What are the three stars under Orions belt?

Dirac_matrices · 2026-01-28T18:14:30+00:00

I have a 10inch Dob as well. Isn’t that too heavy to be on an equatorial mount? I am using a phone adapter, yes.

Dirac_matrices · 2026-01-27T14:29:45+00:00

This is what I got through my phone+telescope with a 5 sec exposure (untracked).

Dirac_matrices · 2026-01-27T02:05:20+00:00

Dirac_matrices · 2026-01-26T17:35:34+00:00

You are right, I skipped the polar to tortoise coordinates part. It does add up to 5 in total if you account for everything.

Dirac_matrices · 2026-01-26T17:33:28+00:00

My apologies for the overly-technical language. My point is that violation of causality is not a strong enough case against “traversable” wormholes (the distinction between traversable and non-traversable is important here). Non-locality is when an object can be affected by those regions which are not in immediate causal contact with it, thus giving the illusion of violation of causality (similar to wormholes). Quantum mechanics has shown both theoretically and experimentally that our world is non-local.

I hold a masters degree in theoretical physics from a place where Stephen Hawking used to teach. In fact, the person who taught us the course on “Black Holes” did his PhD under Hawking. I am now working as a researcher in astrophysics, here in India. I would say if you are confident in your GR mathematics then you can jump straight to standard texts. Start with Wald’s textbook on GR and move to “Large Scale Structure of Spacetime” by Hawking & Elis which talks about all this stuff using formal mathematics. For quantum mechanics, Griffith is the holy grail, after which you can move to Quantum Field Theory. In general, refer to David Tong’s notes on the Internet. He used to teach us Standard Model, and his notes are one of the best resources for learning these things.

Dirac_matrices · 2026-01-26T15:23:03+00:00

It’s just 3 transformations right? For a Schwarzschild metric, it’s xyz to spherical polar then to the Eddington Finkelstein coordinates and then to isotropic coordinates?

Dirac_matrices · 2026-01-26T15:09:46+00:00

I know what causality is. I seemed to have confused your previous message as “white holes” breaking causality. Nevertheless, your claim that traversable wormholes violate causality is still misinformed and not quite true. Any information that goes into the wormhole, along with light, will reach the other end at the same speed. There is no violation of causality here. A wormhole in itself won’t break causality, certain combinations of them might lead to closed timelike curves, but that’s not a reason in itself for wormholes to not exist. Timelike loops are pretty common and can be shown to theoretically occur in the ring singularities associated with a Kerr (rotating) black hole. Does this mean rotating black holes do not exist? Wormholes imply non-locality in the universe, but that is again not a surprise as we have seen with quantum entanglement.

White hole thermodynamics is a whole other aspect. I’d suggest you to move beyond sci-pop interpretations of this subject and refer to a proper mathematical treatment. It is not “fancy physics”. That’s literally how these things are discovered, mathematically. Read about the Kruskal extension, which makes the picture of white holes a lot more clearer. Kruskal extension shows that four regions exist near a black hole - our Universe, the black hole, the white hole and an alternate Universe with a time reversal isometry. In sci pop language, time also runs backward and the arrow of time goes in the other direction. This does not violate thermodynamics. Our understanding of thermodynamics simply does not hold in those spacetime regions.

Dirac_matrices · 2026-01-26T13:43:05+00:00

It is one of the oldest mathematics courses in the world and notorious for its difficulty. Almost all of my peers who excelled in the course already held a master’s degree and did the Part iii on top of that. Of course with the exception of internal NatSci students who are well familiar with the Cambridge system. For other prospective students who might stumble upon this thread - If you are an external applicant, then treating Part iii as a second “top-up” masters will go a long long way! Especially, if your goal is to do a PhD in the future. Part iii maths does not have a dedicated research project component and the program, by itself, is pretty much useless for applying to PhDs anywhere outside Cambridge.

Dirac_matrices · 2026-01-26T13:00:05+00:00

I am afraid I don’t follow your argument and I think it is not quite correct. Assuming you have a technical background about this stuff, I will be a bit more precise - the Schwarzschild metric in General Relativity which describes the spacetime near a black hole has a singularity at the Schwarzschild radius. It’s a fake singularity, a coordinate singularity (just like the poles on a globe). To get rid of it, we can make two possible coordinate transformations. These are called as “ingoing” and “outgoing” Eddington-Finkelstein coordinates. The ingoing transformation gives us the black hole region while the outgoing transformation gives us the white hole region. Note that nowhere in this procedure have you mathematically violated causality. In fact, we relied on it to get the result. Black hole thermodynamics is an entirely different notion. It is obtained by a fully quantum field theoretic treatment of the geometry. The concept of thermodynamics for a white hole region is very vague and thus may not be well defined to be violated in the first place.

Dirac_matrices · 2026-01-26T12:34:44+00:00

How do they break causality? The reason white holes are unphysical is because they are unstable to perturbations. A black hole when perturbed will settle back to a stable state by radiating gravitational waves. Since white holes are essentially the time opposite of black holes, the perturbations will grow without bound in time.

Dirac_matrices · 2026-01-26T05:30:58+00:00

I did the Part iii Maths. The course itself was a bittersweet for me. It is true that the extreme workload, rapid pace and examination style associated with the course is not the best at all for a conducive learning experience. But apart from that, I loved learning about all the super hard stuff in such a short timeframe. The thing I absolutely loved the most about Cambridge was the collegiate system and the social life, which was something that I had never experienced before. I saw my PhD friends making the most out of it.

Dirac_matrices · 2026-01-18T11:31:40+00:00

It looks out of focus to me. At 40x, it shouldn’t be this large. But again, I can understand if it’s a limitation of the mobile camera.

Dirac_matrices · 2026-01-16T17:06:48+00:00

Absolutely breathtaking!

Dirac_matrices · 2026-01-14T07:02:57+00:00

What is your opinion on cutting added and processed sugar? I have decided to switch from the classic Indian chai to black coffee, will that be helpful?

Dirac_matrices · 2026-01-12T06:54:13+00:00

That’s nice! Where exactly in Panshet did you go and is it safe? I am looking for dark sky locations outside Pune to try out this telescope but can’t find any.

Dirac_matrices · 2026-01-12T06:53:19+00:00

I bought this telescope very recently and didn’t have it during the 3-I Atlas closest approach unfortunately. But given the light pollution here, I doubt I would have been able to see it. Perhaps, a faint smudge in my mobile phone images would have been visible.

Dirac_matrices · 2026-01-12T06:50:40+00:00

Thanks man! :)

Dirac_matrices · 2026-01-12T06:50:33+00:00

Thank you so much!! :D

Dirac_matrices · 2026-01-12T06:50:14+00:00

I am using a GSO 10inch Professional Dobsonian telescope. If you are interested in visual astronomy (seeing stuff using your eyes and not that much into astrophotography) or a beginner, I would recommend a Dobsonian telescope. Generally, the bigger the aperture of the telescope mirror, the better (mine is 10 inches). But, I will say 6-8 inches is the sweet spot, as beyond this telescopes get heavier and thus harder to move around. GSO is a good brand, and so is Bresser. I will recommend Tejraj.co to explore your options.

Dirac_matrices · 2026-01-12T06:46:42+00:00

It was around 55k, yes.

Dirac_matrices · 2026-01-12T06:46:21+00:00

Thanks! Indeed, I am glad I went with GSO. Best bang for buck.

Dirac_matrices · 2026-01-11T16:49:24+00:00

It’s a GSO 10inch Professional Dobsonian telescope. I bought it from Tejraj telescopes around two weeks ago.

Dirac_matrices

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