<p>Your question is difficult to answer exactly, because it touches the question of consciousness, which is problematic in general. But the answer is basically this: </p>

<p>Theory of relativity describes the space-time as four-dimensional space that exists as a whole. You are described by a <a href="https://en.wikipedia.org/wiki/World_line" rel="nofollow">world-line</a>, which contains all states you go through from birth to death. There is many slices, which describe "you" in different times. What you can see is given by what information reached your sensory inputs (your senses) and how they are processed by your brain. The brain creates a model of reality based on your sensory inputs, which is stored in space-like slice of your world-line in the space-time, which we call present. This is what "you" can see. So the reason basically is in how the brain processes the data it is getting.</p>

<p>Along you world-line, there is many versions of you at different ages and each version feels its own present and the versions more in the future also have memories of the past (because the brain stores the past sensory inputs). There is no single "present time" in the theory of relativity, only the space-time as a whole.</p>

<p>But you should't forget that the theory of relativity is still only a very well working model. Even within the theory of relativity, the question whether space-time exists as a whole, or whether there is "present state", which evolves in time, is rather philosophical than scientific, because there is no observable difference between the two.</p>

CC BY-SA 3.0
2015-11-08T10:13:49.420Z
2015-11-08T10:13:49.420Z
Irigi
<p>Time isn't quite like space. <a href="https://i.sstatic.net/x1ETQ.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/x1ETQ.gif" alt="enter image description here"></a></p>

<p>The first difference is that we can't stop moving in time.</p>

<p>In this picture time is on the vertical axis, and space is horizontal. You have a history and a future. if you don't move you will travel straight up the vertical axis. Even if you do move you can never escape the cone, which shows the path that light takes in spacetime.</p>

<p>You can receive information from anything in the past light cone, and you can send information to something in the future light cone. Points in spacetime outside the cone can never give or get information of you.</p>

<p>Secondly, there is Entropy: Entropy increases with time. This gives a direction to time. This prevents us from remembering the future.</p>

CC BY-SA 3.0
2015-11-08T11:17:00.943Z
2015-11-08T11:17:00.943Z
James K
<p>I've recently learned about the theory of relativity and time.  I'm trying to understand it more.  </p>

<p>My (basic) understanding is that there is no distinction between past present and future and that all of time already exists.</p>

<p>If this is true, what prevents us from seeing the past and the future? And/Or what causes us to only be able to see the "present"?</p>

CC BY-SA 3.0
2015-11-08T04:46:42.550Z
The restaurant at the end on the universe. Actually, I don't think you are talking of relativity, but rather some exotic theory of a multiverse. Or science fiction.
Eubie Drew
CC BY-SA 3.0
2015-11-08T11:01:37.587Z
There are lots of sources of information on relativity, good and bad, and at all sorts of levels. Where have you been learning about it?
James K
CC BY-SA 3.0
2015-11-08T11:04:41.850Z
Time begins where space ends, and it reaches all the way to here in the center where the future is created.
LocalFluff
CC BY-SA 3.0
2015-11-08T12:15:03.713Z
The reason we can't see 1 year into the past is because all the light from 1 year in the past is 1 light year away.    We can only see (assuming we're looking at things close to us) what happens very very very recently.   The past does still exist in a sense, from a very distant perspective, for example, the stars we see in the sky are years in the past.    That's probably kinda obvious, but that's my thoughts on this.
userLTK
CC BY-SA 3.0
2015-11-08T18:23:18.020Z
@JamesKilfiger This video (and similar documentaries) is where my questions are stemming from. https://www.youtube.com/watch?v=vrqmMoI0wks
batman
CC BY-SA 3.0
2015-11-08T19:44:48.960Z
@userLTK Interesting answer. So assume there was an Earth like planet orbiting a star in the sky and we had a powerful enough telescope to see "humans" on that planet.  When we watched those "humans" from Earth would we see what they were doing years ago?
batman
CC BY-SA 3.0
2015-11-11T21:41:13.777Z
@batman The sun you look up in the sky is approx 8 minutes in the past. Likewise, from Earth.. we look deep in the universe to find out what had happened in the early stages of universe.
Selvakumar Arumugam
<space-time><time-dilation>
Does all of time exist and if so where is it?
batman
# Does all of time exist and if so where is it?

(Asked by: username_0 on 2015-11-08)

I've recently learned about the theory of relativity and time. I'm trying to understand it more.

My (basic) understanding is that there is no distinction between past present and future and that all of time already exists.

If this is true, what prevents us from seeing the past and the future? And/Or what causes us to only be able to see the "present"?

**Tags:** space-time, time-dilation

> **Comments:**
> **username_1**: The restaurant at the end on the universe. Actually, I don't think you are talking of relativity, but rather some exotic theory of a multiverse. Or science fiction.  
> **username_2**: There are lots of sources of information on relativity, good and bad, and at all sorts of levels. Where have you been learning about it?  
> **username_3**: Time begins where space ends, and it reaches all the way to here in the center where the future is created.  
> **username_4**: The reason we can't see 1 year into the past is because all the light from 1 year in the past is 1 light year away.    We can only see (assuming we're looking at things close to us) what happens very very very recently.   The past does still exist in a sense, from a very distant perspective, for example, the stars we see in the sky are years in the past.    That's probably kinda obvious, but that's my thoughts on this.  
> **username_0**: @JamesKilfiger This video (and similar documentaries) is where my questions are stemming from. https://www.youtube.com/watch?v=vrqmMoI0wks  
> **username_0**: @username_4 Interesting answer. So assume there was an Earth like planet orbiting a star in the sky and we had a powerful enough telescope to see "humans" on that planet.  When we watched those "humans" from Earth would we see what they were doing years ago?  
> **username_5**: @username_0 The sun you look up in the sky is approx 8 minutes in the past. Likewise, from Earth.. we look deep in the universe to find out what had happened in the early stages of universe.  

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## 2 answers

### Answer by username_6 on 2015-11-08. Score: 3

Your question is difficult to answer exactly, because it touches the question of consciousness, which is problematic in general. But the answer is basically this:

Theory of relativity describes the space-time as four-dimensional space that exists as a whole. You are described by a [world-line](https://en.wikipedia.org/wiki/World_line), which contains all states you go through from birth to death. There is many slices, which describe "you" in different times. What you can see is given by what information reached your sensory inputs (your senses) and how they are processed by your brain. The brain creates a model of reality based on your sensory inputs, which is stored in space-like slice of your world-line in the space-time, which we call present. This is what "you" can see. So the reason basically is in how the brain processes the data it is getting.

Along you world-line, there is many versions of you at different ages and each version feels its own present and the versions more in the future also have memories of the past (because the brain stores the past sensory inputs). There is no single "present time" in the theory of relativity, only the space-time as a whole.

But you should't forget that the theory of relativity is still only a very well working model. Even within the theory of relativity, the question whether space-time exists as a whole, or whether there is "present state", which evolves in time, is rather philosophical than scientific, because there is no observable difference between the two.


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### Answer by username_2 on 2015-11-08. Score: 2

Time isn't quite like space. [![enter image description here](https://i.sstatic.net/x1ETQ.gif)](https://i.sstatic.net/x1ETQ.gif)

The first difference is that we can't stop moving in time.

In this picture time is on the vertical axis, and space is horizontal. You have a history and a future. if you don't move you will travel straight up the vertical axis. Even if you do move you can never escape the cone, which shows the path that light takes in spacetime.

You can receive information from anything in the past light cone, and you can send information to something in the future light cone. Points in spacetime outside the cone can never give or get information of you.

Secondly, there is Entropy: Entropy increases with time. This gives a direction to time. This prevents us from remembering the future.


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