swansont

Ah, the Superman theory. "I have trouble seeing through lead." Technically, nothing "blocks" x-rays. What you have is an attenuation which is an exponential. The advantage of lead is that has a very large attenuation coefficient due to the large number of electrons and dense structure. Aluminum has fewer electrons, and is a much less favorable target for interaction. So you are correct — anything will eventually attenuate x-rays. Lead is used because it is more efficient at doing so than most other materials and is readily available, but a thick block of aluminum could be more effective than a thin sheet of lead, depending in the actual numbers. This shows the mass attenuation coefficient for various elements http://en.wikipedia.org/wiki/File:Photon_Mass_Attenuation_Coefficients.png There's also a table here http://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html For example, at 1 MeV the mass attenuation coefficients are comparable, but lead is much more dense and is a much better attenuator.

We do try to remember to amend the title to include [Answered: Yes/No] to help clarify things to the casual reader.

The rules of QM do not allow the system to get rid of the energy.

Gravity is not the same thing as gravitational potential energy, which is the work gravity has done. The acceleration from gravity is g, the force of gravity is mg, and GPE is mgh (when g is a constant). NOBODY has said that g has changed, or mg has changed. If that was the purpose, it was the right forum, and has long been answered. All the rest is squabbling about semantics, which is distilled in the last sentence here — you seem to think that "state" and "form" have different meanings in this context, and they do not. There is no physics being discussed by you. Thread closed

Like the quoted part explained, the constants are an artifact of the unit system used. By convention, it has a certain value.

Potential energy is work done by a conservative force. Total energy does not change — this is shown by Noether's theorem; conservation of energy is a consequence of physics not changing over time. All the rest is a discussion of semantics of the merits of using "convert," and there's already a consensus. Deal with it. This is a physics board, and the thread is not discussing physics. I don't really see any reason to leave it open.

No, it's not wrong to use "convert." to change from one form or function to another and to exchange for an equivalent are both relevant. Nobody has claimed that the volume of water has changed. The physical attributes of the water are not affected here — it is the classification of the type of energy that the water has. We have potential energy, due to position, and we have kinetic energy, due to motion. The water can also do mechanical work, which will change the energy it has. Didn't you mean to say, we classify the types of energy, potential and kinetic, into different forms and the changes in them due to work being done? Didn't you mean to say, any change is always, not sometimes, reffered to as converting the energy to a different type? Type and form are interchangeable in this discussion. I didn't say "always," because some people might not use it. One could use e.g. transform, change or turn. Potential energy is being converted into kinetic energy, and/or mechanical work. I find it ironic that you feel like I am being obtuse when I am just trying to understand all the terms that are continually missused. If you don't understand what I mean go back to the middle of this post and reread. I asked a question, since there were (to my mind) two options at this point. And I have to note that you didn't answer it. The terms aren't being misused. They are defined in a certain way and are used consistently within those definitions. You appear to want to apply different definitions, and are apparently surprised that it causes confusion.

I never said anything about converting velocity. I don't think anyone has proposed anything about volume (or mass) changing, either. You are the only one bring that up, and it's a non-sequitur, a strawman. A big part of this seems to be a semantic argument about the word "convert." We classify the forms of energy — potential and kinetic, and the changes in them due to work being done. Any change is sometimes referred to as converting the energy to a different type. That's simply the way it is. Merged post follows: Consecutive posts merged Nobody is claiming to convert gravity. Stop it already. What is being discussed is energy, and converting it from one form to another. Energy due to being in motion is called kinetic energy. I have to ask: are you being intentionally obtuse, or are you trying to tackle this problem without the benefit of having taken physics 101? It wasn't clear from your earlier post if you've learned all of this from Google

No, because of there is no turbine, the water has more kinetic energy. The potential energy is the same. The potential energy it started with gets converted into either kinetic energy of the turbine, or of the water (ignoring heat and sound for the moment) No, you are anthropomorphizing the situation (known as that pathetic fallacy). The amount of energy the turbine generates is dictated by the energy of the water, not the the way around. —— Since energy is conserved, you can look at the problem at any point. Right before the water hits the turbine, it has a certain amount of kinetic energy (which was potential energy earlier). This does work on the turbine, and reduces the kinetic energy of the water.

From conservation of energy this could be the case, but it's also possible that the string more efficiently couples to the primary mode and less into the harmonics.

PE = mgh Your potential energy, which is going to be the maximum amount of work you could extract from the water, is zero at the bottom, where h=0. It does not matter if there is a turbine in the way or not. If there is a turbine there, you do work on it, and it means the water has less kinetic energy when it reaches the bottom. [math]KE_o + PE_o + W = KE_f + PE_f[/math]

Yes. The potential energy is solely due to the position. What you have done with it is convert some of it to work, but you didn't have to.

You can't see steam either. What you see is small water droplets that have condensed from steam.

Some people do challenge accepted science, but they only get a serious audience when they do it within the proper framework of science. I saw a poster at a recent conference discussing an experiment concerning the implications of photons having mass, and ways to test those implications, which was what they were doing. And that's perfectly good science to do. But there's a huge difference between "if X is wrong, here's how we would know and here's our attempt to measure this effect" and simply going with "X is wrong, full stop."

Who is doing this?

Here, finally, is a prediction, and something that is potentially testable. Mainstream physics predicts that gravity is solely dependent upon energy density (classically, mass). Even our own sun should change behavior as protons fuse into helium, which means the creation of neutrons and the ejection of neutrinos. This should have some effect in when different fusion cycles occur, since that depends on gravity. Now all that there is to do is coming up with some evidence that supports this.

That's the actual mechanism. The best places to do this are the bottoms of your feet, your palms and your ears, because of the density of blood vessels and the surface area. I recall some research I read about a few years ago, with a device that drew a weak vacuum while cooling one's hand; the lower pressure kept the blood vessels from constricting, which is one thing that normally happens when you slap something cold on the skin, and it restricts heat flow.

The way MacGregor put it is easily discerned by reading the linked passage. Wrong emphasis "the force that two symmetric spheres exert upon each other is the same as if each sphere were replaced by its equivalent particle." There is no claim that it is a single particle. You would get a different relationship for the ratio. Truly meaningful relationships between constants that describe nature, like the fine structure constant, are unitless. Mathematical prediction is one thing that separates science from nonscience. There is a current thread on this very topic.

If energy is not conserved it means that the laws of physics change over time.

What fraction is left after 4.6 half-lives? That will support your answer quantitatively.

Oh, stop already. A passage is not the same as the whole book. I provided a freaking link to the page in Google books, where you find the context of the passage in question. MacGregor at least provides a context for the discussion, whereas you do not — you made it sound like the electron being treated classically is a perfectly acceptable thing to do, and upon reading the entire quote one realizes that this is not what MacGregor is claiming. He admits that the QM viewpoint is almost universally accepted, and if one were to only look at your quote, one would not get that impression. It's what separates science from nonscience. Rigor vs ad-hocery. Last column of the first table in the first post. And this is where the wheels come off the wagon. No, mass is not treated as one particle — that's missing the point, as it were. They are treated as point objects, because that's a perfectly valid mathematical treatment. Any spherically symmetric mass of radius R can be treated as if all mass were at the center for r>R (Gauss's law, or Newton's shell theorem). And even if not symmetric, if r>>R, it reduces to that case if you expand the equations. That's all math, and nothing more. There are no other claims made as to the physical nature of the bodies. Your units don't match up. Which means that the relationship between the two depends entirely on the unit systems chosen — if you did this in english units, or even cgs, you would not get the relationship you claim. That indicates that it is accidental rather than physical. Numerology.

And if your particle is in a box of length L, the lowest state is a half-wave fitting into it, so the wavelength will be 2L (or a bit longer, depending on the depth of the well, since the tail of the wave goes into the sides a little), which is exactly what you've shown, and what hermanntrude suggested.

I haven't read the book, nor did I claim to. I was just pointing out that there's more to it than the snippet you quoted. The existence of a book does not make the information contained in it true, however. You need e-v-i-d-e-n-c-e, i.e. you need to come up with a way of testing the claim in a way it can be falsified. Rqmc/Rc will give you a constant because that's all there is left — the QM correction term (which MacGregor gives as sqrt(3)) What are the units for mr? What are the units for G?

Lorentz transformations are invertible, i.e. you can transform from A to B and then do the reverse transform and get back to A. Thus, you cannot do a thought experiment, using relativity, which negates relativity. If you get an inconsistent answer, it means you applied the theory incorrectly or made a math error. IOW, once you have removed any kind physical experiment from the discussion, it is no longer a physics problem. It is then a math problem, and you are discussing the shortcoming of math. The only way to disprove relativity is by actual experiment disagreeing with the predictions of the theory.

My objection was the use of the classical electron radius as a physical value, as it is a value derived from equating the electrostatic self-energy with the mass. In reality, the data are consistent with the electron being a point particle. The main thrust seems to be that if you take a number and divide it by a larger number, you get a fraction. elas is selectively quoting MacGregor; if you read the entire passage you'll see that he says that experiment confirms that the electron is indeed a million times smaller (at least) than the classical radius, and that as a result classical physics does not apply. The compton radius depends on the mass of the particle, and AFAIK the QM corrections to it are a constant, so it's not surprising that certain ratios give you a constant. 5/10 is the same as 3/6. OMG!