Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Do orbiting bodies accelerate?

This is just a series of thoughts leading to a “conclusion”. I would appreciate comments/criticism, please.

1. Velocity is a vector which includes speed and direction.
2. Acceleration is change in velocity.
3. Change of speed with constant direction = acceleration.
4. Change of direction with constant speed = acceleration.
5. A body orbiting at constant speed is constantly accelerating.
6. Gravity is not a force that holds an orbiting body as though it were on a string.
7. Gravity alters the geometry of spacetime such that it becomes curved.
8. The curve thus formed is a geodesic, and is defined as the most direct path from A to B in curved spacetime.
9. Thus, a geodesic is equivalent to a straight line in flat (non-curved) spacetime.
10. A body travelling at constant speed in a straight line is not accelerating.
11. It should be reasonable to argue that a body following a geodesic at constant speed is not accelerating.
12. It should, therefore, be reasonable to conclude that an orbiting body is not accelerating.

You are totally correct but still totally wrong and you can thank your teachers and classical physics

You sort of reach the right conclusion in (12) after a couple of wrong turns. The problem is acceleration is defined, as are all things in classical physics static universally and global.

You then switch to GR curved spacetime without changing your definition of acceleration. The classical physics version of acceleration is totally ambiguous and meaningless in the GR framework except on a case by case conversion.

When you look at Bill S standing on the earth, you will conclude the same that gravity is accelerating you towards the ground using classical physics

Definition problem again .. redefine acceleration properly to fix it

https://en.wikipedia.org/wiki/Proper_acceleration

If you can't measure an acceleration you aren't

Don't mix frameworks as you can't, the definitions of spacetime differ and you will just get confused. Your statement (12) is correct in GR because you can't measure any acceleration with an accelerometer not because of any classical physics calculations. It is true by definition in GR and requires NO calculations.

GR is not an addition to classical physical physics it redefines everything. I am going to suggest you put the word "proper" infront of terms when you wish to use GR/SR so you remember it's different to it's classical physics counter part, so proper time, proper distance, proper acceleration etc.

So in classical physics you standing there you have an acceleration of 9.8m/s towards earth. In GR/SR you have a proper acceleration of 0m/s and it doesn't really require any explaining although countless webpages seem to want to try and just confuse people. It's that way because the frameworks define it that way ... the end !!!

People get fuel consumption of 1 gallon per mile does not equal 1 litre per kilometre yet we can't seem to get them to understand the above. Just because GR/SR gives different answers to classical physics nothing is wrong the unit definitions aren't the same.

All of the above is also the answer to the other problem with speed of light you were playing with and I was trying to get you to self realize. The speed of light in relativity is BY DEFINITION the same to all observers and here you were talking about different speeds of it without considering that was just from your assumption or inferring from your reference point. You were doing a Dave Profitt and going with your observation as a global truth ... try putting yourself as an observer where you see it slowed. Remember measuring or seeing something only ever makes it true from that reference frame.

What I might start doing is when you mix classical physics and relativity just simply prompt you with "Does 1m/g = 1km/l" as a reminder.

So your two problems are true by definition and can only be equated on a case by case basis with different adjustments under classical physics. Why ... because spacetime is static in one framework and relative with global zero frame forbidden in the other. There is no simple identical conversion between the two frameworks, in all situations that will hold.

1. Velocity is a vector which includes speed and direction.

correct.
but the direction such as north or south or whatever
is not used unless needed.

2. Acceleration is change in velocity.

correct.
but over time. ie ... ms^2

3. Change of speed with constant direction = acceleration.

correct.

4. Change of direction with constant speed = acceleration.

correct.

5. A body orbiting at constant speed is constantly accelerating.

correct.

6. Gravity is not a force that holds an orbiting body as though it were on a string.

correct.
gravity is the force that holds a orbiting body.
but not like it was on a string.

to achieve an orbit around a body , gravity is the force
that must be counteracted by the force of the orbiting
objects mass x its velocity.

the velocity for instance is like the tension on the string.
if the orbiting object increases velocity the tension on the string increases , if the string were elastic then the orbiting object would gain altitude.

if the orbiting object decreases velocity the tension on the string decreases , if the string were elastic the orbiting object would loose altitude.

f=mv

for instance a object that normally weighs 1 kg on the earths surface must achieve a orbital velocity that would counteract the pull of gravity that it feels ( 1 kg on earths surface )
but less as the orbit increases , in order to counteract the pull of gravity and maintain a given orbital distance around the body being orbited the orbiting object must achieve a certain velocity in order to achieve an angular acceleration that is the product of the orbiting objects velocity and
the orbiting objects mass and the gravitational pull between the orbited body and the orbiting object that balances the
forces acting on the orbiting object thereby causing the orbiting object to maintain a certain orbital height as it
constantly accelerates towards the earth.

a orbit is simply a balancing act.

7. Gravity alters the geometry of spacetime such that it becomes curved.

no belief = no comment.

8. The curve thus formed is a geodesic, and is defined as the most direct path from A to B in curved spacetime.

no belief = no comment.

9. Thus, a geodesic is equivalent to a straight line in flat (non-curved) spacetime.

no belief = no comment.

10. A body travelling at constant speed in a straight line is not accelerating.

correct.

11. It should be reasonable to argue that a body following a geodesic at constant speed is not accelerating.

incorrect.
you cannot follow a geodesic without accelerating towards
or away from the sections of a geodesic shape as you travel above the sections that make up the geodesic shape.

12. It should, therefore, be reasonable to conclude that an orbiting body is not accelerating.

incorrect.

there can not be an orbiting body that does not accelerate
around a orbited body.

an object will travel in a straight line if it is
not accelerated in another direction away from the straight line.

If you can't measure an acceleration then the measuring tools
that you use are worthless and you should toss them in the
worthless tool bin where they have always belonged.

orac , if you were standing on the equator of the earth
right now and holding an accelerometer in your hand and maintaining an exact distance from the ground and standing in the exact same spot.

1) would the accelerometer register any acceleration?

2) would your whole body be accelerating in a direction?

3) if gravity were suddenly removed from the earth would
you remain on the surface of the earth or would you begin
to fly off into space at 1,667,923 METERS PER HOUR ?

or do you wear super glue shoes?

also: since your religion dictates that gravity is due
only to the energy and velocity of a object , just how
do the prophets of your religion explain why your feet
stay on the ground all day long or is it that they intend
to reclaim that the surface of the earth is actually flat
after all and the reason our feet stay on the ground
is because our feet understand how QM , and all the Einstein bullshart works.

Paul, you aren't interested in the answer as made clear by your spray at end, so why expect me to waste time answering?

Perhaps measure it all yourself, or ask your GOD what the answer is .. why do I care what a religious fruitloop believes

Don't claim you don't have access to an accelerometer there will be a pile of school classroom excercises on the net to build one with a bottle. If you have an I-phone there is a free app that will show you the phones acceleration. So there are two simple options, and who knows maybe even the religious can learn things by experimentation. Feel free to show us what you measure, which I will be happy to discuss.

Now for the record there is widerange accelerometers on board the International Space Station which is orbitting at 27,600 km/h. The reference page is (http://www.nasa.gov/centers/glenn/about/fs11grc_prt.htm) which includes links to the outputs which update every 20 minutes. The instruments are so sensitive they can detect small accelerations from the operation of hardware, crew activities, dockings and maneuvering.

Want to guess what the nominal value the ISS accelerometers measure?

The ISS accelerometers meassure zero. Because all the components are subjected to exactly the same forces. An accelerometer can only measure the difference in the forces applied to different parts of the accelerometer. Typically an accelerometer uses 2 major components, a 'fixed' body and a sprung mass. The acceleration is calculated as the difference in location between the body and the sprung mass. If both of them are subjected to the same force then they don't sense any acceleration.

Bill Gill

Orac
From Bill s's post.



your reply to bill s's #12




my reply to bill s's #12




you seem to think or is it that you believe
that you are not undergoing constant acceleration
because you cannot measure that acceleration.

you really do need to go back and first learn the
basics of physics before you try to dump on classical physics.

if your belief or the GR belief believes that ...



then that clearly tells me that your belief and the
belief system of GR is false and invalid.



LOL



your argument always seems to include some type of
anti religious remarks when your knowledge fails to
rescue you from the really stupid situations you get
yourself into because of your lack of knowledge.

try learning the basics of physics orac , it cant hurt
and may actually help you in your quest for the fantastic
that you have submerged yourself into.

Now lets see if you can extend that with a bit more intelligence than Paul. Assuming you and the accelerometer are in the same reference frame, can you be accelerating if the accelerometer measures zero?

Hint: You probably don't need it but you correctly identified all the forces must sum to zero for the accelerometer to read zero.

What is the classical physics name of this law?

Extension Hint: If we wan't to go deeper with classical physics you are probably going to have to break into linear and non-linear acceleration types and introduce the concept of fictional forces.

Yes, if you are in freefall. You and all the components of the accelerometer will be subject to the same force. If there are no counteracting forces, such as standing on the floor of an elevator, the accelerometer will not be able to detect the acceleration. Basically the accelerometer can only measure the difference between the net force on the body of the accelerometer and the net force on the sprung mass.

Bill Gill

oh please let me attempt an intelligent answer to this mr wizard.



if myself and the accelerometer are in the same reference
frame then it would certainly appear to me that we were
both accelerating around the planet as we both would observe things such as the stars rising , crossing the sky , and disappearing over the horizon
... this would repeat every day leading me to gain the
knowledge that the earth that I and the accelerometer are
on is not flat and is rotating.

thus from this gathered data I could easily conclude that
I and my accelerometer would obviously be traveling in a circle and that even though we could not measure any acceleration that would in no way mean that we are not accelerating because basic physics math tells me that I and my accelerometer are accelerating , and that there is no need
to include any linear acceleration or any fictional forces to determine that I am accelerating around the planet.

I could simply draw a circle on the ground with a stick.

knowing that I must accelerate the point of the stick
towards the center of the planed circle clearly tells me
that I too must be accelerating ... else the line I draw
would not form a circle.

you always come up with some really stupid questions
when you are found to be wrong in an attempt to cover
up the errors in your knowledge base , if you would have gained
some measure of knowledge before you flooded your
brain with fantasy you might have been capable of not
making so many mistakes that you have to cover up.

Define freefall please it will help you see the problem you just introduced

Perhaps you may care to review Newtons second law (https://en.wikipedia.org/wiki/Newton's_laws_of_motion).


So any suggestions how we should reconcile these two concepts?

So far you have freefall = something that has acceleration yet measures zero net force and yet Newtons second law states "net force on the body is zero, the momentum of the body is constant"

Those two statements are very inconsistent ????????????

You are on the right track but need some better hand waving

Hmm lets think about a hint for you: (https://en.wikipedia.org/wiki/Gravimeter) or perhaps google bucket argument


Show me the maths ... I sense poor Newtons motion laws going down

Without making fun of you that is why centripetal acceleration is described as a pseudo force or a fictitious force ... google it.

If it helps (https://en.wikipedia.org/wiki/Fictitious_force) and it's one way out of Bill G's predicament.

It's probably different in Paul physics but that is how it is in classical physics because we need to do a patch job to allow all the laws to coexist. If you make the centripetal acceleration real you will violate Newtons laws of motion and all hell breaks loose with your physics.

It will be most interesting to see how both of you tackle resolving this.

I personally feel no great need to feed your ego by trying to reconcile your clay pigeons.

Bill Gill

I really don't care , just thought you might be interested to resolve it.

The interesting comment for you in gravimeters you may want to consider


Is your definition of free falling the same

You may want to consider will an absolute gravimeter measure anything under your definition of free falling.

At the end of the day this is classic physics at it's core and since you like this framework it's interesting to see where it breaks down and what underpins it.

The question posed is ancient going back to Newton and his bucket and when we talk of motion, and by extension change in motion over time (AKA acceleration), we need to be very careful "with Respect to what are we measuring". You blatantly pulled a universal reference frame and I just inverted it on you, so your classic laws come into conflict. Your answer, like all answers to this problem, is sometimes correct in certain reference frames but it isn't a universal solution by any means.

There are as many answers to this problem as there are reference frames and you can't give a definitive answer in classical physics and that was the memo.

An interesting video from the ISS on this is the re-boost operation. Which is free falling during the video the ISS or the astronauts as the ISS is boosting to go back closer to zero gravity condition ... it's lucky you know what is going on !!



One bailed, so lets see what Paul goes with.

A gravimeter is not an accelerometer. A gravimeter is used to measure the force of gravity at a place on the surface of the Earth. They may include accelerometers but they aren't accelerometers. Don't try changing the rules of the game in the middle.

Bill Gill

I will tell you the elements and methods you will need to know
in order to calculate it yourself but I will include an example.


1) you need to know the acceleration that is the result
of the attraction of gravity between yourself and the earth.

(9.8 ms^2)

the above 9.8 ms^2 acceleration is the force that pulls you towards the earth (980 N) if your mass is 100 kg.

2) you need to know your mass.(kg)

3) you need to know the distance from yourself to the center
of the earths gravity field.

4) I will find the needed orbital velocity.


in order to maintain a orbit around the earth all you need
to do is to match or balance the force of gravity
( the inward pull towards the center of the earths gravity field)
and the force caused by angular acceleration
( the outward force that pulls you away from the center of the earths gravity field due to the angular acceleration of
your body as it travels in a circular path around
the earth)

in essence you need to achieve a certain velocity to do this.

using the centripetal force formula you can calculate
the amount of orbital velocity that you must achieve in order to achieve a orbit with a constant altitude away from the center of the earths gravity field.

F(centripetal) = mv^2/r

if you know your mass equals = 100kg

and you know the force is 980 N ( 9.8 ms^2)

then you need to counteract the acceleration of
a force of 980 N against a mass of 100 kg

980 N will accelerate a 100 kg mass a distance of
9.8 meters in 1 second.

lets say your radius from the earths center of gravity is
in maximum low earth orbit (2000 km above surface )
adding in the 6,371 km radius of the earth you have a total
radius from the center of the earths gravity field of 8,371 km

radius = 8,371,000 meters

using the knowns to find the nedded velocity to establish a orbit.

100 kg
8,371,000 meters radius
9.8 ms^2 acceleration

find velocity

the formula results in a F (centripetal) that is the result of a division
of (mass x velocity squared / radius)
we know that the acceleration is 9.8 ms^2
so we multiply the radius by 9.8

were counteracting the acceleration caused by the force of gravity acting against a 100 kg mass with a force caused
by the resistance of an object to undergo angular acceleration
or simply put the resistance of an object to change its
direction so the result F in the centrifugal force formula
will be given as an acceleration not a force.

8,371,000 meters (radius) x 9.8 = 82,035,800

this gives us the result of mass x velocity squared
so we divide by the mass to get the velocity squared.

82,035,800 / 100 (mass) = 820,358 (velocity squared)

we then find the square root of velocity squared to get the velocity.

sqr of 820,358 = 905.73 ms (velocity)


so your orbital velocity needs to be apx 905.73 ms
in order to stay in orbit around the earth at a orbital
altitude of 2000 km.

ROFL .... ready

Look at the relative version of gravimeter its described thus


Now lets see how Bill G described his accelerometer


A GRAVIMETER IS A SINGLE AXIS ACCELEROMETER

But you especially referenced a gravimeter that measured the acceleration of a mass in free fall. Stop trying to change the rules of the game in the middle.

Bill Gill

There now we have what you don't get

It's the same thing .. try work out why ... there is only one way to formulate acceleration.

Hint: Try to find a reference point. Try the old drop big object and little object from a building. So the free falling mass gravimeter is going to read what when in free fall?

Edit: Didn't think but the video above has the astronauts on the ISS free falling. So they are your mass in free fall what acceleration are they showing?

Final Hint: Are Newtons laws (the laws our device is using to measure) valid in a non inertial frame.

Paul that is a huge post about absolutely nothing ... I am pretty sure I know how to calculate centripetal force. What you haven't addressed is the centripetal force REAL, against what is it pushing to push the orbiting body out.

Go right to the center pivot of any gravitational centripetal setup and the force goes into a single point which is a singularity. Why a singularity because the pivot has a size of zero. Pressure is force per unit area and the pivot has an area of zero.

So Pressure at pivot space = Some force / zero

In other words the pressure on space for any given centripetal setup you just described is INFINITY. We can usually talk around it on physical bodies but now try a spaceship pulling a circle manouvre in empty space.

If you want to test the force and pressure put a weight on the end of a string and swing it around.

So in the physical situation the pivot or axle has width and structural strength. We don't have either of those in the gravity based version.

The very classical formula's you are using will also prove that what is happening can't happen.

That is why centripetal acceleration is called an fictitious force in classical physics, it arises from nowhere and disappears to nowhere. The force is much easier to describe from an inertia frame of reference but in classical physics there is supposed to be an absolute frame and this shows the problem. If I pull an absolute frame then I get an infinity.

Structurally gravity works the same way the force while measurable disappears to nowhere. It's the problem Bill G is struggling with it all sort of makes sense until you try to follow this to an absolute reference and it all blows up in your face and you will get infinity or zero.

What Bill G has not cottoned onto is when he is standing on earth he is in free fall it is just the fall is opposed. When he drops the gravimeter into free fall it will read zero because it is no longer opposed. You can either argue gravity is a fictional force and the gravimeter is just reading the fictional force or you can go the frame of reference is different route like your centripetal acceleration.

yes the centripetal force is real.
it is pushing against gravity.
force vs force.

I know what the problem is that you are struggling with.
its the forces at play.
you cant see the forces or measure the forces so you think that they are not REALLY there.

heres a good experiment you can try for yourself.

get your iPhone out and open up the accelerometer that
is causing you all this grief.

climb up to the top of a ladder and keeping your eyes on
the accelerometer step briskly off the top of the ladder
observing the indicator on the acceleration guage of the
app.

dont look at anything else , only the accelerometer.

1) did the app register an acceleration?
2) did the ground move towards you when you steped off?
3) what pushed the ground up towards you?
4) what pulled you towards the ground if nothing pushed the ground towards you?
5) was it a real force that caused your feet to land back
on the ground?
6) if you didnt measure any acceleration then you didnt accelerate , correct?
7) should you now try the experiment using a tall building
knowing the results from your initial experiment?

You turned this into what I believe ... I can work in many different frameworks and they all have problems. Again the function of physics is to be useful and predictive not worrying about what is believed.

The problem in classical physics framework is exactly as you have worked out you get forces you can't see or measure and the results of those forces can go to infinity or zero. Yet you have an effect that is real and observable.

To layman that may not be a problem by in physics that is unacceptable because it means we are missing something.

orac

when you are sitting in a chair and you stand up.

1) is your body applying a force that causes you to
stand?
2) if so is that force being applied against the earth
or against gravity?
3) if the earth had no gravity field would your body
need to apply a force to.

a) the earth
b) the atmosphere
c) the gravity field of your body
d) none of the above

I can't answer you questions without nominating a framework they differ markedly depending what you choose.

1.) Is the same for all frameworks .. YES

The rest depends which framework you choose.

You have agreed on the problem classical physics runs into with "hidden" forces and GR gives us a different way to look at things but it changes some definitions.

GR may not ultimately be exactly correct but it is giving us more answers with fewer "hidden" forces and you can resolve all the answers back to classical physics, so why wouldn't we use it?

what are we missing orac?

pick a framework and answer the question.

the only forces we are discussing are gravity and forces due
to motion.

do you require that a force actually be seen?
can you see any force at all?

tell me which force is not a hidden force?

have you ever seen the force that is the result of a
baseball bat hitting a baseball?

you have never seen a force is a truthful statement.

Go back to the must cut down version of this which is Newtons bucket argument

https://en.wikipedia.org/wiki/Bucket_argument

The curvature of the water surface of the spinning bucket makes perfect sense to anyone in the bucket. It makes absolutely no sense to someone standing outside the bucket where you ask "rotation relative to what?"

You now need to make the rotation complicit to every body in the universe and those forces must transfer INSTANTLY no matter how far away the body is.

Yes of coarse you can how else would you measure it. Seen does not mean human eye type stuff it means you can measure cause and effect.


Every other force except our four fictional forces in classical physics are directly measurable. Our four problem forces in classical physics are sometimes measurable in some situations but not all.


What I have never seen is a baseball fly off by itself without being able to attribute where the force came from. In your classic physics world gravity is dragging the ball down, so where is it getting the energy?

Now I need to give you a warning if we go down this path you are going to end up needing all the energy to be present at the start of the universe. This may come into conflict with your religious beliefs.

the reason the people outside the bucket dont understand
is because they do not understand how liquids behave and
react to rotational forces.

what has this got to do with what we are discussing?

which is how you are not accelerating while you are reading this.

lets discuss these fictional forces.

name them.

In classical physics you need to create four fictional forces. We could use term observational forces if you like, which is what we do in Russian physics, as fictional has bad meaning. The forces are real in certain frames just can't be brought back to a universal reference frame.

Centrifugal force
Coriolis force
Euler force
Gravitational force

The first three are inertial frame issues being translated back to the static global frame classic physics demands. Gravity is problematic because we don't know what causes it and it comes from nowhere and goes to nowhere.

The first three cause problem because you can't find a zero reference. For example you feel the forces if you spin on earth yet earth is spinning itself. The earth is also moving around the sun and the sun and earth moving around the galactic center. Then that whole galaxy is also moving.

Now try and construct the force with all those motions back to some stationary point in space that classical physics says is possible and I believe you are saying.

It's easy if you just use the local reference and don't ask what's it pushing against, which is how we hand wave at school level

By default in doing the above we just went into relativity in a rather sneaky way. However classic physics demands a global reference frame so convert those forces to a global frame. The other part of the problem is that force must also be INSTANT no matter how far away.

In case you don't know Newton's gravity law's requires instant transfer for the same reasons.

not sure about the euler force as it only deals with
reference frames.

centrifugal force can certainly be measured.
Coriolis force can certainly be measured.
gravitational force can certainly be measured.

if a force can be measured then its not fictional.

it is a word that is used to describe an effect.

I was thinking you were going to include centripetal force
because you were saying that it was a fictional force earlier
and although the words "centripetal force" and centrifugal force are similar they do have opposite meanings as one is
the inward acting force and the other is the outward force.

some idiots still believe that there are no outward forces
in rotation.

it would be a true statement to say that there are no
inward forces in rotation because there are no inward
forces in rotation.

note: when I say outward force I mean a direction away from the center of rotation.

if there were no outward forces then centrifuges would not work.

satellites would not orbit the earth ... etc.... etc.

can you name a force that cannot be measured?

All of those forces can only be measured by the person on that reference frame they can't be measured and make no sense to someone not on that frame. To a static person the force looks like it comes out from some point in space and disappears off at infinity with a whole pile of other infinities along the way.

That was the issue Bill G was having, Gravity can only be measured via a reference to mass. The moment we put that mass into what Bill G referred to as free fall it disappears as it's a non inertial reference frame, Newtons laws implode.

The problem is Newtons laws (classic physics lovelies) are only valid in inertial frames of reference ... that is ones not accelerating. In accelerating frames, like your rotating one, or Bill G's "free fall" you have to try and patch the laws if you want to keep them. It doesn't seem to worry you that you can't bring the forces back to static reference frame and in that regard your physics looks more and more like relativity which apparently you think is wrong and gave Einstein a spray.

In your post above you almost appear to be arguing for relativity and against classical physics and it's universal reference frame?

You can't have Newton's laws and relativity forces the two are incompatible that is what I beat Bill G over the head with.

So again I ask the question what framework are you using?

Lets give you the general definition of relativity physics .... don't confuse this with GR and Einstein
(https://en.wikipedia.org/wiki/Principle_of_relativity)

So do you believe in relativity as described above and not classical physics? It has to be one or the other you can't have both.

There are many versions of relativity yet layman seem to think all of them are Einsteins versions.

Lets try one of the simpler versions of relativity, so I am going to give you Galilean relativity to look at which as you will see dates back to 1632

https://en.wikipedia.org/wiki/Galilean_invariance

Is that close to what you want, its a sort of fusion between Newtonian physics and relativity and is probably the closest thing to classical physics with relativity mixed in.

your entire post seems to give some value to reference frames
as if a reference frame has anything to do with reality.

if a man on the ISS is in free fall then the ISS is also
in free fall , both are accelerating.

the only way that you can orbit a planet is if you travel
around the planet in a circular path , and in order for
you to travel in a circular path you must accelerate away
from the straight line that your space ship wants to travel along.

can you imagine how much energy would be required to establish and maintain a orbit around the earth if the earth had no gravity?

the space ship that you were orbiting the earth with would
need to supply all of the energy for every split second of
course correction as it traveled along its orbital path and
it would have to correct its course every split second if
you wanted the space ship to maintain a precise orbital altitude for optics or whatever reason.

you may be able to say that the man inside the ISS is not
in free fall if your brain only accepts the things you can
see or feel or measure and you are in front of him seeing
that he is not falling anywhere , and you can reach out and touch him and he's not moving away from you and you could even measure his fall if he was falling , so in his frame of reference and your frame of reference he is not falling.

both of these frames of reference will give false information.

still he and the ISS are in free fall this is evident because
the ISS is not gaining or loosing altitude.

a frame of reference is just another way of thinking about or looking at a physical occurrence and has nothing to do with
physical occurrences.

so frame it any way you wish , the man and the ISS are in
free fall.


and free fall is simply put nothing more than a balance between the forces that are acting on an orbiting
object.

you keep pointing to accelerometers to somehow prove that
you are correct when in fact the accelerometers prove that
the man in the ISS is in free fall by the zero reading he
would see on his accelerometer.

he and the ISS have achieved a balance between the forces which is why he and the ISS do not move closer to the earth
or further from the earth.

why do you think the men moved when the ISS boosted / accelerated to gain velocity?

it was because the ISS was gaining velocity / accelerating
to maintain a certain orbital altitude.

but the men inside were not accelerating with the ISS
until they held onto the ISS.

and as soon as they let go of the ISS the ISS began moving faster than they were moving.

I think that you are giving waaaay to much importance to
false things such as reference frames.

its almost as if you are trying to use them as tools to
change the reality of physical occurrences.

that wont happen.

within the context of what we are discussing can you point to where one of Newtons laws would implode?

my thoughts are that either your calculator , your math
or your reasoning is distressed if you have found a flaw in one of Newtons laws.

lets discuss this.

Newtons laws ASSUME an inertial frame he defined that condition it is covered here ... read it

https://en.wikipedia.org/wiki/Inertial_frame_of_reference

Galileo had everything Relative in his physics

Newton needs to fix everything to a single position he does this


So Newton assumes some star or point or something is not moving and thus he deals with forces coming from movement as fictional.

WHY DID HE DO THIS?

The answer is energy ... Newton is all about energy what he is trying to do is exchange energy in all references.

The problem he is struggling with is if energy arises in a relative frame (that is locally) how does it relate to something else. Take a spinning weight I allow the energy in the forces to create locally but now I create another spinning weight. When I smash the two into each other how does the energy of one system relate to the other I need some common reference.

So Newton made his first law ... READ IT VERY CAREFULLY.

First law: When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.

Newton is well aware his laws won't hold in accelerating (non inertial frame) he assumes that an inertial frame must exists and asks you move the calculation to there and bring the acceleration effects in as fictional forces. Don't complain to me about it ... that is what Newton did and so go complain to him. Your teacher at school probably left that bit out. Newton goes into elaborate detail about how to find an inertial frame but no layman ever bothers to read his works.

The bit layman never seem to get Newtons laws are not valid in accelerating frames they were never intended to be (AKA the 1st law). Newton isn't stupid almost any calculation in an accelerating frame is going to violate them. That is what happened to Bill G and I was curious to see if he knew why. His argument was you simply find a nice inertial frame move all the calculations to there include all the fictional forces and there you have problem solved. The sting in the tail is if there isn't at least one point in space that is stationary you aren't going to be able to use it on calculations on the universe as a whole because you can't satisfy the first law.

What happens in versions of relativity is you are going to link energy using a different reference not universal co-ordinates like Newton did. Most versions of relativity will link it thru Mass ... Einsteins version is E=MC2. That allows you to connect energies in relative frames and explains why the energy in one local system is related to another in always the same way.

There is nothing to really discuss this is all very basic, just layman never seem to get it that Newtons first law restricts where you can use the laws from ... that is it's intention by design.

So are you happy with all that, or do you still want to try and insist you can use Newton laws in an accelerating frame and we throw Newton's first law out?

I don't recall saying anything like that. As I recall you talked about the accelerometers on the ISS and what they would read. I clearly pointed out that they would read zero. You then took it and tried to show that I am so dumb that I can't say anything right. The fact is that I was completely correct. The accelerometers show zero acceleration. That is because they are in free fall and there are no forces acting on the separate parts of the accelerometers. You asked me to define free fall, but I don't think it is my job to teach you. You should study up on the subject and find out for yourself instead of just trying to show how smart you are.

Bill Gill

No I know you aren't dumb I was checking you understood what was going on and that a free falling frame has two interpretations and I asked a question. You answered the question with a reference to "free fall" and I asked you to define it so you could clearly see a problem.

You like the good little classic physics boffin took the normal stance on the problem but none of your classic laws will hold in that frame and you can't create a valid proof.

As I said this goes all the way back to the Newtons bucket argument and there are no laws in classical physics that will allow you to resolve this. As per Mr mach I will always be able to find a frame in which I can ask accelerating/rotating in respect to what?

Newtons answer is take a frame not on the "free falling frame" and resolve from there and you will have to introduce gravity as a fictional force in that situation which is what I was trying to make you do. That is what the Newtonian framework says you have to do via Newtons first law. This harks to what I said way back if we go much further we will need to talk about fictional forces in classical physics.

I am assuming here you will not do what Paul did and get confused with the layman definition of the words "fictional forces" or "pseudo forces". It is a translation of Newtons choice of word to fix frame references in Principia Mathematica and what it means beyond that is conjecture.

Your answer is correct in THE CLASSICAL PHYSICS FRAMEWORK with gravity injected as a fictional force that can't be measured in a free falling frame. The extension of that is you can't use a gravimeter in a free falling frame if it is using the laws of classical physics to measure gravity. You accelerate such a device up/down in any way it will miss read. Your answers on that subject totally perplexed me but lets ignore that, I am not trying to upset you and it's a side issue.

Bill G you sort of claim you believe in GR but don't find your answer somewhat problematic or that you at least need to qualify it?

I asked the question "can you measure zero force and yet be accelerating?" because I know the answer to it needs a framework and was trying to get you guys to see that.

Bill G you said and still insist ... that you can measure zero force and yet be accelerating .... NO QUALIFICATION OFFERED.

It isn't the measuring zero I am asking you to look at BUT the accelerating bit ... you focused on the wrong bit.

MY FULL ANSWER: YES in classical frameworks and NO in relativistic frameworks and for someone with your intelligence it shouldn't be that hard to know why.

The problem boils down to should I trust the accelerometer or should I trust what is inferred by classical physics laws. I am pretty sure you know what GR does and we change to "proper acceleration".

When I ask questions rather than give an answer there is usually a good reason, and yes they are often loaded

Most of the time what you see as attacking you is me simply asking you to consider there is a different valid answer at least qualify your response. There are heaps of things in physics with multiple answers, we can't distinguish between unless you identify the assumptions.

I have asked repeatedly can we get what framework we are using for this discussion because there are many conflicting answers to this stuff. Paul appears to be using some form of relativistic framework (no fictional forces) and Bill G is using classic physics (fictional forces) and somehow I am supposed to relate discussion to you both.

There you go again! I specifically addressed only the question of what the accelerometers on the ISS would measure. My answer had nothing to do with any reference frame. It works for both Newtonian physics and GR.

You may see what you say as a teaching experience. I see it as an attempt to show how much smarter you are than anybody else. If you are really trying to teach us something you might try explaining what you are trying to teach.

Bill Gill

Bill G please look .... after your zero answer ... I said.


I was agreeing with you and simply wanted to extend the discussion about the zero ... and now you give us the fact that you will get a zero on two different frameworks for two different reasons ... TADA.

Apparently in trying to get you to clarify that fact which you only now volunteered you saw it as being smart. I actually alienated Paul with that comment. Really I meant the word logic rather than intelligence but I missed the translation, and Paul had far more complain about than you. He gave me a spray about it so I didn't bother addressing.

I asked you to define "free fall" because to describe it between the two frameworks is rather different isn't it. I was not being smart or cute with it.

I am happy just working with what you guys know, and am happy not insisting on answers because every physics framework is ultimately broken and I certainly can't give you a "right answer". I will give you a guarantee I will never insist you are wrong unless you violate the framework you are working in, or try and take the framework somewhere it breaks.

I now get that you thought I was saying the answer wasn't zero, when I was really looking for more about the framework hence the question rather than an answer.

We have multiple parties in these discussions, so if something comes across like above please just pull me up and ask what am I really asking. I try to consistently answer any serious question asked to me, although some test my patience with stupid questions they don't want answered. Often I am trying to frame one answer in reference to include the other party. You and Paul appear to be on vastly different frameworks, he really doesn't want fictional forces and comparing answers is therefore tricky.

why cant you just answer a question and stop at that point
soon afterwards.



1) we are discussing why you are not accelerating.

2) in the context of (1) above , where do newtons laws implode?

without drifting off to the vast expanse of the cosmos
and without reducing everything down to an unknown point
in the cosmos to use as a starting point to measure from.

please try to comprehend that the vastness of the cosmos
is not important when calculating a physical occurrence
that is local.

and deliver a answer as to where newtons laws break down
when you are trying to calculate why you are not accelerating.

SHOW ME THE MATH ...

and uhhh , I sense designer math coming into play.

as a matter of fact lets just give you a short test.

if a 1 kg mass were placed in a level to the ground
centrifuge 1 meter from the center of the centrifuge.

note: the mass is not attached to the centrifuge or the rotor.
and is being held in place only by its own weight (the force of gravity).

also , the mass is a cube , 5 cm x 5 cm x 5 cm
(to prevent you from using a ring)


1) at what velocity would the mass begin to move away
from the center of the centrifuge?

2) why did the mass move away from the center of the centrifuge and not toward the center when the centripetal
force acting on the mass became large enough to cause the
mass to move?

(because centripetal force acts toward the center of rotation)

3) knowing now that a mass will travel in a straight line
unless pushed or pulled by a force that is pointed in another direction other than the direction that the mass is traveling.

would you agree that the 1 kg mass moved away from the center of rotation because the force that held it in place was less
than the force caused by the rotation (centripetal force)?

4) knowing that the mass did move away from the center of
rotation would you agree that the force ( gravity ) that
held the mass in place was not strong enough to continue
accelerating the 1 kg mass in a circular path because the
angular velocity of the 1 kg mass became to great for
any angular acceleration of the 1 kg mass to occur?

I would like to read your answers to all of the above
questions so that I can form an opinion of how your brain
handles questions.

this will help me to understand how your brain functions
so that I can discuss things with you on your level.

That is a point I have been trying to make to Orac. He won't just explain one point. He tries to show how smart he is by extending his reply out of all recognition in the context of the original question.

Bill Gill

You almost have that correct in a round about way but you still need a little more input in order for me to fully
judge your reply , let me give you 10 or 20 more tasks to perform if you want to continue with the discussion on those grounds but before we can continue and before I can answer your reply you must first read the following books and web pages so that you will have some background on the subject.

Hint: you should begin by reading the internet.
heres a web site that might be of some help and could
possibly lead you to the internet.

https://en.wikipedia.org/wiki/Internet

then to further your understanding you might want to
read the books at the world library just to make sure that
you have read all that there is to read you may not need to
read all 3 million books but I would prefer that you did.

http://www.worldlibrary.net/

Extended Hint: once you have read everything and if we are still alive and
you can remember what you asked me , I will ask more questions
and assign more reading for you , surely there will be more books by the time you finish.

It has nothing to do with being smart .. please look up at the question posed in this post ... that is called CONTEXT.

Do orbiting bodies accelerate?

The answer is YES or NO depending on the framework you use ... WE ALL AGREE ON THAT ANSWER TO THE QUESTION NOW

It's sort of a silly question unless you isolate a framework. Now if I had have just said outright it's a stupid question I would have also been told I was being smart. Oh but wait I sort of did say that to Bill S as my first comment which I was trusting he would get as me not being smart but prompting it's a stupid question. I even gave details of framework switches he had made under that.


So I answered the question DIRECTLY ... but then Paul and later Bill G enter ... please review the thread from the top and what happened from there .... AND YOU BLAME ME.

Basically there is nothing I can do that won't be wrong. As for you two, there is never anything you are ever wrong on. I do find you both funny, in you concentrate so heavily on arguing me, you forget what the argument is about.

The ZERO wasn't answering the question posed. I wasn't being smart, or discussing anything beyond the question asked

Had you even realized we now have actually answered the OP question asked now?

I answered the question correctly in one post, and then dragged you two kicking and screaming to the same answer .... THE END.

You get the irony of you two complaining that it was me who put you two thru a whole pile of not needed discussion. Bill G knew the answer to the question but obviously decided just to answer the part about the accelerometer, so why don't you complain about him Paul? Bill G why aren't you complaining about Paul, he was the one that wouldn't accept the answer we have all now come back too? Bet I don't get an apology for wasting my time from either of you.

So stop complaining .... we all got there .... next thread please ... OP question answered and agreed by all after a lot of wasted time.

Orac , you are totally wrong and totally wrong.

heres the OP and there is NOTHING MENTIONED ABOUT A
REFERENCE FRAME OR A FRAMEWORK !!!!



your answers ... all of them are wrong.

I answered correctly.

I am really curious how you would calculate a physical occurrence of a orbiting body using your non classical physics that you hold so dear.

but I think you said something about your non classical forms of physics not believing that a orbiting body accelerates
or something like that , and later you claim that newtons laws of motion implode ... haaaa

since your non classical physics cant even calculate something
as simple as the reasons why an orbiting body orbits then why
should people who look at the occurrences in the physical world using the tools of classical physics to calculate those
occurrences ever even have a need or desire to change the
tried and true tools that they use that have never failed them.

I honestly want to see your maths and an explanation of the
maths showing why a object orbits.

otherwise your just talking.
nothing more , nothing less.

Paul, I'm very happy for you to quote me, but using red ink is contrary to my posting ethics.

Hehe it's just dawned on Paul what just happened an now wants to re-open it. The trick Paul is to worry less about me and more one the argument itself.

I don't want to be accused of giving you information you don't need, so the the simplest answer to all you other stuff is thus

Answer: Follow how the other frameworks define things. It's like metric/imperial you simply convert between them, sometime what you are seeing as a different answer isn't, just like values in kmph don't equal mph. If you claim they are wrong then you must be wrong as well as you give the same answer. In fact every valid physics framework gives the same answer for this question and all agree with observed measurement.

Calculation: The calculation in any valid framework will look exactly the same just in different units so it's a waste of time to do it. You will get an accelerometer will read zero for reasons within the framework which is what is measured.

Paul if you still really want to see the calculation, write out your calculation and pick the other framework and I will write the conversion next to your figures. That will minimize me wasting time.

So once again this thread is done every framework gives the same answer just expressed in different units and discussion is pointless.

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Wile E


(a) if you use the correct units in math you will get correct answers to the math , there is no sometimes in math.

(b) then every valid? physics framework uses classical physics
math and not the fake BS math to answer this question.



that is complete BS , a laser accelerometer that measures acceleration between the ISS and the earth will measure a constant acceleration of the ISS as the ISS orbits the earth.

and this measurement of acceleration ( that your brand of BS physics ignores ) will be the same measurement that classical physics measures with its tried and true math.



LOL , dude at some point in the future your going to need
to be capable of choosing the correct formula yourself when
you need to provide a answer ... you wont always have knowledgeable people around who know which formula to use.

and besides Im under the impression that you don't know how
to do the math and that is the main reason you chose the BS physics vs actual physics in order to avoid things such as classical physics math which doesn't accept BS answers.



looks like Newtons laws and classical physics are the
only ones that remain standing at this point

while any implosions that have occurred have occurred
within in the realm of your BS physics.

Dare dego, forte loras in erro. Demaint loras, dema trux, fullo causa 'n ens an dux!

quia non est responsum
Firmabo super te meliorem doctrinam
Numquam enim succumbet, falsam doctrinam

orac , I was saving this , but since you bailed ...

did you question why the ISS boosted?
was it because the ISS never did accelerate towards the earth and never did lose some of its orbital altitude?

or was it because the ISS is in constant acceleration towards
the earth and did lose some of its orbital altitude and the
boosting brought it back to the proper angular velocity
required to maintain the desired orbital altitude?

I know Im saying this to the back of your head as your leaving
the discussion but hopefully even as you are leaving you can still hear the questions that you cant answer because your
brand of physics chooses to dictate physical occurrences rather than to observe and measure physical occurrences.

The ISS was boosted because its orbital velocity had been reduced and the orbit had become lower than they wanted/needed.

The reason its orbital velocity was reduced was due to air resistance. We talk about the top of the atmosphere as if it were a fixed place. Below that point is atmosphere, above it is none. In fact it just slowly fades off until there is a height that we can say the presssure is too small to measure. It is still there and it does produce a small drag on the ISS and other satellites in LEO (low Earth orbit). So they occasionally have to boost it to get it back to the correct altitude.

Bill Gill

Quis est homo monotonus
Qui cotidianum dronus?
Rogo ut abiret eum,
Ut pacem sempiternam mecum.

OK, I know the last two lines don’t rhyme, but it’s closer than most Latin verse.

yes that is correct Bill , the orbit had become lower because the orbital velocity had decreased.

this also means that the ISS had accelerated closer to the
earth.

the reason that the ISS accelerated closer to the earth is
because the orbital velocity of the ISS decreased due to
the drag caused by air resistance.

this caused a resultant lowering the centripetal force that is caused by the angular acceleration of the ISS that acts against the force of gravity .

which is what I am trying to get orac to understand.

Your mistake is you seem to think I care, or what you say matters .. I have better things to do with my time

Poor Orac can never get anything right, and he discusses things way beyond what is needed, and he is a bad person who kills GOD.

Discuss it with Bill G he agreed with my answer, and you both agreed you each only discuss things with the "right detail". Get Bill G to explain it to you, I am happy to go with whatever he says

In the meantime, I am sure physics is quaking in it's boots that Paul has proved it all wrong. It's already trembling with Marosz who has done the same, I am sure it is going to fall over any moment and I am out looking for a new job.

sorry to see you leave again orac.

but that's a good idea you had about discussing this
with Bill G.

Bill G.

I believe know that orbiting bodies DO accelerate
and Im prety sure that you do to.

if so then we can end this one on a happy note
unless orac really hasn't left again.

even then theres no real point in carrying it further
would you agree?

or we could agree with orac to cheer him up.

Nope I am definitely out, this guy on the internet proved Einstein wrong and they are closing our whole department. I know when I am beaten, we all know the guy on the internet is always right.

Many jobs going in your religion?

no worries orac , your job may be going but science itself will
greatly benefit as the sensible people who avoided physics
and its current path down the fantasy highway lined with mirrors and illusions and magic tricks to entertain and
light the way to help the gullible find their dictated way and enjoy their trip while the sensible people were forced to line the highway as the performers presented their magic show of illusion and trickery wondering when the show would
end so that they could walk out without applauding the antics that they were forced to observe can then enter into a place of scientific higher learning that doesn't more resemble a school of art and magic.



classical physics and actual science is a discipline
unlike the new BS physics and BS science religions that have surfaced recently that you were force fed while attending whichever BS school that you attended.

and don't worry orac , teachers can learn also.

just ask your newest students when you have difficulty understanding reality.