• Question: what is 4d?

    Asked by rarr to Meeks, Pete, Stephen, Steve, Tom on 25 Jun 2010 in Categories: .
    • Photo: Stephen Curry

      Stephen Curry answered on 18 Jun 2010:

      Hey rarr – 4D refers to the four-dimensional space-time that we live in. This has three dimensions of space and one of time. It seems odd to consider time a dimension but that is because, in our every day experience, we only really deal with three spatial dimensions and there is no sense that time should be connected with space.

      But when you start to think about things that are travelling at or near the speed of light, it becomes apparent that the speed of time is not fixed and that you have to think of space and time as intimately connected.

      This isn’t a fantastic explanation. If you ever get the chance to study einstein’s theory of special relativity, it will become clearer. Honest!

    • Photo: Pete Edwards

      Pete Edwards answered on 20 Jun 2010:

      Hi rarr
      I think the best way to think of our 4d universe is to imagine how you would tell somebody where to find you in a building. You would tell them to go to the entrance and then how far they would have to walk to the left or right (1st dimension), how far they would have to walk towards the back of the building (2nd dimension) whether to go up or down in the lift (3d dimension) and also what time you’d be there to meet them (4th dimension). In physics if we are going to fix the position of something we have to give three special coordinates plus a time at which the object will be at that place. We talk about our universe being formed from space time which has 4 dimensions.
      Einstein used this picture to develop a whole new theory of gravity, but that’s another story!

    • Photo: Marieke Navin

      Marieke Navin answered on 22 Jun 2010:

      if you’re asking about cinema, then it’s usually a 3D experience in which
      the audience are moved around. a 5d cinema has more sensory experience such
      as touch and smell.

      otherwise the fourth dimension with respect to space, is time

    • Photo: Steve Roser

      Steve Roser answered on 22 Jun 2010:

      If you mean what is it in cinemas – I think it is used when they use 3D film, and add in things like gusts of air and spray, and smells – in glorious smell-o-rama!

    • Photo: Tom Hartley

      Tom Hartley answered on 25 Jun 2010:

      Hi rarr,

      This could refer to the three dimensions of space (front-back,left-right, up-down) plus time – e.g. in fMRI we take a whole series of 3D “pictures” of the brain, one every three seconds. We call the resulting “image” (more like a movie) a 4D image, it has three spatial dimensions and one of time.

      However in Maths, Physics and elsewhere in science it’s quite common to thing to imagine more than 3 spatial dimensions, and many people think they may actually exist. I often use the idea of dimensions in a more abstract sense – for example, you could think of a particular face as having a particular location in the space of all possible faces. This “space” might have many dimensions (e.g., eye-brow distance, length of face, nostril size, cheek-width) but you can still think of it as a space. Quite often in the brain it seems that things that are near together in this type of space are represented by cells that are near together in the brain.

      When I was growing up, I got interested in extra dimensions and I found this explanation of 4-dimensions really interesting. I think this programme might have had quite a big effect on the way my thinking works today: