If we agree that objective reality exists, then a closely related question will be: What is the truth about reality? How do we know about reality? This is by no means a simple question if we think deep into it. I am not an expert in epistemology. In this post, I just want to share a simple thought about truth:
Absolute truth exists despite apparent contradictory facts.
Some people hold that everything is relative, and nothing is absolutely true. I think a simple example from special relativity would illustrate that there are some facts that only exist relative to each other, but there are absolute truths behind.
Special relativity tells us that for two observers, A and B, moving at a constant speed relative to each other, they will see things quite differently. The difference would be dramatic when their relative speed is close to the vacuum speed of light, which is 299,792,458 meters per second. As an example, we consider A to be sitting on a chair on the roadside, while B is sitting inside a train and is passing A.
One may say, “Of course they see things differently! A see himself as stationary, sitting on a chair and enjoying a drink. While B would say A is moving and is holding a drink on A’s hand”. But special relativity says more than that. If each of A and B are holding a glass of the same size when they are both stationary, and B can somehow measure the size of A’s glass (the act of measurement must be quick!), B will find A’s glass to be smaller than B’s glass. Furthermore, B will see A’s clock goes slower. A minute showed on A’s stopwatch takes more than a minute in B’s stopwatch.
One may be tempted to make the following conclusion: “That’s it! Everything is relative! A says his glass is of this size, but B says according to B’s measurement, A’s measurement is wrong. A says something took a few minutes to finish, but B looking at the same thing would find that it took more than a few minutes. It definitely shows that there is no absolute truth, and everything is relative!”
However, the contradiction is only apparent in the sense that there is no measurement to confirm anything. Can we perform an experiment to compare the two glasses that A and B hold, and see really if the sizes are different? We cannot. Why? Because A and B are in constant relative velocity, and after B passes A, B can never return to A unless B turns back. In order to turn back to A, B has to make an acceleration. Then, A and B are not in constant relative velocity, and special relativity does not apply anymore.
To confirm or invalidate the apparent contradiction that special relativity seems to imply, we need to find an experimentally verifiable situation. That will be the subject of my next post.
