What are the '10 dimensions' that physicists are always talking about?
The first four are the ones we all know and love: Three dimensions for space and one dimension for time.
The other 6 are called 'internal degrees of freedom' and are related to the number of fundamental symmetries present in the physical world at the quantum scale. The equations that physicists work with require these additional dimensions so that new symmetries can be defined that allow physicists to understand physical relationships between the various particle families. They think these are actual, real dimensions to the physical world, only that they are now 'compact' and have finite sizes unlike our 4 dimensions of space and time which seem almost to be infinite in size. Each point in 4 dimensional space-time has another 6 dimensions attached to it which 'particles and forces' can use as extra degrees of freedom to define themselves and how they will interact with each other. Do not confuse them with 'hyperspace' because the particles do not actually 'move' along these other dimensions. They are not 'spatial' dimensions, but are as unlike space and time as time is unlike space!
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