Does Flat Earth/UA reject the concept of spacetime?
« on: October 08, 2020, 04:18:35 PM »
The reason I ask is because UA rises and falls (pun intended) on the equivalence principle, but the equivalence principle logically leads (at least according to Einstein) to the gravitational and inertial effects of falling bodies as determined by spacetime...or as he calls it in the quote below the "g-field"

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Inertia and gravity are phenomena identical in nature.  From this and from the special theory of relativity it follows necessarily that the symmetric "fundamental tensor" determines the metric properties of space, the inertial behavior of bodies in space, as well as the gravitational effects.  We shall call the state of space which is described by this fundamental tensor, the "g-field"


https://einsteinpapers.press.princeton.edu/vol7-trans/49?highlightText=metric

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Offline Tom Bishop

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Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #1 on: October 08, 2020, 04:35:02 PM »
In GR the surface of the earth is accelerating upwards through spacetime. It is Einstein's way of getting the upwardly accelerating Earth concept to work in RE, since experimental evidence and lack of inertial resistance shows that the Earth is accelerating upwards and that it is not an invisible phenomenon pulling bodies down to the Earth.

Gravity: A Very Short Introduction by Cosmologist Timothy Clifton:

    “ Consider a skydiver jumping out of an airplane. The skydiver falls freely, up to the effects of air resistance. According to Einstein, the skydiver's path is the straightest line possible through the curved space-time around the Earth. From the skydiver's perspective this seems quite natural. Except for the air rushing past her, the skydiver feels no perturbing forces at all. In fact, if it weren't for the air resistance, she would experience weightlessness in the same way that an astronaut does in orbit. The only reason we think the skydiver is accelerating is because we are used to using the surface of the Earth as our frame of reference. If we free ourselves from this convention, then we have no reason to think the skydiver is accelerating at all.

    Now consider yourself on the ground, looking up at the falling daredevil. Normally, your intuitive description of your own motion would be that you are stationary. But again this is only because of our slavish regard to the Earth as the arbiter of what is at rest and what is moving. Free yourself from this prison, and you realize that you are, in fact, accelerating. You feel a force on the soles of your feet that pushes you upwards, in the same way that you would if you were in a lift that accelerated upwards very quickly. In Einstein's picture there is no difference between your experience sanding on Earth and your experience in the lift. In both situations you are accelerating upwards. In the latter situation it is the lift that is responsible for your acceleration. In the former, it is the fact that the Earth is solid that pushes you upwards through space-time, knocking you off your free-fall trajectory. That the surface of the Earth can accelerate upwards at every point on its surface, and remain as a solid object, is because it exists in a curved space-time and not in a flat space.

    With this change in perspective the true nature of gravity becomes apparent. The free falling skydiver is brought to Earth because the space-time through which she falls is curved. It is not an external force that tugs her downwards, but her own natural motion through a curved space. On the other hand, as a person standing on the ground, the pressure you feel on the soles of your feet is due to the rigidity of the Earth pushing you upwards. Again, there is no external force pulling you to Earth. It is only the electrostatic forces in the rocks below your feet that keep the ground rigid, and that prevents you from taking what would be your natural motion (which would also be free fall).

    So, if we free ourselves from defining our motion with respect to the surface of the Earth we realize that the skydiver is not accelerating, while the person who stands on the surface of the Earth is accelerating. Just the opposite of what we usually think. Going back to Galileo's experiment on the leaning tower of Pisa, we can now see why he observed all of his cannonballs to fall at the same rate. It wasn't really the cannonballs that were accelerating away from Galileo at all, it was Galileo that was accelerating away from the cannonballs! ”
« Last Edit: October 08, 2020, 04:38:10 PM by Tom Bishop »
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #2 on: October 08, 2020, 05:27:43 PM »
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In GR the surface of the earth is accelerating upwards through spacetime. It is Einstein's way of getting the upwardly accelerating Earth concept to work in RE, since experimental evidence and lack of inertial resistance shows that the Earth is accelerating upwards and that it is not an invisible phenomenon pulling bodies down to the Earth.

I get that in GR, gravity is not a force per se.  But it is still a process (for lack of a better term) which causes objects to be attracted to one another.  This process is caused by the warping of spacetime.

Gravity as a force and gravity as warping of spacetime may be two different things, but they have the same effect. In order to maintain a flat earth, it seems to me that both would have to be rejected.

And what experimental evidence is there that the earth is accelerating upwards? 

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #3 on: October 08, 2020, 07:11:04 PM »
In GR the surface of the earth is accelerating upwards through spacetime. It is Einstein's way of getting the upwardly accelerating Earth concept to work in RE

In the same paper quoted by fisherman (last paragraph), Einstein says:
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The universe then must be closed in itself, and its geometry deviates from that of a spherical or elliptical space only little, and only locally, as, for example, the shape of the earth’s surface deviates from that of an ellipsoid.

You are confusing frames of reference, as used in GR, with reality. Einstein does not have an actual flat Earth actually accelerating upwards; he acknowledges in that quote above that Earth is ellipsoid-like in shape.

You should remember what AATW said in a very recent post, that you step off a chair and see the world accelerate upwards towards you: AATW, who is standing nearby, sees you step off a chair and fall. Both views are valid, but neither in itself proves or disproves a flat, upwards accelerating world. You might as well adopt the view of a skydiver falling headfirst who sees the world accelerating downwards towards her.
« Last Edit: October 08, 2020, 07:13:48 PM by Longtitube »

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #4 on: October 08, 2020, 09:01:07 PM »
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You are confusing frames of reference, as used in GR, with reality.

He also says in the same paper that the g-field is caused and determined by the energy tensor of matter...he doesn't say that an accelerating earth causes the g-field.

I will add to this with another quote from Einstein.  You'll need to read the first part of the paper to get the the context, but the point he makes here is important.

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I must warn the reader against a misconception suggested by these considerations.  A gravitational field exists for the man in the chest, despite the fact that there was no such field for the co-ordinate system first chosen.  We might also think that, regardless of the kind of gravitational field which may be present, we could always choose another reference body such that no gravitational field exists with reference to it.  This is by no means true for all gravitational fields, but only for those of a quite special form.  It is, for instance, impossible to choose a body of reference such that, as judged from it, the gravitational field of the earth (in its entirety) vanishes.

https://einsteinpapers.press.princeton.edu/vol6-trans/333

The wiki implies that an accelerating earth is the only logical explanation for the equality of gravitational and inertial mass.  It is misleading to use so heavily the work and reasoning of Einstein , when he came up with an entirely different explanation.   

« Last Edit: October 08, 2020, 09:03:34 PM by fisherman »

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Offline Tom Bishop

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Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #5 on: October 09, 2020, 01:12:26 AM »
No. There is a reason for why Einstein and physicists have the upwardly accelerating elevator and rocket analogies. It's because experimental evidence shows that gravity behaves as if the Earth were accelerating upwards. These experiments are why Newton's theory of objects falling down through space to the earth was rejected. Gravity operates as if the Earth is accelerating upwards, and this is reflected in the equivalence principle experiments.

https://wiki.tfes.org/Evidence_for_Universal_Acceleration

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The Pound–Rebka Experiment

The Pound-Rebka experiment and Pound-Rebka-Snyder experiments are optical tests of the Equivalence Principle, where light redshifts or blueshifts when traveling vertically upwards or downwards. Like with the previous section, light behaves differently when traveling upwards or downwards. In General Relativity (Archive) by Prof. Benjamin Crowell, its author explains that the experiment is a test of the Equivalence Principle:

  “ The Pound-Rebka Experiment

The 1959 Pound-Rebka experiment at Harvard was one of the first high-precision, relativistic tests of the equivalence principle to be carried out under controlled conditions ”

From Special and General Relativity (Archive) by Norman K Glendenning on p.28 we read an analogy with an upwardly accelerating spaceship:

  “ One can also see the role of the equivalence principle by considering a pulse of light emitted over a distance h along the axis of a spaceship in uniform acceleration g in outer space. The time taken for the light to reach the detector is t = h (we use units G = c = 1). The difference in velocity of the detector acquired during the light travel time is v = gt = gh, the Doppler shift z in the detected light. This experiment, carried out in the gravity-free environment of a spaceship whose rockets produce an acceleration g, must yield the same result for the energy shift of the photon in a uniform gravitational field f according to the equivalence principle. The Pound-Rebka-Snyder experiments can therefore be regarded as an experimental proof of the equivalence principle. ”

The Pound-Rebka-Snyder experiments are the same 1959 experiment, conducted with an additional researcher, which has been improved and repeated over the years to increasing precision (Archive).

Summarily, light will be redshifted or blueshifted when traveling upwards or downwards because "gravity" operates exactly as if the earth were accelerating upwards. When light is traveling downwards from a light source on the ceiling to a detector on the ground, the earth is rising quicker into the photons and will cause a blueshift (its frequency will increase). When light is traveling upwards from the ground to a detector on the ceiling, the detector on the ceiling is moving away from the photons and they will redshift (frequency will decrease).

Experiment Overview Diagram



Left: Light moving downwards - Blueshifted
Right: Light moving upwards - Redshifted

(Source) (Archive)

Redshift and Blueshift of Light

In connection with the above, in the following Redshift-Blueshift Doppler Shift of Light diagram we can see that when a body that emits light is receding from you it would cause a red shift, and when is approaching you quicker it will cause a blue shift:



(Source) (Archive)

In the Pound–Rebka Experiment when the light suspended on a ceiling travels downwards towards the upwardly moving earth it blueshifts (approaches the detector quicker), and when the light travels away from the earth to the upwardly moving ceiling it redshifts (approaches the detector slower), just as would happen if the building were sitting on an upwardly accelerating earth. Light behaves differently when moving with the motion of the earth than against it.

Sometimes this experiment is called a "proof of General Relativity," but it is a test of the Equivalence Principle which exists within General Relativity. The Equivalence Principle was created years prior to GR. The Equivalence Principle, with the same experimental results, would need to exist in any alternative theory of gravity, such as the theory of the Graviton messenger particles as proposed by Quantum Mechanics. The cornerstone of the Equivalence Principle maintains that gravity and all physical effects operates as if the earth were accelerating upwards.
« Last Edit: October 09, 2020, 01:15:06 AM by Tom Bishop »
"The biggest problem in astronomy is that when we look at something in the sky, we don’t know how far away it is" — Pauline Barmby, Ph.D., Professor of Astronomy

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #6 on: October 09, 2020, 12:26:31 PM »
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The cornerstone of the Equivalence Principle maintains that gravity and all physical effects operates as if the earth were accelerating upwards.

The operative words here are "as if". "As if", not that the earth is actually accelerating upwards.

In the links I provided, AE himself defined the equivalence principle "as the symmetric "fundamental tensor" determines the metric properties of space, the inertial behavior of bodies in space, as well as the gravitational effects." And he specifically warns against doing exactly what you are doing, taking the analogy literally and trying to make it mean that there is no actual gravitational field.

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The EFE can thus also be written as

{\displaystyle R_{\mu \nu }-{\tfrac {1}{2}}Rg_{\mu \nu }+\Lambda g_{\mu \nu }=\kappa T_{\mu \nu }.} {\displaystyle R_{\mu \nu }-{\tfrac {1}{2}}Rg_{\mu \nu }+\Lambda g_{\mu \nu }=\kappa T_{\mu \nu }.}
In standard units, each term on the left has units of 1/length2.

The expression on the left represents the curvature of spacetime as determined by the metric; the expression on the right represents the matter–energy content of spacetime. The EFE can then be interpreted as a set of equations dictating how matter–energy determines the curvature of spacetime.

https://en.wikipedia.org/wiki/Einstein_field_equations
The field equations only include calculation for the curvature of spacetime, not for acceleration of the earth.

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #7 on: October 09, 2020, 03:23:06 PM »
Gravity operates as if the Earth is accelerating upwards, and this is reflected in the equivalence principle experiments.
Which only holds in the local context. In the local context you can't tell whether a force is pulling you down or something is pushing you up.
Gravitational variations across the globe show that we don't live on an upwardly accelerating plane, and the Einstein quote which has been highlighted to you shows that he was clear about the shape of the earth.
"On a very clear and chilly day it is possible to see Lighthouse Beach from Lovers Point and vice versa...Upon looking into the telescope I can see children running in and out of the water, splashing and playing. I can see people sun bathing at the shore
- An excerpt from the account of the Bishop Experiment. My emphasis

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #8 on: October 09, 2020, 04:45:15 PM »
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You should remember what AATW said in a very recent post, that you step off a chair and see the world accelerate upwards towards you: AATW, who is standing nearby, sees you step off a chair and fall. Both views are valid, but neither in itself proves or disproves a flat, upwards accelerating world.

This is a good point, but I would add that in order for both viewpoints to be valid, there must be a physical cause of the acceleration in both view points. Acceleration requires a force...or a cause if you don't want to define gravity as a force.

The person in the air can assign UA as the reason the ground is rising up.  But what cause for accelerating down can the person on the ground assign to the person in the air if there is no gravity?  If there is no cause for the person to accelerate down, then both scenarios cannot be equally valid.

This is where the logic that the equivalence principle does away with gravity falls apart.  It only works if you assume that a gravitational field exists in the first place.

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"Principle of Equivalence. Starting from this limiting case of the special theory of relativity, one can ask oneself whether an observer, uniformly accelerated relative to [inertial coordinate sytem] K in the region considered, must understand his condition as accelerated, or whether there remains a point of view for him, in accord with the (approximately) known laws of nature, by which he can interpret his condition as "rest."...

The answer runs: As far as we really know the laws of nature, nothing stops us from considering the system K' as at rest, if we assume the presence of a gravitational field (homogeneous in the first approximation) relative to K'; for all bodies fall with the same acceleration independent of their physical nature in a homogeneous gravitational field as well as with respect to our system K'.

The assumption that one may treat K' as at rest in all strictness without any laws of nature not being fulfilled with respect to K', I call the "principle of equivalence."


https://einsteinpapers.press.princeton.edu/vol6-trans/249?highlightText=Kottler




Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #9 on: October 13, 2020, 05:05:45 PM »
Although it should be clear from my user tag (or distinct lack thereof), I should preface with saying that my views are my own.  I do not speak for "flat earthers", other flat earth researchers, or the flat earth society (including UA).  I can only speak for myself.

Spacetime is a joke.  It's profoundly stupid.  It's supposed to keep an idiot busy and it's been, sadly, effective.

There is no time of any kind. It is not a dimension, it cannot be an independent variable; it is a fictional human concept with no reality.  There is no time dilation, travel, or manipulation of any kind.  Light's path can only be diverted by direct interaction with matter.  Most all of relativity is junk/wrong, but like most all of the incorrect frameworks that came before it - it has limited use.

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #10 on: October 13, 2020, 09:59:52 PM »
Jack, your unsupported opinions are no more credible than the strange guy on the street on a Saturday afternoon shouting about the Martians planning to kill us all. You need to back up your claims with evidence if they’re to be considered seriously. Other people here, on both sides, produce grounds for their opinions - facts, observations, experimental evidence, and the debate goes on. You just insist something is bunk but don’t back it up, so there’s no debate or conversation to be had.

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #11 on: October 13, 2020, 10:30:02 PM »
@longitube

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Jack, your unsupported opinions are no more credible than the strange guy on the street on a Saturday afternoon shouting about the Martians planning to kill us all.

You are clearly hanging out on some wacky streetcorners! Are you in mesa or phoenix?

I state facts, "matter-of-fact"ly, as most people do.  If you want to know more, you should try asking questions!

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You need to back up your claims with evidence if they’re to be considered seriously.

What evidence do you require? What evidence do you have now that needs refuting or is contradicted by the facts I listed?

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Other people here, on both sides, produce grounds for their opinions - facts, observations, experimental evidence, and the debate goes on.

I don't engage in debate.  It is beneath me, and all intellectuals.  It's just a silly game / base pageantry for the egotistical sycophants that perform and the entertainment of the audience and judges.  It has no place in establishing what is, or isn't.  It has no place in science.  The fallacies are worth learning, but don't forget about the fallacy fallacy!

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You just insist something is bunk but don’t back it up, so there’s no debate or conversation to be had.

That's because you don't ask questions (or disagree, or otherwise "converse" in any way)!  I am not here to submit research papers with detailed citation - I'm here for rational discourse!  You are always free to ignore me, and learn nothing new!
« Last Edit: October 20, 2020, 01:18:27 AM by jack44556677 »

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Offline Tumeni

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Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #12 on: October 13, 2020, 10:58:52 PM »
That's because you don't ask questions (or disagree, or otherwise "converse" in any way)!

Yes, we do.

We just don't ask the questions you want to hear, so you either ignore them, or evade them by rambling about why you ignore them.
=============================
Not Flat. Happy to prove this, if you ask me.
=============================

Nearly all flat earthers agree the earth is not a globe.

Nearly?

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #13 on: October 14, 2020, 02:30:49 AM »
@Tumeni

Do you have an example?

There are many questions I don't have answers to - is that "evading" to you?  Or is it because you find my answers unfulfilling / unsatisfying that you think I am doing so intentionally?
« Last Edit: October 14, 2020, 02:34:06 AM by jack44556677 »

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #14 on: October 14, 2020, 09:56:28 AM »
I state facts, "matter-of-fact"ly...

I don't engage in debate.  It is beneath me ...

I'm here for rational discourse!  You are always free to ignore me ...

“Facts” like
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Spacetime is a joke.
or
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There is no time of any kind.

These are unsubstantiated opinions, with no reason to believe them given.

However, since debate is beneath you and I’m free to ignore you, forgive me for wasting your valuable time and thank you for the option.
« Last Edit: October 14, 2020, 01:03:19 PM by Longtitube »

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #15 on: October 15, 2020, 10:42:41 PM »
@Longitube

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These are unsubstantiated opinions, with no reason to believe them given.

They are facts with no evidence to the contrary.  Sorry time travel nerds, it's all fantasy!

Thermodynamic process is unidirectional.  There is no past, there is no future.  There is only now.

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However, since debate is beneath you and I’m free to ignore you, forgive me for wasting your valuable time and thank you for the option.

Debate is beneath me, and all smart people - perhaps you as well? I engage for discussion!  I am happy for you to supply any evidence for your fiction, at your leisure!

Re: Does Flat Earth/UA reject the concept of spacetime?
« Reply #16 on: October 16, 2020, 08:26:41 PM »
All this means that the Earth has infinite space above to move into.
The existance of infinity in one direction shows the existance of infinity in all other directions.
What is in that infinite space?
Other "Earths"?
So many people directly measure so many things.
And they are getting more precise each day.