software engineering and FE

Quote from: rabinoz on March 12, 2019, 03:55:53 PM

Quote from: John Davis on March 08, 2019, 08:10:22 AM

Let's say you are on a satellite then. Let's say it is in a perfect orbit above the earth, which is to say it's altitude is constant, and those on board feel no acceleration. In other words, its in an inertial frame of reference.

We know from Newton that must mean that it is traveling a straight line at a constant speed through space time, or that it is not moving at all. We can safely enough assume it is traveling at a constant speed and not accelerating. Can you agree with this?

Newton had no concept of spacetime (I assume that is what you meant by "space time").

Newtonian spacetime is simply a four dimensional space without relativistic junk. I am not sure whether Newton himself had an idea of this, (though if memory serves he did), but its well documented after that.

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So we cannot assume that, "Newton . . . must mean that it is traveling a straight line at a constant speed through space time".

Newton regarded space and time as quite unrelated.
Hence he looked on orbiting objects (moons) being subject to a gravitational acceleration which causes the centripetal acceleration needed to maintain circular motion.

When I say "we know through Newton" I mean through his laws of motion.

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But there is no way in the world that Newton would have considered it "traveling a straight line at a constant speed through space time".

Under General Relativity, however, the satellite is travelling along a geodesic in spacetime but I find calling that a straight line is simply confusing.

Not if you define a straight line by the shortest distance between two points.

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In the spacelike components of spacetime (x,y,z if you like) the satellite might be travelling in a circular or precessing elliptical orbit but
in the timelike component of spacetime (t if you like) that satellite is travelling at almost exactly 1 sec/sec.

But, while some do it, I find that calling such a helix-like path in spacetime a straight line simply leads to confusion and possibly quite incorrect conclusions.

I'm not sure I follow. Can you restate this?

Yes, have done. I had "i sec/sec" that should have been "1 sec/sec" and should have said "helix-like path" not "spiral-like path", have edited the post and added a rough diagram.
This is the amended bit:

A circular orbit in the spacelike components of spacetime combined with the "linear motion" in the timelike component of spacetime leads to a helix-like path in spacetime something like:

Satellite's orbit in x, y and time of Spacetime << I'll try to get an improved diagram when possible. >>

Sorry about that.

edit: Again, only in Newtonian spacetime would it be a spiral.

First, angular acceleration is what you have when you're traveling on a curve. Discussion of relativity to determine FE/RE will not work, it will go off into the weeds.

John Davis, can you explain how a sextant gives latitude correctly on FE and where the north star is?

Can you explain how an equatorial mount works on FE?

You said you can explain, that was a while back. I have been waiting to see your explanation, honestly looking forward to it. I have your assurance, but do not know how to get your explanation.

If it is not changing direction or speed, and the bounding space is comprised also of such theoretical objects that are not changing direction or speed, then the bounding space of these satellites at altitude x must be "flat", which is to say comprised of geodesics that form a plane that surrounds the earth.

I assure you I'm not going into the weeds by describing general relativity (and thus also special relativity.) I have shown that the Orthodoxy already believes in a flat earth and thus how a sextant works in one theory of the flat earth.

Its right here Jimster. The details are required whether you wish to state the earth is round or flat. I have provided them. Do you contest any particular point I made?

Looks like another victory, confirmed!

Just out of curiosity: What is the projection model you're using on your flat earth models? I'm a software developer and uses Proj4 (v 5.2) on a daily basis to reproject coordinates on maps, and it would be interesting if you'd defined the projection your using so I (and anyone else who wants to very their FE assumptions) could reproject coordinates and calculate distances, velocities, angles, etc. If this can't easily be done it'd be the mother of all kludges, but given how confident you guys are it's probably very trivial.

Quote from: John Davis on March 11, 2019, 05:09:00 PM

If it is not changing direction or speed, and the bounding space is comprised also of such theoretical objects that are not changing direction or speed, then the bounding space of these satellites at altitude x must be "flat", which is to say comprised of geodesics that form a plane that surrounds the earth.

I assure you I'm not going into the weeds by describing general relativity (and thus also special relativity.) I have shown that the Orthodoxy already believes in a flat earth and thus how a sextant works in one theory of the flat earth.

Its right here Jimster. The details are required whether you wish to state the earth is round or flat. I have provided them. Do you contest any particular point I made?

I'm curious as to how a plane can surround a flat earth. Do have some simple explanation that a non-scientist non-physicist might understand?

Also why is it that photos taken from these satellites "not changing direction or speed" and that orbit in these "geodesics that form a plane that surrounds the earth" always seem to show this sort of thing?
You claim that you "have shown that the Orthodoxy already believes in a flat earth" yet we seem to see different facets of this "flat earth" in different photographs.

Why is it so?

 

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Well, according to Einsteins general theory of relativity this is true, but it took many decades to prove this since this curvature is so small in our minuscule gravity field that it required extremely precise gyroscope in satellites in.. erm.. orbit (around some undefined mass). And why apply the theory of relativity to one thing but not the other? To calculate you position from the radio signals received from the GPS (and Galileo and GLONASS) satellites you have to take this into account, because they are moving quite fast, but even then we're talking minuscule amounts.

Yet, the distortions required to get from the measurable real world distances to the azimuthal equidistant projection of the FE map is HUGE, and would require something much more significant than the current known laws of general relativity (particularly considering the distortions it describes is completely different). But hey, if someone can come up with a proof that all the scientists has been wrong for the last 3-4000 years, sure, why not. But I'd recon it would need to be a relatively solid proof.

If I’m following this correctly, the idea is that because satellites can be said to be traveling in a straight line through curved spacetime, then it follows that the surface of the earth is “flat”, only curved in spacetime.

Problems I see with this are:

1.  Satellites can only be in a stable circular orbit at a precise speed for any given altitude, yet we always perceive the Earth’s curvature the same regardless of velocity wrt the Earth’s surface, including stationary.

2.  It falls apart if you apply this line of thinking to other planets and moons (which we can and do put objects into orbit around).  The moon for example has a much weaker gravitational field than the Earth, being much smaller.  Yet if we’re saying the curvature is due to to spacetime distortion, if should require a stronger field to have a tighter curve.

3.  But why stop there?  If we’re saying something that appears spherical is actually flat, only curved by spacetime, should we then apply this to all spherical objects?  Is a football (soccer ball) really also flat?

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

Quote from: Ski on March 23, 2019, 11:55:15 AM

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

It seems Unconvinced is referring to gravity itself, not the distortions in spacetime (effectively a twirl) I (and apparently you) where thinking about in GR.

Anyhow, it'd be interesting to know the imagined math behind the observed distances and directions and the typical FE map (if there is such a thing), and just using for example Proj4 one can easily calculate all these distortions and observe them firsthand (if one dares challenge his/her belief).

Quote from: rabinoz on March 23, 2019, 02:44:21 PM

Quote from: Ski on March 23, 2019, 11:55:15 AM

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

It seems Unconvinced is referring to gravity itself, not the distortions in spacetime (effectively a twirl) I (and apparently you) where thinking about in GR.

Anyhow, it'd be interesting to know the imagined math behind the observed distances and directions and the typical FE map (if there is such a thing), and just using for example Proj4 one can easily calculate all these distortions and observe them firsthand (if one dares challenge his/her belief).

If you dare mention a FE map here the usual answer is that there is no official FE map.

Quote from: Ski on March 23, 2019, 11:55:15 AM

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

If this is the case, then why is its acceleration 0?

It is possible you are mistaking gravitational lensing as a measure of how much space curves due to relativity. This is rather how much a "massless" photon might be affected. It would be silly to measure things from the point of view of light, wouldn't it?

Quote from: rabinoz on March 23, 2019, 02:44:21 PM

Quote from: Ski on March 23, 2019, 11:55:15 AM

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

It seems Unconvinced is referring to gravity itself, not the distortions in spacetime (effectively a twirl) I (and apparently you) where thinking about in GR.

Anyhow, it'd be interesting to know the imagined math behind the observed distances and directions and the typical FE map (if there is such a thing), and just using for example Proj4 one can easily calculate all these distortions and observe them firsthand (if one dares challenge his/her belief).

I usually use Matlab or Octave for my work, except where these tools are insufficient and have to be done by hand. It is possible we are mincing definitions of 'projection' here a bit as I am sometimes referring to it in a specific mathematical sense and otherwise to the methodology followed by cartographers.

If I’m following this correctly, the idea is that because satellites can be said to be traveling in a straight line through curved spacetime, then it follows that the surface of the earth is “flat”, only curved in spacetime.

Problems I see with this are:

1.  Satellites can only be in a stable circular orbit at a precise speed for any given altitude, yet we always perceive the Earth’s curvature the same regardless of velocity wrt the Earth’s surface, including stationary.

I'm not sure why this is a problem, or perhaps I'm missing something in the "wrt". Can you expand on this?

2.  It falls apart if you apply this line of thinking to other planets and moons (which we can and do put objects into orbit around).  The moon for example has a much weaker gravitational field than the Earth, being much smaller.  Yet if we’re saying the curvature is due to to spacetime distortion, if should require a stronger field to have a tighter curve.

They are large enough to support their own mass and orbits. The field is the same relation. Smaller objects typically orbit small bodies.

3.  But why stop there?  If we’re saying something that appears spherical is actually flat, only curved by spacetime, should we then apply this to all spherical objects?  Is a football (soccer ball) really also flat?

To your actual question: Is the football flat? No, various forces are keeping it in its shape, gravity not one of them in the sense we are talking - though understand that it would apply just as easily at smaller scales - its just might not productive to worry about the frame of reference of an electron (or perhaps it might...). This is perhaps where the argument "its just a slight deviation due to the force" might be noteworthy, not in the pseudoforce that apparently bends objects in circles around round bodies.

To a more interesting point - Take the path of all soccer balls as they are kicked or as they are stationary; at their apex they are traveling a straight line through spacetime as they are not suffering from acceleration. Taking its apex, one can extrapolate by noting its felt acceleration where it might be if it was not suffering from this affliction. This path would be tangent to the apex, and flat at a constant altitude, much like the orbit. Taking the space of all these solutions, we end up with a space consisting of spaces of planes comprised of these points.

It is possible you are mistaking gravitational lensing as a measure of how much space curves due to relativity. This is rather how much a "massless" photon might be affected. It would be silly to measure things from the point of view of light, wouldn't it?

No.
Light and a comet are affected the same due to gravitation.

Quote from: rabinoz on March 23, 2019, 02:44:21 PM

Quote from: Ski on March 23, 2019, 11:55:15 AM

What exactly would you expect the world to look like if space was curved and light travelled without changing direction?

Why is it even relevant when the effect of any curvature in the spacelike component of spacetime near the earth causes difference no more than 1 few parts in 10⁹?

If this is the case, then why is its acceleration 0?

Light in a vacuum can't accelerate.
It always travels at c and it travels along the shortest path in spacetime, a geodesic. If the geodesic is curved light follows a curved path.

But the question I was answereing was Ski's "What exactly would you expect the world to look like if space was curved and light travelled without changing direction?"
And what he called "space", presumably short for the spacelike component of spacetime has no significant curvature near earth hence the world would look the same as it does now.

Ski's question was a hypothetical one but I would think that any curvature caused by the modest mass of the earth is so slight that even "if space was curved and light travelled without changing direction" we would see nothing different.

Quote from: Unconvinced on March 23, 2019, 01:59:41 PM

If I’m following this correctly, the idea is that because satellites can be said to be traveling in a straight line through curved spacetime, then it follows that the surface of the earth is “flat”, only curved in spacetime.

Problems I see with this are:

1.  Satellites can only be in a stable circular orbit at a precise speed for any given altitude, yet we always perceive the Earth’s curvature the same regardless of velocity wrt the Earth’s surface, including stationary.

I'm not sure why this is a problem, or perhaps I'm missing something in the "wrt". Can you expand on this?

wrt = with respect to

I probably should have said relative to.  Although that was still not quite right, as orbital speed isn’t relative to rotation on surface anyway.  What can I say- there was some booze involved in that post.

Anyway, the basic point is unchanged.  The curved path of an orbiting object is entirely dependent on it’s speed.  You only get an orbit going by at the right speed, depending on altitude.

By that’s not how things are when we look at the surface of the earth.  The curve is the same, no matter how fast we go.

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2.  It falls apart if you apply this line of thinking to other planets and moons (which we can and do put objects into orbit around).  The moon for example has a much weaker gravitational field than the Earth, being much smaller.  Yet if we’re saying the curvature is due to to spacetime distortion, if should require a stronger field to have a tighter curve.

They are large enough to support their own mass and orbits. The field is the same relation. Smaller objects typically orbit small bodies.

But we can achieve an equivalent orbit around the moon to Earth at much lower velocity, so the moon’s field (I’m avoiding the G word) must be weaker.

But if the surface is only curved because of a distortion in spacetime, it should require a stronger field than the earth, because it’s more tightly curved.

Any correlation between orbits curved by spacetime and the surface curved by spacetime is in the wrong direction than your hypothesis suggests.

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3.  But why stop there?  If we’re saying something that appears spherical is actually flat, only curved by spacetime, should we then apply this to all spherical objects?  Is a football (soccer ball) really also flat?

To your actual question: Is the football flat? No, various forces are keeping it in its shape, gravity not one of them in the sense we are talking - though understand that it would apply just as easily at smaller scales - its just might not productive to worry about the frame of reference of an electron (or perhaps it might...). This is perhaps where the argument "its just a slight deviation due to the force" might be noteworthy, not in the pseudoforce that apparently bends objects in circles around round bodies.

To a more interesting point - Take the path of all soccer balls as they are kicked or as they are stationary; at their apex they are traveling a straight line through spacetime as they are not suffering from acceleration. Taking its apex, one can extrapolate by noting its felt acceleration where it might be if it was not suffering from this affliction. This path would be tangent to the apex, and flat at a constant altitude, much like the orbit. Taking the space of all these solutions, we end up with a space consisting of spaces of planes comprised of these points.

I was being a bit facetious with the football comment.  Sorry.

It seems Unconvinced is referring to gravity itself, not the distortions in spacetime (effectively a twirl) I (and apparently you) where thinking about in GR.

Gravity is the normal explanation for distorting spacetime in this manner in relativity, but for sake of argument, I’m happy to go along with there being a distortion for whatever reason.