• Question: can you explain what does spacetime means?

    Asked by 07quiambaoj to Alastair, Emma, Hywel, Keith, Vicki on 18 Jun 2010 in Categories: .
    • Photo: Alastair Sloan

      Alastair Sloan answered on 18 Jun 2010:

      Spacetime as I understand it is a mathematical model which combines space and time into one single entity. By combining these two things together yoiu can simplfy some physical theories about the universe and describe the workings of the universe

    • Photo: Vicki Stevenson

      Vicki Stevenson answered on 18 Jun 2010:

      If you want to pin down where an event happened you need to know the x, y and z coordinates (you’ve probably used those in school).
      By adding time as a coordinate, you can also specify when it happened.
      Spacetime is a way of combining the x, y, z and time coordinates.
      Time needs to be specified as well as position because time is slowed down at very high speeds (see Einsteins’ special relativity theory if you’re interested). This has been confirmed by noting that the very accurate atomic clocks on the space shuttle don’t agree with the earth-bound atomic clocks.

    • Photo: Keith Brain

      Keith Brain answered on 18 Jun 2010:

      The concept of spacetime is really very difficult, and not something that I’m on top of – perhaps only professional astrophysicists (people interested in physics and astronomy) really are. Here’s my simple take on it:

      – We’re used to thinking about space (3 dimensions) and time as separate things, however
      – In Einstein’s General Theory of relativity, Einstein said – lets suppose that space and time are really the same sort of thing, and that we really live in 4-dimensional space – then lets try to do some physics!
      – Einstein’s General Theory of relativity looks particularly at how this 4-dimensional space is altered by the presence of mass (we can think of this as how gravity affects space and time).
      – There are a couple of strange implications: one is that mass (or gravity) affects how time passes; the other is that light, which we think of travelling in straight lines, can be bent because of nearby mass (and not by passing through it, as in a refractive index difference, but just passing nearby).
      – For most questions in Physics, and essentially all things in daily life, we don’t need to think about spacetime – we can think of space and time as quite separate things – luckily!

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