[alancalverd]

And an apology! v = √2as = 14 m/s or so, not 196, after 10m at 1g! Forgot the square root....Even so, that's one heck of a rate of climb - 2600 ft/min beats a Spitfire!

[alancalverd]

Let's drop the ball (or accelerate the planet) from 10 meters.  Now the planet hits the ball and stops moving

As you said, you're teasing. You know this is nonsense.

Ipsi dixit. And both Newton and Einstein agree.

[gem]

Hi all,

So if we use Harri's example of a light beam passing through the experiment and also factor in Colin's point 

Think. What have you fastened the light beam equipment to?

lets say you use sunlight as your light source, passing through a pinhole into the room/lab, streaming across the mid point would that not discriminate the points under discussion ?

[Colin2B]

lets say you use sunlight as your light source, passing through a pinhole into the room/lab, streaming across the mid point would that not discriminate the points under discussion ?

The pinhole is fixed to a wall which is fixed to the floor and so they move together, see explanation by @Janus

[gem]

Hi all

lets say you use sunlight as your light source, passing through a pinhole into the room/lab, streaming across the mid point would that not discriminate the points under discussion ?

The pinhole is fixed to a wall which is fixed to the floor and so they move together, see explanation by @Janus

Janus started with:

(Okay, we will assume that the source of the light is fixed relative to the ground)

Therefore the angle of the light stream will be altered if the earth/lab was moving significantly. Rather than the other way round.
Given the walls will have thickness. It would be like trying to line up the light source through 2 pinholes.

[Colin2B]

Given the walls will have thickness. It would be like trying to line up the light source through 2 pinholes.

is that a problem?

[Janus]

Hi all,

So if we use Harri's example of a light beam passing through the experiment and also factor in Colin's point 

Think. What have you fastened the light beam equipment to?

lets say you use sunlight as your light source, passing through a pinhole into the room/lab, streaming across the mid point would that not discriminate the points under discussion ?

Then there would be aberration and the effect gravity had on the light before it entered the pin hole. But all that would do is alter the initial angle that the light exits the hole relative to the chamber. It would be the same as a fixed light source that wasn't aimed at a point directly across from it.
This can be simply accounted for by arranging to perform your experiment when the combination of the two above effects leads to light entering the pin hole parallel to the floor of the chamber.

[gem]

Hi All
So if I was following the logic correctly

Given the walls will have thickness. It would be like trying to line up the light source through 2 pinholes.

is that a problem?

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.   

Given we could very easily set the ball and feather to drop say 10 metres and the points observed of the stream light passing across the vacuum the deviation from straight/horizontal would be negligible, I.E across the length of the football pitch at Wembley   105 metres it would drop 6.017 x10^-13 metres.

So if you used the center mark on the vacuum tube as suggested by Harri as the equivalent as your  traveler in a set of boning rods 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.
 

[Eternal Student]

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.

[gem]

Hi all,

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.

Ok just to clarify are you therefore stating, the beam of sunlight will reach the bottom of the tube before the ball and the feather, which is dropped from the top of the tube ?

[Eternal Student]

Ok just to clarify are you therefore stating, the beam of sunlight will reach the bottom of the tube before the ball and the feather, which is dropped from the top of the tube ?

   Janus gave a good explanation earlier.   Reply #20 I think.   If you followed the first photons that were put into the tube and allowed them to continue their path out beyond the other side of the tube, then they hit the ground before the feather and the ball would hit the ground.  Janus sets out all the assumptions (e.g. the surface of the earth remains flat, rather than being the curved surface we know it is).

[gem]

Hi all

So ES as I stated earlier and put a value to the drop due to gravity, of light across the length of the pitch at wembley, or if you prefer the drop of a photon for a meter of horizontal travel at earths surface gives approx  5.458 x10^-17 m
 
But this is not whats under consideration, if the Earth is really accelerating upwards as you are postulating, the beam of sunlight where it intersects the 10 m tube  at the midway point I.E

At 5 m   then in your scenario the beam will intersect the bottom of the tube at point 0

1.0096 seconds after the ball/feather is released

and ball/feather reaching that point 0.418 seconds later

Also If what you and others are postulating here was correct you would be able to increase the sunset time at lets say; latitude London.
By approximately 25 seconds just by dropping an object from 10m above sea level.

 

[Colin2B]

Also If what you and others are postulating here was correct you would be able to increase the sunset time at lets say; latitude London.
By approximately 25 seconds just by dropping an object from 10m above sea level.

 

I don’t understand how you reach that conclusion
Yes indeed as you say “???”

[gem]

Hi all,
Morning Colin
So

Also If what you and others are postulating here was correct you would be able to increase the sunset time at lets say; latitude London.
By approximately 25 seconds just by dropping an object from 10m above sea level.

 

I don’t understand how you reach that conclusion
Yes indeed as you say “???”

If it’s postulated that the surface of the earth accelerates up to meet the ball and feather then if you did this at a sea shore or a large body of water from a height of 10 m just as the sun dropped below the horizon, and the earth really did lift, then it would bring part of the sun back into view.

[Eternal Student]

Hi.

@gem
    The surface of the earth is always accelerating upward at 1g.   It does this whether you drop the ball and the feather or not.
    Whatever effect is happening to the suns rays due to this acceleration of the earth's surface, it doesn't happen more (or less) just by dropping objects from 10m above the earth's surface.
    Nice picture of a sunset by the way, thanks for including that.

Best wishes to you.

[Janus]

Hi all,
Morning Colin
So

Also If what you and others are postulating here was correct you would be able to increase the sunset time at lets say; latitude London.
By approximately 25 seconds just by dropping an object from 10m above sea level.

 

I don’t understand how you reach that conclusion
Yes indeed as you say “???”

If it’s postulated that the surface of the earth accelerates up to meet the ball and feather then if you did this at a sea shore or a large body of water from a height of 10 m just as the sun dropped below the horizon, and the earth really did lift, then it would bring part of the sun back into view.

The Sun is 149.6 million km away.  A change of 10 meters in your viewing position would only result in an angular shift of 0.00001378 seconds of arc.    That's magnitudes less than even the angular resolution of the Hubble telescope.
As a comparison, a 1 meter high wave on the horizon would subtend 68 seconds of arc from your viewpoint.
In other words, waves on the ocean would make the edge of the Sun appear and disappear by a far greater amount than the Earth shifting 10 m.

[alancalverd]

The surface of the earth is always accelerating upward at 1g.

Both in the UK and in Australia. It's amazing that we can still talk to one another at an ever-increasing distance. Thanks to relativity, our relative speed cannot exceed c, but the fact that you can still send parcels by ship
(about 10^-8c) in time for Christmas is a positive mark for the post office.

Or maybe the earth really is flat.

[gem]

Hi all

So Janus

Hi all,
Morning Colin
So

Also If what you and others are postulating here was correct you would be able to increase the sunset time at lets say; latitude London.
By approximately 25 seconds just by dropping an object from 10m above sea level.

 

I don’t understand how you reach that conclusion
Yes indeed as you say “???”

If it’s postulated that the surface of the earth accelerates up to meet the ball and feather then if you did this at a sea shore or a large body of water from a height of 10 m just as the sun dropped below the horizon, and the earth really did lift, then it would bring part of the sun back into view.

The Sun is 149.6 million km away.  A change of 10 meters in your viewing position would only result in an angular shift of 0.00001378 seconds of arc.    That's magnitudes less than even the angular resolution of the Hubble telescope.
As a comparison, a 1 meter high wave on the horizon would subtend 68 seconds of arc from your viewpoint.
In other words, waves on the ocean would make the edge of the Sun appear and disappear by a far greater amount than the Earth shifting 10 m.

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.html

There’s plenty of links on line that would suggest it is

And ES

Hi.

@gem
    The surface of the earth is always accelerating upward at 1g.   It does this whether you drop the ball and the feather or not.
    Whatever effect is happening to the suns rays due to this acceleration of the earth's surface, it doesn't happen more (or less) just by dropping objects from 10m above the earth's surface.
    Nice picture of a sunset by the way, thanks for including that.

Best wishes to you.

If the surface of the earth is always accelerating up at 1 g

Then what’s it’s velocity ?

If you state it accelerates upwards to the objects it must have a change in velocity, if it’s not detected then your in the realms of flat earth argument,

Given the method I am describing to measure the diameter of the earth is a well known counter argument to the flat earth believers.


https://www.omnicalculator.com/physics/flat-vs-round-earth

You want to have a sniff at what you’re selling.

👃💩

[Eternal Student]

If the surface of the earth is always accelerating up at 1 g

Then what’s it’s velocity ?

   Very Large with respect to a local inertial frame established at the surface of the earth 10 years ago (in cosmological co-ordinate time).
   Medium  w.r.t. an inertial frame established at the surface of the earth yesterday.
   0   w.r.t.  a local inertial frame established at the surface of the earth just now.

If you state it accelerates upwards to the objects it must have a change in velocity, if it’s not detected then your in the realms of flat earth argument,

   It does have a change of velocity (see above).  Actually, we are in the realms of a flat earth argument.  It was stated many replies back that the equivalence principle applies Locally and not globally where there are tidal forces or a non-uniform gravitational field.  Further back than that, Janus described how the photons would fall by assuming the surface of the earth remained flat indefinitely but also described the more realistic situation where the surface is curved.
   Locally, the surface of the earth is accelerating upward at 1g with respect to an inertial frame as defined in GR (this is a frame in free-fall).
    I haven't followed the link you provided, sorry.  I've not heard of omnicalculator before and I'm a bit cautious of pointing my web browser at it.

[alancalverd]

Whilst folk are throwing the equivalence principle at each other, it might be worthwhile stating it for the benefit of newcomers to this bear pit. Wikipedia is succinct:

  In the theory of general relativity, the equivalence principle is the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

Which is very dull because it doesn't invoke a flat earth hurtling at ever-increasing speed towards whatever you choose to drop, or a spherical planet tearing itself to pieces every time a Kiwi hits a six or converts a try. 

Back in the benighted Sixties, one campaign slogan of the NAACP (I'm not allowed to say what the  initials stand for because that would nowadays be considered offensive to its own members) was "equivalent is not the same". Well worth remembering in this context.