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bio website motls.blogspot.com
location Czech Republic
age 40
visits member for 3 years, 8 months
seen 3 hours ago

Hi, I am a string theorist and a publicist.


Sep
3
comment Gravity in spacetime
Incidentally, the correct claim about "straightening of trajectories" is one that one may derive from the relativistic theory of gravity, general relativity, but the dynamics isn't trying to make the trajectories "parallel to other objects' trajectories". Instead, general relativity implies that the trajectories of freely falling bodies are straightest possible (geodesics) according to the local (generally curved) geometry of the spacetime.
Sep
3
comment Gravity in spacetime
But you have been given the answers several times in about 10+ comments here (starting with Danu's "No") so why do you keep on repeating the stuff that you want others to "confirm" your claims? Has there been any ambiguity about the conclusion that your proposition is incorrect? How many kilobytes of texts do you need to understand "No"?
Sep
3
comment Gravity in spacetime
No, special relativity prohibits any curvature of spacetime. It is really hard to talk about these matters if you confuse special and general relativity - which is a pretty elementary mistake - yet you seem extremely self-confident about all the wrong things you are writing down. ... I don't believe that you will accept (or even upvote) an answer that unequivocally implies that your question - something you self-evidently consider a big discovery - is really just a basic confusion and mistake. That's why I am avoiding the controversy that results from posting answers to "very wrong" questions.
Sep
3
comment Gravity in spacetime
Your line of thought is not correct according to special relativity and it has nothing to do with special relativity. In fact, special relativity (in the strict sense, not including general relativity) is a theory that explicitly prohibits any gravity. Your line of thought is incorrect according to any viable theory – especially classical mechanics – too. You are really asking about the simple properties of the fate of the direction of velocities under the gravitational influence and any viable theory that isn't immediately ruled out confirms that what you say about the convergence is wrong.
Sep
3
comment Gravity in spacetime
I am saying that gravity is a Newtonian phenomenon because Isaac Newton is the #1 person in the human history who may be credited for that phenomenon because he published the universal law of gravitation, back in 1687, and it was the key part and application of his more general theory of classical mechanics. This Newtonian picture of gravity is surely sufficient to answer questions such as whether world lines tend to align or misalign themselves which is why I pointed out that any discussion of relativity in this rudimentary context is pure red herring.
Sep
3
answered Quartic terms as two particle interaction?
Sep
3
comment Derivation of formula of potential energy by a conservative force
In general I allow the velocity to be any vector, too. But due to the rotational (or parity) symmetry, this question about the sign, and many others, may be answered without a loss of generality by assuming a particular direction/sign.
Sep
3
comment Derivation of formula of potential energy by a conservative force
Dear BMS, a positive dot product means the positive force because of the convention that I explicitly articulated at the beginning, that $dx$ (or $v_x$) is positive. In the 1D case that the OP actually asked about, there are just 2 directions, and I chose the positive one for the motion.
Sep
3
comment Gravity in spacetime
At any rate, it is bizarre to discuss these trivial - Newtonian - phenomena with words such as "Minkowski spacetime". Relativity is clearly not needed to see whether gravity makes two velocity vectors approach each other or the opposite. So relativity has nothing to do with the simple Newtonian exercise. Relativity has nothing to do with making distant objects' properties directly change, either. In fact, a key point of relativistic theory of gravity -general relativity - is really the opposite one. Objects only influence each other through the spacetime medium in between, not instantaneously.
Sep
3
comment Gravity in spacetime
Well, if they are flying from each other, the attractive force makes them "more aligned". Once they are aligned, gravity continues to "misalign them", to approach each other, but then they reach the minimum distance (avoiding collision, assume it) and the description is different again. Gravity sometimes aligns them, sometimes does the opposite.
Sep
3
comment Derivation of formula of potential energy by a conservative force
No, BMS, the kinetic energy increases exactly when the force and the velocity are "equally oriented" (or with angle less than 90 degrees). It's because $\vec F \cdot \vec v$ is the power which is the change of the kinetic energy per unit time. If the angle between $F,v$ is below 90 degrees, the inner product is positive, the power is positive, and the kinetic energy goes up.
Sep
3
answered Electron Charge is 150%?
Sep
3
answered Derivation of formula of potential energy by a conservative force
Sep
3
comment Diff(M) as a gauge group and local observables in theories with gravity
In other words, what is wrong about your description is that you don't seem to care whether the transformation of coordinates is a symmetry (of the laws of physics) or not. Writing the words "the same point" in bold can't replace that. Whether we talk about points at all and say that something is "the same point" depends on conventions; it's really a psychological issue. What's not is whether the phase/Hilbert space contains many copies or just one, and whether the laws are symmetric under some symmetries.
Sep
3
comment Diff(M) as a gauge group and local observables in theories with gravity
Dear Nevermind, positions at (complicated enough) manifolds always require to use patches and different coordinates in each patch. So the first part of your description is inevitable whenever a theory is defined on a general manifold. However, there are special theories in which diff is a local symmetry whose basic laws of physics are the same in all coordinate systems (because the metric is dynamical etc.). These diff-inv. theories are the same for which diff is the local symmetry algebra.
Sep
3
comment $\mathrm{CO_2}$ rate of deposition
It doesn't matter whether he actually wants it or not. If someone is proposing to deliberately manipulate with the CO2 level, it is a good idea to know which levels are safe and which levels are not, isn't it? I was just explaining that the OP is wrong when he says that the CO2 concentration is excessive. It's far closer to the minimum level compatible with life than to high levels that would be dangerous because they are high.
Sep
2
comment How does Dirac show that $\langle B|\bar{\bar{\alpha}}|P\rangle\;=\; \overline{\langle P|{\bar{\alpha}}|B\rangle}\;=\; \langle B|{\alpha}|P\rangle$?
It's just hermitian conjugation. It obeys $(ABC\dots Z)^\dagger = Z^\dagger Y^\dagger \dots C^\dagger B^\dagger A^\dagger$. The Hermitian conjugation of a $c$-number $\alpha$ is simply the complex conjugate $\bar \alpha$, and adding the bar (or dagger) twice is like erasing both.
Sep
2
comment $\mathrm{CO_2}$ rate of deposition
Thanks for your recommendation but I am not taking any tablets.
Sep
2
comment $\mathrm{CO_2}$ rate of deposition
Despite widespread misconceptions, there is nothing such as "excess atmospheric CO2 problem". The economically and ecologically optimum concentration of CO2 would be around 4,000 ppm. The current concentration is 10 times lower than that. The Earth's ecosystem are CO2-starving, in a technical sense, but of course they got adapted to that. However, most existing plant species are unable to adapt to concentrations below 150 ppm. Dropping below that value would pretty much mean the end of life on Earth, at least temporarily.
Sep
2
awarded  Guru