However, if the wormhole is stable, Alice and Bob (and seperately Carol and Dave) would be effectively adjacent, so you wouldn't see tha causality problem.
I'm not sure about that, though. I just have no idea how you'd draw the diagrams when the plot of routes from Alice to Bob is not continuous, and the shortest route and the shortest route that doesn't use the wormhole are time-like and space-like respectively.
It just still seems like if Alice and Bob were cruising past the opening of the wormhole, and Alice dropped in a message pod destined for Bob, you could still end up with the situation in the diagrams.
Relativity is probably as wrong as Newtonian mechanics. I.e. it works on one scale but not another. I have no doubt we will find something that applies on quantum scale and galactic scale. I am just too stupid to help out in that endeavor.
LOL, agreed on all counts.:)
But I'm also too pessimistic to think Relativity will turn out to be wrong in a way that lets all of my fantasies come true. Going from Newton to Einstein didn't undo all the stupid restrictions of Newton's world, like Conservation of Momentum which is a real drag for flying saucers or Inertial Dampeners. Or that stupid Second Law of Thermodynamics. I have a feeling whatever replaces Relativity as the Best Model isn't going to undo causality or the universal speed limit and the best hope we have of visiting other stars is really boring generation ships that have absolutely no pep.
These are all salient observations that must be taken into consideration. I just can't get behind calling what is almost entirely an up-front fixed cost a fuel cost. Each extra pound of coal has significant and real costs associated with acquiring it. But once you've built sufficient mirrors to collect all the light you want, the ongoing cost for the sunlight that mirror reflects is, what, the power needed by a one-revolution-per-day tracking motor? You could amortize the fixed costs over the total watts reflected over the lifetime of the mirrors and call that the 'fuel cost', but that's just not how normal accounting is done.
Special Relativity is, as the name implies, a special case. It doesn't apply in the more general (ah!) case, and especially doesn't apply in a strong gravitational field.
That's backwards.
Special Relativity applies everywhere, but does not sufficiently describe situations involving acceleration. That doesn't mean that inside a strong gravitational field the SR assumptions of constant c etc don't apply. They do. You just need GR also to fully describe these situations.
the title of his paper is telling: "Rotating Cylinders and the Possibility of Global Causality Violation"
Yes it is very telling. It tells me that the author of the paper understands the implications of FTL travel, and that their device, if it worked, could violate causality.
Causality is a base assumption of GR, too. Violating causality means violating the basic assumptions of General Relativity.
I would restate the dogma that "FTL is impossible" to "FTL may be impossible, but at very least, it is very difficult".
The 'dogma' is "FTL is impossible in a Relativistic universe", and that remains true.
It is quite possible that Relativity is wrong, very probable really. However it is not guaranteed that it is wrong with regards to the aspects that make FTL impossible. I'd call that improbable, even, since it'd have to be really wrong for that to happen and yet still keep a causal universe.
If you're trying to argue that modifying some technology to make it more efficient will necessarily make it cost less per unit of energy, then that is patently false.
Why even have a conversation with someone who only sees the possibilities that "efficiency doesn't matter" or "increased efficiency necessarily reduces cost regardless of mechanism" and argues against one idiotic half of this false dichotomy to prove the other?
Any technology with a different efficiency is a different technology, full stop.
Nonsense, because many technologies have different efficiencies at different scales or other parameters. If you want to define a diesel generator and a diesel generator that is 0.1% larger or with an operating RPM 0.1% slower as "different technologies" then be my guest at abusing semantics in ways nobody will ever agree with.
With CHP systems, turbine efficiency doesn't matter.
What a silly thing to say. That's only true if the only thing you care about is heating, and the only use for electricity you have is to power electric heaters. Otherwise, efficiency is going to affect the size of system you need to achieve a given desired amount of P.
In fact, a small system can be more efficient as well as cheaper than a larger one by utilizing the 60% waste heat produced.
Larger systems can make more effective use of waste heat, too.
But cost is clearly the biggest factor. And it should be plainly obvious that the relationship between cost and efficiency is tenuous at best.
What's plainly obvious is that efficiency effects cost, in particular within the parameters of a given technology, and can make the difference between it being practical for a given use or not.
It's why you aren't going to have a molten salt solar collector, or a sugar cane plantation with biodiesel generator plant in your yard, but you might have roof solar panels. While for large-scale city/region sized deployments, the opposite will be true.
What's also plainly obvious is that the statement "efficiency does not matter in renewable energy" is false.
I've never seen a decent prrof of the claim that an ansible necessitates a violation of causality.
It doesn't necessitate, it enables in what are from the point at which you have an ansible trivial ways. In other words, not every ansible usage violates causality, but there are ansible usages that do.
but if you create an ansible by changing the topolgy of space such that two points are closer together, that doesn't seem to break relativity.
If that occurs only for the duration of the communication, then the space-time diagrams in the example apply. So even though you haven't technically violated the SR restriction against FTL, you have violated causality.
Of course it does. A bigger solar concentrator is more expensive than a smaller one, and a bigger sugar cane field is more expensive than a smaller one.
You can't directly compare the efficiencies and costs of wildly different technologies, but that's a vastly different statement than saying efficient does not matter! If you are converting sugar cane with an efficiency 1/10th of someone else, that is going to mean you're growing 10 times as much sugar cane for the same output as someone else and that will significantly impact your cost in insanely obvious ways.
For the matter actually under discussion, molten salt solar concentrators and possible home use, it works like so: To collect enough energy for a given application (city/region vs a residential home) you need a certain size of collector. However, smaller turbines are less efficient. Therefore the power output/size curve and thus cost/desired power output curve is not linear, and favors larger installations.
Efficiency is going to directly impact the size of the collector you need for a given application, and thus cost. So yes, efficiency is quite important in solar power, as it is in every other renewable energy source. It is less important than with other energy sources, yet still quite important. And it could easily mean that below a certain size of application, the technology is economically infeasible.
Perhaps Relativity "allows" FTL travel in the sense that there appear to be ways to manipulate the gravitational rules to create the effect of FTL travel.
However in a very explicit sense Relativity does not allow FTL travel by any method whatsoever, even if the mechanism itself has nothing to do with relativity. According to Special Relativity, any method of FTL travel would make it possible to create scenarios by which effects happen before causes. For example with the help of two spacecraft equipped with Ansibles (instantaneous communication devices whose workings are completely irrelevant) you could effectively send yourself a message and receive it before you sent it -- sending it backward in time, violating causality.
Causality is one of the basic assumptions of relativity, and all the equations and workings of relativity are a consequence of maintaining causality in concert with a speed of light that is constant for all reference frames (and of course the assumption that the laws of physics must hold relative to all reference frames). It's possible that causality is a bad assumption, but it doesn't make much sense to me to imagine creating a device to get around that assumption based on equations which require it to be true.
Thanks, I'm glad you got my point and that it made some sense without ending up still sounding like unwarranted blaming of professionals.:)
But really, is there anything that can be done except for the movie-going public to spontaneously and for no apparent reason stop going to see movies that are little more than vehicles for special effects?
Is it even possible when I have to admit that I'll sometimes enjoy a movie that is utter garbage except for beautiful special effects? Are there alternatives that aren't worse?
I thought my point was clearly not a binary statement of cheap-n-easy special effects vs no special effects at all, yet also not that subtle either. I guess I was wrong.
Yeah, you're completely right, nobody cares, and if any of them did start turning down money, it'd probably just be the first step of them going out of business. It was, like I said, ridiculous.:)
In case you don't remember, there was significant public protest over Cassini:
Let's think about this for five seconds.
There were "significant" public protests over Cassini.
Cassini launched anyway with its RTG as planned, as have missions both before and since.
Conclusion: ZOMG enviro-wackos have the power to prevent NASA from using RTGs!
Seriously?!
the associated hinges/etc to unfurl them together likely weigh about the same as an RTG.
I do not think that is likely. Solar panels are thin and lightweight. That's their advantage. I see no reason a pair of hinges that needs to operate once are going to weigh more than a battery, and the motor to move the lightweight panel, again once, is going to weigh more than another battery, with the panels themselves massing as much as both batteries combined to equal the total mass of an RTG.
But you know, I'm not certain. What I am certain of is that NASA made the decision to go with solar panels instead of an RTG for mission engineering reasons and it had fuck-all to do with some disorganized protesting idiots.
An interesting conjecture, but wouldn't anything using reaction drives
Aka "anything" since we're talking about known physics, like Conservation of Momentum. Otherwise the possibility of FTL throws a wrench into pretty much everything.:)
light itself up quite nicely when it moved around? That is one of the conclusions over at Atomic Rockets [projectrho.com].
Er, I'm going to take the statement that Shuttle Main Engines could be seen past Pluto to mean it's plausible that we'd see the probe if our telescopes were pointed at it while it was burning. I don't expect a probe to need much in the way of acceleration, but I am allowing for a very large probe. So that's a good point.
But that whole page is in the context of stealth, like in a space-war, so a lot of the objects just aren't relevant in this case. As in the section about "Thrifty Engine Burns":
"Well fine!", you say, "I'll just burn once and drift silently"
But now you will be months in getting to your target. The extra time increases the chance that the enemy will spot you.
Not to mention the fact that once your initial burn is spotted, the enemy will be able to calculate your future position anytime in the future.
Except the probe already spent perhaps hundreds of years getting here from whatever nearby star it was replicated at and is going to spend hundreds of years quietly and passively observing our solar system. Once here the only time it's ever going to need to fire its engines are for station keeping, which depending on the orbit may be practically never, and will require minute amounts of thrust anyway.
Our only chance to spot alien probes via their engines may actually be when the newly minted probe-copies push off for whatever stars are next in the list. Since we're looking at the "why hasn't this already happened yet?" hypothesis, we have to consider the possibility that this already happened and our only decent chance at seeing them with today's technology happened yesterday, when we weren't looking.
And on that note the Atomic Rockets page seems to be assuming that "passive" sensors, aka the only kind we have, are omni-directional, which ours most certainly are not. Even if we can see the probe that doesn't mean we will. For an alien probe in our solar system, stealth in space is imminently achievable.
Again, interesting observation, but "so if aliens exist, why haven't we seen a probe yet?" still isn't a very interesting question.
I wish people would stop saying that the VFX are ruining moves. We're a tool used by the director (or, more often, by the studio) if that Director (or again, the studio) fail to utilize us within the story properly, how is it the VFX that are ruining movies?
In the same way vodka ruins Bob's personality. Of course it's actually Bob's problem, and vodka is just a neutral tool that can be used for bad or for awesome, but it would still miss part of the point to ignore the vodka's role in enabling Bob to start sucking. Before vodka came along, Bob was okay most of the time. Well, some of the time.
Just to be clear, when we (or I) say "VFX are ruining movies", we are blaming it on the lack of creativity of Hollywood. It's just unfortunate yet true that the existence of affordable and good VFX allows that lack of creativity to flourish.
There's a lot to be said for limitations and how it can make movies better.
Look at Jaws, Spielberg's breakout movie. Think of how horrifying the opening scene is, when you never even see the shark as the woman is (you presume, under the water) being torn apart. How often that movie is positively compared to Hitchcock, the master of suspense. Yet that's not the movie Spielberg set out to make! Originally, it was going to be a crappy monster movie in the ocean with Jaws front and center the whole time literally chewing up the scenery. But because they couldn't get their giant hydraulic-powered animatronic shark to work in salt water (the ocean's just a big wavy lake, right?), he had to make adjustments and go for a much subtler, and ultimately more effective, style.
Or the biggest example of something "ruined by VFX": Star Wars. Lucas luurved his effects even back then and Star Wars had the best around. But nevertheless, they couldn't afford to do endless lightsaber effects so we only had a few instances of them being used heavily in dramatically important moments, and so they were more awesome. He couldn't have a million jedi and robots and lasers to make them all stupid and boring. He had to have real locations and sets that looked real and that actors could interact with. He had to have character moments because he couldn't fill the entire movie with action sequences to make you forget that you didn't care about anyone on screen. Hell, maybe the only reason we didn't have a bouncing spinning light saber Yoda in Empire was because there was no way for him to do that on the end of Jim Henson's hand. Well, that and Lucas had little to do with that movie...
Anyway.
I know it's not the VFX studio's fault that so much VFX is used in place of actual good ideas and story and character. It would be completely ridiculous to blame you for doing your work better, faster, cheaper. But uh, that's exactly what enabled a lot of this crap. It would be completely ridiculous to say VFX companies shouldn't accept checks from the producers of crappy movies, but uh, that's exactly what you'll have to start doing if you don't want to hear "VFX are ruining movies" anymore.
Hey, actually, I never thought to ask that... Do effects companies ever turn down work? Good actors will turn down work, because they don't want their name associated with some piece of crap. Maybe if only the directors with talent or just good ideas got to work with the best VFX, maybe something positive would happen. *shrug* I don't know.
No reason to avoid Earth... but if Eris is more attractive to you, then so are all Oort clouds - no reason to get anywhere near
Er... that really wasn't part of my line of reasoning.
I'm saying, a very large space observatory would be able to study our entire solar system from a distance at which it would be invisible to us. Eris was just a reference point and hypothetical source of materials, not the (sole) object of study. In order to point out that we could have had our very best telescopes pointed right at an alien probe and been completely unable to see it.
considering the timescales and probable scale of "production", we could notice something weird with the spectra of comets by now
Are these Von Neuman probes or Slylandro probes?
It just needs to make a handful of copies to head off to the next nearest stars and repeat the process. Periodically make copies for replacement of 'our' probe -- they can already survive interstellar journeys so they should be pretty hardy, but you would want some backups made in advance -- and even kilometer-scale observatory/factories wouldn't come close to making a dent in Eris (which seems more likely a source of materials than comets, but either way) to the degree that we would notice it.
I don't really see any reason to assume that someone sending probes to study would damage what they are studying beyond necessity by letting exponential growth run unchecked.:p
If we had the collective courage [read - no enviro-wackos] to use RTGs [wikipedia.org] on our Mars probes, we wouldn't have lost Spirit to freezing temperatures brought on by low power from the solar cells.
LOL, that's why you think Spirit and Opportunity didn't use them? Enviro-wackos?
The real reason is simply optimizing for the mission profile. The MERs were relatively small devices with very tight mass budgets, and an RTG of sufficient power would have been too heavy compared to the solar panel/battery combo they went with instead. It was an engineering trade-off. They did, by the way, use RHUs to heat components but this was not sufficient to stave off freezing by itself.
The Mars Science Laboratory is going to use an RTG. It is a much larger rover, with power demands beyond what solar panels could provide, and with a more generous amount of mass to dedicate to the power system.
We used 'em on quite a few spacecraft [wikipedia.org] - why they aren't used more often for solar power-limited missions escapes me.
Yeah, which I would think would have suggested that maybe enviro-wacko objection to the concept of RTGs had nothing to do with it. This is a lobby with surprisingly less power than you might think.:)
If someone else did this already, they hid their probes pretty well...
Um... What makes you say that?
It doesn't seem like they would have to be hiding much, or at all for that matter, for us to miss them.
Look at a recent development at the limits of human observational ability: We just discovered that Eris is, despite its greater mass, may not actually be larger in diameter than Pluto. We did not do this by actually resolving the disk with sufficient resolution to answer the question, but by timing how long it occluded a background star. While certainly an awesome and impressive feat, it raises a very pertinent question:
Just how big/close would an alien probe need to be for it to be hard to miss?
Imagine a probe, many times larger than any telescope we have even on the ground, observing from the outer solar system. This probe could be orbiting Eris right now, while it's duplicator-unit scurries around the surface of the body making the next generation of probes to send to our stellar neighbors, and we'd have virtually no way of knowing.
I have other issues with this an other versions of the Fermi Paradox, but the crux is the part where one asks "then why haven't we seen them already?" as if this is in any way a paradox, or even a puzzling mystery.
Because it's really, really, REALLY, REALLY freaking expensive. You're talking a big task considering the need to develop the technology both for the probe and for on-orbit assembly
Good thing in-orbit assembly is one of the capabilities NASA's new plan intends to develop! Not because it would help a specific project, but because there are many projects this would help, or make feasible in the first place.
Too bad Congress damaged this exciting plan in the name of sustaining pork^H^H^H^H a strategically important manufacturer of ICBM components!
From the blurb: Now a leaked EPA document reveals that the agency allowed the widespread use of a bee-toxic pesticide, despite warnings from EPA scientists.
You've already disproven your own theory on how things work.
Ha!
All this shows is that sometimes government regulation fails to prevent the damage that would have happened anyway in the absence of any government regulation. Which is hardly surprising, unless you subscribe to the false dichotomy that private and public entities must be entirely good or bad and opposite of each other.
To actually disprove the thesis, you would have to demonstrate something completely contrary to every fact: That situations without environmental regulations (or, in some cases, the threat of regulation) are better for the environment than with. The entire history of the EPA and similar organizations, including all of their missteps, contradicts that idea. Your vehicles, your air, your water, all are measurably and demonstrably cleaner because of government regulation.
As if Bayer would have never released a dangerous pesticide justified by a shoddy study if the EPA didn't exist. Well, perhaps not, because they would have had no reason to conduct a study. So more likely the contribution of this chemical to hive collapse would continue to be unknown.
But this discussion does not actually hinge on hypothetical situations. The reality of unregulated industry can be compared to the reality of the regulated. This comparison is not favorable to the unregulated situation at all. Yes regulation can fail to do its job, it can even make things worse in the case of particularly misguided rules, yet the overall trend is not even close to a tough call. History is flagrantly clear on what happens when industry is allowed to run free.
I've seen the likes of you before and none of you have ever let facts or logic
Your concept of facts and logic are hilarious.
By not complaining that the EPA is flawed and should be improved (very true), but rather that this example disproves the entire thesis that environmental regulation is necessary or that we are better off because of it, you're just spitting in the face of logic and reality for the sake of an ideology.
Some organic growers use it. They use a lot less of it,
I see a lot of [citation needed] following the crucial statements in support of this claim. "Reduction and elimination of chemical pesticide use is technically challenging." however does have a cite.
only specific chemicals (with little to no synthetic stuff):
"Synthetic" by itself does not particularly concern me. There are certainly synthetics -- like, say, the one in TFA -- that are bad. But it's not the "synthetic" descriptor that makes it bad, nor does describing something as "non-synthetic" make me embrace it in my tree-hugger arms.
For example, sulfur is a "non-synthetic" anti-fungal used in organic farming. And there's no obscure study by the Bayer corporation needed to demonstrate the dangers of sulfur runoff from farming.
Here's a Nature article which says (with offline cite) that it isn't clear whether organic farming is better or worse in terms of environmental damage from runoff -- which is a larger issue than just pesticide use but clearly affected by it.
Don't get me wrong; I'm not bashing organic farming as useless or counter-productive. It has it's benefits, not the least of which is trying to figure out how to solve these problems without saying "well what can we cook up in the chemical plant?". I'm not convinced the pesticide issue is actually one of them, not inherently anyway.
In relativity nothing can travel beyond light speed because that would imply an infinite energy,
Not exactly. In Relativity nothing with rest mass can travel at the speed of light because that would imply infinite energy.
Nothing at all, not even information, can travel faster than light because that implies that you could create scenarios where from certain reference frames, effects appear to happen before causes. As in time travel, or causality violation, and both Relativity theories (and the rest of physics) assumes causality to hold.
Ten years after Einstein's death we discovered a universal velocity reference in the microwave background dipole, so one of the main tenets of special relativity is not true anymore.
Not true. All Special Relativity says is that there is no preferred reference frame, as in the laws of physics must appear to hold true according to every observer. There is not one "special" reference frame where causality only needs to hold for it.
There was never anything in Relativity saying that there couldn't be some convenient reference against which to measure your velocity. Which is all the CMB dipole really is, and in the sense of what it implies for Relativity is no different than arbitrarily deciding the Andromeda Galaxy is our reference.
I believe the future lies in information theory.
The present and recent past lies is information theory. Information theory, which arose from QM, is fundamental to explaining many situations encountered today, like limits on the efficiency of irreversible calculations or the decay rate of black holes. However there is nothing in Information Theory that suggests information can travel faster than light. Indeed, quite the opposite, and this limit is key to understanding things like quantum entanglement and why it cannot be used for information transfer.
Assuming observable events happen in the universe, and assuming that causality exists, i.e. that if some event causes another that relation will exist under all circumstances, then we can think on how information about different events is transported through the universe. Again, this would be a truly absolute limit, not one imposed by our limitations in measuring and calculation.
That's pretty much how it's already done -- assume causality holds for all reference frames, and you can see that information cannot travel faster than light.
However at the end of the day no matter how elegant a mathematical model you have constructed, there are going to be variables whose values in our universe must be determined experimentally. Like c. You can get c via direct measurement, you can calculate it based on other constants which must themselves be measured. Either way.
Yet as our measurements get more precise, the values for these constants becomes more precise, and doesn't suddenly change values to something outside the error bars on previous less precise measurements. We're still depending on measurement, but we aren't going to up-end physical theories at some point when we hit the 32nd digit of c and suddenly nothing works.
This only seems like a problem if it bothers you for some reason that you can't derive all physical constants from a mathematical model, and instead the only way to know what values to place in that model of the universe is by actually looking at the universe.
Yeah, I originally said that the inside of the black hole beyond the event horizon was unknowable, but that seemed presumptuous and a little like begging the question.
I'm not sure Hawking radiation, if it exists, is going to tell us much more than the rate of virtual particle creation. Nothing is actually escaping the black hole, and it seems like the radiation would have very high entropy. But maybe someday...
Slashdot Mirror
However, if the wormhole is stable, Alice and Bob (and seperately Carol and Dave) would be effectively adjacent, so you wouldn't see tha causality problem.
I'm not sure about that, though. I just have no idea how you'd draw the diagrams when the plot of routes from Alice to Bob is not continuous, and the shortest route and the shortest route that doesn't use the wormhole are time-like and space-like respectively.
It just still seems like if Alice and Bob were cruising past the opening of the wormhole, and Alice dropped in a message pod destined for Bob, you could still end up with the situation in the diagrams.
Relativity is probably as wrong as Newtonian mechanics. I.e. it works on one scale but not another. I have no doubt we will find something that applies on quantum scale and galactic scale. I am just too stupid to help out in that endeavor.
LOL, agreed on all counts. :)
But I'm also too pessimistic to think Relativity will turn out to be wrong in a way that lets all of my fantasies come true. Going from Newton to Einstein didn't undo all the stupid restrictions of Newton's world, like Conservation of Momentum which is a real drag for flying saucers or Inertial Dampeners. Or that stupid Second Law of Thermodynamics. I have a feeling whatever replaces Relativity as the Best Model isn't going to undo causality or the universal speed limit and the best hope we have of visiting other stars is really boring generation ships that have absolutely no pep.
These are all salient observations that must be taken into consideration. I just can't get behind calling what is almost entirely an up-front fixed cost a fuel cost. Each extra pound of coal has significant and real costs associated with acquiring it. But once you've built sufficient mirrors to collect all the light you want, the ongoing cost for the sunlight that mirror reflects is, what, the power needed by a one-revolution-per-day tracking motor? You could amortize the fixed costs over the total watts reflected over the lifetime of the mirrors and call that the 'fuel cost', but that's just not how normal accounting is done.
Special Relativity is, as the name implies, a special case. It doesn't apply in the more general (ah!) case, and especially doesn't apply in a strong gravitational field.
That's backwards.
Special Relativity applies everywhere, but does not sufficiently describe situations involving acceleration. That doesn't mean that inside a strong gravitational field the SR assumptions of constant c etc don't apply. They do. You just need GR also to fully describe these situations.
the title of his paper is telling: "Rotating Cylinders and the Possibility of Global Causality Violation"
Yes it is very telling. It tells me that the author of the paper understands the implications of FTL travel, and that their device, if it worked, could violate causality.
Causality is a base assumption of GR, too. Violating causality means violating the basic assumptions of General Relativity.
I would restate the dogma that "FTL is impossible" to "FTL may be impossible, but at very least, it is very difficult".
The 'dogma' is "FTL is impossible in a Relativistic universe", and that remains true.
It is quite possible that Relativity is wrong, very probable really. However it is not guaranteed that it is wrong with regards to the aspects that make FTL impossible. I'd call that improbable, even, since it'd have to be really wrong for that to happen and yet still keep a causal universe.
But hey, if we ditch causality, all bets are off.
If you're trying to argue that modifying some technology to make it more efficient will necessarily make it cost less per unit of energy, then that is patently false.
Why even have a conversation with someone who only sees the possibilities that "efficiency doesn't matter" or "increased efficiency necessarily reduces cost regardless of mechanism" and argues against one idiotic half of this false dichotomy to prove the other?
Any technology with a different efficiency is a different technology, full stop.
Nonsense, because many technologies have different efficiencies at different scales or other parameters. If you want to define a diesel generator and a diesel generator that is 0.1% larger or with an operating RPM 0.1% slower as "different technologies" then be my guest at abusing semantics in ways nobody will ever agree with.
With CHP systems, turbine efficiency doesn't matter.
What a silly thing to say. That's only true if the only thing you care about is heating, and the only use for electricity you have is to power electric heaters. Otherwise, efficiency is going to affect the size of system you need to achieve a given desired amount of P.
In fact, a small system can be more efficient as well as cheaper than a larger one by utilizing the 60% waste heat produced.
Larger systems can make more effective use of waste heat, too.
But cost is clearly the biggest factor. And it should be plainly obvious that the relationship between cost and efficiency is tenuous at best.
What's plainly obvious is that efficiency effects cost, in particular within the parameters of a given technology, and can make the difference between it being practical for a given use or not.
It's why you aren't going to have a molten salt solar collector, or a sugar cane plantation with biodiesel generator plant in your yard, but you might have roof solar panels. While for large-scale city/region sized deployments, the opposite will be true.
What's also plainly obvious is that the statement "efficiency does not matter in renewable energy" is false.
I've never seen a decent prrof of the claim that an ansible necessitates a violation of causality.
It doesn't necessitate, it enables in what are from the point at which you have an ansible trivial ways. In other words, not every ansible usage violates causality, but there are ansible usages that do.
Here's the simplest and clearest explanation I've found explaining how, and that the mechanism doesn't matter.
but if you create an ansible by changing the topolgy of space such that two points are closer together, that doesn't seem to break relativity.
If that occurs only for the duration of the communication, then the space-time diagrams in the example apply. So even though you haven't technically violated the SR restriction against FTL, you have violated causality.
Collector size has nothing to do with cost.
Of course it does. A bigger solar concentrator is more expensive than a smaller one, and a bigger sugar cane field is more expensive than a smaller one.
You can't directly compare the efficiencies and costs of wildly different technologies, but that's a vastly different statement than saying efficient does not matter! If you are converting sugar cane with an efficiency 1/10th of someone else, that is going to mean you're growing 10 times as much sugar cane for the same output as someone else and that will significantly impact your cost in insanely obvious ways.
For the matter actually under discussion, molten salt solar concentrators and possible home use, it works like so: To collect enough energy for a given application (city/region vs a residential home) you need a certain size of collector. However, smaller turbines are less efficient. Therefore the power output/size curve and thus cost/desired power output curve is not linear, and favors larger installations.
Efficiency directly affects cost. Efficiency matters.
Whether that actually makes it impractical for home use or not is another question.
Efficiency is going to directly impact the size of the collector you need for a given application, and thus cost. So yes, efficiency is quite important in solar power, as it is in every other renewable energy source. It is less important than with other energy sources, yet still quite important. And it could easily mean that below a certain size of application, the technology is economically infeasible.
Perhaps Relativity "allows" FTL travel in the sense that there appear to be ways to manipulate the gravitational rules to create the effect of FTL travel.
However in a very explicit sense Relativity does not allow FTL travel by any method whatsoever, even if the mechanism itself has nothing to do with relativity. According to Special Relativity, any method of FTL travel would make it possible to create scenarios by which effects happen before causes. For example with the help of two spacecraft equipped with Ansibles (instantaneous communication devices whose workings are completely irrelevant) you could effectively send yourself a message and receive it before you sent it -- sending it backward in time, violating causality.
Causality is one of the basic assumptions of relativity, and all the equations and workings of relativity are a consequence of maintaining causality in concert with a speed of light that is constant for all reference frames (and of course the assumption that the laws of physics must hold relative to all reference frames). It's possible that causality is a bad assumption, but it doesn't make much sense to me to imagine creating a device to get around that assumption based on equations which require it to be true.
Thanks, I'm glad you got my point and that it made some sense without ending up still sounding like unwarranted blaming of professionals. :)
But really, is there anything that can be done except for the movie-going public to spontaneously and for no apparent reason stop going to see movies that are little more than vehicles for special effects?
Is it even possible when I have to admit that I'll sometimes enjoy a movie that is utter garbage except for beautiful special effects? Are there alternatives that aren't worse?
I thought my point was clearly not a binary statement of cheap-n-easy special effects vs no special effects at all, yet also not that subtle either. I guess I was wrong.
Yeah, you're completely right, nobody cares, and if any of them did start turning down money, it'd probably just be the first step of them going out of business. It was, like I said, ridiculous. :)
In case you don't remember, there was significant public protest over Cassini:
Let's think about this for five seconds.
There were "significant" public protests over Cassini.
Cassini launched anyway with its RTG as planned, as have missions both before and since.
Conclusion: ZOMG enviro-wackos have the power to prevent NASA from using RTGs!
Seriously?!
the associated hinges/etc to unfurl them together likely weigh about the same as an RTG.
I do not think that is likely. Solar panels are thin and lightweight. That's their advantage. I see no reason a pair of hinges that needs to operate once are going to weigh more than a battery, and the motor to move the lightweight panel, again once, is going to weigh more than another battery, with the panels themselves massing as much as both batteries combined to equal the total mass of an RTG.
But you know, I'm not certain. What I am certain of is that NASA made the decision to go with solar panels instead of an RTG for mission engineering reasons and it had fuck-all to do with some disorganized protesting idiots.
Duh, shoulda remembered that.
An interesting conjecture, but wouldn't anything using reaction drives
Aka "anything" since we're talking about known physics, like Conservation of Momentum. Otherwise the possibility of FTL throws a wrench into pretty much everything. :)
light itself up quite nicely when it moved around? That is one of the conclusions over at Atomic Rockets [projectrho.com].
Er, I'm going to take the statement that Shuttle Main Engines could be seen past Pluto to mean it's plausible that we'd see the probe if our telescopes were pointed at it while it was burning. I don't expect a probe to need much in the way of acceleration, but I am allowing for a very large probe. So that's a good point.
But that whole page is in the context of stealth, like in a space-war, so a lot of the objects just aren't relevant in this case. As in the section about "Thrifty Engine Burns":
Except the probe already spent perhaps hundreds of years getting here from whatever nearby star it was replicated at and is going to spend hundreds of years quietly and passively observing our solar system. Once here the only time it's ever going to need to fire its engines are for station keeping, which depending on the orbit may be practically never, and will require minute amounts of thrust anyway.
Our only chance to spot alien probes via their engines may actually be when the newly minted probe-copies push off for whatever stars are next in the list. Since we're looking at the "why hasn't this already happened yet?" hypothesis, we have to consider the possibility that this already happened and our only decent chance at seeing them with today's technology happened yesterday, when we weren't looking.
And on that note the Atomic Rockets page seems to be assuming that "passive" sensors, aka the only kind we have, are omni-directional, which ours most certainly are not. Even if we can see the probe that doesn't mean we will. For an alien probe in our solar system, stealth in space is imminently achievable.
Again, interesting observation, but "so if aliens exist, why haven't we seen a probe yet?" still isn't a very interesting question.
It's been said that 90% of everything is crap. That includes MY crap too, unfortunately.
Only 90% of your crap is crap?
Uh... yeah, that does sound unfortunate! I'd ask a doctor about that!
I wish people would stop saying that the VFX are ruining moves. We're a tool used by the director (or, more often, by the studio) if that Director (or again, the studio) fail to utilize us within the story properly, how is it the VFX that are ruining movies?
In the same way vodka ruins Bob's personality. Of course it's actually Bob's problem, and vodka is just a neutral tool that can be used for bad or for awesome, but it would still miss part of the point to ignore the vodka's role in enabling Bob to start sucking. Before vodka came along, Bob was okay most of the time. Well, some of the time.
Just to be clear, when we (or I) say "VFX are ruining movies", we are blaming it on the lack of creativity of Hollywood. It's just unfortunate yet true that the existence of affordable and good VFX allows that lack of creativity to flourish.
There's a lot to be said for limitations and how it can make movies better.
Look at Jaws, Spielberg's breakout movie. Think of how horrifying the opening scene is, when you never even see the shark as the woman is (you presume, under the water) being torn apart. How often that movie is positively compared to Hitchcock, the master of suspense. Yet that's not the movie Spielberg set out to make! Originally, it was going to be a crappy monster movie in the ocean with Jaws front and center the whole time literally chewing up the scenery. But because they couldn't get their giant hydraulic-powered animatronic shark to work in salt water (the ocean's just a big wavy lake, right?), he had to make adjustments and go for a much subtler, and ultimately more effective, style.
Or the biggest example of something "ruined by VFX": Star Wars. Lucas luurved his effects even back then and Star Wars had the best around. But nevertheless, they couldn't afford to do endless lightsaber effects so we only had a few instances of them being used heavily in dramatically important moments, and so they were more awesome. He couldn't have a million jedi and robots and lasers to make them all stupid and boring. He had to have real locations and sets that looked real and that actors could interact with. He had to have character moments because he couldn't fill the entire movie with action sequences to make you forget that you didn't care about anyone on screen. Hell, maybe the only reason we didn't have a bouncing spinning light saber Yoda in Empire was because there was no way for him to do that on the end of Jim Henson's hand. Well, that and Lucas had little to do with that movie...
Anyway.
I know it's not the VFX studio's fault that so much VFX is used in place of actual good ideas and story and character. It would be completely ridiculous to blame you for doing your work better, faster, cheaper. But uh, that's exactly what enabled a lot of this crap. It would be completely ridiculous to say VFX companies shouldn't accept checks from the producers of crappy movies, but uh, that's exactly what you'll have to start doing if you don't want to hear "VFX are ruining movies" anymore.
Hey, actually, I never thought to ask that... Do effects companies ever turn down work? Good actors will turn down work, because they don't want their name associated with some piece of crap. Maybe if only the directors with talent or just good ideas got to work with the best VFX, maybe something positive would happen. *shrug* I don't know.
No reason to avoid Earth... but if Eris is more attractive to you, then so are all Oort clouds - no reason to get anywhere near
Er... that really wasn't part of my line of reasoning.
I'm saying, a very large space observatory would be able to study our entire solar system from a distance at which it would be invisible to us. Eris was just a reference point and hypothetical source of materials, not the (sole) object of study. In order to point out that we could have had our very best telescopes pointed right at an alien probe and been completely unable to see it.
considering the timescales and probable scale of "production", we could notice something weird with the spectra of comets by now
Are these Von Neuman probes or Slylandro probes?
It just needs to make a handful of copies to head off to the next nearest stars and repeat the process. Periodically make copies for replacement of 'our' probe -- they can already survive interstellar journeys so they should be pretty hardy, but you would want some backups made in advance -- and even kilometer-scale observatory/factories wouldn't come close to making a dent in Eris (which seems more likely a source of materials than comets, but either way) to the degree that we would notice it.
I don't really see any reason to assume that someone sending probes to study would damage what they are studying beyond necessity by letting exponential growth run unchecked. :p
If we had the collective courage [read - no enviro-wackos] to use RTGs [wikipedia.org] on our Mars probes, we wouldn't have lost Spirit to freezing temperatures brought on by low power from the solar cells.
LOL, that's why you think Spirit and Opportunity didn't use them? Enviro-wackos?
The real reason is simply optimizing for the mission profile. The MERs were relatively small devices with very tight mass budgets, and an RTG of sufficient power would have been too heavy compared to the solar panel/battery combo they went with instead. It was an engineering trade-off. They did, by the way, use RHUs to heat components but this was not sufficient to stave off freezing by itself.
The Mars Science Laboratory is going to use an RTG. It is a much larger rover, with power demands beyond what solar panels could provide, and with a more generous amount of mass to dedicate to the power system.
We used 'em on quite a few spacecraft [wikipedia.org] - why they aren't used more often for solar power-limited missions escapes me.
Yeah, which I would think would have suggested that maybe enviro-wacko objection to the concept of RTGs had nothing to do with it. This is a lobby with surprisingly less power than you might think. :)
If someone else did this already, they hid their probes pretty well...
Um... What makes you say that?
It doesn't seem like they would have to be hiding much, or at all for that matter, for us to miss them.
Look at a recent development at the limits of human observational ability: We just discovered that Eris is, despite its greater mass, may not actually be larger in diameter than Pluto. We did not do this by actually resolving the disk with sufficient resolution to answer the question, but by timing how long it occluded a background star. While certainly an awesome and impressive feat, it raises a very pertinent question:
Just how big/close would an alien probe need to be for it to be hard to miss?
Imagine a probe, many times larger than any telescope we have even on the ground, observing from the outer solar system. This probe could be orbiting Eris right now, while it's duplicator-unit scurries around the surface of the body making the next generation of probes to send to our stellar neighbors, and we'd have virtually no way of knowing.
I have other issues with this an other versions of the Fermi Paradox, but the crux is the part where one asks "then why haven't we seen them already?" as if this is in any way a paradox, or even a puzzling mystery.
Because it's really, really, REALLY, REALLY freaking expensive. You're talking a big task considering the need to develop the technology both for the probe and for on-orbit assembly
Good thing in-orbit assembly is one of the capabilities NASA's new plan intends to develop! Not because it would help a specific project, but because there are many projects this would help, or make feasible in the first place.
Too bad Congress damaged this exciting plan in the name of sustaining pork^H^H^H^H a strategically important manufacturer of ICBM components!
Here's hoping the new plan isn't crippled.
From the blurb: Now a leaked EPA document reveals that the agency allowed the widespread use of a bee-toxic pesticide, despite warnings from EPA scientists.
You've already disproven your own theory on how things work.
Ha!
All this shows is that sometimes government regulation fails to prevent the damage that would have happened anyway in the absence of any government regulation. Which is hardly surprising, unless you subscribe to the false dichotomy that private and public entities must be entirely good or bad and opposite of each other.
To actually disprove the thesis, you would have to demonstrate something completely contrary to every fact: That situations without environmental regulations (or, in some cases, the threat of regulation) are better for the environment than with. The entire history of the EPA and similar organizations, including all of their missteps, contradicts that idea. Your vehicles, your air, your water, all are measurably and demonstrably cleaner because of government regulation.
As if Bayer would have never released a dangerous pesticide justified by a shoddy study if the EPA didn't exist. Well, perhaps not, because they would have had no reason to conduct a study. So more likely the contribution of this chemical to hive collapse would continue to be unknown.
But this discussion does not actually hinge on hypothetical situations. The reality of unregulated industry can be compared to the reality of the regulated. This comparison is not favorable to the unregulated situation at all. Yes regulation can fail to do its job, it can even make things worse in the case of particularly misguided rules, yet the overall trend is not even close to a tough call. History is flagrantly clear on what happens when industry is allowed to run free.
I've seen the likes of you before and none of you have ever let facts or logic
Your concept of facts and logic are hilarious.
By not complaining that the EPA is flawed and should be improved (very true), but rather that this example disproves the entire thesis that environmental regulation is necessary or that we are better off because of it, you're just spitting in the face of logic and reality for the sake of an ideology.
Some organic growers use it. They use a lot less of it,
I see a lot of [citation needed] following the crucial statements in support of this claim. "Reduction and elimination of chemical pesticide use is technically challenging." however does have a cite.
only specific chemicals (with little to no synthetic stuff):
"Synthetic" by itself does not particularly concern me. There are certainly synthetics -- like, say, the one in TFA -- that are bad. But it's not the "synthetic" descriptor that makes it bad, nor does describing something as "non-synthetic" make me embrace it in my tree-hugger arms.
For example, sulfur is a "non-synthetic" anti-fungal used in organic farming. And there's no obscure study by the Bayer corporation needed to demonstrate the dangers of sulfur runoff from farming.
Here's a Nature article which says (with offline cite) that it isn't clear whether organic farming is better or worse in terms of environmental damage from runoff -- which is a larger issue than just pesticide use but clearly affected by it.
Don't get me wrong; I'm not bashing organic farming as useless or counter-productive. It has it's benefits, not the least of which is trying to figure out how to solve these problems without saying "well what can we cook up in the chemical plant?". I'm not convinced the pesticide issue is actually one of them, not inherently anyway.
In relativity nothing can travel beyond light speed because that would imply an infinite energy,
Not exactly. In Relativity nothing with rest mass can travel at the speed of light because that would imply infinite energy.
Nothing at all, not even information, can travel faster than light because that implies that you could create scenarios where from certain reference frames, effects appear to happen before causes. As in time travel, or causality violation, and both Relativity theories (and the rest of physics) assumes causality to hold.
Ten years after Einstein's death we discovered a universal velocity reference in the microwave background dipole, so one of the main tenets of special relativity is not true anymore.
Not true. All Special Relativity says is that there is no preferred reference frame, as in the laws of physics must appear to hold true according to every observer. There is not one "special" reference frame where causality only needs to hold for it.
There was never anything in Relativity saying that there couldn't be some convenient reference against which to measure your velocity. Which is all the CMB dipole really is, and in the sense of what it implies for Relativity is no different than arbitrarily deciding the Andromeda Galaxy is our reference.
I believe the future lies in information theory.
The present and recent past lies is information theory. Information theory, which arose from QM, is fundamental to explaining many situations encountered today, like limits on the efficiency of irreversible calculations or the decay rate of black holes. However there is nothing in Information Theory that suggests information can travel faster than light. Indeed, quite the opposite, and this limit is key to understanding things like quantum entanglement and why it cannot be used for information transfer.
Assuming observable events happen in the universe, and assuming that causality exists, i.e. that if some event causes another that relation will exist under all circumstances, then we can think on how information about different events is transported through the universe. Again, this would be a truly absolute limit, not one imposed by our limitations in measuring and calculation.
That's pretty much how it's already done -- assume causality holds for all reference frames, and you can see that information cannot travel faster than light.
However at the end of the day no matter how elegant a mathematical model you have constructed, there are going to be variables whose values in our universe must be determined experimentally. Like c. You can get c via direct measurement, you can calculate it based on other constants which must themselves be measured. Either way.
Yet as our measurements get more precise, the values for these constants becomes more precise, and doesn't suddenly change values to something outside the error bars on previous less precise measurements. We're still depending on measurement, but we aren't going to up-end physical theories at some point when we hit the 32nd digit of c and suddenly nothing works.
This only seems like a problem if it bothers you for some reason that you can't derive all physical constants from a mathematical model, and instead the only way to know what values to place in that model of the universe is by actually looking at the universe.
Yeah, I originally said that the inside of the black hole beyond the event horizon was unknowable, but that seemed presumptuous and a little like begging the question.
I'm not sure Hawking radiation, if it exists, is going to tell us much more than the rate of virtual particle creation. Nothing is actually escaping the black hole, and it seems like the radiation would have very high entropy. But maybe someday...