What is this all about?: At 12 May 2022 at the ESO official announcement live streaming event the EHT representatives claimed that the Sgr* BH accretion disc spin axis is sort of facing Earth's position thus BH spin axis possible not perpendicular to the Milky way galaxy accretion disc?! https://...

I have a problem in understanding why we can write the expectation value of an operator $\hat{O}$ as the trace of $\hat{\rho}\hat{O}$ where $\hat{\rho}$ is the density matrix defined for pure state. In this link: http://www.cithep.caltech.edu/~fcp/physics/quantumMechanics/densityMatrix/densityMat...

I have difficulty interpreting mathematical operations in a physical way. For example, I see many people reading Newton's second law as "Resultant force equals mass times acceleration", however I now see a theoretical physics professor reading as "Resultant force is the same as giving mass an acc...

Since a star heats up when it radiates more heat (via gravitational compression), and since that's also how protostars turn into stars, I was wondering what are the chances of Jupiter reaching the point where nuclear fusion kicks off within it given that it survived long enough?

Newton's second law is a coordinate agnostic statement, we can use it to calculate the forces in a coordinate system, and hence, the motion of the body in that coordinate system. However, depending on the choice of the coordinate system, the difficulty maybe more or less. Sometimes the DE may its...

It has been said that the Big Bang started from a singularity. Think about a balloon radially growing over time. Fix a time $t_0, t_1 > 0$, and let $M_0, M_1$ be two balloons at time $t_0, t_1$ respectively. I can find a two-parameter diffeomorphism $\phi(t_0, t_1): M_0 \rightarrow M_1$. However,...

There's a line in a book which states that the combination of lens helps create a sharper image, but I don't understand how. Does more magnification mean sharper image?

If the angular momentum of a particle is conserved and it is also 0, then is it true that the particle moves along a line? If so, how can we derive the equation for the trajectory from both the above fact and knowledge of initial position? (This question was inspired by the fact that if angular m...