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Space time

  1. Jul 30, 2004 #1
    Can anyone explain 4D space-time in a simple form ?
    Some say the Hawking's expalanation is the simplest but I don't get it :biggrin:
  2. jcsd
  3. Jul 30, 2004 #2
    Sure. It takes 3 numbers to locate of an event in space - represent that as (x, y, z). The collection of all triplets (x , y, z) is called "space". It takes 1 number to specify the time of an event, t. Collect those two numbers into one set of numbers (t, x, y, z). That is called an "event". And event is a point in space at a given time. The collection of events (t, x, y, z) is called "spacetime".

  4. Jul 30, 2004 #3
    Can you give me some examples ?
  5. Jul 30, 2004 #4


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    I know this example has probably been beaten to death by numerous layman physics books, but it is very simple and it works to illustrate the concept of spacetime. Let's say you have an appointment in a particular office located in a particular building, which itself located at a particular street junction. To get to your appointment, you have to know three coordinates for space (the x and y coordinates are used to locate the building, while the z coordinate is used to locate which floor the office in the building is located.) And one coordinate for time (the time the appointment takes place.) Simple, no?
  6. Jul 30, 2004 #5
    Thank you.
  7. Jul 30, 2004 #6
    One example is the same as the other. What you're asking is analogous to asking us for an example of space. Can you give me an example of space?

  8. Jul 30, 2004 #7
    That is an example of an event. Not an example of spacetime.

  9. Jul 30, 2004 #8
    I don't care whether it is an event or an example of space time. :smile:
    Because it is exactly what I meant. I don't know how GZA always gives me exactly the right thing.
    Anyway, Pete, thank you very much.
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