[Janus]

So Janus, your disputing the method of measuring earths diameter by difference in time of sunset by height is not detectable ?

http://astronomy.nmsu.edu/geas/lectures/lecture10/slide05.htm

That is a completely different measurement than the one you suggested.  Determining the diameter of the Earth from sunset time at ground level vs. head level, as shown in the link depends on the Earth's rotation,  Not on a displacement of the Earth in position.  It also depends on the distance of the horizon as viewed from two different heights (ground and head). At typical head height, the horizon is ~ 5 km away, (vs no distance at ground level)  this results in a viewing angle difference of ~70 arc sec.  This measurement is totally independent of the Sun's distance.
However, any change in  viewing angle caused by the Earth being displaced by 10 m does depend on the distance to the Sun.  And would result in the extremely small value I gave in my Earlier post.

[Colin2B]

Then Harri was trying to get a handle on, was what was actually accelerating the bowling ball and feather or the Earth, given Halcs and Alans counter arguments with GR and Newtons laws of motion.
But first I think we need to do away with the dropping of light in the gravity field as being a separate point, and isn't really the point under consideration, as the light beam suggested can be treated as straight enough to discern whats accelerating.   

The light beam is a red herring, you are right to ignore it. Any light source - including a pinhole - is still connected to the same frame as the ground. If the light falls, it won’t tell you whether the surface is accelerating upwards or not. I suggest you reread the posts by @Janus

However, we do need to drag you and @Harri out of this gravitational well you’ve fallen into:

If it’s postulated that the surface of the earth accelerates up to meet the ball and feather

The problem is that you have to consider things from a relativity point of view and ask “relative to what”.
In SR you are used to understanding that you can’t tell whether you are moving, only that you are moving relative to something else. Einstein gave a comparison between gravity and acceleration, saying you can’t tell the difference.
Just for clarification, as Alan says, Einstein never said they were the same, only equivalent. He also assumed a uniform gravitational field (which is approximately true in a small volume like an elevator) so no tidal effects or variations of g with height.
So, you can’t tell the difference between gravity and acceleration, but how do you know if you are accelerating? You feel the force. If you are in a car which is accelerating the seat pushes your body forward and you feel the force on your back. If you don’t feel the force you must be at rest or moving at constant speed.
There is an instrument that will tell you if you are accelerating, an accelerometer. Imagine a ballbearing in a horizontal tube, if the car you are in accelerates the ball, due to inertia, will try to stay where it is as the tube moves forward and if there is a sensor in the tube you can measure the force between ball and tube f=ma, hence measure a, acceleration. However, tip the tube vertically and it will register an acceleration of 1g, the same as if the car had been accelerating at 1g; but let the tube freefall and it will register 0g, it is not accelerating.
The acceleration we measure in this way is called proper acceleration and is what is used in GR, and freefall is the GR equivalent of an inertial frame in SR - no acceleration.
The problem is that you are used to measuring what we call coordinate acceleration, that is the rate of change of speed. Sitting in your car if the speedo shows increasing speed you are accelerating; but wait a minute speed is relative in SR so how do we know we are moving? Take 2 spaceships side by side in deep space, are they at rest, moving at same speed, or accelerating? The only one we can measure is acceleration using our trusty accelerometer, so this is what we use in GR.
However, coming back down to earth, does the earth move for @gem?
Well, if you are measuring the ball and feather relative to the surface of the earth (coordinate measurement) then they are accelerating towards you at the same 9.8m/s² - just remember to wear your vacuum suit or we get vacuum packed gem!
So if your reference frame (coordinates) is the vacuum chamber, fixed to the earth, with a light source or pinhole fixed to the side of the chamber then not only the ball and feather, but also the light beam are falling (relative to those coordinates - the frame of the earth’s surface).
So, the surface of the earth is not moving upwards relative to the earth’s centre, but it is accelerating if we use proper acceleration as our measurement.
So next time the earth moves for you, don’t assume it’s the ground coming up to meet you 

[gem]

Hi all
Yes thanks Colin I agree with what you’re saying, However why you believe I think the earth and the tube are rising up is beyond me,

Hi.

you would expect the line of sunlight to accelerate down the tube at 9.81 m^-2 if you postulate only the earth is accelerating.

   It does.   However one photon (one bit of light) is travelling with horizontal velocity ~ c.  It's only in the tube for a tiny fraction of a second.  The Earth and the floor of the tube hasn't had much time to move up toward that photon.

It is others whom stated it.

Which I was highlighting was ridiculous and misleading.

Compared to your statement Colin:

(So, the surface of the earth is not moving upwards relative to the earth’s centre)

Yes quite agree 🧐💋

As you say Alan covered this,some times people get mixed up what equivalence actually is, and state things which are misleading.

And Janus you seem to be arguing the lifting of the local area
(💋which isn’t happening💋)
is undetectable via a local change in height.

The  point I was making if you look back to the boning rods/line of sight is we are not in an elevator with no windows and if parts or all of the earth moved upwards as ridiculously suggested by others, we would be able to a detect that movement by the same principle of the boning rods/line of sight.
I suppose what you’re definition of local is comes into it, but if the ground came up by 10m every where in your line of sight from the centre of the earth, it would be detectable,.

If it came up across the whole earth 🌍 it would be detectable
Because the day would become longer.

[Colin2B]

Compared to your statement Colin:

(So, the surface of the earth is not moving upwards relative to the earth’s centre)

Yes quite agree 🧐💋

You still have to be very clear what you are actually talking about.
My statement is a coordinate statement relative to earth centre based on velocity (and acceleration) as a 3-vector, GR deals with 4-velocity which is a 4-vector, not 3. In that system the surface of the earth can be considered to be moving up towards to ball and feather even though there is no spacial movement of the surface. Note, this is a short very incomplete answer, but you get the drift.

Don’t let it drag you down, looked at properly it can be quite uplifting 

[gem]

HI all,

Compared to your statement Colin:

(So, the surface of the earth is not moving upwards relative to the earth’s centre)

Yes quite agree 🧐💋

You still have to be very clear what you are actually talking about.
My statement is a coordinate statement relative to earth centre based on velocity (and acceleration) as a 3-vector, GR deals with 4-velocity which is a 4-vector, not 3. In that system the surface of the earth can be considered to be moving up towards to ball and feather even though there is no spacial movement of the surface. Note, this is a short very incomplete answer, but you get the drift.

Don’t let it drag you down, looked at properly it can be quite uplifting 

MMMM yes I must say all this proper acceleration is slowing me down. but its more uplifting than you know.

[yor_on]

:)