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Some science to consider

tom67 said:
View attachment 2740600

that's interesting from a different perspective: Earth rotation. in theory the equator goes way faster than, lets say, Alaska. the 'speed' DIFFERENCE can be 600mph between countries, even within America. think about it. do you feel a speed difference between 30mph and 100mph when driving a car?
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I think Calvin is contemplating the constantly decreasing sampling rate.
 
Mr Creosote said:
The average LP has about 1,500 feet (460 m; 0.28 mi) of groove on each side. The average tangential needle speed relative to the disc surface is approximately 1 mile per hour (1.6 km/h; 0.45 m/s). It travels fastest on the outside edge.
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That would only be ~16.8 minutes per side and it seems to me an LP is ~22 minutes per side.
 
similost said:
I've always wondered why they decided to make the defacto speed exactly 1/3rd of 100 RPM?
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To match up the film with sound, a company called Vitaphone introduced a system that used a standard 3600 RPM motor to rotate a soundtrack disc. To make the audio last the same 11 minutes, the math dictated that the motor be geared down to 108:1. That gives us a rotational speed of 33.33 RPM.
 
Coolhandjjl said:
Just chance. Nothing calculated or scientific about it.
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I don't know.. Kinda hard to believe that..

So, since my mind is so inquiring, I decided to try that google thing...

33 1/3 or 33.33333333 was chosen to be easy for both 60 Hz power as in US or 50 Hz in most of the world. As a stroboscope could be easily made. 180 dots in a circle gave 33.33333333 on 50 Hz AC and 216 dots for 60 Hz. then RCA invented the 7 inch disc at 45 rpm.

And there you go.. .supposedly it all boils down to a strobe for speed.. WOW.. so glad, because all my tables have had strobes, and I like those :)

I think I like Tom67's explanation better..
 
tom67 said:
To match up the film with sound, a company called Vitaphone introduced a system that used a standard 3600 RPM motor to rotate a soundtrack disc. To make the audio last the same 11 minutes, the math dictated that the motor be geared down to 108:1. That gives us a rotational speed of 33.33 RPM.
Click to expand...
That actually makes sense :thumbsup:

VR
Andy
 
tom67 said:
View attachment 2740600

that's interesting from a different perspective: Earth rotation. in theory the equator goes way faster than, lets say, Alaska. the 'speed' DIFFERENCE can be 600mph between countries, even within America. think about it. do you feel a speed difference between 30mph and 100mph when driving a car?
Click to expand...

Ever heard of the phrase "inertial frame of reference"? What that means is that unless you are subject to an external applied force which creates acceleration you are in an "inertial frame of reference" and cannot detect the difference between any "velocity" that you might have.
If you are in a closed box you absolutely cannot tell the difference between any supposed "velocity" that you might have versus any other.
That's also what allows us to declare that gravity is not in fact a force as when you are in free fall and in your own particular inertial frame of reference you cannot detect it except by observing something in a different inertial frame of reference. In essence you are travelling along something called a geodesic where you are simply following the curvature of spacetime, and that curvature is created mostly by changes in, effectively, the rate of flow of time due to the presence of mass.
Really spooky stuff...
 
wyn palmer said:
Ever heard of the phrase "inertial frame of reference"? What that means is that unless you are subject to an external applied force which creates acceleration you are in an "inertial frame of reference" and cannot detect the difference between any "velocity" that you might have.
If you are in a closed box you absolutely cannot tell the difference between any supposed "velocity" that you might have versus any other.
That's also what allows us to declare that gravity is not in fact a force as when you are in free fall and in your own particular inertial frame of reference you cannot detect it except by observing something in a different inertial frame of reference. In essence you are travelling along something called a geodesic where you are simply following the curvature of spacetime, and that curvature is created mostly by changes in, effectively, the rate of flow of time due to the presence of mass.
Really spooky stuff...
Click to expand...

Not all that "spooky" and much is theoretical. Although it can be spooky in a good SF movie or TV series. :thumbsup:

From Wiki:

In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. It is a frame in which an isolated physical object — an object with zero net force acting on it — is perceived to move with a constant velocity (it might be a zero velocity) or, equivalently, it is a frame of reference in which Newton's first law of motion holds. [1] All inertial frames are in a state of constant, rectilinear motion with respect to one another; in other words, an accelerometer moving with any of them would detect zero acceleration.

It has been observed that celestial objects which are far away from other objects and which are in uniform motion with respect to the cosmic microwave background radiation maintain such uniform motion.[2]

Measurements in one inertial frame can be converted to measurements in another by a simple transformation, the Galilean transformation in Newtonian physics and the Lorentz transformation in special relativity. [3]

In analytical mechanics, an inertial frame of reference can be defined as a frame of reference that describes time and space homogeneously, isotropically, and in a time-independent manner. [4]

In general relativity
  • in any region small enough for the curvature of spacetime and tidal forces[5] to be negligible, one can find a set of inertial frames that approximately describe that region.[6]
  • the physics of a system[7] can be described in terms of an inertial frame without causes external to the respective system, with the exception of an apparent effect due to so-called distant masses.[8]
In a non-inertial reference frame, viewed from a classical physics and special relativity perspective, the interactions between the fundamental constituents of the observable universe (the physics of a system) vary depending on the acceleration of that frame with respect to an inertial frame. Viewed from this perspective and due to the phenomenon of inertia the 'usual' physical forces between two bodies have to be supplemented by apparently sourceless inertial forces.[9][10] Viewed from a general relativity theory perspective appearing inertial forces (the supplementary external causes) are attributed to geodesic motion in spacetime.

In classical physics, for example, a ball dropped towards the ground does not move exactly straight down because the Earth is rotating. This means the frame of reference of an observer on Earth is not inertial. As a consequence the science of physics has to take into account the Coriolis effect—an apparent force— to predict the respective small horizontal motion. Another example of an apparent force appearing in rotating reference frames concerns the centrifugal effect, the centrifugal force. (Inertial frame of reference - Wikipedia)
 
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