lohacurrent.blogg.se - Causality physics

On the other hand, if (i) were false we might have no way of finding out, because the lack of causal connections would make it impossible for us to detect the existence of the other universes represented by the other parts disconnected from our own universe.

According to the Big Bang theory, it seems likely that the network is connected, since all events would presumably connect back to the Big Bang.

To see what these conjectures would entail, let's discuss a few examples that may draw on knowledge from outside Alice and Betty's experiences.

not only are the events ordered, but the ordering can be modeled by sorting the events out along a line, the time axis, and assigning a number tt, time, to each event.

that the events are globally ordered, so that for any two events 1 and 2, either 1 could cause 2 or 2 could cause 1, but not both.

that the universe's entire network of causality is connected, rather than being broken up into separate parts.

Alice and Betty may also make a number of conjectures that would say much more about causality.

Even if she refrains, there was the potential for a causal linkage between her dinner and Betty's forehead.īetweenness is very weak. For example, if Alice and Betty are eating dinner, Alice could choose to throw her mashed potatoes at Betty. With this geometrical interpretation in mind, it will be useful to think of events not as actual notable occurrences but merely as an ambient sprinkling of points at which things could happen. We say that they are both ordered geometries. The invariance of betweenness is a basic geometrical property that is shared by both Euclidean and non-Euclidean geometry. You may have heard that relativity is a theory that can be interpreted using non-Euclidean geometry. They find that this agreement holds regardless of whether one twin is standing on her head (i.e., it's invariant under rotation), and regardless of whether one twin is sitting on the couch while the other is zooming around the living room in circles on her nuclear fusion scooter (i.e., it's also invariant with respect to different states of motion). One general rule they infer from their observations is that there is an unambiguously defined notion of betweenness: if Alice observes that event 1 causes event 2, and then 2 causes 3, Betty always agrees that 2 lies between 1 and 3 in the chain of causality. Certain events result in other events, forming a network of cause and effect. Putting yourself in the twins' shoes, imagine giving up all your preconceived ideas about space and time, which may turn out according to relativity to be completely wrong, or perhaps only approximations that are valid under certain circumstances.Ĭausality is one thing the twins will notice. The robot, in accord with the latest fad in education, is programmed to encourage them to build up a picture of all the laws of physics based on their own experiments, without a textbook to tell them the right answers.

They're raised entirely by a robotic tutor on a sealed space station, with no access to the outside world.

Updating Plato's allegory of the cave, imagine two super-intelligent twins, Alice and Betty.