timo

Did you try it yourself and did it work? Spontaneously, I have no idea how it works. My guess would be a chemical reaction that draws thermal energy from the water; not sure what you can to with NaCl, H20 and O2. Assuming the trick really works and isn't some fake, that's a very nice video.

Even if it didn't, the Mt Everest does not exactly rise from the sea but from the Himalaya highlands. One could try to guesstimate the height from which Mt Everest rises from the 12 s and the 42 s (which btw. are approximately correct - a free fall over 8 km with a gravitational acceleration 10 m/s² takes 40 s).

Assuming that was in reply to my post. Yes. But: Define the distance d between the two balls with position p1 and p2 as d(t) = |p1(t) - p2(t)|. Then, your condition is equivalent to setting both positions equal, i.e. d(t) = |p1(t)-p2(t)|=0 <=> p1(t) = p2(t). I see no hint about 15 stories (what size are the people in your area ). The ball travels exactly at the velocity that it travels at, as given by the equations in my previous post. There is no need to use approximations here (except ignoring air resistance), I don't even think it's justified doing so.

Preface: The follwing might seem a bit too complicated to some. But I think following the path 64th took to solving the problem is a good idea, pedagogically. Preface 2: The equation of motion for an object with constant acceleration is [math] \vec x(t) = \vec x_0 + \vec v_0 t + \frac{1}{2} \vec a t^2 [/math] with [math]\vec x(t)[/math] being the position at time t, [math]\vec x_0[/math] being the initial position (the position at time 0), [math]\vec v_0[/math] being the initial velocity (guess at which time ) and [math]\vec a[/math] being the acceleration. This equation, in conjunction with [math] \vec v(t) = \vec v_0 + \vec a t [/math], is all the physics you need to know/remember for those types of questions about motion with constant acceleration (note that "no acceleration" is also a constant acceleration) - the rest is rearranging equations and using rational thinking. 64th, I've not read any of your equations, they seem a bit confusing to me. Anyways: Let's follow this approach. It's the pedestrian version but leads to a result and is potentially easy to understand: Draw those charts into a graph (position over time) for both balls. At the position where the two lines (where with "line" i mean "curve", they are not straight lines) intersect, both balls have the same position at the same time -> that's exactly what you are looking for if I'm not mistaken. This graphical way of solving the problem definitely is a solution to the problem. If you want a more elegant solution, then think about how to convert that way into mathematical expressions: - Can you express the lines in the graphs in a mathematical way? Hint: Yes, of course. I wouldn't propose it if it wouldn't work. Judging from the graph you drew it should be appearant that expressing both lines via a function of position as a function of time seems like a good approach. - Hopefully having expressions for both lines, the next question is how "the lines intersect in one point" translates to a mathematical expression. Well, I've already mentioned the mathematical expression for the two intersecting lines: They have the same value X for position at the same time T, i.e. position_of_ball_1(at time T) = position_of_ball_2(at time T). - This equation can then be solved for the time T at which they meet. Depending on the number of additional assumptions you put into your initial conditions, T will be a function of some number of variables (those variables being exactly those initial conditions that you assumed no value for). For a start I strongly recommend fixing all of the initial conditions you mentioned as not being given to some (ideally sensible) value, e.g. the initial velocity of the upper ball being zero and the lower ball starting at a height of zero.

And since you cannot have a spaceship travelling at the speed of light, that statement is pointless. Nope. Strange wording, but I think what you meant is correct. The rate of your rest frame, just as you defined it in your previous sentence, meaning the time measured in the ship equals that of your rest frame. ? ?? You mean speed as in "meters per second"? Possibly. There is something similar to what you seem to be talking about: For mathematical reasons, the "velocity" (the term is highlighted with "" to emphasize that it's not the canonic meaning of velocity") through spacetime is undetermined by a real factor f. What we do is scaling the velocities such that the norm we use on the velocity vectors equals 1. Well, maybe it's c in case you don't use a system where c=1; I don't know for sure (I always use c=1 and plug in c's afterwards, if needed). So (almost) all velocities have a norm of 1. The funny thing is, that there is one exception to that rule, namely the velocity of light-like objects. The norm of all their possible "velocities" is zero, so it's not possible rescaling them to 1 (no number times zero equals one). This is in fact the reason (or a symptom of - probably depends on point of view) why there is no rest-frame for light, why you can't reach the speed of light, ... Depends, see above.

Why would you want to do that? People could just turn up and write PMs to you asking for help rather than posting in the forums.

That's amazing. I didn't know it's possible to stay in Kindergarden so long. Didn't it get boring after a few centuries?

EDIT: I somehow didn't notice the posts after #11 so maybe part of the following might be redundant: . At least you're not proposing this to be the newest theory of everything. Perhaps I should mention why I had to grin here: You use the very definite attribute "exactly" in a completely indefinite context - what is exactly opposite? Just try not being smart and just look at the equations. If you rearrange s=v*t into t = s/v, the application on this scenario would read [math] 10 h = \frac{3000 km}{v} + \frac{3000 km}{v} [/math] for the first case and [math] 12 h = \frac{3000 km}{v + w} + \frac{3000 km}{v - w} [/math] (with w being the wind speed) for the 2nd case. I would say you better look at the individual variations; I don't see how they'd easily cancel. Why? Substracting the velocities would make sense if the wind was always blowing against the movement of the plane. I don't think that's the case here. I don't think so, but I don't understand it - perhaps try being less smart...

It means v(t) for the case t=0 s, i.e. the velocity at time t=0 s. I have the nasty habit not to add units to zeroes (because the zeroes remain zeroes under scaling) - the correct expression would be v(0 s) or, if you prefer that, [math]v_0[/math]. You should really know the two equations I posted, especially since they are the only two relevant for the typical "constant acceleration"-problems (the only two I can currently think of, at least).

For a): T = 3.6 s v(T) = v(0) + a*T = 53 m/s s(T) = 0 m + v(0)*T + a*T²/2 = 140 m How many unknowns, how many equations? => No problem solving that. EDIT: To clearify: t=0 s means the start of the 140 meter distance crossed, not the point where the car was at rest (which is asked in b). Yes Yes No. I suppose we agree that maximum velocity, minimum (starting at the beginning of the 140 m) and average velocity are related by [math] v_{avg} = \frac {v_{max} + v_{min}}{2} [/math]. The correct calculation follows directly from that. The idea is nice, but it's beaten by one of the most important rules in physics: Never try being smart! If there is a dumb way of solving a problem (brainless writing down of the relevant equations and solving for the unknowns, here), then by all means take that way. Being clever only means opening paths to a lot of more or less artistic ways to shoot yourself in the foot.

One would think getting the five hundred bucks would be easy because Well, from a quick glance I would say that any theory that makes at least one quantitative prediction about gravity is more accurate than a theory that does not make a single one quantitative prediction (although I might have missed the quantitative predictions during skimming the text). Newtonian Gravitation (which indeed is a very, very good theory of gravity), for example. However, he's gonna keep his money because... ... afaik, there is no such thing as a copyright on a gravitational (or any other scientific) theory. You could still try the trick with Newtonian Gravity and hope he'll not find out that Newton does not hold a copyright on it - drink a beer on my health if you manage to get the money.

I don't think it is. A typically-used analogy is that of a massive ball rolling on a rubber sheet. At the position of the ball, the rubber sheet is deformed due to the weight of the ball (let's ignore that the deformation is supposed to be the cause for gravity, not something caused by gravity working on the objects in it - it's just an analogy). The point is: Even though it's slightly deformed, there still is some part of the sheet below the ball - the ball does deform but not replace the sheet. This part of the rubber-sheet analogy holds true to the real theory. Objects are located in spacetime (perhaps see it as attached to some point or area of spacetime), they do not replace it. You are talking about interpretation. Interpretation naturally is arbitrary to some extent and generally you can interpret any physical effect/model/... however you want to (nature won't care, anyways). So I cannot definitely say "no, you can't interpret it this way". I can only tell you that I see no sensible or useful way to interpret any relativistic equation in the way of your "baseball in water"-example.

I assume the people whose unexplained experimental results are suddenly explained in a consistent way would be very happy.

I wouldn't even know which statement to overstretch to come to that interpretation.

What's the definition of a bilinear form? Why don't you just check the conditions by hand?

I don't understand what you say. There is no reason the rocket should be travelling on a geodesic. It's a rocket, not a rock. There is no reason that a coordinate system should lead to inertial frames in every spacetime point (in fact it is, iirc, possible to prove that for arbitrary spacetime structure this is impossible) -> there'd better not be a need for GR to only work in inertial frames or in frames where (t,0,0,0) is a geodesic. Could it be that you're talking about a different problem than the original one?

Wohoo, my post got lost. But I can probably make it short: C++ seems to be a good choice for you. C++ code will work on all relevant OS. For programming c++, download and install an integrated developement enviroment (IDE). Microsoft Visual Studio is supposed to be one of the best IDEs but will probably not work on non-Windows systems. Other possible IDEs are Dev-Cpp (also win-only, I think), Netbeans with c++-plugin (never got it to work myself) and Code::Blocks (the one I currently use for c++). Perhaps google around a bit; there's other good IDEs out there, too.

Because SR is a conspiracy by the CIA and the MIT and you'd get into real problems if you publically spoke out against it. It's pretty obvious to people being able to think outside the box: According to E=mc², all you need to do to build a nuke is putting two half-spheres of plutonium together. Why doesn't every country in the world have nukes, then? Because it's a lie! SR is a scam as every sane person instantly realizes without ever having to bother with the mathematics behind it. The CIA holds back the real theory to prevent <insert a trendy enemy here> from getting their dirty hands on nuclear weapons. The real theory of course is a quantum theory because at the atomic level we need quantum theories. Einstein knew that his theory was wrong and that a quantum theory secretly replaced his - that's the reason why he spokre out against quantum mechanics and ultimately was killed by the CIA for doing so.

That's an interesting statement considering I've never seen a commercial advocating a GPS-based navigation system with "it's based on a hundred year-old physics theory you don't understand, anyways".

Yet, my handbook on emergency medicine (which admittedly is neither the size of a handbook, not really written on a ambitious level and not exactly new - it's just the book we learned from in our training) claims heart rate in case of a cardiogenic shock is "tachycard, possibly bradycard, possibly arrythmic". That does of course not necessarily invalidate your post - heart rate could just go tachycard (increased rate) and make things worse.

It might be helpful if you sketch the reasons why you are interested in those two fields - from my perspective they seem very unfamiliar.

I think that on the page http://www.dbunked.com/about/experts , when you write "Our experts are qualified and knowledgeable in their particular fields,..." it would be a good idea to actually list the field on the list of names. The specific field certainly is a much more important information than an academic title (e.g., when it comes to physics, I trust a 4th semester physics student much more than a Prof. Dr. Dr. h.c. mult(9) med.).

Apart from the obvious solution I think it's probably safe to just lay down in your bed in such a case. Afaik, there is not a single case of death caused directly by consumption of marijuana, so from the position of evaluating the immediate dangers that's probably safer than not smoking in the first place and going for a bike-ride instead (though the latter is more healthy of course). Feeling unwell at least at times should imho be an occasion to rethink the idea of smoking weed at all.

I should note that with "pulse", I meant the frequency with which the heart throws out blood - I'll call it "heart rate" from here on and use the term "pulse" to mean a single pressure wave (that also transports blood) travelling through the arteries and veins. First of all: Blood pressure is usually characterized by two values, the diastolical value which is kind of the base value, and the systolical value which is the maximum value reached when a pulse travels through the arteries. Assume you'd increase the heart rate and leave all other parameters constant. Why would that increase either the base value or the amplitude a single pulse has? I'd assume (ok, effectively I demanded it) that the blood pressure remains the same while the volume of blood rotation is increased. Effectively, the increase of heart rate can be a reaction of the body to an insufficient pumping volume of a single pulse - what the body ultimately needs is a sufficient supply of oxygen via blood, blood pressure, heart rate, volume of a single pulse etc. are just parameters which influence this in a non-trivial way. The definition of a shock in fact is (something like, better look it up somewhere) an insufficient supply of oxygen to vital organs. Afaik, the increased heart rate is a typical reaction of the body which tries to compensate for the insufficient supply of oxygen. A cardiogenic shock must not necessarily result in increased heart rate - it's caused by a disfunction of the heart in the first place. Blood pressure is mostly dependent on the amount of blood available and the volume of the arteries and veins (btw, which is the english common name for both, arteries and veins?). The anaphylactic shock Revenged mentioned afaik is the result of an increase of volume of arteries and veins due to an allergic reaction. Counter-question first: Why are you asking these questions and what do you need/want the answers for? It might or might not be symptoms - I just don't know. For practical reasons, these symptoms alone (i.e. without any of the others I mentioned) would rather induce me to give the patient a blanket and transport him to a warm place than to lay him down into shock position or applying infusions.

Well, let's start with a simple one: Apart from possibly giving a handle to describe quantum gravity, are there any other reasons to believe in strings that are not already features of less exotic models (most notably supersymmetry and GUTs). Which ones?