If we shoot a burst of light from our most powerful laser into space…how far could it travel before fading, it it doesn’t hit anything? And would it travel straight?
In: Physics
As others have said, without air or other matter to absorb/scatter the photons, they will travel forever.
That being said, the intensity of the light will fade simply because the light will spread out as it travels. Laser beams have a property called divergence that describes how quickly the beam spreads out as it travels (you can picture the beam as a very narrow cone, and the divergence is the cone angle). If you point a laser pointer at something close and then something farther away, you’ll notice that the spot is larger on the surface that is farther away. So as the beam travels through space, it will get dimmer, not because the photons are lost, but simply because they’re spread out over a much larger area.
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