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| bio | website | |
|---|---|---|
| location | ||
| age | 64 | |
| visits | member for | 1 year, 7 months |
| seen | 6 hours ago | |
| stats | profile views | 452 |
I have a PhD in physics, but for my career, I worked as a software engineer. In my retirement, I have gone back to my first love, Physics. I attend lots of physics colloquia, seminars, conferences and summer schools mostly in astrophysics, cosmology and particle physics.
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Apr 21 |
comment |
Is there any true inertial reference frame in the universe? @Anixx - According to en.wikipedia.org/wiki/Inertial_frame_of_reference - "All inertial frames are in a state of constant, rectilinear motion with respect to one another; an accelerometer moving with any of them would detect zero acceleration." So since an accelerometer would have non zero acceleration on the Earth's surface, it would not be an inertial reference frame. Remember that gravitation and acceleration are exactly the same thing according to the principle of equivalence and General Relativity. Only if you are in FREE FALL in gravity then it would be an inertial frame. |
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Mar 20 |
revised |
What happens to a photon in a black hole? typo |
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Mar 19 |
comment |
metric signature explanation You say often just add the numbers to signature of 2 but I have never before heard the signature of Minkowski spacetime referred to as 2. I have always seen the (1,3) notation (or -,+,+,+ or +,-,-,-). It doesn't make sense to add the diagonal elements and say the signature is 2. A flat 2 dimensional plane space would also have signature 2 by that method which certainly is not the same as (1,3). |
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Mar 19 |
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What is the link between the metric signature of spacetime and fundamental field equations? I read the answer claiming the signature is 2 but I have never heard it referred to as 2. I have always seen the (1,3) notation (or -,+,+,+ or +,-,-,-). It doesn't make sense to add the diagonal elements and say the signature is 2. A flat 2 dimensional plane space would also have signature 2 by that method which certainly is not the same as (1,3). |
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Mar 17 |
revised |
What is the current induced in a straight wire when a magnetic field is turned from on to off? edited title |
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Mar 16 |
awarded | Nice Answer |
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Mar 15 |
revised |
How do we know Dark Matter isn't simply Neutrinos? Explain hot, warm and cold. |
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Mar 12 |
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Why does space expansion not expand matter? @kbelder Two objects connected by a spring, when all oscillations die away due to friction (in the spring itself if not due to air etc) will have an equilibrium separation that would be very very slightly larger appart in an accelerated expanding universe and when there is oscillation out and back, they would just oscillate around that new equilibrium location. |
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Mar 6 |
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Why does weak equivalence principle say gravity is equivalent to acceleration? You didn't at all explain how the weak equivalence principle would tell how light would bend in an accelerated reference frame or gravitational field. |
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Mar 6 |
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Will two trains running along the equator in opposite direction experience same wear out? @stevenvh - Thanks for the great suggestion, I added the SI units. |
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Mar 6 |
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Will two trains running along the equator in opposite direction experience same wear out? Added SI units |
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Mar 2 |
revised |
Equation of motion for average acceleration edited tags |
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Feb 26 |
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What are the uses of proper length as a parameter? Thanks @JohnRennie, I added that summary to the answer. |
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Feb 26 |
revised |
What are the uses of proper length as a parameter? Minor edits |
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Feb 25 |
revised |
What are the uses of proper length as a parameter? edited body |
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Feb 25 |
answered | What are the uses of proper length as a parameter? |
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Feb 18 |
answered | What's the exact gravitational force between spherically symmetric masses? |
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Feb 15 |
comment |
Why does the presence of a battery change whether a circuit is in parallel or series? Just to complete the answer, mention that in the second circuit, with respect to the real battery, the two capacitors are in series... |
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Feb 8 |
comment |
How to comoving volumes depend on the evolution of the Universe? @ChrisWhite Thanks, made correction! |
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Feb 8 |
revised |
How to comoving volumes depend on the evolution of the Universe? correction |
