Perhaps we should call it a meta-conspiracy theory. Al-Qaeda plotted an actual conspiracy (a pretty large one at that, and one they continued denying for a couple years after the event before deciding that owning up was better for recruiting), and the people we call conspiracy theorists believe that conspiracy was fictional and replace it with something even more bizarrely inexplicable.
It was a coverup to prevent development of the EMDrive.
Wouldn't that violate conservation of energy (which is preserved within a rest frame)?
Yup. Energy is not conserved in General Relativity. There is an analog of energy conservation in GR (Stress-Energy Conservation), but it only ensures local conservation of energy, not global: energy can appear or disappear as long as it does not flow across a geometric boundary.
Or to put in another way, if two photons are travelling in opposite directions, expansion will redshift them both, according to anyone who might detect either of them. But that means their momentums have changed by opposite amounts, so they can't both have been "slowed"
It's the magnitude of the momentum that matters. Think of it in terms of energy: as photons propagate through an expanding space, their wavelengths increase, i.e. they lose energy. This is true regardless of the direction in which the photons are propagating. The same happens to massive particles, except in that case, they actually do slow. Observers with in different Lorentz frames will see the photons redshifted or blueshifted in different ways, but that is an independent effect.
You have to think in terms of coordinate invariants.
A particle moving in any reference frame will experience "Hubble drag" from expansion, with regard to that reference frame.
Uh, no. Hubble drag drives velocities exponentially to zero in one particular reference frame, which is the comoving frame. Anything at rest with respect to the comoving frame stays at rest. There is no conflict with relativity here: the fundamental laws of nature are true irrespective of reference frame, but the particular realization of the spacetime induces a preferred frame. This is akin to spontaneous symmetry breaking in particle physics (i.e., the Higgs mechanism).
It's not actually special, though, is it? Things will slow down because they'll be hit by higher energy photons from one side than the other unless they're at rest (on average) with the CMB frame - is that what you were getting at?
No, the slowing would happen even in the absence of a photon background. It's a direct result of spacetime expansion. Think of it in terms of the equivalence principle: a photon moving in an expanding universe redshifts, i.e. loses momentum. Therefore, a massive body must also lose momentum, relative to the rest frame of the expansion, which is the same as the CMB frame.
If the universe stopped expanding tomorrow, wouldn't it still be the case?
The difference with ether is that the behaviour of light would change depending on your motion relative to the ether. The CMB is a frame of reference that is visible to everyone, but it is no different from any other frame of reference you choose.
No, this is incorrect. In an expanding universe, the CMB rest frame is unique.
It's one thing to consider Everett's interpretation of the waveform collapse function. It's another thing to consider an alternate universe where Hitler is president of the United States, and I dated the homecoming queen.
In that case, doesn't the CMB radiation represent a frame of reference, kind of like the (discredited) Ether idea?
Yes. The CMB rest frame is a special frame of reference. Any free body in motion relative to that reference frame will eventually slow down and come to rest with respect to the CMB frame. This is an effect due to cosmic expansion, and does not contradict relativity.
EMDrive is real, because it is proven by NASA scientists. NASA! Scientists! NASA!
The thing that really gets me is it's the same people who are guilelessly credulous about the EMDrive and lecture everybody else about having a Proper Scientific Attitude who are also global warming deniers.
Correcting myself before somebody else does. There was, in fact, a thruster failure, but they knew about it before landing and gave the lander a go anyway.
I don't like to talk bad about the labors of perhaps good engineers
Then don't.
And forget about the grappling hooks which are unusual, how do you screw up a simple thruster
Um, the lander bounced. It wasn't a thruster failure. Yeah, landing on Mars is a bitch, but I think you are vastly underestimating the challenges involved in landing on something which for all intents and purposes has no gravity at all. Especially when, you know, nobody's ever done it before.
Thanks for that, Armchair Rocket Scientist. Now please tell us all about how Elon Musk is an overrated hack, and why the EMDrive is being suppressed by a conspiracy.
Yes, put our country back to work, let the market decide which technologies are efficient enough to take on coal. Why is our government only choosing energy production that only works when it's sunny or windy? Why is Bill Gates funding nuclear technology advancement in China and not here? Government shouldn't be picking winners and losers.
And furthermore:
- Canned talking point - Canned talking point - Unsubstantiated "fact" - Canned talking point - Political dog whistle
Now please quit arguing that since China isn't doing anything, there's no point in the U.S. doing anything either. Fact is, the U.S. and China together are responsible for more than 38% of global greenhouse gas emissions, more than the EU, Russia, India, Japan and Brazil combined. We have a unique responsibility in the fight against global warming.
I expect momentum to be transferred in the direction of the impactor, not perpendicular to that direction, chewing up structure along the way. This structure was too stiff.
Don't get me wrong, I'm all for allowing people to live there lives the way they want. It's none of my business whether someone digs women, men, mayonaise or any combination of those. But how is it, evolution-wise, not a mental disorder?... If it's not that, what is it?
Normal variation. Behavioral diversity within a species creates a stronger evolutionary pressure than the corresponding reduction in individual reproductive fitness.
Slashdot Mirror
Perhaps we should call it a meta-conspiracy theory. Al-Qaeda plotted an actual conspiracy (a pretty large one at that, and one they continued denying for a couple years after the event before deciding that owning up was better for recruiting), and the people we call conspiracy theorists believe that conspiracy was fictional and replace it with something even more bizarrely inexplicable.
It was a coverup to prevent development of the EMDrive.
Wouldn't that violate conservation of energy (which is preserved within a rest frame)?
Yup. Energy is not conserved in General Relativity. There is an analog of energy conservation in GR (Stress-Energy Conservation), but it only ensures local conservation of energy, not global: energy can appear or disappear as long as it does not flow across a geometric boundary.
Well yes, it's unique, but it isn't particularly special. Physics works exactly the same whether you're in the CMB frame or not.
No! It really is special. In any frame except the CMB rest frame, a moving particle experiences Hubble drag from the expansion.
Wrong.
There's absolutely nothing in that Wikipedia page that contradicts anything I've said. You're just not understanding it properly.
Or to put in another way, if two photons are travelling in opposite directions, expansion will redshift them both, according to anyone who might detect either of them. But that means their momentums have changed by opposite amounts, so they can't both have been "slowed"
It's the magnitude of the momentum that matters. Think of it in terms of energy: as photons propagate through an expanding space, their wavelengths increase, i.e. they lose energy. This is true regardless of the direction in which the photons are propagating. The same happens to massive particles, except in that case, they actually do slow. Observers with in different Lorentz frames will see the photons redshifted or blueshifted in different ways, but that is an independent effect.
You have to think in terms of coordinate invariants.
A particle moving in any reference frame will experience "Hubble drag" from expansion, with regard to that reference frame.
Uh, no. Hubble drag drives velocities exponentially to zero in one particular reference frame, which is the comoving frame. Anything at rest with respect to the comoving frame stays at rest. There is no conflict with relativity here: the fundamental laws of nature are true irrespective of reference frame, but the particular realization of the spacetime induces a preferred frame. This is akin to spontaneous symmetry breaking in particle physics (i.e., the Higgs mechanism).
Well yes, it's unique, but it isn't particularly special. Physics works exactly the same whether you're in the CMB frame or not.
No! It really is special. In any frame except the CMB rest frame, a moving particle experiences Hubble drag from the expansion.
It's not actually special, though, is it? Things will slow down because they'll be hit by higher energy photons from one side than the other unless they're at rest (on average) with the CMB frame - is that what you were getting at?
No, the slowing would happen even in the absence of a photon background. It's a direct result of spacetime expansion. Think of it in terms of the equivalence principle: a photon moving in an expanding universe redshifts, i.e. loses momentum. Therefore, a massive body must also lose momentum, relative to the rest frame of the expansion, which is the same as the CMB frame.
If the universe stopped expanding tomorrow, wouldn't it still be the case?
No.
The difference with ether is that the behaviour of light would change depending on your motion relative to the ether. The CMB is a frame of reference that is visible to everyone, but it is no different from any other frame of reference you choose.
No, this is incorrect. In an expanding universe, the CMB rest frame is unique.
It's one thing to consider Everett's interpretation of the waveform collapse function. It's another thing to consider an alternate universe where Hitler is president of the United States, and I dated the homecoming queen.
As long as you didn't date Hitler, it's all good.
In that case, doesn't the CMB radiation represent a frame of reference, kind of like the (discredited) Ether idea?
Yes. The CMB rest frame is a special frame of reference. Any free body in motion relative to that reference frame will eventually slow down and come to rest with respect to the CMB frame. This is an effect due to cosmic expansion, and does not contradict relativity.
So, does this mean there is no Axis of Evil in the CMB radiation?
This seemed to be a thorny problem that wasn't going away as per many expert opinions not long ago, but now everything's fine again?
The Axis of Evil is still there, but is of dubious statistical significance. These guys were looking for different patterns from the AoE.
EMDrive is real, because it is proven by NASA scientists. NASA! Scientists! NASA!
The thing that really gets me is it's the same people who are guilelessly credulous about the EMDrive and lecture everybody else about having a Proper Scientific Attitude who are also global warming deniers.
It wasn't a thruster failure.
Correcting myself before somebody else does. There was, in fact, a thruster failure, but they knew about it before landing and gave the lander a go anyway.
Armchair Rocket Scientist #2:
I don't like to talk bad about the labors of perhaps good engineers
Then don't.
And forget about the grappling hooks which are unusual, how do you screw up a simple thruster
Um, the lander bounced. It wasn't a thruster failure. Yeah, landing on Mars is a bitch, but I think you are vastly underestimating the challenges involved in landing on something which for all intents and purposes has no gravity at all. Especially when, you know, nobody's ever done it before.
Rescue mission!
I somehow feel quite certain it would be cheaper to just build a half-dozen copies of Philae and launch those.
Thanks for that, Armchair Rocket Scientist. Now please tell us all about how Elon Musk is an overrated hack, and why the EMDrive is being suppressed by a conspiracy.
Increase the number of checkpoints and screeners?
Do I win?
Yes, put our country back to work, let the market decide which technologies are efficient enough to take on coal. Why is our government only choosing energy production that only works when it's sunny or windy? Why is Bill Gates funding nuclear technology advancement in China and not here? Government shouldn't be picking winners and losers.
And furthermore:
- Canned talking point
- Canned talking point
- Unsubstantiated "fact"
- Canned talking point
- Political dog whistle
Now please quit arguing that since China isn't doing anything, there's no point in the U.S. doing anything either. Fact is, the U.S. and China together are responsible for more than 38% of global greenhouse gas emissions, more than the EU, Russia, India, Japan and Brazil combined. We have a unique responsibility in the fight against global warming.
a bowl of petunias and a very surprised looking whale....
i wonder if it will be friends with me? ...
- Douglass Adams RIP
Oh, no. Not again.
... the drinking age is 18, or even lower, many college campuses have undergraduate pubs, and binge drinking is a vastly smaller issue.
Americans are stupid.
I expect momentum to be transferred in the direction of the impactor, not perpendicular to that direction, chewing up structure along the way. This structure was too stiff.
ZOMG! It's a conspiracy, just like Bush did 9/11!
Don't get me wrong, I'm all for allowing people to live there lives the way they want. It's none of my business whether someone digs women, men, mayonaise or any combination of those. But how is it, evolution-wise, not a mental disorder? ... If it's not that, what is it?
Normal variation. Behavioral diversity within a species creates a stronger evolutionary pressure than the corresponding reduction in individual reproductive fitness.
Sorry to go all science on you there, asshole.
Crazy transient radio signal isn't aliens? What am I supposed to do with my EMDrive now?
OB Feynman.