"There are two kinds of group meditations: 1. Many sitting at the same time and the same place, and 2. Sitting at the same time, but not at the same place.
Yoga Philosophy views the mind as Universal field; its waves passing through us and becoming our individual minds. This Universal mind is a radiant force and is also known as a Universal Guru within.
When all sit together at the same time even in different parts of the world, they connect to the Universal Guru mind and generate a strong field, like so many magnets being joined together and forming a much stronger magnet; the strength of each then equals the combined strength of all.
Thus it is when we join together in meditation, and together enter the Guru-mind's Field. On certain days of the year the Wave of Beauty and the Wave of Bliss flows very strong. These are the sacred days."
~ Swami Veda Bharati, Rishikesh, India