A universe with more phantom energy is an accelerating universe, expanding at an ever-increasing rate. However, this implies that the size of the observable universe and the particle horizon is continually getting smaller — the distance at which objects are moving away at the speed of light from an observer becomes ever closer, and the distance over which interactions can propagate becomes ever shorter. When the size of the particle horizon becomes smaller than any particular structure, no interaction by any of the fundamental forces can occur between the farthest parts of the structure, and the structure is "ripped apart". The progression of time itself will stop. The model says that after a finite time there will be a final singularity, called the "Big Rip", in which the observable universe will reach zero size and all distances will reach into infinite value.