Recent content by BHL 20

Was just wondering if there is anything fundamentally preventing a system of planets being in permanent orbit around a black hole, without ever spiralling in. Assuming that the black hole doesn't absorb any significant amount of additional mass. Of course I know it wouldn't provide any energy to...

Thanks to everyone for the advice. It seems hard to find something like this through a direct search on any website, and I don't think any of professors at my college specialize in neurostimulation, but I managed to find a study like I described being cited in different paper I was reading. The...

I'm doing a master's degree, and I would like to research the long-term effects of neurostimulation on the brain. It would be really helpful if I could find at least one research study that: (1) Performed MRI scans on a cohort of patients, preferably using diffusion MRI. (2) Had this cohort of...

I'm just wondering why lecturers and textbooks make such a big deal at the end of a derivation when the ground state energy comes out to be zero. "In classical physics we can have a harmonic oscillator at rest with zero energy, but in quantum mechanics it must always have some energy." If it...

Since the eigenvalue problem can't distinguish between a non-existent wavefunction (and therefore a non-existent particle), and the energy being zero. This is the next thing that has started bothering me on my journey to understand quantum mechanics. For example, in the algebraic derivation of...

Yes I may have not finished my degree but I certainly know the difference between vectors and scalars 🤣. I just didn't think that uncertainity in direction would count as satisfying the uncertainty principle. I was thinking of uncertainty as having to be more like a continuous probability...

It's been a few years since I failed my physics degree but I still really want to reach an understanding of QM, and I'm currently going through a QM textbook. One thing I cannot understand no matter how much I think about it, is momentum uncertainty. In classical mechanics a specific kinetic...

It's from a vectors and tensors course. It was an example used to illustrate the definition of a vector.

So I learned that if a vector (a1, a2, a3) is transformed to a different set of coordinates, and the components of the resulting vector are squared like so: (a1'2, a2'2, a3'2), this result is not itself a vector. The proof for this simply shows that each component ai'2 does not transform to ai2...

I'm asking this to help with making subject choices. One thing I'd like carry away from this degree is an overall understanding of the origin and structure of the universe. I'm wondering how much quantum mechanics and quantum field theory should I take to gain this understanding. I have heard of...

Thank you everyone for the replies. So I guess this means that if we improve our theories, we may eventually be able to get rid of the singularity. Interesting.

One more thing, but this is probably a big thing. I'm shocked by this: No singularity? I know Wikipedia isn't the most reliable but a lot of people get their information from it, and in the introduction to the article in it on the Big Bang it says that it "postulates that at some moment all of...

If you're correct, that's very deceptive.

But I've read many assertions about the size of the early universe such as "after inflation the universe was the size of a grapefruit". This paper http://arxiv.org/PS_cache/astro-ph/pdf/0305/0305179v1.pdf even graphs the size of the universe against time on page 30. How can an infinite amount...

My astrophysics lecturer did Olbers' paradox today in class, and while discussing it, it seemed as if she actually believes that the universe is infinite (infinite amount of space and infinite amount of matter). I came and questioned her about this afterwards, and when I said I had always...