Why can we see space, but not time?

[Jupiter60]

If space and time are really related, why is it that we can see space, but we can't see time?

 

[ZapperZ]

How are you able to see space?

Zz.

 

[Jupiter60]

I can see space right now. The space between me and my computer. I can see myself move through space, though not through time. I have to look at a clock to see my movement through time. Are space and time really related?

 

[Dale]

We don't see either space or time, we see light.

 

[ZapperZ]

I can see space right now. The space between me and my computer. I can see myself move through space, though not through time. I have to look at a clock to see my movement through time. Are space and time really related?

Actually, you don't see space. You see the object! And you do you know why you think you are seeing a 'distance'? Because (i) you have depth perception because of your two eyes and (ii) the light from the object reaches your eyes AT DIFFERENT TIMES! In other words, your sense of distance actually depends on some time differences! So if we apply your "logic" of seeing space, I could also argue that you're seeing time as well!

Zz.

 

[Chestermiller]

If space and time are really related, why is it that we can see space, but we can't see time?

By not being able to see time, I assume what you mean is that you can't see into the 4th dimension, even though you can see in the 3 spatial dimensions. This is because you are inherently a 3 dimensional being, and suffer from the physical limitation that you cannot see into your own fourth dimension. You can however see partially into the 4th dimension of other reference frames and objects that are moving relative to yourself.

 

[dipole]

You have to be precise asking these kinds of questions, and define what you mean when you say you can "see" space. Your eyes are able to gauge distance because of parallax - the image each eye sees is slightly different, depending on how far away something is. You measure distance, or percieve it, by measuring the parallax.

With time, you don't have a sensory organ specifically devoted to sensing time, at least not one you're so consious of as with your vision. However, you can feel the passage of time, you know that what you did this morning happened several hours ago, and that you went to sleep before you woke up.

You can "see" time by watching a clock, or water dripping, or anything which occurs in some regular way, but your eyes aren't directly meant to measure it.

 

[Emilyjoint]

We don't see either space or time, we see light.

mmmmmm...I don't think we do see light ! we see what light shines on.
I look at a candle and I see the flame because of light. I look from the side but I cannot see 'the light' from the candle pass me. If we could see light the space in front of me would be covered with criss cross lines of light ! Like a spider web or a mesh of some kind.

 

[ModusPwnd]

mmmmmm...I don't think we do see light ! we see what light shines on.
I look at a candle and I see the flame because of light. I look from the side but I cannot see 'the light' from the candle pass me. If we could see light the space in front of me would be covered with criss cross lines of light ! Like a spider web or a mesh of some kind.

I don't think so. Light is the only thing we can see. Light is what enters the eye. Of course you cannot see the light crossing in front of you... It has not entered your eye.

 

[A.T.]

The eyes see light.
The brain sees space.

 

[Dale]

mmmmmm...I don't think we do see light !

The function of the human eye is well studied. We see light.

 

[Dale]

The eyes see light.
The brain sees space.

That is a reasonable point. The brain "sees" time every bit as much as it "sees" space.

 

[A.T.]

The brain "sees" time every bit as much as it "sees" space.

And the brain doesn't need eyes to see space. People born blind grasp 3D space just fine.

 

[Emilyjoint]

The function of the human eye is well studied. We see light.

You have not given my quote as it was stated !

 

[Dale]

You have not given my quote as it was stated !

I quoted you exactly. Your quote, as it was stated, was wrong.

Our eyes see light, not objects, not space, not time.

 

[Jupiter60]

I don't think so. Light is the only thing we can see.

Not really. Well, not for most of us. There are some people though who have no more vision than to tell the difference between light and dark. Those people only see light. They have only light perception.

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

Those described as having only light perception have no more sight than the ability to tell light from dark and the general direction of a light source.

 

[Drakkith]

Not really. Well, not for most of us. There are some people though who have no more vision than to tell the difference between light and dark. Those people only see light. They have only light perception.

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

I don't know what you're getting at. The eye detects one thing and one thing only. Light. The brain then interprets the signals sent by the eye to form an image that you "see".

 

[Dale]

And the brain doesn't need eyes to see space. People born blind grasp 3D space just fine.

Another excellent point (you are on a roll A.T.!)

 

[Jupiter60]

I don't know what you're getting at. The eye detects one thing and one thing only. Light. The brain then interprets the signals sent by the eye to form an image that you "see".

What about shapes? The eye detects shapes. Shapes aren't light though. Though people with very severe visual impairment can't see shapes, only light.

 

[Drakkith]

What about shapes? The eye detects shapes. Shapes aren't light though. Though people with very severe visual impairment can't see shapes, only light.

The eye does not detect shapes. It detects the presence of light. Based on the pattern of signals your brain puts together the image, including the shape of things.

 

[Algr]

The eye can only sense photons that happen to enter the iris. It can detect the number of photons, (Brightness) some info about their frequency (Color) and also direction relative to the eye itself. (Shapes)

From there, the brain invents ideas such as "Space" and "Time" to develop a model of what it thinks is going on around you. Other senses like sound and touch can contribute to and extend this model. But you don't really "see" space; it might be better to say that you infer it.

 

[pbuk]

If space and time are really related, why is it that we can see space, but we can't see time?

Because although they are related, they are not the same thing. You may as well ask "if thunder and lightning are really related, why is it that we can see lightning, but we can't see thunder?"

 

[phinds]

Because although they are related, they are not the same thing. You may as well ask "if thunder and lightning are really related, why is it that we can see lightning, but we can't see thunder?"

Nice analogy !

 

[A.T.]

But you don't really "see" space; it might be better to say that you infer it.

The question remains why the concept of time seems different than the concept of space. Is it because they are objectively physically different, or because the way the brain works? Maybe it is because the thought process itself inherently requires the passage of time, and state changes over time.

 

[ZapperZ]

The question remains why the concept of time seems different than the concept of space.

But a priori, why should they be the same?

I wonder if an alternate universe, if these two concepts appear the same, someone's going to ask why they are not different?

Zz.

 

[Dale]

Is it because they are objectively physically different, or because the way the brain works?

They are objectively physically different. Space is measured with rods and time is measured with clocks. Since the same physical device cannot measure both it is clear that they are physically different.

The brain "sees" both space and time as you have eloquently pointed out, but that doesn't mean that they are both the same.

 

[Jupiter60]

I guess we don't actually see space. We have depth perception, but we're not seeing space.

 

[B4ssHunter]

i think that time is not something we can see , but rather something that just exists , its a 4ourth dimension but that doesn't mean we should be able to see it , you don't see space , you see object , and as objects come closer or go further or even stay in their position , time passes on and you know that , you can't go and watch a movie for instance then claim you didn't sense time or you didn't know time passed , its a perception that we might have created , the perception of time , whether it exists or not .

 

[mfb]

Actually, you don't see space. You see the object! And you do you know why you think you are seeing a 'distance'? Because (i) you have depth perception because of your two eyes and (ii) the light from the object reaches your eyes AT DIFFERENT TIMES! In other words, your sense of distance actually depends on some time differences! So if we apply your "logic" of seeing space, I could also argue that you're seeing time as well!

Zz.

For humans (and all other living creatures), it is impossible to use the tiny time differences to estimate any distances on earth. Light is just too fast. It is possible for sound, as that is slower.
With the moon or other objects, it would be possible - if we would have flashlights bright enough to see their spot on the moon (we do not).

Electronic sensors are better, they can measure distances with a precision of millimeters based on the propagation time of light.

 

[Borg]

Visually understanding objects is learned by the brain. The July edition of Scientific American had a good article about previously blind children in India who were given sight for the first time. They have a lot of difficulty assembling parts of a scene into a coherent whole which causes difficulty in even discerning two dimensions.

Here is a TED discussion by the author:
Pawan Sinha: How brains learn to see

 

[TheDemx27]

why you think you are seeing a 'distance'? Because (i) you have depth perception because of your two eyes and (ii) the light from the object reaches your eyes AT DIFFERENT TIMES! In other words, your sense of distance actually depends on some time differences!

Are you meaning to say that a person's sense of distance is based on how much time it takes for the light to enter somebody's eye? If so I must say that cannot be true. First of all, light coming reflecting off of objects with varying distances from your eye will being entering your eye at the exact same moment; if the light source is continuous. Secondly, I believe it is near impossible for anyone's brain to recognize such small differences in time.

I'm pretty sure that distance is judged exclusively by depth perception and how the brain interprets the object with reference to its environment. Forgive me if I misunderstood.

 

[bitewhite]

As many of the people in this thread have been getting at, the sensation of space is algorithmic in nature, not an actual sense. Our sensation of space is largely derived from our brain's processing of the raw input of light that picked up by the rods and cones in our eyes which is really no different from the many other conceptualizations of space that exist. For instance, bats achieve a sensation of space an entirely different way by using sound waves which their brains are then able to make sense of. So essentially the question of how and when raw inputs like light and sound translate into a conscious observer experiencing the phenomena of "space" is left up to the philosopher.

 

[lightarrow]

If space and time are really related, why is it that we can see space, but we can't see time?

I can: if I look at my watch, I see the hands moving...
(To "see" here I mean to "perceive").

 

[A.T.]

Richard Feynman on whether we "see objects" or "see light":

http://www.youtube.com/watch?v=EyssfKRsgMU#t=4512

 

[D H]

Actually, you don't see space. You see the object!

Sometimes you don't even see the object if the object is reflecting or emitting light in a strange way.

Example: Plop down in your favorite sofa or chair and plop a movie in your home entertainment center. Your eyes see light; the source is irrelevant. Your brain interprets the signals from the eyes not as a strangely lit panel but as the movie you wanted to watch.

 

[meBigGuy]

The eyes respond to light, the brain processes it and then constructs our sense of objects. We sense patterns of brightness and color. A blind person given sight cannot perceive or recognize a coke bottle until he touches it. It just a pattern of intensity and color, not an object. (read "Breaking Through") And, the higher level neurological processes that process the light/dark/color patterns can easily be confounded. (all starting with the eye's frequency sensitive sensors)

We perceive both space and time, but they are very different experiences. We perceive the 3 spatial dimensions much differently than we perceive the passage of time.

 

[mfb]

A blind person given sight cannot perceive or recognize a coke bottle until he touches it.

That is just a matter of training. That person needs training just as a newborn baby needs (but it is easier for the newborn).

 

[bahamagreen]

1] "Seeing" ultimately occurs in the occipital lobes at the back of the brain, and all the brain has to work with is nerve cells, action potentials of nerve cells exciting or inhibiting subsequent nerve cells... the brain does not "see" physical objects, nor the light from objects, it has only the signals from upstream nervous activity with which to abstract the experience of seeing.

2] Detection of edges, angles, shapes, lateral movements, rotations, and many other features are extracted within the ten layers of the retina before the signals leave out the optic nerve.
The surface of the cortex of the brain also has ten functional processing layers, and the retina is very much a specialized projection of the brain's cortical surface through the optic nerve to the back of the eyeball.

3] A pair of lateral geniculate nuclei take signals from each half of each retina and form six layers from the two eyes - six layers of processing structures. This is where much of the processing of depth is done by comparing and processing the different signals in adjacent layers from the two eyes.

4] Very many more things are going on... there is a very complicated system that allows you to shift your eyes from looking at one object to another without causing a mass movement of the background across the field of vision - so you can move around and move your eyes around and still percieve a "steady" field of view...
But ultimately we only perceive our own nervous system from the inside out; we don't actually see objects or light, we don't hear sounds, etc. We abstract our entire perception of the world... space, distance, size, color, perspective, time, motion, and all conceptual relations of these.

5] Just to be clear; when you watch a tennis match and think you are "seeing" the moving yellow ball, the part of the brain that process the identification of the shape as a ball, the part that processes the color yellow, and the part that processes the motion of the object... all three of those features are processed in physically separate and different structures. Yet, these are integrated by further processing and you "see" a moving yellow ball as a single whole object of perception - so the level and degree of feature detection, abstraction, and integration is very subtle and sophisticated. Virtually nothing is known about how it really works even today.

 

[D H]

Just to be clear; when you watch a tennis match and think you are "seeing" the moving yellow ball ...

And this happens even when one watches the tennis match on a TV screen, where there obviously is no moving yellow ball.

 

[jacassidy2]

ModusPwnd and A.T. - Your comments raise a basic fact I'd like to explore. I see the light energy or feel the heat energy from a star or a lighted earthbound globe in my room as if it only traveled from the object to my eye or skin, which is not true. I don't see the wave energy in a plane perpendicular to my position, unless there is some dust in the air that reflects the waves, in the case of light, or some appropriate sensor in the position I want to measure. How come? Why can't I see the wave from the side? I say here it's because even a light wave is somehow (don't know how) like a mechnical wave like sound or waves in the ocean. The wave is not seen in the energy that produced it, but in the disturbance in the medium through which it passes. WOW

 

[Drakkith]

I don't see the wave energy in a plane perpendicular to my position, unless there is some dust in the air that reflects the waves, in the case of light, or some appropriate sensor in the position I want to measure. How come? Why can't I see the wave from the side? I say here it's because even a light wave is somehow (don't know how) like a mechnical wave like sound or waves in the ocean. The wave is not seen in the energy that produced it, but in the disturbance in the medium through which it passes. WOW

You can't see the wave from the side because the wave itself must enter your eye in order for it to interact with your retina and allow you to see.

 

[jacassidy2]

You can't see the wave from the side because the wave itself must enter your eye in order for it to interact with your retina and allow you to see

Yes and do you find that interesting and worthy of investigation? Are waves vectors? How many dimensions are involved and how does that affect human perception? And you made no comment on the difference between mechnical and electromagnetic waves. ANy thoughts there?

 

[Drakkith]

Yes and do you find that interesting and worthy of investigation?

I might have if I had lived in the 1800's when this stuff was first being figured out.

Are waves vectors?

Yes, EM waves are oscillations of the electric and magnetic field vectors.

How many dimensions are involved and how does that affect human perception?

I don't really understand this question. There are 3 spatial dimensions. Their "effect" on human perception is that our perceptions are the result of us living in a 3d universe and not another one.

And you made no comment on the difference between mechnical and electromagnetic waves. ANy thoughts there?

The difference is that mechanical waves involve particles pushing up against each other in some way while EM waves are oscillations in the EM field.

 

[Dale]

Why can't I see the wave from the side?

Why does this surprise you at all? Are you similarly surprised that you cannot taste food that is not in your mouth or sounds that do not arrive at your ears? Are you surprised that you cannot feel the texture of an object that you are not touching? If you understand that all of your other senses require the thing sensed to interact with your body then why would you be surprised that vision is the same?

The fact that you are at all surprised by this seems very strange to me. IMO, what you are suggesting would be FAR more surprising. I really don't understand your reasoning here.