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Physics, Astronomy & Cosmology / Re: What happens to the spacetime interval between two events as they approach a BH?

« on: 20/02/2021 16:19:26 »

Is it fair or noteworthy  to say all these events in GR are treated as point objects even though they are actually spatio-temporally extensive?

Events are by definition mathematical points in spacetime, say the event of a photon being emitted and such.  In practice, yes, they're spread out, so one can speak of the event of the sinking of the Titanic even though the ship is fairly large and moved around quite a distance during the hours-long process. It just means we lose precision when we talk about that event.
Billiard balls are modeled as point events (the event of the contact between two balls) when in fact the contact takes finite time, involves finite (but very large) acceleration, and finite surface area of contact.

Is that where a theory of  quantum gravity might be useful?

It's just geometry. No, quantum gravity solves other issues.

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Physics, Astronomy & Cosmology / Re: How do electromagnetic waves propagate through a vacuum?

« on: 30/09/2017 19:11:07 »

I thought fields extended indefinitely in space.That image seems to show the two fields  extending a finite distance .Do they actually extend indefinitely in the direction at right angles to the direction of propagation? (the image being for illustrative purposes)

Electromagnetic fields do extend indefinitely into space. What you are seeing in the image is the amplitude of the photon, which is different from the range of the field that makes up the photon. Amplitudes are finite. Even for a hypothetical, infinite ocean, the waves in the ocean will have a limited amplitude.

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Physics, Astronomy & Cosmology / Re: Is spacetime real?

« on: 26/09/2016 22:07:20 »

geordief, your skepticism of Atkhenaken's claims are well-warranted. I would recommend being highly skeptical of those who make such extreme claims (look up some of their other posts, and you might see a pattern develop) Atkhenaken does not believe that viruses exist, or that medicine is anything other than a scam...

To those who are interested in this thread, I would also recommend paying attention to PmbPhy. He is very knowledgeable regarding physics, especially relativity (we have our disagreements too, but on this particular subject, he is an expert!) evan_au is also a knowledgeable and well-intentioned member of this forum.

Thanks ,yes of course . I look forward to PmbPhy's contributions down the line hopefully.

The phrase "logical certainly " certainly rings alarm bells  as the stand up performer  Tim Vine  might put it

https    ://www.youtube.com/watch?v=HcFd5j1cios

Perhaps I don't have enough posts to post a link on this site yet?

Yeah, I don't remember what the required number of posts is before you can link urls directly, but I think you are close. Maybe 20?

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Physics, Astronomy & Cosmology / Re: Is spacetime real?

« on: 26/09/2016 20:16:36 »

Having drifted into talking about particle spin, this might be worth looking at.  I’m not always happy with the answers here, but this seems not bad.

http://www.askamathematician.com/2011/10/q-what-is-spin-in-particle-physics-why-is-it-different-from-just-ordinary-rotation/