Re: [Vo]:weight and uniform motion on a horizontal surface

[H LV]

Galileo made the assumption when he argued for the equivalence of the
experience being below deck on ship at rest vs below deck on ship in
uniform motion. (see passage below). By omitting the rotation of the Earth,
Galileo was able to formulate a practical rule. Newton later elevated the
rule into a law of nature.
>From a purely experimental standpoint without knowing anything about
Newton's laws of mechanics or predicting the trajectory of an artillery
shell, it is possible with precise enough measurements to invalidate
Galileo's rule. I can't prove this, but I suspect Galiloe knew this might
be a possibility, but at the time he was more interested in arguing that
the rotation of earth did not lead to spurious predictions as was the
contention of people who insisted the idea of a rotating Earth was absurd.

"Shut yourself up with some friend in the main cabin below decks on some
large ship, and have with you there some flies, butterflies, and other
small flying animals. Have a large bowl of water with some fish in it; hang
up a bottle that empties drop by drop into a wide vessel beneath it. With
the ship standing still, observe carefully how the little animals fly with
equal speed to all sides of the cabin. The fish swim indifferently in all
directions; the drops fall into the vessel beneath; and, in throwing
something to your friend, you need throw it no more strongly in one
direction than another, the distances being equal; jumping with your feet
together, you pass equal spaces in every direction. When you have observed
all these things carefully (though doubtless when the ship is standing
still everything must happen in this way), have the ship proceed with any
speed you like, so long as the motion is uniform and not fluctuating this
way and that. You will discover not the least change in all the effects
named, nor could you tell from any of them whether the ship was moving or
standing still. In jumping, you will pass on the floor the same spaces as
before, nor will you make larger jumps toward the stern
 than toward the prow
 even though the ship is moving quite
rapidly, despite the fact that during the time that you are in the air the
floor under you will be going in a direction opposite to your jump. In
throwing something to your companion, you will need no more force to get it
to him whether he is in the direction of the bow
 or the stern, with yourself
situated opposite. The droplets will fall as before into the vessel beneath
without dropping toward the stern, although while the drops are in the air
the ship runs many spans. The fish in their water will swim toward the
front of their bowl with no more effort than toward the back, and will go
with equal ease to bait placed anywhere around the edges of the bowl.
Finally the butterflies and flies will continue their flights indifferently
toward every side, nor will it ever happen that they are concentrated
toward the stern, as if tired out from keeping up with the course of the
ship, from which they will have been separated during long intervals by
keeping themselves in the air. And if smoke is made by burning some
incense, it will be seen going up in the form of a little cloud, remaining
still and moving no more toward one side than the other. The cause of all
these correspondences of effects is the fact that the ship's motion is
common to all the things contained in it, and to the air also. That is why
I said you should be below decks; for if this took place above in the open
air, which would not follow the course of the ship, more or less noticeable
differences would be seen in some of the effects noted."

*Dialogue Concerning the Two Chief World Systems*, translated by Stillman
Drake , University of
California Press, 1953, pp. 186 - 187 (Second Day).

Harry




On Wed, Aug 17, 2022 at 7:35 PM Jed Rothwell  wrote:

> H LV  wrote:
>
> Lets assume the earth is not rotating.
>>
>
> Will our assumption stop it from rotating?
>
> WWII Admiral Willis Lee was one of the world's top experts in artillery.
> He would calculate battleship gun trajectories including the effects of the
> earth's rotation. He would include so many factors that physicists and
> other artillery experts said they couldn't keep up with him. He also won
> battles.
>

Re: [Vo]:weight and uniform motion on a horizontal surface

[Jed Rothwell]

H LV  wrote:

Lets assume the earth is not rotating.
>

Will our assumption stop it from rotating?

WWII Admiral Willis Lee was one of the world's top experts in artillery. He
would calculate battleship gun trajectories including the effects of the
earth's rotation. He would include so many factors that physicists and
other artillery experts said they couldn't keep up with him. He also won
battles.

Re: [Vo]:weight and uniform motion on a horizontal surface

[H LV]

Lets assume the earth is not rotating.
Harry

On Tue, Aug 16, 2022 at 3:17 PM Robin 
wrote:

> In reply to  H LV's message of Tue, 16 Aug 2022 14:38:42 -0400:
> Hi,
> [snip]
>
> You also need to take into consideration that objects in motion relative
> to the Earth's surface will experience more or
> less centrifugal force depending on their direction of motion relative to
> the rotation of the planet.
> All "stationary" objects actually experience a small centrifugal force,
> that slightly reduces their true weight.
> This varies with latitude, maximum at the equator, zero at the poles.
> It's the primary reason that the Earth is not perfectly spherical.
>
> >Hey vorts, this is a question about weight. No advanced physics is
> >involved.
> >Suppose you have a surface with built in sensors so it will tell you the
> >weight of an object placed anywhere on it.
> >Assume the surface is flat and level and the acceleration due to gravity
> is
> >everywhere constant.
> >Will the *registered* weight of the object be the same when the object is
> >at rest with respect to the surface
> >as when it is moving with uniform motion with respect to the surface?
> >
> >It seems to me that the object will effectively weigh slightly less
> because
> >it takes time for the object to exert its full weight
> >on the sensors. The true or full weight can only be ascertained when the
> >object is at rest with respect to
> >the surface.
> >
> >
> >
> >Harry
> If no one clicked on ads companies would stop paying for them. :)
>
>

Re: [Vo]:weight and uniform motion on a horizontal surface

[Robin]

In reply to  H LV's message of Tue, 16 Aug 2022 14:38:42 -0400:
Hi,
[snip]

You also need to take into consideration that objects in motion relative to the 
Earth's surface will experience more or
less centrifugal force depending on their direction of motion relative to the 
rotation of the planet.
All "stationary" objects actually experience a small centrifugal force, that 
slightly reduces their true weight.
This varies with latitude, maximum at the equator, zero at the poles.
It's the primary reason that the Earth is not perfectly spherical.

>Hey vorts, this is a question about weight. No advanced physics is
>involved.
>Suppose you have a surface with built in sensors so it will tell you the
>weight of an object placed anywhere on it.
>Assume the surface is flat and level and the acceleration due to gravity is
>everywhere constant.
>Will the *registered* weight of the object be the same when the object is
>at rest with respect to the surface
>as when it is moving with uniform motion with respect to the surface?
>
>It seems to me that the object will effectively weigh slightly less because
>it takes time for the object to exert its full weight
>on the sensors. The true or full weight can only be ascertained when the
>object is at rest with respect to
>the surface.
>
>
>
>Harry
If no one clicked on ads companies would stop paying for them. :)