Particles in our universe undetectable by us

[ufarad]

Is there any reason that there could not be particles in the same universe as us that had their own fundamental forces of strong nuclear, electroweak, and gravity equivalent to those we know and love but which did not affect our particles nor ours theirs all around us (i.e., totally undetectable by us but nevertheless right there in front of us)? At first, I was thinking that on the one hand since most of an atom is empty space, if two particles didn't exert any force on each other, the likelihood of collision would probably be very low, but then I thought to myself, what IS a collision if two particles don't even recognize each other's mass or fundamental forces at all?

 

[phyzguy]

If they are totally undetectable by us, and don't interact with our universe in any way, then there is no way to prove whether they even exist or not, and it becomes a question of philosophy and not one of physics.

 

[ufarad]

My friend, that is why I posted this thought in the philosophy section.

 

[nismaratwork]

Particles like that would... basically be the makings of another universe, much as a different weight for the proton would be. Different, but equivalent forces that have no interaction with our universe would be a decent definition of a parallel universe occupying the same space.