andrew s

See here the sun's gravitational [removed word] is approximately equivalent to 633 m/s receeding. Regards Andrew Removed word was shift !

All velocities are relative. You only have a velocity with respect to something else. Change the "something else" and you (may) change the velocity. Being earth bound we tend to only think of a singular velocity relative to the ground. Regards Andrew

Currently, the earliest data we can get is from the CMB. We may potentially be able to get information from before that from primordial gravitational waves but don't hold your breath. The infered initial ratio of H to He & Li also give information on the first nuclear synthesis and hence the conditions at that time. Regards Andrew

In GR spacetime is just geometry with a well defined metric. Add an equation of state of the contents and you're away. To provide experimental data to test such a mathematical model you don't just need photons you need to build both clocks and measuring sticks and an intelligence to use them. Once you are reasonably happy with the models predictions v your observations you can extrapolate to the time before clocks (or photons) as time like space is just a parameter in the model. The tricky bit is having an equation of state not the geometry. Regards Andrew

The speed of light isn't really (or just) the speed of light! It's is a shorthand for the upper speed limit to the propagation of information in a spacetime governed by GR. That's partly why we need inflation to explain the amazing uniformity of the CMB as otherwise it could not be in the near perfect thermal equilibrium we observe. Without it, regions of space would get too far apart to "communicate" about their temperatures. Inflation stops them from getting out of equilibrium as the expansion is too fast to allow it. Regards Andrew

You are Zermelo are quite right. In the curved space time of GR comparing velocities of separated objects is generally impossible. However, locally the speed of light is always measured to be the same i.e. c. To see the issue of comparing velocities. Take two cars on opposite side of the equator heading north at a velocity v. Initially, their relative velocity is zero. But, by the time they get to the pole they are heading for a collision at relative velocity 2v. Regards Andrew

This may help you. Regards Andrew

Time has many faces. We have our experience of it passing, our psychological time, and its rate can slow and speed-up with our moods. In physics time is a parameter in a space-time geometry that we find effectively underpins our best theories. There is no requirement for them to be the same. Regards Andrew

The simple answer is we don't know. There are several theories covering the proposed period of inflation. It is still an active area of research but unless we get a quantum theory of gravity it is all very speculative. As @saac points out all the forces were unified. Particles only condensed out after inflation so our normal ideas of entanglement etc. don't apply. Regards Andrew

Yes but becoming a Vampire is a high price to pay 🧛‍♂️🦇 Regards Andrew

Just because you don't have a reflection in a mirror @JeremyS is no reason to dislike Newts 😅 Regards Andrew

Platesolving should not depend on camera orientation. Not sure what software you are using so can't comment on settings. Regards Andrew

I have the Swarovski CL 8x25 a perfect pocket bino. Ideal for hikes and casual through the window observing. Not tried the Zeiss. Regards Andrew

We were out when the postman tried to deliver 3 parcels today. One required a signature. Later today he returned to try again as he had seen my wife jogging so new we were about. Can't better that. Regards Andrew

The interplay between mathematics and theories physics is fascinating. Sometimes mathematics has led other times physics. Several attempts at using new maths have been tried as by Penrose and Twistor Theory. Personally, I don't think we are lacking in ideas and effort by theoretical physicists or in mathematics. Rather, we don't have any new observations to motivate particular lines of enquiry. The LHC has failed to find convincing evidence for physics beyond the standard model. Cosmology has dark energy and matter but efforts to go further refining what they are other than numbers in LCDM lack motivation. I hope the JWST can find some new observations to light the way. It seems we have reached a point where we have probed most of the scales and energy ranges experimentally available to us on Earth so we are left with looking up at the sky for guidance. Regards Andrew