It is often said that Einstein considered time to be an illusion, and web sites which collect notable quotes often just claim that Einstein said “Time is an illusion“. This a classic case of taking a quote and posting it out of context. What Einstein actually said was more complex and more subtle.
The distinction between the past, present and future is only a stubbornly persistent illusion.
He did not claim that time is an illusion, but that the moment of “now” is an illusion. In fact his equations give time the same status as space. For instance, the square of the space time interval between two events is defined by combining the square of the space interval minus the square of the time interval interval. (Provided all values are expressed in the same units.)
The details don’t matter too much here. The point is that time is treated equally with the space dimensions, and no one is claiming that Einstein was arguing that space does not exist. There are many references to be found on the Internet which explain Einstein’s ideas with variable clarity and accuracy.
I said above that Einstein argued that the instance of “now” is an illusion, but I was over simplifying. What I believe that he was saying was that while we experience a “now” now, we also experienced a “now” ten seconds ago, and one second ago, and one instant ago. There is nothing special about the “now” moment and all instants of time are “now” moments.
This isn’t that surprising really. If you consider where you are at a particular place and at a particular time, not only is there a “now” moment, there is also a “here” place. When you move to another place, you have another “now” moment, and another “here” place. To experience an event you have to have both.
If we are taking a road trip we have no difficulty with the concept that the “here” place changes continually and that a place we have passed through was a “here” place when we passed through it, and that a place further on will later be a “here” place. Where ever we are we are “here”.
You might argue that time is fundamentally different from space, in that we can see what is in front of us in space but we can’t see what is in front of us in time. This is true, but maybe we just don’t have the physical equipment to do so. We can use sight to look around as see what is not “here”, to some extent, but we don’t have complete visibility to things around us.
If we did we would not bump into things and fall off of things as much as we do. We use sight to build a picture of things around us, but we don’t have physical access to those things until we move up to them.
Since we don’t have “time vision” we have use whatever abilities we can to work out what is in the future, such as reason and intuition, both of which have limited success. We do have some ability to fairly accurately guess the future, as evidenced by our abilities to catch a ball thrown to us. If you have ever watched a top table-tennis match, you will no doubt be amazed at how accurately we can so this, as the ball whizzes from end to end of the table.
Time is measured in seconds and space is measured in metres (or hours and yards or other equivalent units). This seems to be a difference between the space dimensions and the time dimension.
However it is easy to show that there is little fundamental difference. Distances are often measured in terms of time – astronomers refer to a light year, which is the distance that light travels in one year. It is not often, however, that the opposite is true. Times could be measured in terms of light metres, or the time it takes light to move a given number of metres, but this is not usual, possibly because a light metre is such a very short period of time.
Interestingly some people claim to be able to “see” the future. They are claiming that they have a sense similar to vision which they use to determine what is going to happen in the future. While it is possibly conceivable to have such a sense, there appear to be no organs in the body which could be used to “view” the future.
Such organs would have to have receptors which would have to receive information about the future just as the eyes receive information about things that are relatively distant, and that information would have to travel in time from the future to reach the receptors in the present. This appears to be counter to all known physics. Possibly “unknown physics” would allow this, but I suspect not.
In any case the human body doesn’t appear to have any receptors which could possibly serve this purpose, and although not everything is known about the human body, such organs, if such existed and could be used by some people, would be probably be apparent.
What about the brain? Could the brain perhaps receive information about future events in some way? Well, the brain is an organ for processing information, not for receiving information from the future. There is nothing like a receptor in the brain, though it is connected via nerves to receptors which terminate those nerves and when stimulated excite the nerves which then pass the stimulation to the brain.
In my opinion, which of course could be wrong, there is no way that information from the future could be detected by the human body, and in particular by the brain acting as a receptor. That does not mean that time is in any way different from space as a dimension. What it does mean is that we are able to perceive the dimensions of space differently from the dimension of time.
That doesn’t address the question as to why the space dimensions are accessible to vision and time is not. It only addresses the question of why we can “see” the space dimension, but cannot “see” the time dimension. Something links the space dimensions into one seeming whole, while the time dimension seem singularly different.