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How far is up?

U

usakicksass

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I have a RPL-225, when I shine it into the night sky it looks like the beam goes maybe a 1000 feet into the air. However when I shine it at something land based it obviously goes further than 1000 feet. When I shine it into a cloud filled sky I see the beam impinge on the cloud . I was wondering how far does the beam go into a cloudless sky. Is there a layer, perhaps one of the inversion layers that stops the beam cold. Or am I seeing the beam 50 miles into space? Wish I knew.
 





Razako

Razako

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Would someone in the space station be able to see the light from a standard 300mw green laser? This is assuming that you can keep the beam pointed at the space station as it flies through the sky and the guy on the station is looking straight into the beam.
 
C

Chad

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^
if the divergence was damn near 0 mRad, then yeah. Otherwise, notta chance.

And yes, it does technically go forever... there's just a threshold where it gets to dim for our eyes to process.
 
T

Things

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Yup, it all depends on divergence. If you have a 0 Mrad laser and a telescope, you'd be able to see the dot on the moon, but by the tme the laser gets to the moon, the dot would be around 10M big! :eek:
 
JLSE

JLSE

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Razako said:
Would someone in the space station be able to see the light from a standard 300mw green laser?  This is assuming that you can keep the beam pointed at the space station as it flies through the sky and the guy on the station is looking straight into the beam.
Click to expand...

I would bet a 300mW green with decent optics could be seen at the other end. With nothing to absorb the light, and from say a boat (reduced dust), no cloud etc. I would imagine if they were looking at the exact spot, they could see a faint glare. Keeping in mind of course, a couple of key elements. They circle around us 16 times per day, traveling at 17,500 mph in an orbit varying 208 to 285 miles from Earth. Just trying to catch it with a telescope would be a challenge in its own. Plus it would help if you were in communication with one of its residents :)

NASA actually runs a page with a java app. which locates unmanned satellites in relation to your zip code found here-

http://science.nasa.gov/RealTime/JPass/25/JPass.asp
 
M

Murudai

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Things said:
If you have a 0 Mrad laser and a telescope, you'd be able to see the dot on the moon, but by the tme the laser gets to the moon, the dot would be around 10M big! :eek:
Click to expand...

Actually, if it was a 0 mrad laser the dot would be the same size as it would be exiting the laser :) But of course, we know they don't exist :)

Does anyone know what the lowest mrad that has been managed?

And it'll be funny in 10-20 years when laser pointers get so good that you can shine them at space stations :) Think shining at planes will have big fines and jail sentences? Imagine the fines for shining them at spacecraft :eek: :eek: :eek:
 
D

Dingers

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Murudai said:
[quote author=Things link=1209442719/0#5 date=1209447381]If you have a 0 Mrad laser and a telescope, you'd be able to see the dot on the moon, but by the tme the laser gets to the moon, the dot would be around 10M big! :eek:
Click to expand...

Actually, if it was a 0 mrad laser the dot would be the same size as it would be exiting the laser :) But of course, we know they don't exist :)

Does anyone know what the lowest mrad that has been managed?

And it'll be funny in 10-20 years when laser pointers get so good that you can shine them at space stations :) Think shining at planes will have big fines and jail sentences? Imagine the fines for shining them at spacecraft :eek: :eek: :eek:
[/quote]

lol nothing would happen.

Orbital velocity is maintained through automated thrusters.
 
Switch

Switch

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Pointing lasers at astronauts performing maintenance routines on satelites. :D Punishment would probably be execution , if you get 14 years for carrying a laser around.
 
roSSco

roSSco

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MB500 said:
No beam in space though. No beam in a vacuum.
Click to expand...
Please elaborate. :-? I think light has little trouble traveling through space. How else could we see many light years away?
 
Cyparagon

Cyparagon

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Strictly speaking, UP is a direction, not a distance.

How many gallons long does your left elbow weigh?
 
A

Ace82

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The more dust, pollution, moisture, crap in the air, the more visible the laser beam.  In a “vacuum” (space, or inside a light bulb) is no air, therefore no particles.  I believe that the air pressure has a type of density where at a certain altitude limits these beam-revealing particles.  I believe the actual light will continue on forever, lessening in power as it diverges and collides with particles.  Is a 300mW laser light visible from space?  I would believe so, on a perfectly clear night, maybe from a mountain top, I vote yes.

Edit: A vacuum is the absence of air pressure, or negative air pressure if in the atmosphere.  When you break a light bulb, it actually implodes not explodes.  On a turbo car, you have the vacuum PSI (-), then 0, then (+) PSI which is boost.  Back to the light bulb, I believe it was Thomas Edison who invented the light bulb in a vacuum tube so the oxygen wouldn't burn up the filament. http://dictionary.reference.com/browse/Vacuum
 
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