# If we had no memory, would we observe motion?

#### brum

if we had no memory, would we observe motion??

would we observe motion if we have no memory??

i.e. a ball rolling on a table -- if we had no memory at all, then would we be able to remember that an instant ago, the ball was a little over there?

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#### MrCaN

Would we be able to make a ball?

#### Evil

without memory we wouldnt have evolved to make the ball

#### eNtRopY

Originally posted by Evil
without memory we wouldnt have evolved to make the ball
Well, let's suppose he is asking what if an individual had no memory; would he or she be able to observe motion?

The answer is no.

Remember, velocity is the first derivative of position with repect to time. The definition of derivative of a function is:

dx/dt = lim T-->0 { [x(t+T) - x(t)] / T }.

We see that such an expression requires a minimum of two points in time. Without memory of a previous instant, there can be no comprehension of velocity.

Here is a more illustrative example. Imagine viewing a movie of a ball rolling down an incline frame-by-frame. Now imagine viewing a single slide of that movie. Without at least two slides, there is no appearance of motion.

eNtRopY

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#### MrCaN

Enntropy I have to take a diffrent stance, I think the person could observe motion. For one, for this person to live for more than a few seconds they would have to have some reconition of the world, and second we see by a build up of photons on the eye, so a person could observe something moving faster than the refresh rate of there eyes.

#### climbhi

Originally posted by MrCaN
Enntropy I have to take a diffrent stance, I think the person could observe motion. For one, for this person to live for more than a few seconds they would have to have some reconition of the world, and second we see by a build up of photons on the eye, so a person could observe something moving faster than the refresh rate of there eyes.
Good point, but except for objects which are close up, you really have to be booking to get something to blur becuase it's moving faster then refresh rate of the eyes. Now the question is though, would he be able to recognize a smeary object as having motion, or would they just think that's the way the object looked naturally? I think the later, what about you?

#### MrCaN

I really think this is a needless argument, because one could never find a true answer, and it should be placed in a diffrent category, like phylosophy.

#### Loren Booda

Perhaps the memory is retained in the object as much as the observer. A question remains, though: how does our consciousness change from one spacetime event to another - quantum uncertainty? Between two recorded events, physics maintains as a transient, probabilistic dynamic. There are then the two states of change; observation, and statistical continuity between observations.

#### Eyesee

Originally posted by MrCaN
Enntropy I have to take a diffrent stance, I think the person could observe motion. For one, for this person to live for more than a few seconds they would have to have some reconition of the world, and second we see by a build up of photons on the eye, so a person could observe something moving faster than the refresh rate of there eyes.
How can a person observe motion if he had no memory? Every moment to the next would have no continuity for this person so as far as he's concerned the world would always be at a stand-still. It's like asking "can a slide projector show motion of the pictures"? Obviously not. Can a movie projector show motion? Obviously so.

It's not a coincidence that movies are called motion pictures in case you didn't notice.

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#### STAii

Enntropy I have to take a diffrent stance, I think the person could observe motion. For one, for this person to live for more than a few seconds they would have to have some reconition of the world, and second we see by a build up of photons on the eye, so a person could observe something moving faster than the refresh rate of there eyes.
I wouldn't consider having motion blur on a single frame as 'motion'.
How would you know wether the motion blur is motion blur due to motion or motion blur that is drawn (on a paper for example) as motion blur ?

#### MrCaN

Originally posted by Eyesee
How can a person observe motion if he had no memory? Every moment to the next would have no continuity for this person so as far as he's concerned the world would always be at a stand-still. It's like asking "can a slide projector show motion of the pictures"? Obviously not. Can a movie projector show motion? Obviously so.

It's not a coincidence that movies are called motion pictures in case you didn't notice.
A slide projector can show motion, Now try and follow me here, but what they do is tie a bunch of slides together and show them really fast, for identification purposes they call this a motion picture machine, but it is identical to a slide projector. And this just shows my point, in a movie you are watching thousands of still photos, but because they move faster than your brain can regester them, they look like they are moving, but in reality the pictures aren't moving, they just look like they are.

#### eNtRopY

Well, it is indeed true that our eyes integrate detected phonons over a period of time. So, if someone were to make an observation that lasted for an infintessimally small period of time, they might observe zero impinging photons. However, I think that our vision is "slow." Like you mentioned MrCaN, perhaps there is some mechanism in the human vision system that is similar to a refresh rate.

Anyway, to make this problem easier, let's suppose that the inherent "slowness" of chemical activity in the nervous system allows a person with no memory to at least perceive a single picture for an instant of time. Is there anyway, to observe motion without memory of previous instant? I have shown classically, that this is not possible due to the definition of a derivative, but let's consider relativistic length contraction.

If someone were to know the exact dimensions of an object at zero velocity, then he or she could compare these dimensions with the skewed dimensions of a moving object in order to realize that one object was moving with respect to another. Unfortunately, this scenario also requires memory. A person would have to remember the dimensions of an object in one inertia reference frame and compare them to those of another... not to mention the fact that the person would have to remember the laws of special relativity in order to make sense of these measurements.

The bottom line is that velocity cannot be measured an absolute scale. This means that if you want to detect motion, you will have to remember the conditions of the reference frame you are using for comparison.

eNtRopY

#### eNtRopY

Originally posted by MrCaN
A slide projector can show motion, Now try and follow me here, but what they do is tie a bunch of slides together and show them really fast, for identification purposes they call this a motion picture machine, but it is identical to a slide projector. And this just shows my point, in a movie you are watching thousands of still photos, but because they move faster than your brain can regester them, they look like they are moving, but in reality the pictures aren't moving, they just look like they are.
You are forgetting that each slide represents a set of position coordinates at a specific increment of time. Again,

v = dx/dt = lim T-->0 { [x(t+T) - x(t)] / T }.

So, for slide number 1, t = T; for slide number 2, t = 2T; for slide number 3, t = 3T; ad infinitum.

You have to remember a coordinate x(t) in order to compare it with a coordinate x(t+T) and make sense of the equation for velocity given above.

eNtRopY

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