"While the light travels at about 300,000 kilometers per second, the thoughts reach practically instantly to the place of destination. The thought is finer than the ether (n.n. Shivanada does not speak here about Akasha, the ultimate subtle matter, whose vibrations produce the entire manifestation, hence the thought, but the subtle environment through which the electricity is transmitted), the environment of electricity.

Via a radio broadcast, a singer singing at Calcutta can be heard in our own apartment in Delhi. Any message may be received by means of such transmissions.
In a similar way the human mind behaves. A saint who exudes spiritual waves of peace, harmony and balance, actually sends into the world thoughts of peace and harmony. They travel faster than light in all directions, penetrating into other people's minds and producing, through the subtle phenomenon of resonance, similar thoughts of harmony and peace. Instead, a man engaged in worldly activities, whose mind is full of jealousy, revenge and hatred, emits discordant thoughts that in turn penetrate the minds of thousands of people, creating similar, disharmonious states.

The environment through which the thought travels

If we throw a stone into a pool of water, it will produce a succession of concentric waves having as epicenter the place of impact. The light of a candle will also give rise to waves of ethereal vibrations traveling in all directions, starting from the center.

In the same way, when a thought, good or bad, crosses a person's mind, it gives rise to vibrations in MANAS, (or mental atmosphere), which will travel in all directions, at a great distance from the transmitter.
What can be the environment through which the thought travels from one mind to another?
The best explanation is that MANAS, or the substance of the mind, fills as an ether the entire space, serving as a vehicle for thoughts, just as the PRANA is the vehicle for feelings, light and electricity, and the air for sound. The ether of space records thoughts

The force or power of thought is so great that you can spin the earth through it. It can be transmitted from one man to another. For example, the strong thoughts of the great sages of yesteryear, also called RISHIS, are still preserved in AKASHA.

Clairvoyant yogis can perceive these thoughts-image. They can still read them. We are practically surrounded by an ocean of thoughts. We're floating in this ocean. We all absorb certain thoughts and emit others into this universe of thoughts. Thus each has his own world of thoughts, and all these worlds dissolve into the great ocean of the Cosmic Mind.

Thoughts are vivid

Thoughts live. They are as solid in their world as they are a stone in the physical world. Our body may cease to be, but our thoughts can never die. Each change of thought is accompanied by a new vibration in the mental matter. The thought-force needs a certain subtle matter (an environment) to be able to act. That is why the stronger the thoughts are, the sooner their results will appear. When the thought is focused, being given a certain particular direction, it will produce certain effects, directly proportional to the concentration power of the transmitter (that is, with the force with which it emits the thought). [...]

The wonders of vibration-thought

Any thought that starts from you is a vibration that will never die. He will continue to pass through his vibration all the particles of the universe, and if it is a noble, holy and powerful thought, he will similarly activate all the minds that resonate with him. This mechanism will allow all those who sow you to unconsciously take your thoughts and begin to emit similar thoughts according to their own inner capacity. The result will be that even without knowing the consequences of your own actions, you will have set in motion huge forces, amplified by the power of resonance, which will defeat the evil thoughts emanating from the selfish or evil ones."

Excerpt from the book "The Power of Thought" by Swami Sivananda