How frequent is travel across dimensions?

[Vikkram]

Does cross-over between separate dimensions more frequent than we believe? Do ghosts, supernatural beings or aliens use star-gates or dimension travel to bypass the intergalactic distances?

[Francis]

How can dimensions be separate? The whole point of dimensions, surely, is their connectivity.

In terms of movement in dimensions other than the four we are aware of... it's rarely used intelligently.

[Vikkram]

Thanks for your reply Francis.

The basic premise of the dimensions is that they are separate; if not then why would they be considered two dimensions and not one and the same dimension in the first place? The connectivity is not universal but only at specific ‘points’ sometime called ‘star-gates’. If that was not the case, don’t you think that the human world would have long since been invaded and overrun by powerful entities from other dimension, be they ghosts, jinns or aliens?

Care elaborate on the four dimensions that you have mentioned?

[Francis]

Our usual human awareness is of three spacial dimensions and one temporal, although time is a tricky concept and maybe an emergent phenomenon rather than a fundamental dimension.

'Dimensional travel' usually implies travel along a path that isn't constrained to the familiar three spacial dimensions. Some would say that our three-dimensional universe may be like a rumpled sheet in a higher-dimensional space, and that wormholes could create short cuts, rather like taking two distant parts of the sheet and stitching them together. Of course, the energies required to do this are phenomenal...

Alternatively, the universe could be made of lots of entirely separate sheets, that again could be stitched together.

Or the universe is a Christmas tree and we could, like spiders, connect needles together with silky webs.

[Humberto]

In SciFi there are portals (wormholes), there is also cryptic travel to alternate dimensions. However, scientists are not sure of the 3 dimensions, we could be living in a hologram.
There is plenty of scope for inventing good stories.