1. one time and temporality

2. “Time is what keeps everything from happening at once”

3. What is time? What does the phrase: “the temporal world” mean? What is it contrasted with?

4. Time is the medium of change Temporal entities Have beginnings and ends Undergo change Undergo motion The phrase “temporal world” comes from Catholic metaphysics Augustine: God isn’t temporal God wasn’t created / didn’t have a beginning Change is seen as implying imperfection In Buddhist philosophy, impermanence and change are seen as Fundamental conditions of existence of all objects The ultimate source of neurosis and suffering

5. Cartoon metaphysics The world consists of a set of objects Objects occasionally get created and destroyed Objects have states Spatial: position, speed, etc. etc. Other: alive/dead, hot/cold Relations to one another: above/below, loving/hating, etc. Object state changes On its own As a result of interactions with other objects This is, by and large, the ontology used in most computer simulations (VR, video games, etc.)

6. Causes and effect Time is asymmetric This is deeply weird It drives the physicists and philosophers crazy If I drop a glass, it breaks The dropping always comes “first” The glass never jumps up or reassembles itself And we say the dropping “caused” the breaking

7. Phenomenological time Time is also asymmetric w.r.t. knowledge and action Past Partially knowable (through memory) Unchangeable Present Knowable Arguably changeable Future Partially changeable Completely unknown (except by extrapolating from the past)

8. Time is the medium of existence (Existence means roughly the activity of living) Care and the World Some states and changes matter to us We (generally) don’t want to die, go bankrupt, etc. We (generally) do want to graduate, get a job, etc. Certain changes are caused by us in order to continue our involvements with the World These are called actions

9. Narrative (story) Sequence of events told from a point of view Narrator (person whose point of view is used) Story (sequence of events that happened) Plot (sequence in which the events are given) Characters w/goals, relationships, etc. Conflicts

10. Aristotelian mechanics Basic tendency of objects is to stop Natural motion Basic tendency of things is to go to their natural position Solid things move to the ground and stop Smoke and fire move to the air and stop/disappear Violent motion Some force moves an object away from its natural place Celestial motion Everything naturally moves in circles There is no violent celestial motion

11. Newtonian mechanics Basic tendency is to move at constant speed Objects exert forces on one another Gravity Friction Collision Etc. Forces change an object’s speed

12. Time is also like space We can talk about points in time (now, next Wednesday at midnight, etc.) We can talk about directions in time (before/after) We can talk about distances in time (one hour, fifteen picoseconds, etc.) (And General Relativity says time it actually part of space)

13. Dynamic systems Space of possible states Called a “state space” or “phase space” Law of motion defines how state evolves over time Discrete time Gives new state in terms of current state Continuous time Gives rate of change in state in terms of current state State is then a function of time Function can be derived from the law of motion and the initial state

14. Example: Population dynamics Suppose you’re baking bread You start with one yeast cell Each minute the yeast cells divide into two yeast cells (Yea, yea, I know yeast doesn’t really work this way, but pretend it does for the sake of the example) State space: number of yeast cells (a number between 0 and ∞) Law of motion Number of yeast cells at time t is twice the number at time t-1 State function Cells(t) = 2 t

15. Example: A falling object Suppose we drop a Kenny from South Park from the Sears Tower State space Height (starts at 1450 feet) Velocity (starts at 0 feet per second) Law of motion Height decreases by speed units each second Speed increases by 32 feet per second each second State function (apologies to those who don’t know calculus) Speed(t) = 32t Height(t) = 1450-16t 2

16. Perception of time Perception of duration Depends on a number of factors, including heart rate Gary? Perception of ordering Humans actually turn out to be very bad at this It’s a skill we learn, but doesn’t seem to be built-in Perception of rhythm Uh, class starts in 15 minutes and I haven’t had a chance to look up any thing on this … Gary?

17. Perception of motion The human visual system has two different systems for detecting motion The “gradient-based” system Detects small motions over short time scales The “discrete” system (aka the apparent motion system) Effectively matches features between consecutive images Allows film and video to work Wagon-wheel illusions

18. Perception of change Change blindness Human perception of change relies on Memory Detection of visual motion Easily fooled Film continuity