Planning on buy laser..Safe but awesome?

Hey guys Im planning on buying a laser but I dont want to go about 50mw because Im going to get the laser to prove to my friend that they can >10miles. But the only problem is that Will mW increase or dcrease the seeing distance? I understand about the weather and atmosphere but I want to if mW can affect distance. If it doesnt Which Laser wuold be safe for outside use and can go REALLY far? Im new to this laser thing guys

If you only care about distance, you should pay attention to the divergence of the laser, not so much the power. Lower divergence means lower spread means longer range. If you want to get as low divergence as possible, get a beam expander (google it).

Safe and far would be 5mW with beam expander. But 10 miles ? Hard to say.
If you want to go further, you can increase power (mW), but going beyond 5mW will make it not-safe.