I am going to juxtapose two thoughts, and then ask for commentary.
Thought 1 (the easy one):
“A difference that makes no difference is no difference.” - William James (although often attributed to Spock on Star Trek)
Thought 2 (the complicated one):
If you have been exposed to Einstein’s theory of relativity, you are perhaps familiar with the idea that each of us occupies a unique position in space-time. In other words, your “now” is not exactly the same as my “now” because of the physical distance that separates us. This is beyond the difference in experiential perspective, although it is the cause of that difference as well. Simply put, I’m not you.
If you gesture, it takes time for that motion to arrive at my retina, and even more time for my brain to process it. What I perceive as happening right now actually occurred several milliseconds ago. The sunlight that I see bouncing off a rock and illuminating it, is actually fossil light (though very recent) from the sun. Everything that I see around me and everything that I experience, including the feedback from my own motor control of my body happened in the immediate past, not the present.
Does “the present moment” actually exist?
Is there a locus in space-time, like a point in the physical center of my body, for example, that represents my “now”?