With regards to high-gravity objects, such as neutron stars and black holes, I've been studying the excellent Xaonon Hawking Radiation Calculatior, which I found elsewere in this forum. I have just one question: what are 'surface tides'? I understand surface gravity and the tidal effects of gravity at varying distances from the star in question. But surface tides is something I just don't get.

GK

 

there are a few articles on the web like this one - but I am not sure of their provenance but the idea seems alright . A google scholar search on "black hole" and "surface tides" doesn't give much to get one's teeth into.

 

Why not drop Mike Wisniewski a line - his email is at the bottom of the hawking calculator page?

Many thanks - I'll do just that.

Well, it turns out that 'surface tides' in the above calculator is referring to the tidal force at a black hole's event horizon - e.g. establishing whether an astronaut could cross it without being spaghettified.

Ok that makes sense. It was expressed as change of gravity per metre IIRC