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D H

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Everything posted by D H

  1. That is his point. Nonsense. There is no point other than scientific curiosity in going to Mercury. There is no point at all in sending humans there, at least not in our lifetime. Getting to Mars is cheap. The delta V requirements for a one-way mission to Mars is less than a third, and maybe less than a quarter, of that for a one-way mission to Mercury. A round-trip mission to the surface Mars and back to Earth, while costly, is cheaper yet compared to a round-trip mission to the surface of Mercury and back to Earth. To make matters worse, that factor of 3 or 4 or more in delta V translates into a huge factor in terms of fuel. The amount of fuel needed is not a linear function of delta V. Fuel costs grow exponentially as delta V increases. Any resources on Mercury are much more easily obtained in the asteroids. Or for that matter, right here on Earth. The idea of mining asteroids (or the Moon, or Mercury) and sending the mined items back to Earth is, for now, science fantasy. The first materials that will be mined in space are things that are very easily obtained: water and other volatiles. There is no value in sending these materials back to Earth. Common metals mined in space such as iron and nickel will have zero value back on Earth. They're too common. Only the very rarest of materials might have value on Earth, but mining those falls into the category of "we haven't the foggiest idea how to do that."
  2. Actually, we don't see any 'serious proposals' to go to Mercury for the sort of operations you are proposing. The space settlement advocacy is the quintessential source of non-serious proposals of all sort. Space settlement on an extremely small scale, on close-by objects *might* happen in the next few decades. Space settlement on the scale advocated by those advocacy groups: It ain't gonna happen, not in my lifetime, probably not in yours. You have predicated your Mercury proposal on a large number of technologies that we don't know how to do from an economic or engineering perspective. Space mining? We don't know how to do that. Space manufacturing? We don't know how to do that, either. The same applies to large solar sails, solar thermal propulsion, getting people to and from Mercury. We don't know how to do any of them. All of these are at a very low technology readiness level. TRL 4 is where we can start saying we know how to do that. None of these is even close.
  3. The universe itself. It might have happened when the universe was very young. The tuning wouldn't take all that much because information content (entropy) was very low.The mechanism? Who knows? Saying that it had to be some god is a god of the gaps argument. Or it might be that the universe is infinite and those magic numbers aren't the same across the entire universe. We happen to live in a pocket universe that is amenable to life. The places that aren't? There aren't any beings there to ask this silly question about fine tuning. Or it might be that the universe is but one of a huge number of universes. Our universe is amenable to life. Others aren't, and there aren't any beings in those hostile universes to ask this silly question. This multiverse concept apparently is a leading contender amongst cosmologists. Think of it as the MWI interpretation of quantum mechanics gone wild. Or it might be that there is a "before the big bang", and that this "before" was another universe. This leads to a never starting, never ending cycle of universes. We happen to live in a cycle that is amenable to life. This is Penrose's view.
  4. This is extremely disingenuous quote mining. Susskind advocates for an infinitely large universe in which inflation made for drastically different conditions in different parts of this vast universe. Even if the vast majority of the universe is hostile to life, there are bound to be a huge (potentially infinite) number of pocket universes that are conducive to life. Rees is an advocate for the concept of a multiverse, Smolin advocates for an extreme form of this concept. If something isn't out-and-out impossible, it will happen somewhere in one of those infinite, potentially uncountably infinite, multiverses. Penrose rejects the multiverse concept as unscientific but instead advocates for a cyclical universe. In his mind, we are able to be here because this particular cycle is conducive to life. Cycles that aren't? There aren't any thinking beings in those cycles to ask such silly questions.
  5. This thread sure has been diverted off-topic. Note to krash: Antimatter is not unstable in and of itself. The problem is that antimatter and ordinary matter are markedly unstable when the two meet. It's time to go back to the original topic. The other way around, Moontanman. Physicists know that antimatter has the same inertial mass, including sign, as does ordinary matter. This means that if (and this is a big if) antimatter has negative gravitational mass, it would fall up, not down, due to Earth gravity. The equivalence principle says that inertial mass and gravitational mass are one and the same (including sign), but just because someone says that this is the case does not mean that it is the case -- even if that someone is Einstein. The equivalence principle has been subjected to a wide variety of tests. It now stands as one of the most precisely verified concepts in physics, but only for ordinary matter. Testing how antimatter behaves when subjected to gravitation has been highly problematic because of the proclivity of matter and antimatter to annihilate one another. The best results to date are that the gravitational mass of antimatter is somewhere between -65 and +110 times the inertial mass. That's not very good given that the factor is supposed to be exactly one. These results come from the ALPHA experiment at CERN. This experiment is currently being upgraded specifically for the purpose of studying how antimatter behaves under the influence of gravity. The update should be completed sometime next year, so we can expect results two or three years from now.
  6. Nonsense. I do understand where this nonsense comes from, but that doesn't stop it from being nonsense. A lot of schools now teach that the slug is the US customary unit of mass, and that pounds are a unit of force. This is nonsense. The slug is a non-standard unit used by some (but not all) engineers in the US. Other engineers are quite happy using the pound as a unit of mass and the pounds-force as a unit of force. The pound (Avoirdupois pound) is defined as 0.45359237 kilograms, exactly. The pound-force is defined as 4.4482216152605 newtons, exactly. Weight is legally and colloquially a synonym for mass in the US. Better said, mass is a synonym for weight. Weight is a much, much older word than is mass. English has two words for the same concept for the same reason that the animals that provides pork are called swine. The Norman invaders spoke French, and their French words eventually became English words. It took a few more centuries after 1066 for the descendants of those Norman aristocrats to invade the merchant class. Mass didn't become an English word until the 15th century. We in the technical community don't like it when the lay community pervert our own words. For example, "Evolution is just a theory." To avoid being hypocrites, we in the technical community should avoid doing the same to perfectly good English words such as weigh and weight. The supposed confusion between mass and weight is an invented controversy. As noted above, there is no confusion in everyday English. When your friend says he weighs 155 pounds (or 70 kilograms), fight back the urge to correct him. His usage is correct.
  7. That would have quite the feat of precognition on Newton's part. Linear algebra didn't exist in Newton's time. While Leibniz (but not Newton) did use determinants, it wasn't really linear algebra that he was using. Linear algebra got it's start with Vandermonde in the late 18th century. The vectors we use now in physics weren't invented until the late 19th century. The rather abstract extensions such as Hilbert spaces -- those are 20th century developments.
  8. Yes, it is, swansont. You apparently are thinking of the pound-force, swansont. The pound is a unit of mass. You don't. What you need to do is to be careful with units, particularly when working with English units. The lb in your 0.075 lb/ft^3 is the pound Avoirdupois, a unit of mass. The lb in your 109.165 lb/ft^2 is incorrect. That should be 109.165 pounds-force per square foot, or 109.165 lbf/ft^2. The pound (lb or lbm) is a unit of mass, the pound-force (lbf) is a unit of force. In the metric system, one uses F=ma. That doesn't work with force expressed in pounds-force, mass in pounds, and acceleration in feet per second squared. One must instead use the more generic form of Newton's second law: Force is proportional to (rather than equal to) mass times acceleration. Mathematically, F=kma. A force of one pound-force accelerates a one pound mass 32.174 ft/s^2, so k=1/32.174 with this choice of units. This means your expression "pressure = density x gravity x height" needs a bit of modification to work with English units. With pressure in lbf/ft^2 and density in lbm/ft^3, the correct expression is [imath]P=\frac 1{32.174} \rho g h[/imath]. Since g=32.174 ft/s^2, your expression simplifies to [imath]P=\rho h[/imath] if you express pressure in lbf/ft^2 and density in lbm/ft^3.
  9. I guess you're talking about the Voyager satellites. They didn't have atomic clocks. As far as I know, the only satellites outfitted with atomic clocks are the GPS satellites. Suppose some spacecraft outfitted with atomic clocks goes to the far reaches of the solar system and then returned. On return, the spacecraft clock would probably show a different time than Earth clocks. The spacecraft goes far from any gravitational sources, so general relativistic time dilation would make their clocks tick faster. However, it also went away from the Earth at significant speed (at least initially), so special relativistic effects would have made their clocks tick slower. Which is the dominant effect depends on how fast the spacecraft moves relative to the Earth and how much time it spends far away from the Sun. Atomic clocks at mean sea level all tick at the same rate. The geoid, which is what mean sea level is, is an equipotential surface of the gravitation force and the centrifugal force due to Earth rotation.
  10. That's an ornithopter, not a helicopter, and it flew a couple of years ago. Here's the helicopter that won the Sikorsky prize:
  11. Because they don't. Richard Feynman: "You don't like it, go somewhere else! To another universe! Where the rules are simpler, philosophically more pleasing, more psychologically easy."
  12. I was going to stay out of this thread, but then I saw that someone downvoted md65536. Here's a +1 to counteract that -1, md65536!
  13. Correct. Remember, though, that those masses are in a sealed container. You can't see them. All you can see is the container. If your oscillating masses are balanced, you won't see anything happen. If they aren't, you'll see the container move around a bit but it's mean (average) motion will still be zero. There is no difference between the empty space scenario and the freefall scenario. They are one and the same per the equivalence principle. No, there isn't. You can keep deluding yourself all you want. There's nothing here, and with that, I am done with this thread.
  14. The answer to your question is no. Forget about gravity for a bit. Imagine putting your device in a sealed container and in deep space, far from any gravitational source. Now power it up. What do you think will happen? Keep in mind the law of conservation of momentum. Now let's put it in orbit about the Earth. Power it up. Nothing happens, same as in deep space. I smell something a bit more foul.
  15. Mike, you are starting with a false assumption, that velocity motion due to rotational motion has an effect on gravitation. It doesn't, at least not a realm where Newtonian mechanics is valid. The outer edge of your rotating ring in post #38 (20 meter diameter ring at 1 million RPM) has a velocity of 0.0035 c. That's barely relativistic. Newton's laws are pretty much valid even in this extreme case. Moreover, this rotating ring is physically impossible. That ring would have to be made of unobtainium. A 20 diameter ring made of any normal substance (and that includes carbon nanofibers) would tear itself apart well before reaching 1 million RPM. Bottom line: we safely ensconced in a Newtonian world. This means the acceleration of the center of mass of some object is the net force acting on the object divided by the object's mass: acm=Fnet/m. Rotational behavior doesn't come into play in this equation, at least not directly. Since gravitation force is independent of velocity, it doesn't come into play indirectly either.
  16. Nobody sane uses quantum mechanics to describe everyday events at a macroscopic scale. Too many interactions, for one thing, and for another, quantum mechanics doesn't describe gravitation. QM is not used to describe the weather. The quantum world is very different from what we see at larger scales. Gravity is what keeps the atmosphere bound to the Earth. The Earth's orbit does have an effect on the seasons, but it's very tiny. No, no, and no. I don't know where you got this idea that there is no gravity at the Earth's poles. On the Earth's surface, gravity at the north pole is about half a percent higher than it is on the equator. You are bouncing around from topic to topic in this thread. This makes it hard to respond in a coherent way. Use different threads to ask different questions.
  17. Per the Copenhagen interpretation of QM, Schrödinger's cat is simultaneously alive and dead until the wavefunction collapses. Per the multiple worlds interpretation, the alive cat persists in some alternate reality after the observer sees the cat is dead. Either way, classical logic goes bye-bye. There's nothing saying those laws are sacrosant. Fuzzy logic, for example, essentially is a rejection of the law of the excluded middle.
  18. What oscillating masses? What do you mean by "partial arc"? What rotating ring? You are not defining your terms, and your cartoons do not communicate. The only valid scientific response to this is "Huh?" If you are talking about that gyroscopic lifter nonsense, that's exactly what it is: Nonsense. You talked about using springs. A spring that is more than a thousand kilometer long is exactly what would be needed to accelerate a vehicle to orbital speed without destroying the contents of that vehicle. You talked about using radio waves to somehow boost a vehicle to a higher orbit. The numbers here are even worse than those for a spring. Do the math. That is not physically possible with real materials. Do the math and stop using unobtainium when you do the math.
  19. What device? The one Mike first started mentioning in post #16? I ignored that for three reasons: He didn't mention it until post #16. As far as I'm concerned, Mike is hijacking his own thread. His explanations are rather vague. I am waiting to address this when he has something beyond cartoons. The best I can tell, it's that crackpot gyroscopic lifter nonsense. It's nonsense. Because of point number one, post #16 and most of the posts that follow should be moved into a separate thread.
  20. This thread was bad enough before this latest bout of gyroscopic lifter nonsense. What's next? A magic pixie dust space drive? Mike, there is no way to go 7.9 kilometers per second at 100 meters above sea level. None. The fastest jet ever made, the X-43, attained a velocity of about 2.95 km/s, but it did this at an altitude of over 13 km. Bringing this 2.93 km/s up to 7.9 km isn't just a 2.67 times harder problem. It's at least 2.672 times harder, just based on energy considerations. In fact, it's much harder than that. Drag is a huge problem. It grows quadratically with speed. Heating is an even bigger problem. Bringing this from 13 km altitude down to 100 meters is an even bigger problem. Air density increases exponentially as altitude decreases. If you somehow could get a vehicle moving at 7.9 km/s at sea level it wouldn't last long. Maintaining that speed would require a huge expenditure in energy to compensate for the huge drag. That won't be the main problem. The main problem is that the aerodynamic heating will melt a hole through the vehicle in no time flat. You'll have a 7.9 km/second wind cutting through the vehicle, at a temperature that is much hotter than the surface of the Sun. So what about lifting the vehicle above the atmosphere before applying the springs / gyroscopes / pixie dust? There's a good reason spacecraft pitch down shortly after launch. Going straight up first and then gaining the necessary horizontal velocity after getting out of the atmosphere is an incredibly inefficient approach to getting into orbit. Let's ignore that. We'll go straight up, say to 174 km, and then use springs to obtain orbital velocity, which is 7.8 km/second at 174 km altitude. We have humans onboard, so the acceleration is going to have to be something tolerable to humans. Suppose the peak acceleration is 6g. Note that unless they're extremely fit, some of the passengers will die with this high of an acceleration. This means the uncompressed spring needs to be over 1000 km long. The strength of materials numbers are absolutely astounding. The springs will need to be made of unobtainium. Make the peak acceleration more tolerable than 6g and the spring needs to be even longer. At one g, it needs to be over 6000 km long. If you've ever played with springs you know that they have this nasty tendency to buckle. A spring that is supposed to expand to a length of 1000 km will almost certainly buckle. Ignoring the impossibility of the spring, the tendency to buckle is going to make the whole apparatus come crashing down instead of attaining orbital velocity. Suppose this unobtainium spring somehow does resist buckling and the pair of vehicles are placed into orbit. Let's look at the next idea, using radio waves to magically boost the vehicle to some higher orbit. While photons do have momentum, they are an incredibly bad choice as far as space propulsion is concerned. Suppose we somehow were able to transmit at 1.21 gigawatts, 100% of which hits the vehicle. If the vehicle absorbs this incoming light, that's the equivalent of a paltry 4 newtons of thrust. For a vehicle as large as the one you depicted, Mike, 4 newtons isn't going to accomplish much. To make matters worse, you only have a few minutes while the vehicle is in line of sight of your 1.21 gigawatt transmitter. To make matters worse yet, the thrust direction is wrong. The best thing to do is to thrust along the velocity vector. This transmission scheme has the thrust along the radial vector. Radial thrust doesn't raise a vehicle to a higher orbit. It just makes the orbit more elliptical. Summary so far: Going at orbital velocity at 100 m above sea level won't work. Using springs to obtain orbital velocity won't work. Using radio waves (or photons in general) to boost a vehicle to a higher orbit won't work. What about this latest nonsense of using gyroscopes? That's pure psychoceramics. I don't know what it is that leads some engineers toward crackpottery. It's an interesting but sad phenomenon.
  21. No, it isn't. It contradicts your theory. The Moon is receding from the Earth primarily because of tidal interactions. The Earth is receding from the Sun primarily because the Sun is losing mass. Neither of those apply to stars orbiting the galaxy. The gravity gradient of galactic gravitation across the span of the entire solar system is negligibly small. Across the diameter of a star? It essential doesn't exist. With respect to mass, the exact opposite applies. The galaxy is gaining mass, particularly so the part near the galactic center. The stars should be moving inwards, not outwards, but at an imperceptibly small rate. So what? This does not pertain to stars orbiting a galaxy. You appear to be assuming that because the Moon is receding from the Earth and the planets are receding from the Sun that this is a law of nature. It isn't. This recession of the Moon and the planets is due to circumstances particular to the Moon and to the planets. Those circumstances are not universally true. You are making a hasty generalization by assuming that everything must be receding based on the fact that the Moon and Earth are doing so.
  22. This is getting a bit obnoxious. My user name is D H, not D M. I destroyed your argument and your response is "great news"? I don't get it. No, it's the other way around. It's your "theory" that is pure fantasy. That it's inflow, not outflow: That is an observed phenomenon. Your "theory" is falsified by these observations.
  23. Electron orbitals are not anything like orbits, Mike. You are ignoring momentum. Sorry to be blunt, but this is so wrong that I can't even find a good starting place to start a criticism.
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