How would you define time?
Google defines it as: “The indefinite continued progress of existence and events in the past, present, and future regarded as a whole.” To me that doesn’t say much.
Some people might try to be smart and talk about Einstein’s theories on space-time. But I mean this question a bit more philosophically.
Personally I would have defined it a bit more simply as moving from one event to the next. Brian Cox however gave a much better definition in my opinion:
“Time is Change”
Think about it. If nothing ever changed. Nothing, we didn’t move, the sun didn’t move, everything in the universe just stopped. Would time move? Imagine if everything stopped for just a second. How would we be able to distinguish the end of that second from the beginning?
Your senses work the same way. The brain senses changes. If something flies across our field of vision, an extreme change, that is what we see. We don’t normally concentrate on the standstill landscape in front of us (unless we are trying to see the landscape) but what is happening around us. More importantly, if nothing ever changed we would not sense anything.
Imagine the man in the picture above. Imagine him sitting perfectly still, not a single muscle moving in his body. Imagine that nothing changed in the room, no dust falling etc (light can still be flying about though). If this situation ever became a reality, he would go blind. However this blindness would be temporary, if he moved even a millimetre he would regain this sense of sight.
You can sit and try it now, but it won’t work. We are made so that our eyes are constantly moving. Our heads need to be held up all the time and so can sway from side to side. Even the rest of our body is moving by tiny fractions. All of this makes sure that what we are seeing is constantly changing by little movements, keeping our sight active.
This idea of needing change to be able to see something works for all of the senses. Think of the times where you have rested your hand on something and just stopped really feeling it, or the times where you walked into a place that smells and within a few minutes you didn’t notice it anymore. Again our body is constantly moving by fine tremors, so if we put our mind to it we would feel that surface again, and we could move and receive a slightly different mix of smells so that we could smell again. We are made to make sure our senses stay as active as possible. But if ever we totally stopped these changes, we would sense nothing.
A quick neuroscientific reason is that our nerves signal when something happens. In the eye a nerve can be hit by a ray of light and send off a signal. If that ray of light stays in place then that nerve would do nothing, it has already sent off the signal and won’t do it again until a new ray of light hits it.
In the end I’m trying to make the point that we don’t really sense the world as it is, but by how it changes. It’s not a totally vital principle of sensory neuroscience, but it helps to understand how we interpret the world around us. And to show how active our brains are.