Based on theory of relativity the photon has a relativistic mass. Also, based on theory of gravity everything with mass creates a gravitational field disturbance. Based on these two theories the stream of light creates a gravitational field disturbance. However this stream could be detected as electromagnetic wave only in one direction. Therefore other observers, which is not intersect this stream of light can detect the gravitational disturbance only. For these observers this stream of light will looks like such as a substance with gravitational interactions and without electromagnetic interaction.