Construction Tools HQ

Pointer Distance

 

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How far could the ray from my Laser Pointer travel?

At some clear and starry nites, I often point out the stars with my laser pointer. I wondered, how far does the ray travel? Does it ever reach the distance stars out there?

In the vacuum of space the light from your laser-pointer would, theoretically, travel forever -- except that outward pressure from the photons, from which the the light is composed, eventually disperse the laser's coherent-light beam.

Here on Earth, the energy in the beam is sapped, little by little, from collisions with the gas molecules in the air, as well as the dust particles and tiny water droplets suspended in it (remember that air is not invisible; it is merely transparent, and miles and miles of it add up, the same way that thin glass panes that seem to clear individually form a dark green opaque mass when stacked twenty thick), with all the energy scattered and absorbed.

Still, though your laser-pointer will not illuminate significantly beyond a range of 200-300 feet, its light is still intense enough to trigger the receptors in the retinas of observers a mile or two away. To them it will appear as just a tiny point of light.

PS: In the early 1960s NASA bounced a very powerful laser beam off the surface of the Moon, 238,000 miles away. The beam started out at the source less than a half-inch wide; by the time it struck the moon it was nearly a mile wide (and very faint) as a result of the pressure from the energetic photons (and some inevitable dispersal due to its passing through the Earth's atmosphere on the way to the Moon).

Metal detecting whites bullseye 2 pin pointer distance test


 

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Late run lifts Lady Warriors
SALEM — The Cotter Lady Warriors used a 16-2 fourth-quarter run to distance themselves from Salem and improve to 3-0 in the 2A-2 Conference with a 67-55 victory over the Lady Greyhounds Monday night at the Dawg Pound.