How long is an instant?

[Mart]

When you throw a stone vertically it reaches a maximum height and so for an instant (I'm told) it has zero velocity. How long is this instant?

[JaKiri]

It is equal to 1/(infinity) seconds.

[ed84c]

is that not 0 seconds then?

[Mart]

It is equal to 1/(infinity) seconds.

 

Would that be zero?

[Dave]

Because you're talking about measuring time continously, you can't really talk about "instants" in time. That's the way I think about it anyway.

[Ophiolite]

If I could answer that I would know why the tortoise doesn't beat the hare..

[Jake712]

jakiri is correct, one can and will never determine how long that instant is. The value relies entirely on the sensitivity of the measuring device. It is the same concept as a board which measures 1.3 meters. That board, most likely does not have a length of 1.3 meters. Instead it has 1.345629876...ect meters. It all depends on how precise your measurements are.

Back to the case with the instant in time, a ball thrown up in the air has no definite begining and end to the time that it is moving. Just like the board, the ball could be moving at .0001nm per second, to small to be measured by anything that we have today, but it is still moving. The ball has a velocity of zero for as long as sensitive you measuring device is to when it starts and stops.

Therefore, to answer you question, the instant is, as Jakiri said, 1/infinity seconds. It cannot be measured ever.

[Mart]

It cannot be measured ever.

 

So if i was to say that it was less than 0.1s and more than 0s would that be incorrect?

[JaKiri]

So if i was to say that it was less than 0.1s and more than 0s would that be incorrect?

 

Replace the 0.1 with any positive real number and that's true as well.

[JaKiri]

If I could answer that I would know why the tortoise doesn't beat the hare..

 

The definition of relative motion.

[Mart]

Replace the 0.1 with any positive real number and that's true as well.

 

But if I replace it with say 100 then wouldn't it be true to say that 01. would be closer to the value of the instant which after all you originally said was INYHO 1/infinity?

[Mart]

The definition of relative motion.

 

Or possibly a definition of relative notions.

[JaKiri]

Or possibly a definition of relative notions.

 

Or a definition of relative ootions.

 

I think we've reached the limit of this trend.

[[Tycho?]]

Does anybody remember a paper published a few years ago, some nobody saying that time was not quite what we thought it was. I think one of his ideas is that an "instant" is necessarly a human construct, and that thinking of time as a number of instants is inaccurate, and instead time is continuous, or something.

 

Found some things on it. I dont have time to read it like now, so I dont know if it contradicts my post or not.

 

http://www.eurekalert.org/pub_releases/2003-07/icc-gwi072703.php

http://en.wikipedia.org/wiki/Peter_Lynds

[Guest Mr.Therefore]

When you throw a stone vertically it reaches a maximum height and so for an instant (I'm told) it has zero velocity. How long is this instant?

 

It has no duration, as implied by Newtons III Law.

 

The essence of "an instant" is "one inertial state of an object that moves across a space".

 

Break the words apart: "in" "stunt". "Stunt" imples no movement. The word "stance" implies firmness.

 

An instant or instance of motion is meant to imply an inertial state, meaning a zero velocity state of the stone.

 

There are three periods of time to point out: the time the stone travels vertically, the time the stone is at rest and the time the stone drops.

 

Gravity creates constant deceleration in the first time frame and constant acceleration in the third time frame. We can easily measure the lengths of these two surrounding periods, because the change of position of the stone can be corelated with a time instrument. But the stone detected to be at rest has no change of position, so this makes it difficult, especially when this rest state is perfectly tucked between two acceleration states.

 

Newtons third law implies the time of the rest state has no duration, because "action" and "equal and oppposite reaction" is simultaneous. If action and reaction were not simultaneous (instantly) no two things could interact, because they wouldn't be touching, and therefore no change of direction can occur.

 

Something is so hard inside things that interact that there ceases to be compression, making Newtons third law an indisputable fundemental that is always implied.

 

Waves are based upon instants like indefninte points make Euclids line.

[Panic]

Here is a good example of instant.

 

if we shoot 6 million frames of film for a 1 second interval of a bullet frying accross the camara lense.

 

each frame would represent 1second/6000000 = 0.16667e-6 seconds or 0.16667 micro that is pretty fast ...

 

if we only play back thos frames at a rate of 10 frames per second for only 1 second we have focused our observation at only 1.67 micro second in time the bullet would appear to have slight motion slow but very slight.

 

assuming we could play that on a big screen.

 

now we take another 6 million of that big screen that is playing at 10 frames / seconds

 

we now would have 2.7778e-15 second per frame..

 

playing back only 10 frames per second would result in a bullet that appears to be in suspended animation. no motion what so ever.

 

we could continue to do this till our eyes turn blue but after a sertain point the results would be identical further reducing the observation time would not serve a purpose.

 

In the world of infinitly small, infinite measurements there comes a point where (change in velocity)/(change in time) ~= "0" wich tells use that Velocity at that point is constant.

 

but how we choose to defind that Delta is up to the observer.

How close to "0" ~= "0"

1 m/h ~= 0 when you telling a cop you did stop at a red light! is close enough!

while at the same time

.000 001 ~= 0 if you are talking about fre falling object.

 

So in summary the value of instant is where you as the observer can say

 

"close enough!"