[garygreen]

You think a spinning earth would add additional pull straight down towards its surface? 

Make a thread in the discussion forums about your idea please. I am curious to know what you think the situation is.

this situation already appears in many physics textbooks.  here is an example:



equation 11.6 has two terms: one for the "straight down" acceleration, and one for the "sideways" acceleration.  at 45 deg north, the magnitude of the "straight down" acceleration is 9.8 m/s².  the magnitude of the "sideways" acceleration is 0.0169 m/s².  the sideways acceleration is tiny compared to the downward acceleration.

by F=ma, an 80kg human would experience a "sideways" force of ~1.3 N.  that's only ~2x the force required to press a key on a keyboard.  but it's not localized like when you press a key with your finger; it's distributed throughout the whole volume of your body.

[Tom Bishop]

You seem to be quote-mining in desperation.

If a static planet were put into rotation, why would it cause additional pull directly downwards towards its surface? Please explain for us in your own words.

[Curious Squirrel]

The equation F=ma doesn't universally use kilograms.

The value you got of 0.0212 m/s^2 is 21.2 mm / s^2, which is close to the value that the person in the video got.

That is equivalent to being pulled horizontally with weight of 30 quarters on a 175lb person.

This means that, if we were facing in one direction and being pulled to our left by 30 quarters, that we could turn around by 180 degrees and be pulled to our right by 30 quarters. Please tell us, in a thread in the appropriate forum, why we shouldn't be able to feel this or detect it with experiment.

When you lay it out like that it sure sounds hard to believe doesn't it? But how much is it really on one part of you? Our 175lb person is about 2.5 cubic feet of volume, or 4320 cubic inches. So every cubic inch is being pulled differently by the weight of about 0.08 grams. So the palm of your hand will in theory feel a shift equivalent to less than a tenth the weight of a paperclip (which is approx 1 gram). Why do you expect to be able to feel this again? If someone places a paperclip on your shoulder, do you feel the extra weight? I suspect you might feel how it brushes the hair along your arm, but expect a fair bit of doubt if you claim you can tell when someone places a paperclip on your shoulder from the added weight alone, much less something 1/10 of its weight.

[AATW]

The equation F=ma doesn't universally use kilograms.

The value you got of 0.0212 m/s^2 is 21.2 mm / s^2, which is close to the value that the person in the video got.

That is equivalent to being pulled horizontally with weight of 30 quarters on a 175lb person.

This means that, if we were facing in one direction and being pulled to our left by 30 quarters, that we could turn around by 180 degrees and be pulled to our right by 30 quarters. Please tell us, in a thread in the appropriate forum, why we shouldn't be able to feel this or detect it with experiment.

Ok. The SI unit of mass IS the kilogram, that is just a definition. I guess you can get the same answer in different units if you convert it all but it’s a bit of a clumsy way of working.

Anyway, that rate of acceleration is equivalent to being in a car which is going from 0-60mph in about 21 minutes. I personally doubt you’d be able to feel that, but I cannot prove that.

But, and this is the thing you keep ignoring, MY MATHS IS WRONG. It’s wrong for the same reason the maths in the video is wrong. I have assumed that you are going at 460m/s in a STRAIGHT LINE in one direction and, over 12 hours you change velocity so that you are now going at 460m/s in the opposite direction. That is the logic of the video. But that is not what the heliocentric model claims. It claims we are going in a circle at a constant angular velocity. Because you are moving in a circle, not a straight line, you need to use different maths. I gave you a link in the other thread to the correct maths. That rotation DOES exert a force and you DO weigh a different amount at the equator but:
1) You don’t weigh different amounts during the course of the day, the angular velocity due to the rotation is constant thus the force on the body is.
2) The difference in your weight between the equator and the poles is 0.3%. The maths is in the other thread. If an 180lb person got on a plane at the pole and got off at the equator then their weight would have changed by little over half a pound. If you put on a pound or lose a pound are you seriously claiming you feel noticeably different?

[Tom Bishop]

The equation F=ma doesn't universally use kilograms.

The value you got of 0.0212 m/s^2 is 21.2 mm / s^2, which is close to the value that the person in the video got.

That is equivalent to being pulled horizontally with weight of 30 quarters on a 175lb person.

This means that, if we were facing in one direction and being pulled to our left by 30 quarters, that we could turn around by 180 degrees and be pulled to our right by 30 quarters. Please tell us, in a thread in the appropriate forum, why we shouldn't be able to feel this or detect it with experiment.

When you lay it out like that it sure sounds hard to believe doesn't it? But how much is it really on one part of you? Our 175lb person is about 2.5 cubic feet of volume, or 4320 cubic inches. So every cubic inch is being pulled differently by the weight of about 0.08 grams. So the palm of your hand will in theory feel a shift equivalent to less than a tenth the weight of a paperclip (which is approx 1 gram). Why do you expect to be able to feel this again? If someone places a paperclip on your shoulder, do you feel the extra weight? I suspect you might feel how it brushes the hair along your arm, but expect a fair bit of doubt if you claim you can tell when someone places a paperclip on your shoulder from the added weight alone, much less something 1/10 of its weight.

One dollar bill weighs one gram. Cut out a tenth of that, fold it, and hold it in you hand? Can you feel the weight?

Now, every square inch of your body should also feel that weight, pulling you horizontally. When you turn one way you should feel it pulling in one direction, and then when you turn around you should feel it pulling in the other direction. We should instantaneously feel this deflection. Yet we do not feel this at all.

But, and this is the thing you keep ignoring, MY MATHS IS WRONG. It’s wrong for the same reason the maths in the video is wrong. I have assumed that you are going at 460m/s in a STRAIGHT LINE in one direction and, over 12 hours you change velocity so that you are now going at 460m/s in the opposite direction. That is the logic of the video. But that is not what the heliocentric model claims. It claims we are going in a circle at a constant angular velocity. Because you are moving in a circle, not a straight line, you need to use different maths. I gave you a link in the other thread to the correct maths. That rotation DOES exert a force and you DO weigh a different amount at the equator but:
1) You don’t weigh different amounts during the course of the day, the angular velocity due to the rotation is constant thus the force on the body is.
2) The difference in your weight between the equator and the poles is 0.3%. The maths is in the other thread. If an 180lb person got on a plane at the pole and got off at the equator then their weight would have changed by little over half a pound. If you put on a pound or lose a pound are you seriously claiming you feel noticeably different?

If that pound is trying to fall horizontally, while the rest of you fell vertically, why wouldn't you feel noticeably different? That is an imbalance, and should be detectable.

[Curious Squirrel]

The equation F=ma doesn't universally use kilograms.

The value you got of 0.0212 m/s^2 is 21.2 mm / s^2, which is close to the value that the person in the video got.

That is equivalent to being pulled horizontally with weight of 30 quarters on a 175lb person.

This means that, if we were facing in one direction and being pulled to our left by 30 quarters, that we could turn around by 180 degrees and be pulled to our right by 30 quarters. Please tell us, in a thread in the appropriate forum, why we shouldn't be able to feel this or detect it with experiment.

When you lay it out like that it sure sounds hard to believe doesn't it? But how much is it really on one part of you? Our 175lb person is about 2.5 cubic feet of volume, or 4320 cubic inches. So every cubic inch is being pulled differently by the weight of about 0.08 grams. So the palm of your hand will in theory feel a shift equivalent to less than a tenth the weight of a paperclip (which is approx 1 gram). Why do you expect to be able to feel this again? If someone places a paperclip on your shoulder, do you feel the extra weight? I suspect you might feel how it brushes the hair along your arm, but expect a fair bit of doubt if you claim you can tell when someone places a paperclip on your shoulder from the added weight alone, much less something 1/10 of its weight.

One dollar bill weighs one gram. Cut out a tenth of that, fold it, and hold it in you hand? Can you feel the weight?

Now, every square inch of your body should also feel that weight, pulling you horizontally. When you turn one way you should feel it pulling in one direction, and then when you turn around you should feel it pulling in the other direction. Yet we do not feel this distributed weight at all.

I definitely cannot feel the 'weight' of a dollar bill, much less a fraction of it. Can I feel on in my hand? Yup. My sense of touch is working there. But if I put a glove on and add a dollar bill to it? I have no idea that bill is there. I would also personally call BS if you were to claim that as well based on my own experiences. Go try it yourself though. Put on a glove. Lay a dollar bill on your hand. Or better yet, hold out your gloved hand and have someone else place it on there. See if you can guess better than 50% of the time whether they placed it on there or not. I'd wager money you can't approach that sort of accuracy unless they accidentally brush your hand or something.

[Mysfit]

I often don't feel the weight of my clothes.
I am trying REALLY hard to feel the weight of my vest... I can't.
If I spin a lot, the vest's loose bits (yes i'm not that fat) seem to pull away from me. I think that may not be the effect you're hoping for though.
How would I test this tiny shift in weight without moving?... I actually can't think of a way.

[Tom Bishop]

I definitely cannot feel the 'weight' of a dollar bill, much less a fraction of it. Can I feel on in my hand? Yup. My sense of touch is working there. But if I put a glove on and add a dollar bill to it? I have no idea that bill is there. I would also personally call BS if you were to claim that as well based on my own experiences. Go try it yourself though. Put on a glove. Lay a dollar bill on your hand. Or better yet, hold out your gloved hand and have someone else place it on there. See if you can guess better than 50% of the time whether they placed it on there or not. I'd wager money you can't approach that sort of accuracy unless they accidentally brush your hand or something.

It's not just one dollar. It's more like the weight of 174 dollars, distributed all over your body. When you turn one direction you should feel it pulling in one direction, and when you turn 180 degrees around, you feel it pulling in the other direction. We should instantly be able to turn this on and off, and reverse the effect, by changing directions. Yet this is not felt at all.

The argument of "well if you are wearing clothes..." is irrelevant since it affects all parts of your body and your clothes are resting on you being pulled downwards while your body is being pulled horizontally.

174 dollars, or 174.147246 grams, is a significant amount of weight to shift around and should absolutely be noticeable.

[stack]

It's not just one dollar. It's more like the weight of 174 dollars, distributed all over your body.

That's 6 ounces "distributed all over your body". I fail to see how I would notice it. If you smeared six ounces of butter all over yourself would you feel any weight distribution change? I think not.

[Tom Bishop]

It's not just one dollar. It's more like the weight of 174 dollars, distributed all over your body.

That's 6 ounces "distributed all over your body". I fail to see how I would notice it. If you smeared six ounces of butter all over yourself would you feel any weight distribution change? I think not.

This is horizontal weight, which imbalances you, and can be reversed by changing directions, not vertical weight.

If you had a button which reversed its weight on your body from 6 ounces to -6 ounces whenever you pressed it, would you not feel it?

[Mysfit]

If you had a button which reversed its weight on your body from 6 ounces to -6 ounces whenever you pressed it, would you not feel it?

I think I would, as long as it happened pretty suddenly.
Otherwise, the vertical weight of the button would be more noticeable.
I am assuming this is a big button? I have not been able to follow the maths so far and examples have varied from a paper clip to paper money.

A better example might be a fly on a string, it goes this way and that without having to account for it’s verticality. The dickens.

[Curious Squirrel]

I definitely cannot feel the 'weight' of a dollar bill, much less a fraction of it. Can I feel on in my hand? Yup. My sense of touch is working there. But if I put a glove on and add a dollar bill to it? I have no idea that bill is there. I would also personally call BS if you were to claim that as well based on my own experiences. Go try it yourself though. Put on a glove. Lay a dollar bill on your hand. Or better yet, hold out your gloved hand and have someone else place it on there. See if you can guess better than 50% of the time whether they placed it on there or not. I'd wager money you can't approach that sort of accuracy unless they accidentally brush your hand or something.

It's not just one dollar. It's more like the weight of 174 dollars, distributed all over your body. When you turn one direction you should feel it pulling in one direction, and when you turn 180 degrees around, you feel it pulling in the other direction. We should instantly be able to turn this on and off, and reverse the effect, by changing directions. Yet this is not felt at all.

The argument of "well if you are wearing clothes..." is irrelevant since it affects all parts of your body and your clothes are resting on you being pulled downwards while your body is being pulled horizontally.

174 dollars, or 174.147246 grams, is a significant amount of weight to shift around and should absolutely be noticeable.

Can you prove it? The math indicates laying a dollar on your hand would be roughly equivalent if you can feel your hand change in weight. Might need to use two dollars. Your entire argument right now "Well you totally should!" and we can go about this in circles forever. Test it. Give us an experiment you feel better reflects things than the dollar experiment I outlined above. But remember, anything that you do has to adhere to roughly 1 gram per cubic inch. You can't just put on a backpack and throw 174 grams of something in there and say you can feel it. You've just focused those 174 grams into the area of the straps on your back. Hence my original suggestion of a dollar bill (or two) onto your gloved hand. This controls about as many points as I can think of offhand. It ensures you aren't just using your sense of touch to know it's there by blocking it off with a glove. It localizes the effect to an area about equivalent to our 1gr/inch^3 above. The blindfold should work to reduce or remove the 'ghost' feeling if you can see them being placed on your hand. Lastly having someone else place them on your hand at a random time, helps to reduce the same 'ghost' feeling that you could get by placing them on your hand on your own. If you can successfully 'know' that they've placed it on your hand a percentage of the time greater than what just guessing would get you (a standard deviation or so above 50%) you will have provided evidence to substantiate your claim that you should be able to feel this change in force/weight. If you can't, it's evidence your claim that we should be able to feel it is false. Science!

[garygreen]

You seem to be quote-mining in desperation.

i don't think you know what quote-mining is.  this is just a standard treatment of centrifugal force from a popular graduate textbook on mechanics.  what specifically do you take issue with?

If a static planet were put into rotation, why would it cause additional pull directly downwards towards its surface? Please explain for us in your own words.

it wouldn't.  the centrifugal force acts radially outward from the axis of rotation.  this means that someone standing at 45 deg north experiences an additional "sideways" force (the quarters analogy you keep making).  the equation (11.6) from my textbook tells you how to calculate that force.  the r-hat term is the downward force, and the theta-hat term is the "sideways" force.

the magnitude of the "sideways" acceleration is 0.0169 m/s².  why is it not 0.0212 m/s²?  because not all of the centrifugal force is in the "sideways" direction.  some of it is in the "upward" direction.



again, this tiny acceleration is distributed evenly throughout your entire volume.

[Tom Bishop]

I definitely cannot feel the 'weight' of a dollar bill, much less a fraction of it. Can I feel on in my hand? Yup. My sense of touch is working there. But if I put a glove on and add a dollar bill to it? I have no idea that bill is there. I would also personally call BS if you were to claim that as well based on my own experiences. Go try it yourself though. Put on a glove. Lay a dollar bill on your hand. Or better yet, hold out your gloved hand and have someone else place it on there. See if you can guess better than 50% of the time whether they placed it on there or not. I'd wager money you can't approach that sort of accuracy unless they accidentally brush your hand or something.

It's not just one dollar. It's more like the weight of 174 dollars, distributed all over your body. When you turn one direction you should feel it pulling in one direction, and when you turn 180 degrees around, you feel it pulling in the other direction. We should instantly be able to turn this on and off, and reverse the effect, by changing directions. Yet this is not felt at all.

The argument of "well if you are wearing clothes..." is irrelevant since it affects all parts of your body and your clothes are resting on you being pulled downwards while your body is being pulled horizontally.

174 dollars, or 174.147246 grams, is a significant amount of weight to shift around and should absolutely be noticeable.

Can you prove it?

https://www.quora.com/What-is-the-minimum-amount-of-acceleration-that-a-human-can-detect

What is the minimum amount of acceleration that a human can detect?

A2A: There are many research papers written on this.  If you want greater depth of details, I would suggest doing a search on "treshold of perception for vibration".  As it happens, I did my thesis on a topic along these lines...

First, there isn't one set number.  Second, much of the focus on this is on vibrational accelerations--something you are sensing "moving".  So this is not necessarily applicable, for instance, to a gentle acceleration of an elevator.  For something like an elevator, I would speculate somewhere around 0.1 - 0.5 m/sec^2 would be the threshold, i.e. 0.01 - 0.05g. Often it is the "jerk" that we notice in a situation like this (rather than the constant rate of acceleration itself).

I would say there are 3-4 major variables in-play:

1) Frequency of the vibration (assuming a sinusoidal pulsation)

2) Body part sensing the vibration (feet/hands/seat/whole body)

3) Axis of vibration (fore-aft/lateral/up-down).

4) Length of the vibration

Generally these studies focus on a range of ~2Hz - 200 Hz.  Within this range, the ballpark number for sensitivity threshold is ~0.01 - 0.10 m/s^2 (so roughly 0.001 - 0.010 g).

Taking his advice on searching for "threshold of perception for vibration" I got the following:

https://books.google.com/books?id=-_JV63L6RMcC&lpg=PA262&ots=vNfENVZrtY&dq=acceleration%20threshold%20sensation%20human%20%22m%20%2F%20s%20%5E%202%22&pg=PA262#v=onepage&q&f=false



0.01 m^2 = 10 mm^2
0.02 m^2 = 20 mm^2

[Tom Bishop]

If a static planet were put into rotation, why would it cause additional pull directly downwards towards its surface? Please explain for us in your own words.

it wouldn't.

You started this thread by trying to justify your assertion that a rotating earth would cause downwards acceleration. Now you say that it would not cause downwards acceleration?

There is nothing wrong with just admitting that you were wrong.

[Curious Squirrel]

Snipped for post brevity

Oh, awesome. So the Quora guy agrees completely as he gives 0.1 m/s^2 at the low end, and we're talking about a speed around 20% of that. The second source you link is very clear that it's talking about *vibrating* acceleration, which is not what's being discussed. Even if it were, it suggests our 0.02 m/s^2 is on the very lowest edge of human perception. Both of your sources appear to be in agreement that we should not be able to feel the acceleration due to the spin of the Earth. Even 'best case' suggests it would be likely difficult to do so, assuming a set of circumstances that aren't reality. Thank you for presenting a rather strong case against your own premise.

[Tom Bishop]

Snipped for post brevity

Oh, awesome. So the Quora guy agrees completely as he gives 0.1 m/s^2 at the low end, and we're talking about a speed around 20% of that. The second source you link is very clear that it's talking about *vibrating* acceleration, which is not what's being discussed. Even if it were, it suggests our 0.02 m/s^2 is on the very lowest edge of human perception. Both of your sources appear to be in agreement that we should not be able to feel the acceleration due to the spin of the Earth. Even 'best case' suggests it would be likely difficult to do so, assuming a set of circumstances that aren't reality. Thank you for presenting a rather strong case against your own premise.

Ranges between 0.01 m/s^2 and 0.0221 m/s^2 are in the "probable perception" to "clear perception" range. Yet no one has perceived the rotation of the earth. Why?

The author of the quora article who wrote a thesis on the subject told us to look up vibrational perception. It makes sense. We are detecting different accelerations depending on which direction we face, and can go from minus to plus depending on one's position. Yet again, however, no one has felt this acceleration.

[Curious Squirrel]

Snipped for post brevity

Oh, awesome. So the Quora guy agrees completely as he gives 0.1 m/s^2 at the low end, and we're talking about a speed around 20% of that. The second source you link is very clear that it's talking about *vibrating* acceleration, which is not what's being discussed. Even if it were, it suggests our 0.02 m/s^2 is on the very lowest edge of human perception. Both of your sources appear to be in agreement that we should not be able to feel the acceleration due to the spin of the Earth. Even 'best case' suggests it would be likely difficult to do so, assuming a set of circumstances that aren't reality. Thank you for presenting a rather strong case against your own premise.

Ranges between 0.01 m/s^2 and 0.0221 m/s^2 are in the "probable perception" to "clear perception" range. Yet no one has perceived the rotation of the earth. Why?

The author of the quora article who wrote a thesis on the subject told us to look up vibrational perception. It makes sense. We are detecting different accelerations depending on which direction we face, and can go from minus to plus depending on one's position. Yet again, however, no one has felt this acceleration.

Those ranges are for something vibrating at speeds of 2-20Hz, and I would wager the low vibration end is towards the higher Hz end. He specifically calls out an elevator too, noting the lowest was around 0.1 m/s^2. The elevator is much closer to normal conditions on Earth.

But sure, lets go with just spinning, and we'll go with the best case scenario, looking for 0.0221 m/s^2 is detectable. But wait, we *also* have to account for the 'noise' we'll be making as we spin. That will be far more noticeable most likely. So if we go with our 80kg guy from before. The average length from hip to hip is about 3.6m. We'll cut down to 1.2m radius and 40kg. I think that should give us a rough sort of midpoint, but I'll run a few others too for fun. That gives us a speed of spin of roughly 15 m/s^2 for our 40k, generating centripetal force equal to 7500 Newtons. That's about 764 kg m/s^2 of force. Not sure anyone is gonna notice an extra 0.0221. Well let's see what we can do to get this a bit more favorable, shall we?

Hrmm, the lowest I'm getting, using the shortest person to have lived, gives me about 23.2 kg m/s^2. For whom I was being somewhat generous as well imo. Radius of 0.30m (about his 'center' using a similar method as above), gives us a velocity of 3.7 m/s^2, and a weight of 5kg. I'm not seeing what part of you is supposed to have felt this acceleration Tom, especially not feeling it over simply the force generated by spinning yourself around. Feel free to check my math if you like, I encourage it in fact. But your hypothesis that we should be able to feel it by spinning is looking dead in the water again.

[garygreen]

You started this thread by trying to justify your assertion that a rotating earth would cause downwards acceleration.

at no point has that ever been my argument.  my argument has always been the exact opposite of that, hence the "you weigh less in ecuador" argument.  the centrifugal force always acts radially away from the axis of rotation.

i'm not sure what your beef here is.  the op addresses exactly the thing you are talking about with the quarters.  you can calculate the "horizontal pulling" you describe using the expression shown.  the magnitude of the "horizontal pulling" is 0.0169 m/s².

if you want to talk about how noticeable that centrifugal force is, we can compare it to a merry-go-round.  unlike vibration, that's an apples-to-apples comparison.  recall that by F=ma, an 80kg human would experience a "horizontal pulling" force of ~1.3 N.

centrifugal force = object mass * radius of rotation * angular velocity ².  let's assume the same 80 kg person is riding on a merry-go-round with a 3 meter radius (typical size according to the internet).  for that mass and radius, the angular velocity required to produce a centrifugal force of 1.3 N is 0.074 radians per second.  that's slower than the second hand on a clock.  the period of such a rotation is 85 seconds.

punchline: the "horizontal pulling" you experience at 45 deg north is equivalent to the horizontal pulling you would experience standing on a merry-go-round that takes 85 seconds to complete a single rotation.

[RonJ]

If you want to see all the effects of gravity just go to the 'International Gravity Formula'.  Everything is outlined there.  The effects of centrifugal force should be 0.03382 * Cos^2(Lat).  This is just the difference between what you would experience if the earth were NOT rotating and if the earth was, at the normal 1 rotation per 24 hours.   Of course the centrifugal force would just be a correction to the normal force of gravity because it's a force vector in exactly the opposite direction.  The heliocentric force due to acceleration is just the combination of the earths rotation on it's own axis and the rotation around the sun.  Unfortunately for the FET folks there are increasingly inexpensive MEMS devices out there that can actually measure accelerations on the surface of the earth and they come out with the expected values.  These devices are similar to those found inside your cell phones only better and more sensitive.  Right now the data from these devices can measure the accelerations due to the heliocentric speed changes but it takes a while.  The acceleration data is buried in a lot of noise and you have to take measurements over a period of time, then filter the data points to actually extract the readings you want.  This would mean you could easily take a device like this and take measurements at different latitudes.  If you got anywhere near the expected values than it would prove that the earth was both a sphere and rotating.  Of course there already is a network of instruments around the world that have already done this and they publish their results.  The force of gravity changes constantly due to the fact that the earth is not static.  Gravity is simply one center of mass attracting another.  If the location of that center of mass changes then the force would also change.  The network constantly measures the acceleration forces of gravity in many different locations around the world.  I didn't expect to see this mountain of information coming my way, but I took out and dusted off my own dynamics book that I used in college years ago.  All I have to do now is get myself back up to speed on the subject matter.