Time-thickening

From Tardis Wiki, the free Doctor Who reference

Time-thickening was the increased "thickness" of the underlying foam-structures of space itself.

When an object time travelled, it carried some of the space-time it came from with it. That residue was deposited at the point of arrival. This process was used militarily in the War in Heaven, an example of which being how Gravity Spiders detected enemy timeships. (PROSE: The Book of the War)