[xasop]

Not according to the definition of acceleration. An object that changes its direction of motion accelerates. An object starting on the Earth in UA is already accelerating. As it moves up, it must accelerate even more in order to do so. It then must decelerate to stop, and the Earth to catch up.

No. This is basic high school Newtonian mechanics. If object A moves with a constant velocity, and object B accelerates in the direction of motion of A, then B will eventually overtake A.

I'm not even going to bother demonstrating this because you've been talking down to me this whole time, claiming (or at least implying) that your understanding of relativity surpasses mine. You have just proven beyond any doubt that you are either lying or trolling, so engaging you further is pointless.

[BRrollin]

Not according to the definition of acceleration. An object that changes its direction of motion accelerates. An object starting on the Earth in UA is already accelerating. As it moves up, it must accelerate even more in order to do so. It then must decelerate to stop, and the Earth to catch up.

No. This is basic high school Newtonian mechanics. If object A moves with a constant velocity, and object B accelerates in the direction of motion of A, then B will eventually overtake A.

I'm not even going to bother demonstrating this because you've been talking down to me this whole time, claiming (or at least implying) that your understanding of relativity surpasses mine. You have just proven beyond any doubt that you are either lying or trolling, so engaging you further is pointless.

Hmmm. In UA, the earth accelerates up at 9.8 m/s^2. A rock stationary on the ground must also be accelerating at this value. Now I pick up the rock, and throw it upward. In doing so, it’s speed has changed relative to the earth. That means it’s acceleration is now no longer 9.8, but a value greater. That’s why the distance between the rock and the Earth changes.

They were moving at the same velocity. Now there is a displacement, which means their velocity changed.

Definition of acceleration is change in velocity over time.

I’m guessing you don’t want to show the equations because you realize your mistake. You must, since you claim you’ve taken physics, and this stuff is covered in the first week.

I’m not going to rub it in. We all make mistakes, and I don’t want to be a jerk. I’m more interested in acknowledging the truth and then continuing on.

I am enjoying our discussion

[Pete Svarrior]

I’m not going to rub it in. We all make mistakes, and I don’t want to be a jerk. I’m more interested in acknowledging the truth and then continuing on.

I'm going to have to ask you to stop. Nearly early post of yours in this thread includes a long passage about how much of a super expert you are, and other tangents which can be described as "discussing individuals, not ideas".

We don't do that in the upper. Obviously it will happen to everyone every now and then, but it doesn't look like a one-off oopsie with you.

Secondly, an object that's currently being thrown up is not free-falling, and Parsifal was pretty clear in declaring that that's what he's discussing. You're focusing on the "projectile that goes up" and pretending not to notice that that's simply the set up phase of the thought experiment. I'm not surprised Parsifal missed your little switcheroo, since, y'know, you're supposed to be talking about free-fall.

I asked you to post in good faith, and it was precisely to prevent these sort of non-arguments. Behave.

[BRrollin]

I’m not going to rub it in. We all make mistakes, and I don’t want to be a jerk. I’m more interested in acknowledging the truth and then continuing on.

I'm going to have to ask you to stop. Nearly early post of yours in this thread includes a long passage about how much of a super expert you are, and other tangents which can be described as "discussing individuals, not ideas".

We don't do that in the upper. Obviously it will happen to everyone every now and then, but it doesn't look like a one-off oopsie with you.

Secondly, an object that's currently being thrown up is not free-falling, and Parsifal was pretty clear in declaring that that's what he's discussing. You're focusing on the "projectile that goes up" and pretending not to notice that that's simply the set up phase of the thought experiment. I'm not surprised Parsifal missed your little switcheroo, since, y'know, you're supposed to be talking about free-fall.

I asked you to post in good faith, and it was precisely to prevent these sort of non-arguments. Behave.

I do believe I’m posting in good faith. I’m not trying to muddy the waters or create conflict. Now certainly misunderstanding will happen, but I am doing my best to identify the points of misunderstanding and clear them up.

The issue at hand, Pete, is that we are not in an inertial frame in UA hence SR is invalid. This is what Parsifal disagreed with in the earlier posts.

“Since we are not in an inertial frame in UA, SR is invalid.

Disagree”

The Burj example cited in the disagreement involves motion upwards and then downwards. It was not clear to me that he wanted only to analyse the motion downward - otherwise why include the motion upwards in the first place? Just have an object fall, no hyperloop needed.

But this is immaterial, because even with a falling object, WE are still accelerating in UA, so WE are not in an inertial frame.

Parsifal agreed with this statement initially.

I am not implying that my knowledge of SR is better than anyone else’s, I’m just trying to get to the bottom of this - just like everyone else, and posting my current understanding of the situation.

Also, from some googling, I see that “free-fall” is defined as an object near the surface of the earth that is being influenced only by earth’s gravity. In the UA situation, I suppose this translates to an object near the surface of the Earth while the Earth accelerated upwards. So if my understanding is correct, then an object can be in free-fall regardless of whether it’s instantaneous velocity is pointing up or down.

I think these discussions are useful in figuring out the details of the UA idea. And even if not all aspects are resolved, they help better mold everyone’s conception of the idea, and further lay foundations for developments.

This is my intention. Sorry it has come off as anything else.

[totallackey]

I asked you to post in good faith, and it was precisely to prevent these sort of non-arguments. Behave.

I do believe I’m posting in good faith. I’m not trying to muddy the waters or create conflict.

^ THIS...in the world of BRrollin...equals...

...but I am more concerned with my beliefs being true

^THIS

Sorry...I ain't buyin...

[juner]

I asked you to post in good faith, and it was precisely to prevent these sort of non-arguments. Behave.

I do believe I’m posting in good faith. I’m not trying to muddy the waters or create conflict.

^ THIS...in the world of BRrollin...equals...

...but I am more concerned with my beliefs being true

^THIS

Sorry...I ain't buyin...

totallackey, while I agree with you, this isn't the thread or forum for it.


QED, you can drop the act of "I only want to get to the bottom of it..." Your history and behavior are well known. It seems you are being allowed to post for now, even though your past account was permanently banned for the same nonsense. Anyway, there won't be a long process of warnings and short bans, it will just be a permaban of this alt account in accordance with rule 8.

[BRrollin]

I asked you to post in good faith, and it was precisely to prevent these sort of non-arguments. Behave.

I do believe I’m posting in good faith. I’m not trying to muddy the waters or create conflict.

^ THIS...in the world of BRrollin...equals...

...but I am more concerned with my beliefs being true

^THIS

Sorry...I ain't buyin...

totallackey, while I agree with you, this isn't the thread or forum for it.


QED, you can drop the act of "I only want to get to the bottom of it..." Your history and behavior are well known. It seems you are being allowed to post for now, even though your past account was permanently banned for the same nonsense. Anyway, there won't be a long process of warnings and short bans, it will just be a permaban of this alt account in accordance with rule 8.

What? I have never been banned from this site! But I admit I have had other accounts, but those were using other computers...

Why all this sudden hostility? There is no animosity from my end. I have been polite and cordial, even though that has not always been returned.

This seems like a witch-hunt, the mods ganging up on a poster once the admin got frustrated.

Well, if that’s the case, then that is really childish. I’ve made mistakes in my posts before. So what? Everyone does. Reacting with maturity and humility is an expected standard in collaboration.

[Groit]

“Bottom line, I would like you to answer this one question. Is a 9.8 m s-2 proper acceleration in the observer's frame of reference negligible for the purposes of the muon experiment?”

NO! It is a dealbreaker! In UA,
that is indeed your proper acceleration, and SR is inapplicable. In RET, your proper acceleration standing on the earth’s surface is ZERO - because the Earth’s surface is in the way! If you’re in free-fall, then yes, now you’re fucked.

In UA, just by standing on the Earth, you are in a noninertial frame. In RET, standing on the Earth, you are in an inertial frame.

Nope. GR says that free-fall is an inertial frame of reference because you are following a geodesic in space-time. Being in contact with the surface of the Earth causes an upward proper acceleration of 9.8 m s^-2 to stop you from falling, which is why gravity is a fictitious force. This is the equivalence principle.

There is an equal and opposite force from the Earth, but the acceleration would be   where is the mass of the Earth, so the acceleration very, very small.

 Can't believe I've just said the Earth is accelerating upwards 

[pricelesspearl]

There is an equal and opposite force from the Earth, but the acceleration would be %5Cfrac%7BF%7D%7Bm%7D  where m is the mass of the Earth, so the acceleration very, very small.

Can't believe I've just said the Earth is accelerating upwards 

The "earth" isn't accelerating.  The ground directly beneath you is accelerating you.  That's an important distinction. The acceleration is caused by the normal force, so if there is nothing in contact with the ground...there is no acceleration. 

[BRrollin]

There is an equal and opposite force from the Earth, but the acceleration would be %5Cfrac%7BF%7D%7Bm%7D  where m is the mass of the Earth, so the acceleration very, very small.

Can't believe I've just said the Earth is accelerating upwards 

The "earth" isn't accelerating.  The ground directly beneath you is accelerating you.  That's an important distinction. The acceleration is caused by the normal force, so if there is nothing in contact with the ground...there is no acceleration.

A point of clarification on behalf of UA: from my (imperfect) readings, it could be that the air above the earth’s surface accelerated too - like everything contained in the dome undergoes UA. If true, then contact with the ground is not needed.

I guess in that case the acceleration on us is not caused by a normal force but by whatever drives UA.

I could be mistaken - I am not a UA expert, just wanted to point out a way UA could be interpreted to match observations.

[JSS]

There is an equal and opposite force from the Earth, but the acceleration would be %5Cfrac%7BF%7D%7Bm%7D  where m is the mass of the Earth, so the acceleration very, very small.

Can't believe I've just said the Earth is accelerating upwards 

The "earth" isn't accelerating.  The ground directly beneath you is accelerating you.  That's an important distinction. The acceleration is caused by the normal force, so if there is nothing in contact with the ground...there is no acceleration.

What part of the ground is undergoing the acceleration? If the whole Earth was, then it would effectively be weightless and wouldn't stick together once you dug into it. You could pick up a rock and it would float there if it was being accelerated.

So there has to be a layer underground that is being accelerated, and pushing the rest of the Earth (dirt, rock, mountains, water) upwards.

Any idea how far down it is, and what it's made of?

[pricelesspearl]

What part of the ground is undergoing the acceleration? If the whole Earth was, then it would effectively be weightless and wouldn't stick together once you dug into it. You could pick up a rock and it would float there if it was being accelerated.

So there has to be a layer underground that is being accelerated, and pushing the rest of the Earth (dirt, rock, mountains, water) upwards.

Any idea how far down it is, and what it's made of?

I think you might misunderstand me.  I wasn't arguing for UA.  I was just making the point that the "acceleration" caused by the normal force isn't the same thing as "the earth accelerates" in UA.

[JSS]

What part of the ground is undergoing the acceleration? If the whole Earth was, then it would effectively be weightless and wouldn't stick together once you dug into it. You could pick up a rock and it would float there if it was being accelerated.

So there has to be a layer underground that is being accelerated, and pushing the rest of the Earth (dirt, rock, mountains, water) upwards.

Any idea how far down it is, and what it's made of?

I think you might misunderstand me.  I wasn't arguing for UA.  I was just making the point that the "acceleration" caused by the normal force isn't the same thing as "the earth accelerates" in UA.

Ah, too bad, I was hoping to get some answers. Perhaps someone else knows? Is there some sort of pusher-plate down there?

But I agree, under UA if you had a very tall vacuum tube, a projectile fired upwards would experience no forces as it was overtaken by the accelerating Earth and passed.

[Groit]

There is an equal and opposite force from the Earth, but the acceleration would be %5Cfrac%7BF%7D%7Bm%7D  where m is the mass of the Earth, so the acceleration very, very small.

Can't believe I've just said the Earth is accelerating upwards 

The "earth" isn't accelerating.  The ground directly beneath you is accelerating you.  That's an important distinction. The acceleration is caused by the normal force, so if there is nothing in contact with the ground...there is no acceleration.

There's an upward gravitational force that the small mass exerts on the Earth, which is equal to its weight. Small masses accelerate towards the Earth, and so does the Earth towards the small mass, but the acceleration for the Earth is very, very small. Too small to be measured but its there.

[Groit]

If an apple with mass 0.1 kg falls from a tree, what is the acceleration of the Earth towards the apple?

[BRrollin]

If an apple with mass 0.1 kg falls from a tree, what is the acceleration of the Earth towards the apple?

Assuming the only force on the earth is from the apple:

a = Gm/r^2

Where a is the acceleration of the earth, G is Newton’s gravitational constant, m is the apple mass, and r is the distance between the center of the earth and the apple.

Easier way:

AM=am

A is acceleration of earth, M is earth mass, a is apple acceleration (9., m is apple mass.

First way uses Newton’s gravitational force directly. Second uses Newton’s third law pair forces.

[pricelesspearl]

If an apple with mass 0.1 kg falls from a tree, what is the acceleration of the Earth towards the apple?

Technically none.  Acceleration is caused by net force. I think it’s more accurate to say that the earth’s acceleration of the Apple is reduced by the amount of gravitational force of the Apple on the earth.

Just because a force is directed toward something doesn’t mean it accelerates it.

[xasop]

Nope.

There is....

Look, are you here to have a conversation or not? We have been talking more recently than the post you just responded to:

However, one week later the scientist carry out the same experiment again, and bear in mind that for the past week the Earth has been accelerating so its velocity has increased by
They now find that more muons are reaching the surface of the Earth and thus their relative velocity and time dilation has increased. A week later and they do another test, again different results... and so on.

We don't observe this. What are you basing this claim on?

You never responded to this question. I'm not going to waste my time engaging you if you're going to ignore my responses and instead dig up more posts from a week ago to make "witty" remarks on.

And incidentally, responding to a post talking about general relativity with an analysis based on Newtonian gravitation is neither relevant nor constructive.

[Groit]

However, one week later the scientist carry out the same experiment again, and bear in mind that for the past week the Earth has been accelerating so its velocity has increased by
They now find that more muons are reaching the surface of the Earth and thus their relative velocity and time dilation has increased. A week later and they do another test, again different results... and so on.

We don't observe this. What are you basing this claim on?

I'm not claiming that, If you read the last part of the post I wrote:

UA model does not fit into the way we measure muons at the surface of the Earth. This experiment has been done time and time again over many years and the results are always the same, this is because the Earth is moving at a non-relativistic speed i.e. in its orbit around the sun etc... and the muons are travelling towards the Earth at approx 0.98 c. There is no acceleration for the Earth or muons.

The results for the muon decay experiment are always the same over time. So i would like to know how the UA model could possibly fit into it?

(I didn't respond before because i thought you were taking the P, sorry) 

[xasop]

The results for the muon decay experiment are always the same over time. So i would like to know how the UA model could possibly fit into it?

And I would like to know why you assert that it wouldn't. Your claim is that UA predicts something that conflicts with observations. I want to know what your basis is for making this prediction, given that observations contradict it. That is, you are not basing your prediction on observations, but on something else.