25%

we know the second and third properties must be true because there is nothing relating these paperclips' color to one another - they are two separate tests who's outcomes do not influence the other's. if you did the experiment with 3 particles that way, you could use bells inequality to show that indeed, these tests have no bearing on each other...

N(outcomes where 1st is red and 2nd isn't) + N(outcomes where 2nd is red and 3rd isn't) >= N(outcomes where 1st is red and 3rd isn't)

each outcome is 50% likely, so you end up with: 0.5*0.5 + 0.5*0.5 >= 0.5*0.5 <=> 0.5 >= 0.25

now lets come back to the experiment design and split a canister on two paperclips. because a single canister is used on two paperclips, they are now entangled - the property of color has in a sense now been dished out by reality to these two objects in a single go, it is effectively one 'object' all along to some degree (hence the canister spiel).

so what effect does entanglement have on our test with two paperclips, if run 100 times?
R,R = 0
R,B = 50
B,R = 50
B,B = 0

remember that these are supposed to be independent measurements, tests that we have seen have no bearing on the outcome of one another previously... as you can see though, that no longer works...
Pr(R) = 50% - for the first particle, yes.
Pr(R)Pr(R) = 25% - numerically, but actually?
Pr(R and R) = 0% - what gives?

im not 100% on what multi-entanglement actually looks like, because the order of measurement and the entanglement scheme used, ie, which particle is entangled to which... that said bell's inequality has been proven not to apply for entangled measurements.

if there is zero probability, then that outcome by definition is impossible. in quantum mechanics, the number of outcomes is very important to understanding entanglement (and other things). recall that each paperclip, when not entangled, contained two outcomes - red and blue. you can describe that as a superposition of red and blue color until one is observed, removing the other from reach. for two paperclips, there are four outcomes in total. the fact that there are four outcomes means that the two superpositioned states (one for each paperclip with two outcomes apiece) can still be separated from one another.

for our entangled paperclips, there are only two outcomes possible (red and blue, or blue and red). this implies that the property color is shared between these paperclips. the color outcome is no longer two choices but only one choice, a single superpositioned wavefunction to collapse. that means the two paperclips' color can no longer be described independently of the other's - we have shown this by Pr(R1)Pr(R2) != Pr(R1 and R2).

the flaw is using your knowledge that the paper clips are related by entanglement - when measuring spin on either end, you are expecting one of four outcomes to happen but only ever see two, despite them being unrelated measurements by conventional wisdom.

that took a while to write lol... hope it makes sense...

edit - footnote: the conclusion (that when measuring an entangled property you are collapsing not many but one wavefunction) was originally though of as just a quirk in the math used. bell's inequality was the earliest method used to test and confirm that entangled spin measurements are collapsed in the same instant upon first measurement for both particles as if only a single choice is required, rather than making a second choice by some proxy / information transmission. the quantum eraser experiments went on to show that you can un-collapse entangled particles if you can somehow 'forget' the information obtained from collapsing the wavefunction. and so on...

Good god. We're getting into some pretty heavy physics.
My brain is melting!

brain melting is normal. we have opened the quantum can of worms (or have we). Schrodinger's worms...

i think it's still fine so long as we don't need to discuss the physics of brain melting...

Abstractness wrote:I didn't know Solar wind is a usefull powersource.

If you've seen Star Wars, In one scene, Count Dooku's ship uses a solar sail to move. That is a completely unpowered, passive propulsion system, but it is effective. There are many more examples, but it would take too long to get into them...

The sun is also essentially a gigantic nuclear reactor, with the same risks that would be present if a nuclear reactor on earth melted down. Chernobyl or Fukushima-Daichi anyone?

The solar wind is pretty much pure radiation. The main components of solar wind are photons (Light) and gamma radiation (Which can kill...). If Earth didn't have a magnetic field, it would be a barren wasteland, since it couldn't deflect the solar particles.
Look at Mars to see what could happen: Mars used to be almost Earthlike, but it's core was too small to maintain the protective magnetic field. Once the magnetic field died, the solar wind essentially boiled away the atmosphere and water of Mars. Scary.

On another note: Did you know that you can actually SEE the solar wind with the naked eye?
Here's how: Go up into space, and close your eyes. You should see tiny blue streaks darting around in your eyeballs. This is caused by the solar particles interacting with the fluid in your eyes... Pretty cool, if you ask me...

Nightwing wrote:

Abstractness wrote:I didn't know Solar wind is a usefull powersource.

If you've seen Star Wars, In one scene, Count Dooku's ship uses a solar sail to move. That is a completely unpowered, passive propulsion system, but it is effective. There are many more examples, but it would take too long to get into them...

I wouldn't consider George Lucas a credible expert on astrophysics...

Loki wrote:I wouldn't consider George Lucas a credible expert on astrophysics...

I wasn't saying he was. I was just pointing out one of the many uses for solar wind...

Nightwing wrote:

Abstractness wrote:I didn't know Solar wind is a usefull powersource.

The solar wind is pretty much pure radiation. The main components of solar wind are photons (Light) and gamma radiation (Which can kill...). If Earth didn't have a magnetic field, it would be a barren wasteland, since it couldn't deflect the solar particles.

Fail: Solar wind only consists of the charged particles. Photons aren't charged and aren't part of the solar wind. Gamma rays are photons too. I was aware that photons are useful for pushing solar sails, but the solar wind is about 2000 times weaker, hence almost useless. Solar wind, solar sail, It can be confusing.

Nightwing wrote:
On another note: Did you know that you can actually SEE the solar wind with the naked eye?

All I know, is the green Aurora Borealis which is caused by the solar wind hitting the magnetosphere:
https://www.youtube.com/watch?v=FG0fTKAqZ5g (watch in full HD)
about at 1:20. This is of course also visible from the ground if you live in the polar regions.

Nightwing wrote:
Here's how: Go up into space, and close your eyes. You should see tiny blue streaks darting around in your eyeballs. This is caused by the solar particles interacting with the fluid in your eyes... Pretty cool, if you ask me...

Fail: These flashes are caused by cosmic rays which mainly come from supernovae instead of our sun:
http://en.wikipedia.org/wiki/Cosmic_ray_visual_phenomena

the sun-as-a-nuclear-reactor analogy is not exactly correct. the sun's internal process is nuclear fusion, due to the intense heat and pressure at the core with an abundance of light elements (up to iron). our reactors on earth utilize nuclear fission of very heavy elements, and the fission process is throttled by neutron-absorbing control rods.

meltdown occurs when the fission process goes out of control and depending on the circumstances you may or may not see a nuclear explosion...

nuclear fusion reactors are something else... once you are able to start the reaction, the fusion rate has to be fast enough to maintain the ridiculous heat and pressure under which fusion can occur. if that somehow got out of control the rate of fusion would likely follow suit and result in a fantastic cement block centuries later as a monument of "don't". but far more likely is that the reaction would damage the containment equipment, the plasma escapes damaging the reactor and possibly the immediate area around it. but, if the reaction were to suddenly accelerate enough it may just fuse all the fuel before the containment broke, quite possibly erasing the continent the reactor was on.

physics...

I posted an insane aircraft design here: http://www.physicsforums.com/showthread.php?t=705635

Abstractness wrote:I posted an insane aircraft design here: http://www.physicsforums.com/showthread.php?t=705635

"You just be logged in to view this page."

Got a screen cap you can post here?

Note that this sketch represents the entire aircraft.
Also the aircraft may be much longer than in the sketch.

Needed a second look after my coffee started working

You're proposing a flying wing that rides it's own compression wave inferno? How is this not cool?

Got some questions and confirmations on operation;
Inertia and gas pressure keeps the fuel pressed against the rear of the tank? Presumably you would stop cooling the fuel once you reached cruising altitude; it'll start boiling on it's own from there, though once you got it compressed inside the tank, all you may have to do is close the fuel valve and open it when you need it.
Seems like you'd have to maintain a very fine balance between fast enough and not too fast to keep the ignited fuel from expanding beyond the fuselage. Am I missing something here? No actual measurements or angles to compare too.
How do you get it up to speed to begin with? Standard turbine thrust? Rocket boosters?