We like stability. We like to know that each day the Sun is going to rise, the mailman will bring our paper, and time will march slowly on -- just the same as it always has. What’s more, we like to image that this experience is larger than ourselves. When the Sun rises, we know that it’s rising for everyone, not just for us. When the mailman brings the paper, he isn’t making a special trip; he’ll stop at the neighbors as well. These are the common, everyday experiences that unite is all.
However, as it turns out, we are a bit more isolated that we might initially assume.
When Albert Einstein introduced his Theory of Relativity, he argued that space-time is curved and warped by the existence of matter. To understand this, imagine a kitten playing on a stretched out blanket. Depending on where it is standing, the weight of the kitten will warp the blanket, forming a slight dip in the otherwise even sheet.
If the Earth is a kitten, then the blanket is space-time. And much like the kitten, Earth causes a slight warping of the blanket that is space-time. This means that time will appear to move slower near massive objects (like Earth) because space-time is warped by mass. In 1962, these predictions were proven when scientists placed an atomic clock at the bottom and top of a water tower. The clock at the bottom (the one closer to the massive center of the Earth) was running slower than the clock at the top.
In short, our location alters how we experience time. Admittedly, the time difference is so slight that we don't notice it. But it is different nonetheless.
And it seems that it's not just literal time that is different; our perception of literal time also differs from person to person. This is because our neurons impact how we perceive time. In 2012, scientists from the University of Minnesota conducted research which demonstrated that, in the brain, different neural circuits have their own timing mechanisms for specific activities. This find could explain why time seems to pass so slowly when you are listening to a lecture, and why time flies by when you are listening to your favorite band. Moreover, the researchers note that the perception mechanisms alter slightly from person to person—so a lecture might go by slowly to me, while it goes by REALLY slowly to you.
So in some ways, when you walk past someone on the street (unless you are walking at the exact same speed), you are walking through a different measurement of time. Ultimately, this is just one (very simplified) way of highlighting how, scientifically, you live in your own unique world which only you are able to experience.