# Search results

1. ### What does this quote from Einstein mean?

Einstein wrote in a letter to Max Born that he feels that QM is not the true Jacob, quote: "Quantum mechanics demands serious attention. But an inner voice tells me that this is not the true Jacob. The theory accomplishes a lot, but it does not bring us closer to the secrets of the Old One. In...
2. ### Question about fluid expansion

Hi, When a hot and dense fluid suddenly expands, how much can it cool down. Lets take for example an expansion valve from an AC, does the fluid do work when passing through the valve or does it not even need to do work in order to cool down. What is the lowest temperature that the fluid can...
3. ### Pressure cooker at 1 atmosphere?

Hi, I just read that the operating pressure of a standard pressure cooker is 15 psi or about 1 bar and they claim that water boils at 120C or 250F at this pressure. But atmospheric pressure is 1 bar in Paris and almost 1 bar in most countries in the world, here is a link I found...
4. ### Was Einstein lucky when not considering twin paradox as paradox?

hi, Einstein did not even consider the twin paradox as problematic at all, he argued that it is a simple consequence of his special relativity? obviously he never gave a explanation of why the two twins don't age the same he instead left it to others to do so. was Einstein just having a hunch...
5. ### Scalar field 2 dimensional discontinuous but differentiable

Hi, f(X)=\frac{xy^2}{x^2+y^4} is the function in question, this is the value of the function at ##X=(x,y)## when ##x\neq0##, and ##f(X)=0## when ##X=(0,y)## for any ##y## even ##y=0##. Now, along any vector or line from the origin the directional derivative ##f'(Y,0)## (where ##Y=(a,b)## is...
6. ### Principle of least action?

hi, please if somebody could explain why anybody would consider the "action" and is there any proof that the minimal action actually gives the correct route of a problem?
7. ### Big bang, explain please?

hi, 1. radiation travels faster than matter. 2. our earth was formed much after the big bang. The big bang goes like this. At some point in time and in some point in space (witch we cannot determent so we just leave the location open and say it could have happened anywhere) all the matter...
8. ### IC temperature sensitivity?

How sensitive are ICs to temperature? I recently replaced a digital signal processor IC (IC:cxd3098aq) Sony made on a PlayStation 2 and while doing so I heated the chip first to remove it, then I re-balled all the pads and then put the new chip on the pads applied some flux in the form of paste...
9. ### Why does light have a finite speed?

hy, there is nothing in Maxwells equations that would limit the speed of light. the only way one can get light speed, is to assume that em waves solve Maxwells equations and then one gets c as the square root of something out from Maxwells equations. the same goes for gravity waves, only...
10. ### Electron moving

hi, ive got a really simple question. niels bohr proposed a model of the atom in witch the electron cannot fall into any energy state but must fall be in certain discreet values and this helps explain why the electron doesnt clumb with the nucleus almost instantly. not the atom needed to...
11. ### Angular momentum conservation of two point masses

Hi, Lets suppose we have 2 point masses one fixed and imoveable the other rotateing in a perfect circle around the first imoveable one with constant speed. Regardless of vich force is keeping the rotating mass on its circular orbit. It may be a string or gravitational force or whatever...