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You are correct. Same stuff, much higher energy. Do you drive a car or take public transportation? Eat meat? Consume alcohol?

The field of physics does not completely understand anything. At least that is the fervent hope of hundreds of PhD physics candidates around the world. After all, they have to contribute something new to the field to get those three letters appended to their names. Complete understanding is the realm of religion and crackpots, not science.

Communication satellites like those orbiting the Earth are not an option for the Moon. A lunar satellite with a one month period is well beyond the Moon's Hill sphere; the orbit can't exist. A communications satellite in a halo orbit about the Earth-Moon L2 point is a possibility, but fuel consumption for stationkeeping is an issue here.

Cometary impact remains the dominant hypothesis regarding the origin of water on the Earth. The basis for the hypothesis is that the water has to come from somewhere after all. The water could have arisen either through accretion during the initial formation of the Earth or have been added to the Earth later on via some other mechanism. Most astronomers think accretion is not the answer, as the very early Earth was far too hot. If not accretion, then comets are the next obvious answer. The early solar system had a lot of comet-like objects. The cometary origin hypothesis is just that -- a hypothesis, and some astronomers are beginning to question it.

You can't, if you are talking about the equivalent of a geostationary orbit around the moon. Such an orbit would be well outside the Moon's Hill sphere. If you are talking instead about the Earth-Moon L2 point, there's a big problem with regard to communications: the Moon is in the way. Moreover, the collinear Lagrange points are unstable. There is no such thing as a permanent orbit. Because the Earth:Moon mass ratio is 81:1, halo orbits about the Earth-Moon L1 and L2 points require quite a bit of stationkeeping fuel. A better bet would be the Sun-Earth L2 point. The huge Sun:Earth mass ratio drastically reduces Sun-Earth L2 stationkeeping requirements compared to the collinear Earth-Moon Lagrange points. The WMAP observatory is at the Sun-Earth L2 point; the James Webb telescope will also be located there. Ground-based telescope have a huge advantage over space-based telescopes: platform stability. Space-based telescopes have a huge advantage over Earth-based telescopes: no atmosphere. A Moon-based telescope offers both advantages. The Moon's slow rotation rate makes things even better. Astronomers have wanted a Moon-based telescope for a long, long time.

Picky, picky, picky. Some other terms are intrinsic mass, invariant mass, proper mass, or just mass. Rest mass is yet another name for the same concept.

Note well: I was not being a crackpot when I wrote the referenced post. The photon's rest mass is identically zero according to both the standard model and relativity. Every experiment to date has yielded results consonant with theory. The photon's mass is identically zero as far as I am concerned. Severian, can you truly say that the photon's rest mass is identically zero with absolutely no equivocation? Theories have been overturned in the past, and no experiment has (or ever will) be able to unequivocally reject the hypothesis of a non-zero rest mass. Scientific fact, like law, always has some doubt. Our standards tend to be higher than the "beyond a reasonable doubt" standard legal profession, but there remains some doubt. Theories are occasionally overturned and experimentation can never yield absolute certainty. The media is looking for 100% certainty here. That is not how science works. It is how crackpots and religion work ... until proven wrong. Then they do it all over again, with 100% certainty.

Well, dagn.

Some posters could easily improve others' perception of them by paying just a little bit of attention to spelling and grammar. Maybe that's just a bit to 20th century for some people.

Yikes! Global warming meets the Prisoner's Dilemma! I have a problem with that, too. Not only that, he assumes that the preventative measures work. People will be doubly depressed (economically and mentally) if we put ourselves in a global economic depression and fail to cure AGW in doing so. of preventative measures don't work.

No. Any such law would be a blatant violation of the first amendment. Edit: Good thing for the people at Weekly World News that no such law exists.

The cost of "the end of life" is very high, but not infinite. It is not "something like multiplying infinity by zero". It is something like multiplying a very large number by a very very small number. The result is a very small number. The result becomes even smaller if you do a proper risk assessment and account for the time value of money. Even if the LHC creates a quantum black hole and even if Hawkings is wrong about black holes evaporating (and these are two very, very big ifs), there remains another unknown, which is the amount of time it would take for the purported black hole to gobble up the Earth. A time span that measures in the millions of years reduces the effective risk to almost nothing. A small number times a very very small number is a very, very, very small number.

There is nothing to gain if there is nobody to talk to, which is what the Fermi paradox is all about.

There is a way to decipher messages sent from afar. The laws of physics are the same on a star 1,000 light years away as they are here. The trick, then, is to send a Rosetta stone that describes math, physics, and chemistry along with the signal. The signal would have to be low-bandwidth so we could distinguish it from noise. This alone rules out most broadcast techniques used today; our high-bandwidth broadcasts are nearly indistinguishable from noise. So, no pictures and definitely no TV. Anything beyond a hundred light years or so is essentially one-way communication. Fortunately, that is not a problem yet; the SETI range is much shorter than than. Given the size of the universe, ET most is likely there somewhere. That is, however, completely irrelevant. Our search for ET is not only limited to our own galaxy, but to a very small part of our own galaxy.

Exactly. But I beat you to it in post #5.

I am talking about the key distinguishing characteristic of a fractal.

And abrasive and abusive. Evolution has been and continues to be challenged. Every PhD candidate in the biological sciences has to contribute something new to the body of science, after all. However, because evolution does such an amazing job at explaining the evidence and because evolution has a well-defined mechanism that explains why it occurs, the challenges are in the details rather than a wholesale replacement. There's nothing unique at all in this. Revolutions in science are few and far between. The last major upheaval in the biological sciences was the discovery of DNA. This turned biology upside down and provided the "missing link" in the theory of evolution: a mechanism. Newton developed the basic concepts of physics over 300 years ago. There have been but two major revolutions in physics since then, both in the early part of the twentieth century. Chemistry followed in the footsteps of physics. Changes in physics and chemistry are now incremental, just as they are in biology.

No. A line is "self similar" but lacks all other characteristics of a fractal curve. It is easily described in geometric terms (what shape is easier to describe than a line?) and its Hausdorff dimension is the same as its topological dimension; i.e., one.

Exactly. Suppose some alien civilization does develops the ability to get off its home planet in any quantities. Said species will soon colonize its own star system in short order because civilization is quite fragile. A civilization that stays on its home planet is committing suicide. Life on Earth is very robust; it has even handled some incredible catastrophes (at the expense of losing 90% of all species of life extant at the time). Modern civilization is not nearly so robust. It would take much less than a dinosaur-killer meteorite to wipe out civilization. Once wiped out, its done. We have already used up a significant percent of the reserves of fuel that took hundreds of millions of years to develop and we have depleted all of the easily mineable metals. Without fuel or metal, how will our survivors (or the next intelligent species that comes along) develop past stone age capabilities? Intelligence, defined as the ability to escape the planet, has one, maybe two, chances to arise in the lifetime of the planet. A truly intelligent species would not let that one-time opportunity pass them by. On most planets, I suspect the odds are essentially zero. Advanced (multicellular) life was a fluke. If such a species came across a slime ball of a planet (e.g., Earth for the vast majority of its history), it would and should colonize it. They haven't come here because they don't exist (in this galaxy). There is one exception: Some intelligent species might decides to forego planetary life altogether. Such a species would be even more free to exploit the resources of the galaxy than a planet-bound species. Planets might be a bit tough to attack, but not asteroids. We live in an untamed solar system. They haven't come here either, and its because they don't exist (in this galaxy).

Evolution. We do not teach the theory of evolution as conceived by Darwin because Darwin didn't know about genetics or DNA. His theories have been supplanted by better ones. To think that evolution as conceived by Darwin is the be-all and end-all of biology is akin to thinking that the Bohr model of the atom is the be-all and end-all of modern physics. To the contrary! It is only the starting point. The Bohr model of the atom has been falsified and replaced by theories that better explain how the atom truly behaves. Similarly, Darwinian evolution has been supplanted by the modern synthesis, genetics, and molecular biology. In short, modern evolution.

Even though every physicist "knows" that the photon has zero rest mass, you will never get a physicist to say unequivocally that photon's rest mass is identically zero. While a non-zero rest mass would destroy a lot of the standard model, theoretical physicists will not say with absolute certainty that the photon's rest mass is identically zero. There is always a slim chance that there is some unknown gaping flaw in the standard model. Experimental physicists have performed multiple measurements of the photon's rest mass. No experiment has of yet rejected the hypothesis that the photon has zero rest mass. In fact, the evidence is getting ever stronger that the rest mass is zero. There will always be some experimental error that prevents an unequivocal measurement of zero rest mass. The best experimentation can do is set an upper bound (an incredibly small upper bound). Experimentalists, like theoreticians, cannot say without equivocation say that the photon's rest mass is zero. The point of this discussion: If physicists cannot unequivocally say that the photon's rest mass is zero, how can they possibly unequivocally reject a far-flung and highly dubious conjecture that does agree to some extent with accepted theory? No. It's well past time that the media learn a smidgin of science.

I agree, radiation exposure is yet another unsolved problem with the space elevator concept. Minor quibble with your post, Lance. The last humans to pass through the Van Allen belts were the Apollo astronauts. The Shuttle and the ISS orbit at about 300 km, well within even the inner belt.

Not a chance. The space elevator remains a pipe dream at this time. Putting a construction timetag on something that has barely passed from pure to applied research is downright silly. Analogy: Fusion power. There is plenty of research being done on space elevators, but it is research, not development. Construction is an engineering problem. The research has to be pretty much complete before construction can start. We don't even know what to build it from, alghough carbon nanotubes are a good bet. They are nearly strong enough and we can make them -- in small quantities. Making them in large quantities (huge quantities for the space elevator) is another big problem that is still in the research phase. We don't know how to put the components together; early research phase here. We don't know how to operate an elevator on such a cable. We don't know how to bootstrap the whole process; gettting the first strand going is one of the tougher problems. We don't know about stability and vibrational modes. We don't know the environmental impacts. Those are the things we know we don't know. There are a lot of hidden unknowns, things we don't even know that we don't know. Bottom line: 2015 is only seven years away. Right now, it's still in the hands of scientists. Building can commence when the problem shifts from science to engineering.

Assume two reference frames, one inertial and one rotating. Denote the angular velocity and angular acceleration of the rotating frame with respect to inertial as [math]\mathbf \omega[/math] and [math]\dot{\mathbf \omega}[/math]. Now assume two observers of some vector quantity [math]\mathbf q[/math], one observer fixed in the inertial frame and the other fixed in the rotating frame. The two observers will see substantially different time derivatives of the vector quantity. The derivatives are related via [math]\dot{\mathbf q}_I = \dot{\mathbf q}_R + \mathbf \omega \times \mathbf q[/math] If you want me to derive this result (called the transport theorem in several aeronautics engineering texts), I will. For now take it as a given. Applying this transport theorem twice to the position vector, [math] \ddot{\mathbf r}_I = \ddot{\mathbf r}_R + \dot{\mathbf \omega} \times \mathbf r + 2 \mathbf \omega \times \dot {\mathbf r}_R + \mathbf \omega \times (\mathbf \omega \times \mathbf r) [/math] The left hand side is the subject of Newton's second law, [math]\mathbf F = m \ddot{\mathbf r}_I[/math]. Making those extra terms on the right-hand side look like forces will make [math]\ddot{\mathbf r}_R[/math] act in a manner similar to [math]\ddot{\mathbf r}_I[/math]. To make an acceleration look like a force, simply multiply by mass. To put it on the other side of the equal sign, simply negate. The additive inverse final term on the right-hand side, [math]-\,\mathbf \omega \times (\mathbf \omega \times \mathbf r)[/math] is the centrifugal acceleration. The penultimate term is the Coriolis effect.

Computers almost exclusively use the IEEE floating point standard to represent real numbers. The number is represented in the form sign*(1+fraction)*2^(exponent). Except for very tiny numbers, the "1+" of the mantissa is implied (i.e., not stored). I won't deal with those tiny ("unnormalized") numbers. The very first thing that is done is a gross check on the number. Negative numbers and numbers that are "Not a Number" don't have a square root. The result is "Not a Number". The square root of a positive infinity is positive infinity. The square root of zero is zero. That just leaves positive numbers to deal with. Using the fact that the square root of x*2^(2n) is sqrt(x)*2^n, the first thing that is done is to scale the number by an even power of two to place the result between 0.25 and 1 (or 0.5 and 2, or 1 and 4; it doesn't matter). Then an initial guess of the square root is made. This guess is polished off by Newton's method. The better the guess, the less polishing needed. Newton's method exhibit quadratic convergence near the root. I suspect that most developers use either a Chebychev polynomial or a rational polynomial. What constitutes a good guess function is just a bit of art and a bit of math. The function should use a minimal number of operations to yield a minimax estimate. The minimax criterion for things like sqrt, sin, etc is not RMS (root mean square). A function can have a low RMS error over a range but still might well perform poorly in some subrange. The minimax criterion is instead worst-case error. Chebychev approximations typically come very close to the optimal minimax polynomial. Rational polynomials with the same computation cost are often better than the optimal minimax polynomial, but finding the optimal minimax rational polynomial is an absolute bear of a problem. All of this work is done by the algorithm designer; once built the coefficients are just magic numbers (defined constants) in the function implementation.