Yeah but what they are not accounting for is that the light actually has to come off the mirror. You can demonstrate this with a hand mirror that the illumination spot gets larger quickly at a distance. Take a mirror and find the sun. Send a reflection to the wall nearest you. Then send the reflection to a wall further away. The reflection on the wall further away is larger and therefore, the energy more spread out. The light coming off the mirror is not perfectly parallel as it had to pass through the atmosphere, then interact with the surface of the mirror. We do use mirrors for calibration in satellite remote sensing, but you will get far far far far more power arriving at something like the ISS coming from a much less powerful laser over such a distance. If we controlled by wattage, a laser will absolute crush a mirror in its ability to transmit energy over a distance.
Refraction and reflection. Most non specialty (consumer) mirrors have low quality and standards, so are affected by these more than other specialty mirrors.
Yeah but any mirror that isn’t imaginary has some kind of surface coating that’s a different refractive index than the atmosphere, and then the light has to interact with the surface of the mirror, which is not a perfect reflector and has imperfections, not to mention the light just had to pass through 400km of fluid atmosphere of varying density and composition.
Its a bet I’m very willing to take.
Send a reflection to the wall nearest you. Then send the reflection to a wall further away. The reflection on the wall further away is larger and therefore, the energy more spread out.
I am very confident that you have not tried this for yourself. I want you to show me pictures of this happening (with sunlight); I think you will find the experience educational.
(Edit: The mirror and the wall must both remain at the same rotational angle – if you angle the mirror to move the spot, and the spot becomes elongated because it’s now coming in at a more acute angle, it doesn’t count. Shining a sunbeam on the edge of a doorframe and then through the door to a faraway wall that’s through the doorway would be a good way to do it.)
