Time travels slower in a fast moving reference frame relative to a slower moving reference frame. This has been proven many many times. In fact every time you use GPS. The GPS satellites are traveling quite fast relative to us. Without a proper time dilation correction, GPS fixes would drift km per month. There are many more examples, including having 2 atomic clocks, one on earth one on the spaceshuttle. Decay of particles (muons would not make it to sea level without time dilation), so on and so forth.
This is almost correct, you need to be able to do FTL in at least 2 different reference frames to violate causality. If for example you can only travel faster than light in a fixed reference frame --ie there is a preferred frame, so very not relative. Then you don't get time paradoxes. For my sci fi game, the rest frame of the universe (center of mass of the universe is stationary) is the preferred frame and travel can be instantaneous in this frame. Note in all other reference frames travel is *not* instantaneous and is some frames you travel backwards in time, but then coming back you travel forward again, so you can never visit your past. The universe remains causal.
while air breathing enourmously reduces weight requirements.
Air intakes, drag from these intakes and even the engine itself (the entire bottom of the craft) and are not light or cheap. While LOX and fuel is very cheap. GLOW is *not* a good indicator of cost. Also you still need that last 30% from somewhere and as of yet, not a single result has been published to show that these hypersonic engines produce more thrust than drag.
Block Ciphers and their kin are not cracked by quantum computers. They only reduce the search space by a square root. ie half the key size. Since quite a few modes of using these ciphers gives time/memory trade off attacks that give the same square root key size reduction (ie hash functions and birthday attacks), its not really a problem.
Reversible computing reduces, but does not remove the limit. Basically anything that has a different number of inputs to outputs must have a non zero entropy logic. Since things like adders are like this (twice as many inputs as output) etc, then you can't reduce to levels that solve the problem. Note the calculation on the energy required is not from the entropy limit of a logic gate, but the "entropy" of just that many keys.
You are free to not watch them. Just think if these movies passed into the public domain as was originally intended, how many crap sequels, remakes, recuts there would be. And over all we would *not* be worse off.
Michael Bay takes 100-200Million dollars and turns it into 500Million+ within a few years. That is just good investment. Sure you may complain about the movies he makes, but chances are you go to them anyway. The folks putting up the 100Million want their money back with interest.
That does not imply they are cloneable. You can easily come up with a nonlinear process that is impossible to clone, in that the clone not being a perfect copy will diverge from the original. The brain may or may not be one such machine/computer whatever. You don't need to invoke the "soul" or anything. Just plain physics and chemistry.
The universe may not permit FTL. It certainly looks that way for now. Just because you can dream it does not mean it can be done.
However interstellar travel without FTL is plausible. It may not be you going, but there will not be any shortage of volunteers. Even if its a 30+ year journey.
It explains why stars and other matter slows down while weakly interacting matter does not(aka dark matter). Ultra cold brown dwarfs are stars. They are affected the same way. More or less.
All very good points. I don't really disagree with anything. Except perhaps i thought that current mass bounds on neutrinos means they are not really candidates? But i have been out of the loop for a while now.
Well on the face of it GR is defiantly not "better" than Newtonian physics. But it does fit the data better and passes every test we can throw at it. Even frame dragging! However even in my original department GR effects at a galactic scale where often considered as a candidate. But every time the sims are run or approximations made for pen and paper... the results where never even close to enough to explain galactic rotation (not the only thing that can use dark matter as a explanation).
As for adding new physics before understanding what we have. Well yea of course. Otherwise we would never move forward. Both GR and QCD are not easy to solve in any non trivial setting, that is not a good reason to stop until we can. Just assuming that everything must be wrong at some scale because we can't test it there seems just as disingenuous as invoking a matter field. In fact the matter field seems better because at least you may be able to make some new predictions that can be tested.
Lots of us don't like dark matter any more than the standard model. But they just work. Ok so dark matter is a shadow of the standard model. But its still the best we got. Every modified gravity theory i have seen either only works in one case or not at all, and the only motivation is to explain that one effect and hence have zero new predictions other than fixing one observational issue. Dark matter is just better right now. Got something that works better. There are lots of us that will be all ears.
Changing gravity and requiring massive neutrinos seems like the antithesis of Occam's razor. I was never a huge fan of dark matter. But now its really hard to say its not the best explanation with a straight face.
Evidence: The bullet cluster. The observations imply that there is a huge amount of mass that was moving with each galaxy before the collision, that is not baryonic. That is interacts only via the force of gravity and is not affected (or at least very very weakly interacting) via the other forces, most importantly the electromagnetic force.
There is quite a few other effects that dark matter can explain nicely. We are in fact devising experiments to attempt to observe dark matter particle candidates.
The number of extra planets or dark stars you would need to matter, *would* show up because there would need to be soo many. They have been looked for you know. For example if there are millions more of these cold brown dwarfs than what we already have estimated, then the average distance to them would be so small that we would be able to observe many of them (probably would imply at least a few within the ort cloud). We would see many more micro-lensing events... etc etc.
You can't have your cake and eat it too. If there is enough to explain dark matter, there is more than enough that observing them would be quite trivial.
On top of all that, such objects do not explain other observations of dark matter. In particular, the bullet cluster. We can in fact "see" dark matter.
A lot of people I know on FB the answer is yea they hate it that much. They are there because their other friends are there and these "friends" sux at keeping in touch any other way.
Twisted logic is assuming that Facebook is better *despite* its track record as quite a few post above seem to indicate. Personally i like g+ so far. I get a lot more control than i ever did on Facebook, and Google is far less likely to have serious security issues with the ajax or whatever its called these days.
RS or Farnell sell military grade for many of its components. For the most part its 2-5x more expensive, better MTBF and most importantly a much wider range of usable temperatures and storage temperatures. This matters in many civilian applications where normal components typically are not specified to work below zero (they often do, but don't count on it). Marine environments typically need below zero if you are in the north sea for example. It is easier to use an existing standard that already takes this into account.
True. However that is *not* why commercial heat pumps do badly in cold weather, since cold for thermodynamics reasons is relative to *absolute zero*. Or -273C. Since -25C is cold for a human and inside is often not hotter than 25C. We can calculate the ideal performance of such a heat pump which is T_c/(T_h-T_c), or in this case 248K/(298K-248K)=4.9. In other words for each joule of energy used you get to pump almost 5 joules of heat even at -25C outside. This is of course ideal performance and real performance is less, typically about a factor of 2 less. Or still a COP of 2-3 (compared to resistive heating of COP=1). Note however this assumes the pump is designed for this operating temperature (most are not). There are other issues other than working fluid too, for example icing up the outside heat exchanger. As others have noted, ground heat exchange can work well for this, thou less so for build up areas.
Bottom line is that heat pumps don't work well in cold weather is due to practical design issues, not fundamental physics.
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Time travels slower in a fast moving reference frame relative to a slower moving reference frame. This has been proven many many times. In fact every time you use GPS. The GPS satellites are traveling quite fast relative to us. Without a proper time dilation correction, GPS fixes would drift km per month. There are many more examples, including having 2 atomic clocks, one on earth one on the spaceshuttle. Decay of particles (muons would not make it to sea level without time dilation), so on and so forth.
GR and SP have been pretty thoroughly tested.
This is almost correct, you need to be able to do FTL in at least 2 different reference frames to violate causality. If for example you can only travel faster than light in a fixed reference frame --ie there is a preferred frame, so very not relative. Then you don't get time paradoxes. For my sci fi game, the rest frame of the universe (center of mass of the universe is stationary) is the preferred frame and travel can be instantaneous in this frame. Note in all other reference frames travel is *not* instantaneous and is some frames you travel backwards in time, but then coming back you travel forward again, so you can never visit your past. The universe remains causal.
The photo diode on its own is not bad either. Or get a proper PIN diode for the job, they are cheap enough.
while air breathing enourmously reduces weight requirements.
Air intakes, drag from these intakes and even the engine itself (the entire bottom of the craft) and are not light or cheap. While LOX and fuel is very cheap. GLOW is *not* a good indicator of cost. Also you still need that last 30% from somewhere and as of yet, not a single result has been published to show that these hypersonic engines produce more thrust than drag.
Block Ciphers and their kin are not cracked by quantum computers. They only reduce the search space by a square root. ie half the key size. Since quite a few modes of using these ciphers gives time/memory trade off attacks that give the same square root key size reduction (ie hash functions and birthday attacks), its not really a problem.
Reversible computing reduces, but does not remove the limit. Basically anything that has a different number of inputs to outputs must have a non zero entropy logic. Since things like adders are like this (twice as many inputs as output) etc, then you can't reduce to levels that solve the problem. Note the calculation on the energy required is not from the entropy limit of a logic gate, but the "entropy" of just that many keys.
You are free to not watch them. Just think if these movies passed into the public domain as was originally intended, how many crap sequels, remakes, recuts there would be. And over all we would *not* be worse off.
Michael Bay takes 100-200Million dollars and turns it into 500Million+ within a few years. That is just good investment. Sure you may complain about the movies he makes, but chances are you go to them anyway. The folks putting up the 100Million want their money back with interest.
That does not imply they are cloneable. You can easily come up with a nonlinear process that is impossible to clone, in that the clone not being a perfect copy will diverge from the original. The brain may or may not be one such machine/computer whatever. You don't need to invoke the "soul" or anything. Just plain physics and chemistry.
Don't you mean if? Sure it may be possible. But then again while we don't really understand consciousness yet, its not a given.
The universe may not permit FTL. It certainly looks that way for now. Just because you can dream it does not mean it can be done.
However interstellar travel without FTL is plausible. It may not be you going, but there will not be any shortage of volunteers. Even if its a 30+ year journey.
It explains why stars and other matter slows down while weakly interacting matter does not(aka dark matter). Ultra cold brown dwarfs are stars. They are affected the same way. More or less.
All very good points. I don't really disagree with anything. Except perhaps i thought that current mass bounds on neutrinos means they are not really candidates? But i have been out of the loop for a while now.
Well on the face of it GR is defiantly not "better" than Newtonian physics. But it does fit the data better and passes every test we can throw at it. Even frame dragging! However even in my original department GR effects at a galactic scale where often considered as a candidate. But every time the sims are run or approximations made for pen and paper... the results where never even close to enough to explain galactic rotation (not the only thing that can use dark matter as a explanation).
As for adding new physics before understanding what we have. Well yea of course. Otherwise we would never move forward. Both GR and QCD are not easy to solve in any non trivial setting, that is not a good reason to stop until we can. Just assuming that everything must be wrong at some scale because we can't test it there seems just as disingenuous as invoking a matter field. In fact the matter field seems better because at least you may be able to make some new predictions that can be tested.
Lots of us don't like dark matter any more than the standard model. But they just work. Ok so dark matter is a shadow of the standard model. But its still the best we got. Every modified gravity theory i have seen either only works in one case or not at all, and the only motivation is to explain that one effect and hence have zero new predictions other than fixing one observational issue. Dark matter is just better right now. Got something that works better. There are lots of us that will be all ears.
Google and Wikipedia is your friend. http://en.wikipedia.org/wiki/Bullet_Cluster
Changing gravity and requiring massive neutrinos seems like the antithesis of Occam's razor. I was never a huge fan of dark matter. But now its really hard to say its not the best explanation with a straight face.
Evidence: The bullet cluster. The observations imply that there is a huge amount of mass that was moving with each galaxy before the collision, that is not baryonic. That is interacts only via the force of gravity and is not affected (or at least very very weakly interacting) via the other forces, most importantly the electromagnetic force.
There is quite a few other effects that dark matter can explain nicely. We are in fact devising experiments to attempt to observe dark matter particle candidates.
The number of extra planets or dark stars you would need to matter, *would* show up because there would need to be soo many. They have been looked for you know. For example if there are millions more of these cold brown dwarfs than what we already have estimated, then the average distance to them would be so small that we would be able to observe many of them (probably would imply at least a few within the ort cloud). We would see many more micro-lensing events ... etc etc.
You can't have your cake and eat it too. If there is enough to explain dark matter, there is more than enough that observing them would be quite trivial.
On top of all that, such objects do not explain other observations of dark matter. In particular, the bullet cluster. We can in fact "see" dark matter.
And the bullet cluster observations cannot be explained with MACHOs either.
MACHOs do a poor job of explaining the bullet cluster observations.
Do they all hate Facebook so much?
A lot of people I know on FB the answer is yea they hate it that much. They are there because their other friends are there and these "friends" sux at keeping in touch any other way.
And what name do they use on FB? The vast majority use their common name.
Twisted logic is assuming that Facebook is better *despite* its track record as quite a few post above seem to indicate. Personally i like g+ so far. I get a lot more control than i ever did on Facebook, and Google is far less likely to have serious security issues with the ajax or whatever its called these days.
RS or Farnell sell military grade for many of its components. For the most part its 2-5x more expensive, better MTBF and most importantly a much wider range of usable temperatures and storage temperatures. This matters in many civilian applications where normal components typically are not specified to work below zero (they often do, but don't count on it). Marine environments typically need below zero if you are in the north sea for example. It is easier to use an existing standard that already takes this into account.
True. However that is *not* why commercial heat pumps do badly in cold weather, since cold for thermodynamics reasons is relative to *absolute zero*. Or -273C. Since -25C is cold for a human and inside is often not hotter than 25C. We can calculate the ideal performance of such a heat pump which is T_c/(T_h-T_c), or in this case 248K/(298K-248K)=4.9. In other words for each joule of energy used you get to pump almost 5 joules of heat even at -25C outside. This is of course ideal performance and real performance is less, typically about a factor of 2 less. Or still a COP of 2-3 (compared to resistive heating of COP=1). Note however this assumes the pump is designed for this operating temperature (most are not). There are other issues other than working fluid too, for example icing up the outside heat exchanger. As others have noted, ground heat exchange can work well for this, thou less so for build up areas.
Bottom line is that heat pumps don't work well in cold weather is due to practical design issues, not fundamental physics.