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| All Images: Cumberland Basin, Bristol Floating Harbour, August 2023 |
[Translated Video Transcription]:
What exactly is space-time? So that I can reply, you need to do something for me. First, share your intuition about how time and space work. Your brain may initially resist these intuitions and then hold on to them for life. Don't worry, this is normal - a challenge for everyone (including Einstein). Okay, space-time refers to the external reality based on our collective experiences of the space between things and the time between events. Why add space-time here as an additional concept relative to each other, and count particles as observed time that passes between events? In fact, we don't entirely agree on how far apart things are at any given time. We don't even agree on the chronological order of all the events, and it is completely consistent - meaning none of it is wrong. There are also many other sources that we refer to in the description. We discuss these discrepancies and the experimental evidence for them. Today we'll take it at face value and focus on what it says about the nature of reality, because when you think about it, some of the implications are so surprising (e.g. this disagreement about the order of events). It is serious when two observers cannot rely on the sequence of some events. This means that one person's present death is in another person's future. For nearby events the impact is small, but a disagreement means there is no universal division of events into past, present and future.
This opens up big philosophical cans of worms for things like free will and our belief that we can change the future or subjective words (when they are not part of objective reality). A good starting point for objective reality is a universal agreement, and all observers, so to speak, agree to call it a space-time interval or space-time separation between two events - even if two observers are at different distances in relative motion, and the differences measure the time elapsed between the same two events. They always coincide in the spatio-temporal interval between these events. Now they mean something. You will find that sensitivity comes with abstraction. A space-time interval can be positive, zero, or negative (if it is positive). There are always observers who have different opinions. The first thing that happens when there are no or negative secret signals, where things can move from one event to the next and everyone agrees on their own - is that the space-time interval between events A and B appears to be revealing about whether we can influence something. In other words, even though we can - we disagree about past, present, future, times or distances. So far we all seem to agree on causality, which may seem counterintuitive. We usually think that time is responsible for causality, but in fact it is the other way around, as long as we agree on temporal things to which it is exclusively attributable. As it turns out, causality is what is real.
Einstein's former mathematics teacher noticed that spacetime looks like a strange version of some kind of distance in a so-called non-Euclidean space, and therefore proposed the following radical idea that it may not be a space of three-dimensional reality, not one that has evolved over time - but rather a four-dimensional non-Euclidean mathematical space that simply shows no development. Its points correspond to events everywhere and always, and in this respect only things that correspond to geometric relationships in this space are our objective reality. Just as the measures of time and space do not correspond to anything in themselves, they rather resemble what they do. It doesn't matter whether we place trucks on the dashboard or not. So what if you are the sequence of all the events in which you are present? You are a geometric object in the online part of space-time that connects the dots that represent the events of your birth and death. Are you in the specialist department? There is no movement through space-time. It is not space, it is without tension, and your future is not only predetermined - it already exists.
Time will not deceive you, but I think the following sums it up: Imagine we all read a Gap People flip-book, but we disagree about where on the page events take place, how many pages there are between events, or even the order of some of those events - and yet we also disagree that everyone agrees that I was reading the same book (except the newspaper had no graphics). There are no pages and there is no book. All of this is just a mutation our brain makes to perceive the good. The question that no one really knows is far from it. All of this only happened once with the introduction of so-called flat space-time. General relativity comes into play. We will find that there are many possible space-times with different geometries - making it difficult to determine which is which. I will do my best to answer your questions at the closest causally related point in space-time.
