# Why Won't My Laser Hit Low-Lying Clouds? **URL:** \ **Category:** Factual Questions\ **Created:** [August 28, 2002, 1:47am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865 "2002-08-28T01:47:24Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Jim\_B](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jim_b/32/4338_2.png) [@Jim\_B](https://boards.straightdope.com/u/Jim_B)\ **Post date:** [August 28, 2002, 1:47am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/1 "2002-08-28T01:47:24Z")
I bought one of those pocket lasers a couple of years ago. And shortly after I bought it, I did a little experiment late at night. I took it outside and shined it on various objects to test out its range. It seemed like there was literally no limit to how far I could get it to go. I could shine it on objects literally blocks away. Then I tried shining it on the clouds. And absolutely nothing happened! I know my laser isn’t as powerful as the ones NASA probably has. But shouldn’t my beam go, in theory, out into infinity? Just wondering. 😃 ---
**Author:** ![Berkut](https://avatars.discourse-cdn.com/v4/letter/b/a88e57/32.png) [@Berkut](https://boards.straightdope.com/u/Berkut)\ **Post date:** [August 28, 2002, 1:52am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/2 "2002-08-28T01:52:24Z")
Maybe they weren’t as low as you thought. Also, the cloud probably scatters the light more than a solid object. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 28, 2002, 1:52am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/3 "2002-08-28T01:52:54Z")
I think the problem is you are comparing apples and oranges. First, even a low-flying cloud is likely considerably more than blocks away. Second - you likely are hitting it, but the cloud is not cohesively reflective enough such that your eyes can pick it up. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [August 28, 2002, 1:54am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/4 "2002-08-28T01:54:56Z")
Holy double-dog simulposts, Batman! :eek: ---
**Author:** ![Rhapsody](https://avatars.discourse-cdn.com/v4/letter/r/9de0a6/32.png) [@Rhapsody](https://boards.straightdope.com/u/Rhapsody)\ **Post date:** [August 28, 2002, 1:56am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/5 "2002-08-28T01:56:00Z")
even the best lasers diverge which really explsins why you can see the dot "blocks away’ if the dot didnt get bigger with distance it would be to small for you to see. Anyway all light theoretically will continue on unless stopped by something. The clouds would be hard to see anything from becasue a: they can easily be several miles high, and b: they ae not solid objects. They are vapor/fog what little light does reach that high would be scattered so diffusly that you would not be able to see it unless you started with a very powerful light source to begin with. ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [August 28, 2002, 1:59am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/6 "2002-08-28T01:59:41Z")
Or perhaps the dot that results is simply to small for you to see from that distance? ---
**Author:** ![Morbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/morbo/32/389_2.png) [@Morbo](https://boards.straightdope.com/u/Morbo)\ **Post date:** [August 28, 2002, 2:00am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/7 "2002-08-28T02:00:28Z")
Maybe it’s not working properly…lemme see that… AAAAAUUUUUUUUGHHHHHHHH!!! ---
**Author:** ![Cartooniverse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cartooniverse/32/3084_2.png) [@Cartooniverse](https://boards.straightdope.com/u/Cartooniverse)\ **Post date:** [August 28, 2002, 4:13am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/8 "2002-08-28T04:13:13Z")
> [@](#): > > \*Originally posted by Anthracite \* > \*\*I think the problem is you are comparing apples and oranges. > > First, even a low-flying cloud is likely considerably more than blocks away. > > Second - you likely are hitting it, but the cloud is not cohesively reflective enough such that your eyes can pick it up. \*\* Both true. There may be yet another reason. The hand held laser is capable of FOCUSING for only so far. The light beam may be detectable at some level by highly sensitive equipment ( “light keeps going forever, etc” ), but it does not stay RESOLVED as a tightly focused beam of light past a certain distance. I own some of those too. They’re good for shooting across a sports stadium (indoors), and will show a dot at …what would that be?..200 yards? Maybe a bit more? Hand held commercially sold lasers simply don’t have A) the raw illuminative power, and B) the optics to throw a dot up a few miles to a cloud. Those devices are the purvey of military and scientists, IMHO. I bet Edmund Scientific’s cataloge could prove me wrong, but I can tell you that that hand-held one just doesn’t have the juice. Cartooniverse ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [August 28, 2002, 4:24am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/9 "2002-08-28T04:24:01Z")
A few months ago at work I got my hands on a co-worker’s pointer and shone it up to a level of clouds level with that of the roof of our hotel tower (Ballys Park Place, Atlantic City). I could indeed see the red dot in the sky. ---
**Author:** ![The\_Bad\_Astronomer](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@The\_Bad\_Astronomer](https://boards.straightdope.com/u/The_Bad_Astronomer)\ **Post date:** [August 28, 2002, 4:24am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/10 "2002-08-28T04:24:25Z")
The best way to see it reflected over long distances is to zap a stop sign or car reflector. Otherwise, the beam diverges too quickly to be seen well. There is a brand of green lasers which are better at scattering off junk in the air, and can be seen as a “light saber” for quite some distance. Amateur astronomers use them to point out stars. They are very impressive. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [August 28, 2002, 4:36am UTC](https://boards.straightdope.com/t/why-wont-my-laser-hit-low-lying-clouds/125865/11 "2002-08-28T04:36:42Z")
[World’s Largest Telescope Creates a Virtual Star Over Hawaii](http://www.cosmiverse.com/space01070202.html) > [@](#): > > Scientists have created a “virtual” guide star over Hawaii to be used with adaptive optics on the Keck II telescope to greatly increase the resolution of fine details of astronomical objects. > > The virtual guide star, which achieved “first light” Dec. 23, was created using a 20-watt dye laser to illuminate a diffuse layer of sodium atoms that exists 60 miles above the Earth’s surface. When activated by the laser, the sodium atoms produced a very small source of light, less than 39 inches in diameter, which allowed the adaptive optics system to measure the distortions of the atmosphere. > > ## The resulting virtual star was measured at 9.5 magnitude, about 25 times fainter than anything that can be seen by the unaided eye, but bright enough to operate the adaptive optics system. The star appeared orange, the familiar color of common low-pressure sodium vapor streetlights. > > The Keck virtual guide star system is the world’s most powerful laser currently in use at an astronomical telescope. The laser was developed by LLNL and LLNL staff played a key role in the deployment of the laser at the telescope.