Interacting galaxies are gravitationally bound together, causing tidal distortions in the shape of galaxies. For example, Stephen’s Quintet is five closely spaced interacting galaxies. If galaxies in their motion closely resemble each other, then they can experience strong gravitational interaction at a distance, without even touching. With mutual penetration, galaxies can even merge with each other over several hundred million years.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.