When you point a torch (flashlight) to the sky and turn it on, the light emitted from the torch will travel until it encounters an obstacle or is scattered by particles in the atmosphere. If there are no obstructions or scattering, the light will continue to travel through space indefinitely.
Light, in the form of photons, is an electromagnetic wave that does not require a medium to propagate. In other words, light can travel through a vacuum, such as outer space, without the need for a medium like air or water. This property allows light to travel vast distances.
The energy that allows light to travel at the speed of light (approximately 299,792,458 meters per second in a vacuum) comes from the photons themselves. Photons are particles of light that carry energy. They do not require a continuous source of energy to maintain their speed but rather possess energy by their very nature. This energy is associated with the frequency and wavelength of the light. In other words, the energy of a photon determines the color or intensity of the light.
So, when you turn on a torch, the photons emitted from the light source carry energy, and that energy allows them to propagate at the speed of light until they interact with something that absorbs, scatters, or reflects them.