If you shine a powerful laser, held at dead level, does the level of the beam drop at all?
February 1, 2010 – 7:02 amat any point, like say, a rifle bullet will?
And secondly, how far will it shine into space before it stops, assuming it doesnt hit anything that would block it? is it based on the initial power and strength of the laser? Would two different lasers, one being twice as powerful as the other, shine different distances into space?
8 Responses to “If you shine a powerful laser, held at dead level, does the level of the beam drop at all?”
Short answers -
1- No
2 - Forever, until it hits something
3 - Nope. Even light from a candle travels forever.
4 - Both the same, just the density of photons per area at a given distance will be twice as great in the more powerful one.
Yes, gravity bends light, but here on Earth not near enough to match bullet drop in fact, not enough to be easily detected. You should consider it a perfect straight line, as it would take some pretty sophisticated equipment to detect the bend, even though it can be accurately calculated via general relativity. In fact, in the context of general relativity, the light doesn’t actually bend, but rather space-time is distorted by gravity making the light appear as if it had bent. Odd but true.
The photons sent into space will never stop until they hit something, even from the smallest laser (or other source of light for that matter). But what happens is that the photons disperse, as in the beam widens, so much so that it becomes difficult to see them bouncing off something. For example, the Apollo missions left retroreflectors on the surface of the moon so that we could accurately measure the distance to those points by shining pulsed lasers at them and measuring, down into the fractions of a billionth of a second (light travels about 1 foot per billionth of a second), the time it takes for the photons to go from here to the retroflector and back. I don’t know what power the laser (though likely not more than 100 watts maybe?), but this link
http://www.lpi.usra.edu/lunar/missions/apollo/apollo_14/experiments/lrr/
reports that the laser is passed into a 30-inch telescope which reduces the beam spread, is 5 miles in diameter by the time it gets to the moon (meaning that only a very small fraction of the photons actually hit the retroreflectors), and the spread from retroreflector to Earth is 20 miles, thus only a small fraction of the small fraction actually gets back here. But it is enough for sensitive instruments to detect.
By Gary H on Feb 1, 2010
Sure, gravity bends light…not sure about your other questions.
By Peter C on Feb 1, 2010
Depends on how technical you want to get.
There has never been a perfect laser built that does not dissapate/lose power/widen over distance.
A beam has been shone on the moon from earth that was only so wide (something like 20 or 200 meters??)
A laser beam will be effected by other energy including gravity and magnetism. But practically, the beam will shine perfectly level for construction work purposes etc…
I think the power output and focus determine how far a beam will travel. And I think that the beam will travel to the end of the universe if uninterupted and focussed perfectly
The laser from an old CD burner/player can burn through plastic. Fun experiment.
By instantdegrees_scam on Feb 1, 2010
1. A laser beam would bend to gravity, but not like a bullet. You would need a black hole to bend it.
2. Any light, which is not distracted, will be seen for indefinit distance, depence on the telescope used to see it. But even in space is matter, which will distract it after some distance.
By clambacke on Feb 1, 2010
Gravity will bend the laser and it doesn’t require a black hole as Clambacke says. There have been experiments involving the bending of light during eclipses that have demonstrated that fact. I don’t remember for sure but I think it was a solar eclipse and the gravitational pull of the sun did the bending of light from a star.
By oil field trash on Feb 1, 2010
There are particles even is intergalactic space, there is the imperfection of surfaces of the laser. There is gravity. Those would all limit the straight travel of a laser beam.
By Generalist on Feb 1, 2010
Light (all light, not just lasers) travels through space until it encounters an opaque object. However, the intensity of the light varies with distance, because the original wavefront spreads over a larger and larger areas. The energy of that wavefront is then dissipated over the entire area of dissipation.
The intensity of the light varies as 1/r² (whether it is focused or not, the illuminated are increases by this ratio). The difference is that an equally radiating light shines its energy in all directions, so if the intensity at 1 m is 1 W/m², the original power of the light must have been 4*pi watts. But that same 4*pi W light source, focused into a 1/2 arc-min beam produces an intensity of 1.5 x 10^8 W/m² at 1 m. If one has a detector that can detect intensity of 10^-6 W/m² (which is quite reasonable), the focused beam will be detectable for over 12,000 km, whereas the unfocused light will only be visible for about 3.5 km.
By dansinger61 on Feb 1, 2010
man did you write the riddles for the riddler on batman?
well i can answer this question. how many boxes of wine would you buy for the holidays? ha ha man i cannnot answer that one, you are too much for me these days!!!
By PhatBeatz on Feb 1, 2010