# 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

Thank you, you are very helpful I wish I could somehow give you a thumbs up or something :)
3. ### Question about fluid expansion

Thanks a lot for the answer, that's exactly what I wanted, could you please tell me how much this temperature change is in one cycle is it a small amount and needs to be repeated or can it be large with the right substance? And also, the inversion temperature must be above room temperature in...
4. ### 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...
5. ### Pressure cooker at 1 atmosphere?

Ok thanks man, very helpful :)
6. ### Pressure cooker at 1 atmosphere?

All right so if it says 15 psi its actually 15 psi above atmosphere??
7. ### 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...
8. ### Was Einstein lucky when not considering twin paradox as paradox?

an accelerometer would measure zero in the above case since the rocket would be in free fall.
9. ### Was Einstein lucky when not considering twin paradox as paradox?

I forgot to mention: if the elevator (rocket) accelerates under the influence of an gravitational field (at the turnaround) then what would we have ???? an inertial frame that accelerates ?? even from the point of view of special relativity, this has to be a IRF since the laws of stay...
10. ### Was Einstein lucky when not considering twin paradox as paradox?

what I mean is that if you for example take the equivalence principle, take an elevator witch you can think of as the rocket of the traveling twin. if the elevator is accelerating with uniform acceleration it acts just like if it were in free fall. so even in an accelerated RF (elevator) one...
11. ### Was Einstein lucky when not considering twin paradox as paradox?

also an accelerometer doesn't measure acceleration in free fall only when you stand on the earths suface does it do so, you can see that from the link to Wikipedia http://en.wikipedia.org/wiki/Accelerometer
12. ### Was Einstein lucky when not considering twin paradox as paradox?

you would have to calibrate the accelerometers differently in order for both of them to be zero if they accelerate differently, because if you assume that your accelerating RF is actually stationary then you calibrate your accelerometer to read zero in your reference frame, don't you? and there...
13. ### Was Einstein lucky when not considering twin paradox as paradox?

as I mentioned the new coordinate system would be just shifted compared to the old one, your fictious force ##mA^j## would only be present from the old coordinate systems point of view. but if you fix your new reference frame is accelerating compared to the old one then from the new RF point of...
14. ### Was Einstein lucky when not considering twin paradox as paradox?

To sum up a little bit, A reference frame is inertial if there are no fiction forces present like coriolis and centrifugal forces, witch are associated with rotating reference frames. Then we also have fiction forces due to linearly accelerating reference frames. but how does one make sure...
15. ### Was Einstein lucky when not considering twin paradox as paradox?

I already added this in my last example as you can see, but this doesn't help.
16. ### Was Einstein lucky when not considering twin paradox as paradox?

if the external force is uniform like for example far away from an electric charge where the lines of force are almost parallel and same in magnitude. in this case the accelerometer and the object would be accelerated the same and you would conclude that the other object is accelerating. also...
17. ### Was Einstein lucky when not considering twin paradox as paradox?

could you please explain how you would measure it in the above example I gave?
18. ### Was Einstein lucky when not considering twin paradox as paradox?

ok so what ingredient needs to be added??
19. ### Was Einstein lucky when not considering twin paradox as paradox?

witch one would be turning around? if anyone of them would be acted upon by an external force witch one would be accelerating in this case? you can always say that the other one is accelerating.

hows that?
21. ### Was Einstein lucky when not considering twin paradox as paradox?

if you have only 2 point particles an nothing else, how do you determent witch one is accelerating? so what is your opinion, what would be the IRF ( I stands for inertial) in this case??
22. ### Was Einstein lucky when not considering twin paradox as paradox?

the thing is that you can use all 3 of those diagrams interchangeably on both the earth twin and the traveling twin. 1. inertial frame is fixed at the earth twin and it is determined what time he calculates has passed . in this case the traveling twins time goes slower as he goes away from...
23. ### Scalar field 2 dimensional discontinuous but differentiable

That's a great plot, thanks a lot. but I think I figured it out myself. the mistake I did was to assume that the vector tangent to the parabola would have one more point, besides the origin in common with the parabola. the expression depends on how one approaches the point ##(0,0)## and that's...
24. ### Was Einstein lucky when not considering twin paradox as paradox?

as far as I can tell there is no explanation of the twin paradox just a similar statement in his paper, a statement without deeper inside in why this has to be or a consideration of what would happened if we assume the earth is moving and the rocket twin is still. as I said just a statement...
25. ### Was Einstein lucky when not considering twin paradox as paradox?

All right so how did Einstein understand the twin paradox, did he consider the acceleration of the traveling twin witch goes out of the scope of special relativity or did he argue that the traveling twin uses 2 inertial frames of reference?
26. ### 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...
27. ### 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...
28. ### Principle of least action?

great, thanks a lot on that info that's exactly what I needed. Susskind is a funny guy :)
29. ### Big bang, explain please?

yes indeed but can you believe that in every tv show about space they are talking about a radio bubble that could be picked up by aliens, and they do that for about 50 years even today. isn't that funny :)
30. ### Big bang, explain please?

so the only difference for someone living in a universe very close to the big bang singularity and us living in our universe would be the temperature and density of matter and deadly radiation? there is no intrinsic way of saying, oh im in a more curved space than I have to be, other than the...