[Tom Bishop]

So how come we don't observe this?! in fact most of those smudges of light that we call galaxies are actually redshifted!

Redshifted compared to what? The Sun?

[IronHorse]

Compared to a laboratory spectrum Tom.  In lab we can measure and observe a spectral line at its natural wavelength. If a light source is moving away from Earth the light waves will be stretched and therefore a spectral line will appear at a redder (longer) wavelength that it actually is, and the reverse is true for a light source travelling towards us.

It's just doppler effect except at the wavelengths of light rather than sound.

[Pete Svarrior]

I'll say it again slowly. Equivalence Theory is not a central part of either model.

It doesn't matter how slowly you type, you continue to be wrong. If you disprove EP, then you disprove the physics that directly concludes EP. In doing so, you disprove RET in its current form.

My proposal is that you won't be able to accomplish this, but also that you probably don't want to.

I find it odd that FET states that the effects of the universal accelerator begin to take effect as one gets further away from Earth.

You are expected to develop an understanding of the basics before posting here. Please do so before continuing with the debate.

In FET all celestial bodies are accelerating at the same rate

This statement is false. Your issue stems from making poor assumptions.

All celestial bodies (that we know) share UA, but UA is not the only contributing factor to their motion. If it was, we'd perceive all celestial bodies as stationary relative to one another. Surely you knew this is not the case, so why waste our time with something so poorly thought out?

[AATW]

I'll say it again slowly. Equivalence Theory is not a central part of either model.

It doesn't matter how slowly you type, you continue to be wrong. If you disprove EP, then you disprove the physics that directly concludes EP. In doing so, you disprove RET in its current form.

Right, but you're using RET here to mean "the whole of physics". And yeah, it would fundamentally change our understanding of things. But I think Regicide is talking about RET in the more literal sense of the theory that the earth is round [shouldn't it really be GET, btw?]
The shape of the earth (either way) isn't contingent on Equivalence Theory being true.

[IronHorse]

All celestial bodies (that we know) share UA, but UA is not the only contributing factor to their motion.

So what are these other contributing factors to their motion?

[Pete Svarrior]

Right, but you're using RET here to mean "the whole of physics".

More or less, yes. Does that affect the validity of my argument, in your mind?

If xXx_SuperScienceMan69_xXx comes to the Flat Earth Society to explain how big-brained he is and how he totally pwned FET with FACTS and LOGIC, should he be allowed to just conclude that "basic physics is false, ergo FET debunked"? In my view, the answer is "no", because in doing so he'd be debunking RET as well. This is necessarily the case, because RET (regardless of whether you go for the more broad meaning of the term or a very minimalistic and literal one) is strictly a subset of "the whole of physics".

Similarly, EP is not some novel idea that can be just extracted from physics without breaking everything. If you conclude that EP is false, then you necessarily conclude that the physics that led to it is false. Once again, this does not help defend RET from scrutiny.

So what are these other contributing factors to their motion?

You are expected to develop an understanding of the basics before posting here. Please do so before continuing with the debate.

[Groit]

In FET all celestial bodies are accelerating at the same rate

This statement is false. Your issue stems from making poor assumptions.

All celestial bodies (that we know) share UA, but UA is not the only contributing factor to their motion. If it was, we'd perceive all celestial bodies as stationary relative to one another. Surely you knew this is not the case, so why waste our time with something so poorly thought out?

I'm talking about the stars. In FET the stars are in a layer just a few thousand km above the Earth, and at that distance, if they were not moving with the Earth then we would see their positions move in the sky and the constellations would change before our eyes. The stars must be accelerating at the same rate in FET, don't you think?

If we observe the light from stars that are directly above us, then we should observe a blueshift because the Earth has accelerated from time of emission to time observed on Earth and since Light travels at c in all reference frames then it would be blueshifted.

[Pete Svarrior]

The stars must be accelerating at the same rate in FET, don't you think?

Given that the stars are in motion relative to an Earthbound observer, this is entirely impossible. I already told you that. Asking me again won't change this. If you disagree that we can observe stars moving relative to us, I can't really help you.

Your understanding of redshift and blueshift also appears to be fundamentally flawed, though you haven't been forthcoming enough for it to be completely clear how/why. Somehow, you're trying to tie it to acceleration relative to an external inertial observer rather than objects moving apart/closer together. You're also discussing the speed of the light instead of its wavelength. It's quite messy.

In FET the stars are in a layer just a few thousand km above the Earth

I can't say I agree, but perhaps you're addressing a specific claim made by someone else. Nonetheless, your view that stars are motionless relative to the Earth is going to be a bit of a showstopper.

[Bikini Polaris]

That's at odds with the fact that the flat surface we would be on is now travelling upwards at quite a fast speed (incredibly greater than the speed of light).

Please complete your assertion by answering the following question: Relative to what frame of reference?
Once your assertion has been made complete and coherent, please explain: How have you concluded this?

The frame of reference is irrelevant. If I'm accelerated in a direction and nothing is stopping me, I will acquire speed. In the wiki there's clearly written "Since the Earth is pushing you upwards, you are moving at the same speed as the Earth". So, that's the speed I'm talking about.

How do you conclude this? Well, again basing myself on the wiki, you just realize that if you never apply the Lorentz transformation, because you're not in a different system S' but you are on S, nothing prevents you from having a speed that is faster than light. In RE, a spaceship accelerating at 1g will eventually go faster than light and reach its destination as that was the case (but for the fact that time will have run faster at destination).

Another way to see this is that UA assumes the presence of an energy that act accelerating the earth. But energy is conserved, and so earth must acquire that energy in form of kinetic energy, and that's proportional to speed. The direction of the speed is, of course, 'upward'.

[Groit]

Your understanding of redshift and blueshift also appears to be fundamentally flawed, though you haven't been forthcoming enough for it to be completely clear how/why. Somehow, you're trying to tie it to acceleration relative to an external inertial observer rather than objects moving apart/closer together. You're also discussing the speed of the light instead of its wavelength. It's quite messy.

Its not messy, I'm talking about redshift/blueshift for uniform acceleration which is part of EP and is used as evidence to back UA.

For example, if we have a rocket accelerating at 1g away from any gravitational field with two observers onboard, with observer A at the front of the rocket and observer B at the back. If B sends a light signal to A then A will see the signal redshifted. If A sends a signal to B then B will see it blueshifted, even though both observers have remained the same distance apart.



So if the Earth and the stars are accelerating at 1g due to UA, using the rocket anology, with the stars at the front of the rocket and the Earth at the back. The light from the stars directly above the Earth would be blueshifted and an observer on one of those stars would see the Earth being redshifted.

[Pete Svarrior]

The frame of reference is irrelevant.

Incorrect. The frame of reference is absolutely crucial. If you believe it to be irrelevant, simply choose your favourite one. I'll give you a hint, there are three FoR's that are worth considering here: a local observer standing atop the Earth, a local observer located immediately above the Earth who is initally at rest relative to the Earth, and an external inertial observer.

If I'm accelerated in a direction and nothing is stopping me, I will acquire speed.

Correct, but entirely irrelevant. The magnitude of that speed is the key point here, not the fact that it's increasing. Specifically, your claim that "the flat surface we would be on is now travelling upwards at quite a fast speed (incredibly greater than the speed of light)" contradicts basic physics. You cannot identify a frame of reference in which the Earth is moving faster than c without contradicting Special Relativity. As was the case previously, I suggest that throwing physics out the window is not the best way for you to defend RET.

because you're not in a different system S' but you are on S

If you're on S, your speed relative to S is 0m/s, and the speed of S relative to you is 0m/s. That's significantly lower than c.

Its not messy, I'm talking about redshift/blueshift for uniform acceleration which is part of EP and is used as evidence to back UA.

So, here's the thing. I raised specific objections to what you're saying. Responding with nothing other than "it's not messy" is not going to cut it.

For example, if we have a rocket accelerating at 1g away from any gravitational field with two observers onboard

This is where you fail. The Doppler Effect is experienced when two bodies are in motion relative to one another. I already explained this to you, but you chose to ignore it. Two bodies accelerating upwards at the same rate and with no initial velocity will be stationary relative to one another. Thus, UA itself is not going to have any impact on the Doppler Effect.

The light from the stars directly above the Earth would be blueshifted and an observer on one of those stars would see the Earth being redshifted.

This would be true if the stars were accelerating away from the Earth. As far as UA is concerned, they're not.

[Bikini Polaris]

The frame of reference is absolutely crucial. If you believe it to be irrelevant, simply choose your favourite one. I'll give you a hint, there are three FoR's that are worth considering here: a local observer standing atop the Earth, a local observer located immediately above the Earth who is initally at rest relative to the Earth, and an external inertial observer.

I said it's irrelevant because for an internal observer, the observed speed is zero (like it would be for an astronaut sitting on an accelerating spaceship) and, on the other hand, UA excludes the possibility of talking about "external" observers, let's say someone just below the place where an energy becomes acceleration, or someone outside the ice wall. UA is silent on the current knowledge of what is outside, but it doesn't deny it's existence, because it assumes that there is an energy the converts into movement in a direction.

If I'm accelerated in a direction and nothing is stopping me, I will acquire speed.

Correct, but entirely irrelevant. The magnitude of that speed is the key point here, not the fact that it's increasing. Specifically, your claim that "the flat surface we would be on is now travelling upwards at quite a fast speed (incredibly greater than the speed of light)" contradicts basic physics. You cannot identify a frame of reference in which the Earth is moving faster than c without contradicting Special Relativity. As was the case previously, I suggest that throwing physics out the window is not the best way for you to defend RET.

Special Relativiy is safe, because what you cannot do is *measure* a speed faster than light in any frame of reference. But a traveller on a spaceship that is constantly accelerating at g toward a, let's say ten light years afar, star will reach it quicker than the speed of light,  according *on the spaceship clock*, so it's indirectly a travel faster than the speed of light. The important difference with a travel that would really contradict SR is that the clocks on departure and destination will have run normally, that is faster than the spaceship clocks, and for them the spaceship has never went faster than the speed of light. But again, my main point is that the energy poured by the spaceship engines *must go somewhere*.

because you're not in a different system S' but you are on S

If you're on S, your speed relative to S is 0m/s, and the speed of S relative to you is 0m/s. That's significantly lower than c.

I'm referring to the whole system S, unknown-form-of-energy+earth-surface+the-visible-sky.

Summing up, I do understand that the whole UA describes the known universe as the inside of a spaceship, but still it doesn't rule out that fact that an energy is converting into acceleration in a direction. And this has, as a consequence, that we would *really* be on some sort of spaceship!

[TomInAustin]

What you felt when you fell was a brief experience of weightlessness/free-fall. This, too, can be colloquially described as "feeling acceleration", but it's a wholly distinct phenomenon. It sounds to me that by using an ambiguous term, you accidentally drew an equivalence between the two.

I think I can speak about freefall with as much or more authority than anyone here.   I have 926 skydives and hold a master USPA D license.  When one exits an aircraft moving through the air (90 to 100 mph on average) there are little to no feelings of acceleration.  Mainly because it's a slow transition from 90 to 100 to 120 mph (average freefall speed) and that takes 9 seconds.     However, when one starts falling from a very slow speed there is a huge feeling of acceleration.  That gut thing like what you get on a roller coaster as it goes over that first drop.  Out of 926 jumps all but 4 were regular moving airplanes to freefall to normal deployment.   The 4 in question, one was from a hot air balloon,  one from a helicopter in a near hover, and 2 low-speed* malfunctions that required cutting away the main and deploying the reserve.  In each of these 4 examples, the feeling of falling was very dramatic, and nothing at all like hovering while the ground rushed up.


What would explain that?   Yes, Einstein said acceleration and gravity produce the same effects but that does not come close to explaining why you can feel the acceleration.





* Low-speed malfunction is one where the canopy is deployed but not landable.  A high-speed malfunction is one where there is not enough nylon deployed to slow you from freefall speeds.   https://en.wikipedia.org/wiki/Malfunction_(parachuting)

[pricelesspearl]

Special Relativiy is safe, because what you cannot do is *measure* a speed faster than light in any frame of reference. But a traveller on a spaceship that is constantly accelerating at g toward a, let's say ten light years afar, star will reach it quicker than the speed of light,  according *on the spaceship clock*, so it's indirectly a travel faster than the speed of light.

This is proper velocity, or sometimes called celerity. Observer measured distance/elapsed time on the traveling clock. It has no limit.

[Pete Svarrior]

But a traveller on a spaceship that is constantly accelerating at g toward a, let's say ten light years afar, star will reach it quicker than the speed of light,  according *on the spaceship clock*, so it's indirectly a travel faster than the speed of light.

That has nothing go do with speed, and everything to do with spacetime.

What would explain that?   Yes, Einstein said acceleration and gravity produce the same effects but that does not come close to explaining why you can feel the acceleration.

Didn't we already discuss this in the part you've quoted? The feeling you've described is created by your inner ear, and is not exclusively tied to acceleration.

You say that "the feeling of falling was very dramatic, and nothing at all like hovering while the ground rushed up", but you have no way of contrasting the two. They are, as you've admitted, equivalent.

As for the acceleration component, you've already answered your own question. When you're close to terminal velocity, the forces at play are closed to balanced. The resultant acceleration you perceive is smaller than if you were accelerating downward at g relative to the Earth.

[Groit]

For example, if we have a rocket accelerating at 1g away from any gravitational field with two observers onboard

This is where you fail. The Doppler Effect is experienced when two bodies are in motion relative to one another. I already explained this to you, but you chose to ignore it. Two bodies accelerating upwards at the same rate and with no initial velocity will be stationary relative to one another. Thus, UA itself is not going to have any impact on the Doppler Effect.

I'm afraid this is where you fail Pete.
Two observers on a rocket accelerating at the same rate will indeed see the effects of Doppler shifts, Its part of GR and EP.
Have a look at the diagram below:



For the accelerating rocket, observer A emits a photon at time and observer B receives the photon at time , so the time taken for the photon to reach B is

During the time from emission to receiving, observer B has accelerated so the distance for the photon to travel has increased to

And That distance is: 

Since the distance has increased then observer B will see the light as redshifted.

The opposite effect happens when observer B emits a photon to observer A, the distance for the light to travel decreases given by:

Therefore observer A will see the light as blueshifted.

This is just the 'Equivalence Principle' at work and as you can see from the diagram both observers remain the same distance apart.

 
 

[TomInAustin]

What would explain that?   Yes, Einstein said acceleration and gravity produce the same effects but that does not come close to explaining why you can feel the acceleration.

Didn't we already discuss this in the part you've quoted? The feeling you've described is created by your inner ear, and is not exclusively tied to acceleration.

Yes, we did discuss it but I came to a new way of thinking about it.  4/900 is not a big sample size and I normally associate freefall with terminal velocities.    Your explanation does not explain anything.   The inner ear sensation of falling at the exact moment one starts falling seems pretty clear.   If I was stationary and the ground came up to me I would feel nothing,  but the perfect frame of reference is to be hanging in the air and cutting away to freefall.

You say that "the feeling of falling was very dramatic, and nothing at all like hovering while the ground rushed up", but you have no way of
contrasting the two. They are, as you've admitted, equivalent.

How's this for a contrast?   If I was in a stationary car and another car was 100 meters from me and started to accelerate towards me I would feel nothing,  If the car I was in started to accelerate I would feel it.  What am I missing?


This all sounds like a very Zetetic way to look at this.

[Pete Svarrior]

Two observers on a rocket accelerating at the same rate

At the same rate relative to what? In what direction? It's impossible to judge the correctness of your statement because it doesn't even come close to being complete. In the specific scenario you proposed (Earth and stars under UA), the Earth and stars are stationary relative to one another as far as UA is concerned. In other words, a=0.

Once again, you talk of speed, distance, and an individual photon (for which the concept of Doppler shifts is meaningless). You need to be talking about waves and wavelengths. Until you do so, you're not even discussing the Doppler effect in any meaningful fashion. There's a reason this failure is significant. As much as your upward acceleration will speed up the rate at which the waves hit you, the upward acceleration of the source will slow that rate down. If the two vectors are identical, the effect will cancel out. This is why the Doppler effect concerns the effect of the relative motion of two bodies on the wavelengths of the wave.

What am I missing?

The air. A car accelerating towards you doesn't cause your entire surroundings to start zooming around you. The sensation of falling does.

[Bikini Polaris]

But a traveller on a spaceship that is constantly accelerating at g toward a, let's say ten light years afar, star will reach it quicker than the speed of light,  according *on the spaceship clock*, so it's indirectly a travel faster than the speed of light.

That has nothing go do with speed, and everything to do with spacetime.

Yeah. My point is that if something is above us and it's not "universally accelerated", or accelerated at less than 1 g upwards, we will arrive there pretty quickly (and we would crash with the incredible kinetic energy that we now have). That's the main problem an accelerating spaceship travelling the universe would have (after solving the energy problem etc...).

[TomInAustin]

What am I missing?

The air. A car accelerating towards you doesn't cause your entire surroundings to start zooming around you. The sensation of falling does.

There is still no explanation of why you feel that sensation of falling.  It makes no sense.   Even with airflow.  Freefall at terminal is a very noisy place but there is no sensation of falling at all.  Only pre terminal.