D H

No, it's a very standard definition. Electrons are fermions. They are subject to the Pauli exclusion principle. They occupy space. Photons and other force carriers are bosons. They are not subject to the exclusion principle. They do not occupy space.

No, Pete. juan is not dragging this thread off topic. The standard model does not view photons and other force carriers as matter. Matter is stuff that has mass and occupies space.

That depends on what you mean by "matter". One fairly standard definition is something that occupies space and possesses rest mass. This rules out photons on both accounts. They are massless, so strike 1. They don't occupy space as they are elementary bosons, so strike 2. This second strike also applies to the W and Z bosons, which are not massless. Per this definition, the W and Z bosons are not "matter". This second strike does not apply to mesons even though they are bosonic. Mesons do occupy space because the quarks that comprise them are fermionic and are thus subject to the Pauli exclusion principle.

This is a false dilemma. Both of your two alternatives are false. The rules of logic are not random, and there is no such thing as a logic gene. There is a third choice to your false dilemma, learned knowledge. That learned knowledge is imparted rather than inherited.

The energy should be squared here: [imath]E^2 = (m_0c^2)^2 + (pc)^2[/imath] It's not. E=mc2 is a simplification in the special case that momentum is zero. In other words, it is looking at things from the perspective of the rest frame of the object. Another special case of the general mass-energy equivalence formula results for massless particles ([imath]m_0=0[/imath]) such as photons. There is no such thing as a rest frame for such particles; momentum is never zero in this case. The energy of a photon is given by [imath]E=pc[/imath]. Another way to look at [imath]E=mc^2[/imath] it is that the [imath]m[/imath] in this expression is the relativistic mass. The concept of relativistic mass however is a bit outdated and is no longer widely used.

Stop using HTML! Your posts routinely look like garbage. There's a "Preview Post" button right next to the "Add Reply" button. Use it!

Actually, no I don't. I was using the term as allegorically.

Geir & Geir, the authors of some of the papers described by sammy7, are the American counterparts to Wakefield. Like Wakefield, Geir & Geir have profited immensely from their faked links between vaccines and autism. Like Wakefield, Geir & Geir have had articles redacted. Like Wakefield, Geir & Geir have falsified data and endangered children just to make a profit. The approach by Geir & Geir is particularly heinous. Their treatment was to inject the drug Lupron. Note very well: This is the same drug used in high doses to chemically castrate sex offenders. This drug is dangerous even in lesser doses. It is supposed to be used in children only if they suffering from premature onset of puberty. It is not supposed to be used in children who have a risk of seizures. It is not supposed to be used in children who are going through puberty at an appropriate age. It is not supposed to be used in children unless they have been explicitly tested for premature onset of puberty. Fortunately, their licenses to practice medicine has been suspended. There is no verifiable link between vaccines and autism. There is a huge link between children not getting vaccinated and the recent upsurge in diseases such as measles and whooping cough. There (I hope) is a special place in hell for Wakefield, Geir & Geir, and their ilk.

Nor am I. A bigger question: Why send people to Mars at all? For one thing, it is extremely, extremely expensive. The required technology for a human trip to Mars, fast or slow, is way beyond our current capabilities. Zubrin's approach predicates just as much, if not more, hocus pocus than does Ad Astra's. Yet another big problem with sending people to Mars is that it I fear it will be Apollo all over again. We'll send people there once and then it will be over. The cost for that one trip will be much to high to bear a redo. What is needed is a permanent human presence in space, and not just low Earth orbit. Sending humans to Mars does not accomplish this goal. IMHO, it is counterproductive to accomplishing this goal. Finally, why spend an enormous amount of money to get out of one fairly deep gravity well only go back down into another? If the goal is to get to outer space, well then do that. Go to an asteroid. Mine asteroids. Make human-capable structure out of asteroids. Or go back to the Moon, permanently. Or build a space station orbiting about the Earth-Moon L1 or L2 points. All of these are considerably cheaper than a round-trip to Mars, have a better payback, are scalable, and go much further to creating that permanent human presence in space. Nice science fiction story. So-so on the science, lousy on engineering and technology, and atrociously bad when it comes to politics. This is the kind of venture that can only be funded by governments. Political support for nuclear technologies was close to non-existent prior to Fukushima. It is non-existent in this post-Fukushima world. It's going to be another decade, minimum, before we put Fukushima behind us. New space technologies take 15 to 20 years to go from the beyond the paper (TRL level 2-3) stage to reality (TRL level 9). Nuclear propulsion is something for those being born now to see to fruition. Another political problem are the current economic woes. There are signs that our current economic woes are about to get worse. Greece may bring down Europe and China's economy is starting to falter. Add in the current weirdness of Republican party and the apparent spinelessness of the Democratic party and you get nada for NASA. Thank you. That took both a good deal of courage and and a good deal humility to say that.

The abbreviations for a megaliter, milliliter, and microliter are respectively ML, mL, and μL. They are not the same.

Along the same lines, is a das ten seconds or 0.1 arcseconds?

That document is old and it excludes the mass of the controller. I got my numbers from the DOE fact sheet on the ASRG dated January 2011. http://www.ne.doe.gov/pdfFiles/factSheets/SpaceRadioisotopePowerSystemsASRG.pdf That said, even if you go with your 20 kg versus the 32 kg I used, does it really matter? The mass needed to power one VX-200 is still overwhelmingly large. Reference needed. Everything I've read says 5 or 5.7 newtons, even the fluff pieces out of Ad Astra such as http://www.adastrarocket.com/aarc/VX200 No, it doesn't. You can't just substitute one energy source for another and leave everything else unchanged. You most certainly can't use something that generates so much heat that it can vaporize itself and leave everything else unchanged. And you absolutely cannot use something that is as astoundingly deadly as polonium 210 and leave everything else unchanged. Everything needs to be redesigned. The fuel needs to be diluted and encapsulated to keep it from vaporizing itself. The highly dangerous fuel mandates even stronger safety measures than are used for RTGs or the to-be-flown ASRG. The much larger heat output requires thermal rejection well beyond just dumping the heat to the spacecraft structure. The very short half life means the system would be of very limited use. Tough. My habitual naysaying is mild compared to what happens in a real peer review. The standard line for those proposing new ideas is to "check your egos in at the door." Try 120 rather than 30 SAFE-400s. Read your own source. A SAFE-400 produces 400 kW of thermal power but only 100 kW of electrical power. Another point: That 1200 kg is the mass of the reactor. It does not include the mass of the thermal radiators, and 120 of those generators will require a lot of thermal radiators. Once again, read the source that you provided. I side with Zubrin on the idea of using VASIMR to get to Mars. It's a hoax on the scale of Solyndra.

The main driver behind that push is the fact that domestic production plutonium 238 has been shut down since 1993. Funding to get that domestic production restarted is barely there, and it's only on the NASA side. Producing 238Pu the job of the Department of Energy, and Congress for some reason refuses to fund the DOE side. Logjam. If there was an adequate supply of plutonium 238 NASA would happily continue using RTGs. They are a very simple and very trusted technology. No moving parts. They don't fail. While much more efficient, those Stirling generators are new technology and are significantly more complex than RTGs. Increased complexity means a significantly increased likelihood of failure. That it is new also increases the risk of failure. A lot. The ASRGs will be used for low power consumption devices such as sensors and communications. Using them for a high power consumption device such as a VASIMR engine is not going to get a vehicle to Mars. At least not very fast. Do the math. A VX-200 sucks 200 kW of electrical power, or the output of 1400+ ASRGs. At 32 kg per ASRG, the power source needed to supply a VX-200 masses over 45,700 kg. That's just for the power source, not the housing for those 1400+ units or the electrical cable needed to connect them to the engine. All for 5 newtons of thrust.

No news is most often bad news when in comes to companies that delve into new technologies. Or it might mean they are quietly working on things where progress is measured in years. Many, many years in this case. There's a lot more to RTGs than thermocouples, particularly an RTG that contains 100 billion lethal doses of 210Po. The fuel is encapsulated in ceramic, surrounded by iridium, which in turn is surrounded by high-strength carbon, which in turn are placed in housings, which in turn is surrounded by an aeroshell. There is a whole lot more to an RTG than just the fuel and a couple of thermocouples. Those higher efficiency systems are not RTGs. They are heat engines. Now you have a working fluid, moving parts, a heat exchanger, a generator, and you still need massive amounts shielding to keep those 100 billion lethal doses from escaping in case of some kind of accident. There's a good reason that none of the world's space agencies have gone to these speculative devices. The four fold boost in efficiency is not worth the added mass. Obviously not. Where does it come from? That in situ manufacturing would require building on Mars an automated bismuth mine, an automated bismuth refining plant, an automated nuclear reactor, an automated neutron bombardment facility to bombard the mined and refined bismuth with neutrons, an automated purification system to isolate the polonium, and an automated storage system. It's ludicrous.

No news is no news. Or in some cases, it's bad news. Lots and lots of proposed technologies start with a flourish but then just fade away. What you are doing here is accounting for the mass of the fuel but failing to account for the mass of all of the infrastructure needed to make that fuel useful. The decay of polonium 210 generates heat. VASMIR runs on electricity. You are ignoring the fairly massive infrastructure needed to convert that heat into electricity plus the extremely massive infrastructure needed to ensure that the PO-210 remains safely encapsulated even in the case of an explosion. That alone changes your many kilowatts per kilogram into many kilograms per kilowatt. Then there's the problem of the efficiency of that conversion of heat into electricity. RTGs are simple devices with no moving parts. The downside: They are extremely inefficient. Typically efficiency is about 5%. Your two inch cube of polonium-210 would generate about 7 kW of electricity. Swap it out? With what? Another PO-210 based RTG? Won't work. Polonium 210 is highly radioactive. The polonium doesn't care if the generated heat is put to productive use or is just radiated out into space.

Yes, there is at least one habitable planet or moon in our solar system.

The problem is not that this integral doesn't exist. It most certainly does exist. The problem is that this integral can't be expressed in terms of the elementary functions. All the neat tricks that you have learned are aimed at solving those integrals than can be expressed in terms of elementary functions. Most integrals cannot be expressed that way. For example, students regularly ask how to integrate [imath]\exp(x^2)[/imath] or [imath]\exp(-x^2)[/imath]. Play around with u-substitutions, integration by parts, etc., and no matter what you do you will either get an intractable mess or just get right back to square one. That doesn't mean the integral doesn't exist. It does exist. It turns out that [imath]f(x) = \frac{\,2}{\surd\pi}\int_0^x \exp(-t^2)\,dt[/imath] is a very important function. It appears so often, and in so many different settings, that it has been given a special name (the error function) and a special symbol [imath]\textrm{erf}(x)[/imath]. The error function is just one of many integrals that can't be expressed in terms of elementary functions and that rear their ugly heads over and over again. These "special functions" will be the subject of multiple advanced math classes should you go that far in math. Amongst other things, the arc length along a segment of an ellipse. Elliptical integrals are one of those things that keep coming up again, and hence they are given a special name.

There is no such thing as a heat function Q(U,V,N,...) or a work function W(U,V,N,...). That is why it is better to write heat and work as δQ and δW rather than dQ and dW. Heat and work are inexact differentials. How much heat and work are transferred to/from the environment as a system moves from one point in (U,V,N,...) space to another depends not only endpoints but on the path taken between those endpoints. That is something we agree on.

I thought about telling the OP about elliptical integrals, but then rejected that thought since theOP is "not sure I fully understand how to use substitution."

This function is not integrable in the elementary functions. In other words, you can use all the tricks you know (and all that you don't know) and you will not find the integral.

I was distinguishing from open systems, where the first law of thermodynamics takes on a more complex form. [math]dU = \delta Q + \delta W[/math] still holds in an isolated system; all three terms are trivially zero. It works. You just have to use the right escape. In many other forums you use [tex]...[/tex] to invoke display math mode, [itex]...[/itex] for inline math. At this forum, there is no distinction between display math mode and inline mode, and you use [ math ] LaTeX code [ /math ] (get rid of the spaces) instead of [tex] LaTeX code [/tex].

You are misapplying conservation of energy. It applies to an isolated system only. That the energy of a closed system can change is the difference between an isolated and a closed. Thermal and non-thermal energy can flow into or out of a closed system. The problem here is that you have added a nonsense quantity, [math]d_i E[/math]. The first law of thermodynamics for a closed or isolated system can be written as [math]dU = \delta Q + \delta W[/math], where [math]dU[/math] is the change in the internal energy of the system, [math]\delta Q[/math] is the heat flow into the system, and [math]\delta W[/math] is the work done on the system. In other words, the change in the total internal energy of a system is equal to the total energy flow into or out of the system.There is no extra [math]d_i E[/math]. It is [math]dU[/math]. BTW, please stop with passive aggressive nonsense such as this:

I disagree with your assessment of energy in open and closed systems. Energy is not conserved in such systems. You used a thermometer as an example of a closed system. The energy of the thermometer is not constant; that's the very point of a thermometer.

Freedom of speech is not an absolute. There are limits. You do not have the right To create a clear and present danger such as by falsely shouting "Fire!" in a crowded theater. Schenck v. United States (1919). To incite an imminent lawless action. Brandenburg v. Ohio (1969). (This restricted the Schenck ruling to some extent). To provoke a reasonable person to the point of fighting with your words. Chaplinsky v. New Hampshire (1942). To be extremely crude and vulgar. Miller v. California (1973). To protest in front of someone's house. Frisby v. Schultz (1988). To falsely accuse someone of some heinous act. You can be sued, and on some occasions, put in jail. To have your views expressed in a private forum such as this website. Freedom of speech is a restriction against the government, not a restriction against individuals.

Aside: A sentence ends with one period, not two. Commas between words and the period at the end of a sentence are followed by a space. To answer your question, your conclusion is incorrect. You can't get gravitation from magnetism. Magnetism is a 1/r3 force. Gravitation is a 1/r2 force. Another reason is that gravitational force depends only on mass; it is independent of what constitutes that mass. That is not the case for magnetism.