Four-dimensional Objects ```Name: Unknown Status: N/A Age: N/A Location: N/A Country: N/A Date: Around 1993 ``` Question: I hear that some people claim that they can imagine 4-dimensional objects. I wonder how this can be since our universe only has three physical dimensions - is it really possible to imagine these things and do these people have any proof? I myself find it impossible to imagine anything but projections of these objects onto 3-dimensions. Replies: With some practice in mathematics it is not, in principle, difficult to imagine objects in any dimension. It is a little harder to think about what they would look like. The reason that four dimensions seems to be important is that space (3) and time (1 dimension) are clearly linked by relativity. The large number of experiments in relativistic speeds verify this quite well. So, if our world is fundamentally four dimensional, it means that time and space can be mixed when we make measurements of quickly moving objects. For most of our everyday experience it simply means that we should consider time as our fourth dimension. This means that we are moving through a four dimensional space, but does not mean that there are four dimensional objects in the usual sense. Objects are still only three dimensional at a given time. Their path through four dimensional space time can be represented by a four dimensional volume. Sam Bowen Four-dimensional objects do not exist in our universe because it has three dimensions. I do not know how people can imagine a Four-dimensional object. We live in three dimensions, and it is difficult to imagine another "direction" that is perpendicular to our existing dimensions. Perhaps people with special imaginations can do it. There are some speculations about more dimensions in string theory, but these are only speculations and in any case the size of the other dimension is microscopic. This difficulty would be analogous to color vision. Humans usually see three primary colors, and the brain is able to "see" the full spectrum of colors from these primaries. Some creatures, like insects, have a fourth primary color receptor. They might "see" colors that humans cannot imagine, or at least I cannot imagine. In terms of mathematics, there is no problem with four dimensions or any number dimensions. On the other hand, physics equations describe our reality in three dimensions and usually do not work when extended to four and higher dimensions. That is because physics equations describe physical reality and our reality is three dimensional. One can think about four-dimensional moons orbiting four-dimensional earths, but the equations do not work properly. And if you have a four-dimensional sun, do the nuclear reactions still operate that keep the sun generating heat? Or one can think about four-dimensional atoms and molecules forming a four-dimensional piece of salt, metal, or wood, but what structure and bonding would they have? In four-dimensions, would atoms even exist? At the center of an atom, protons and neutrons that are bound together into the nucleus. In four-dimensions, does this binding still take place? Nobody knows. Bob Erck Click here to return to the Physics Archives

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