Perspectives on Time: Aristotle to Einstein's Relativity Theories

1. What is Time

2. Aristotle • The natural world is the realm of change: everything that is natural is subject to change (Remember his variation on Plato’s Forms) • Time is "a number of change with respect to the before and after" • Requires a soul/consciousness to be capable of “numbering” (perceiving) movement and change • Time is not the same thing as change - change may occur fast or slow • Time is ameasurement of change

3. Isaac Newton • Time is absolute • Time flows at a steady, consistent rate, regardless of the perceiver • Time is not about being perceived • It can only be understood through mathematical principle • Measurement of time outside of an absolute system requires reference points of moving objects • The speed of a moving object can vary or be influenced (by gravity for example), so they do not convey an accurate concept of time • There must be some underlying measurement of time that remains constant and is not affected by the perception of moving bodies

4. Kant • Time belongs to the transcendental ideal – our understanding of it is limited by our perception of it • Time is an a priori intuition – it is understood as the passage of events without having to experience anything • Time is like space in that is all one dimension • different times are just part of one larger time  it is infinite in nature • Time is an “inner sense” – understanding oftime cannot be understood by an external object alone • Time works with space for us to make sense of our surroundings ex. Looking at a house, or watching a boat go by

5. Albert Einstein (Kind of) • Fluctuations in speed and gravity can alter how time is perceived, making time relative • Going at (or close to) the speed of light causes time dilations • particles begin act differently, changing the effects of time • Similar effect in high gravity – particles are effected differently • Perception of time will remain the same • Person on Earth will perceive time as they usually do • Person in a space ship will perceive time as they usually do • The rate of those times will be different because of the speed and gravity A, B, C are events, the line is the observer

6. Models of Time

7. Presentism • The past and future do not exist at all • The only reality is what is present now…now…now…no, now…ok, now… • The observer is thought of as a geometric point in both space and time • They only exist in that specific point in space/time and are un-extended • Time becomes an extended attribute of external objects and can be measured and regarded as a 4th measurable dimension of an object

8. Eternalism • All existence in time is equally real • Past, and future exist, the present is the movement through frames of existence • Time becomes a “place” to go to • The “past” is fixed and cannot be changed • The “future” is undefined, but already in existence based on where the present is going • As time progresses, moments move into the past, and the future becomes the present

9. Growing Block Universe • The past and present exist, but the future does not • The present makes more of the universe known (in that history grows), therefore the universe is growing • Argument breaks down into: • Events in our world are causally related. • Effects depend on their causes so that causes do not depend on their effects. • Acause's effects are not real as of the time of their cause. • Causes occur before their effects • Our universe must, therefore, be a Growing Block. Future Unknown Past Present Time