Laser pointer travelling faster than the speed of light?

[AJ_Dual]

It's quite amazing how if you know the name of something, all the information you could ever want is just a few seconds away, but if you don't know what it is called and don't have access to a learning institution you are SOL.

Just FYI, I didn't know it was called "Superluminal Motion" until I'd found my link. Although I did recall some vague memory that the effect was able to be seen in Astronomy, and while I wasn't 100% sure, I was pretty certain that Quasars, radio galaxies, and supermassive black holes were the things powerful enough to make "Beams" that long. So I was able to plug a few good-guess keywords into Google to find the Wiki for the topic.

"Jet, faster than light, astronomy" was what brought it up for me.

 

[flare09]

Let's 'slow' things down. Go to your backyard, grab your hose and attachment and set it to jet or stream. Now essentially think of the beam of water your laser. Slowed down. Now move your jet across the yard. That's exactly the same thing that happens. Light is not as instintanious as you think. Just really fast.

 

[Encap]

The same thing is happening if you are pointing at a wall 50 feet away or pointing at Saturn.

The speed of light is the speed of light or it would not be called the speed of light.

Even if you could move your wrist faster than the speed of light all that would happen is the beam/dot would pulse.

 

[AJ_Dual]

The same thing is happening if you are pointing at a wall 50 feet away or pointing at Saturn.

The speed of light is the speed of light or it would not be called the speed of light.

Even if you could move your wrist faster than the speed of light all that would happen is the beam/dot would pulse.

If you could move your wrist faster than the speed of light, just flicking it would compress the air around it to plasma, create secondary fusion events in the carbon, nitrogen, oxygen, and hydrogen from the trace water vapor in the air, create lots of X and gamma rays, and it would be similar to the detonation of a nuclear device.

LOL.

Good thing for Kansas that young Superman was careful when spankin' it, thinking about Lana Lane as a boy...

 

[bunny]

Let's 'slow' things down. Go to your backyard, grab your hose and attachment and set it to jet or stream. Now essentially think of the beam of water your laser. Slowed down. Now move your jet across the yard. That's exactly the same thing that happens. Light is not as instantaneous as you think. Just really fast.

This. Think of the light as packets and nothing strange happens. If you change direction of your wrist you aren't bending the existing beam, you have to send new photons again from the source and create a new beam. The dot would move faster than the speed of light in the sense that you could send a photon in the -x direction and the next photon in the +x direction, wait a year, and then say that your laser dot jumped two light years instantaneously!

I believe the astronomical superluminal motion results because there is luminous matter being ejected at near light speeds, so the jet is actually approaching you and continuing to emit at the same time, unlike the case of our laser pointer simply being twisted. Since new radiation is being emitted closer than the older radiation, it gets there faster and causes the illusion of superluminal travel.

 

[L0nghair0o0]

Sorry for ressing this thread, but I wanted to share a youtube channel that I think is great and everyone should check out.

He does a great job of explaining this here


video is broken for me, here is the link http://www.youtube.com/watch?v=lR4tJr7sMPM&list=PLED25F943F8D6081C&index=47&feature=plcp

 

[ZRaffleticket]

to put a video in a post just have the video ID in the youtube tags, so (YT)lR4tJr7sMPM(/YT)

And I agree, it's explained well here.

 

[HighOntology]

Since laser beams are to travel infinitely across the universe until the light is absorbed by matter, let's just say that I take a laser pointer, turn it on, point it at the night sky and flail it across in my wrist hitting saturn from the earth which is about 1.2 billion kilometres away (close enough for the laser beam to reach saturn as it's not lightyears away). Do you think that the laser dot or the beam moving across saturn moves faster than the speed of light? For instance another matter reachable within less than a light year, if saturn is too close for the laser to travel faster than the speed of light or maybe a machine that can move faster than my wrist might be contributing factors for making a laser pointer dot travel faster than the speed of light. The farther away the matter from earth is, the more sensitive the speed of the laser beam with the movement of your wrist is when it hits the matter. Think of it as this, you point your laser pointer at something that's 5 feet and the dot doesn't move as much. Now point it at something that's 500 metres away with the same steadiness as a target at 5 feet, the dot from the laser will move all over the place. Same concept as pointing it at planets and other matter in space. What do you guys think. I hope my explanation isn't too complicated.

There is a famous thought experiment I learned from a physics grad student at UT. Imagine being in a big smooth black cube. Or imagine being inside the gigantic Big Brother Monolith from 2010. You’re in a corner, leaning against the left wall, which extends forward 100 miles. Now, hold your laser close to the wall, aim at straight at the left wall, and begin rotating it parallel with the floor, so that a spotlight is moving forward. The further along it is the faster it goes.

The speed of the spotlight just before it becomes a ray that is parallel with the left wall—that is, just before it jumps from left wall to opposing wall—is indeed greater than c.

 

[steve001]

Since laser beams are to travel infinitely across the universe until the light is absorbed by matter, let's just say that I take a laser pointer, turn it on, point it at the night sky and flail it across in my wrist hitting saturn from the earth which is about 1.2 billion kilometres away (close enough for the laser beam to reach saturn as it's not lightyears away). Do you think that the laser dot or the beam moving across saturn moves faster than the speed of light? For instance another matter reachable within less than a light year, if saturn is too close for the laser to travel faster than the speed of light or maybe a machine that can move faster than my wrist might be contributing factors for making a laser pointer dot travel faster than the speed of light. The farther away the matter from earth is, the more sensitive the speed of the laser beam with the movement of your wrist is when it hits the matter. Think of it as this, you point your laser pointer at something that's 5 feet and the dot doesn't move as much. Now point it at something that's 500 metres away with the same steadiness as a target at 5 feet, the dot from the laser will move all over the place. Same concept as pointing it at planets and other matter in space. What do you guys think. I hope my explanation isn't too complicated.

Yes, you assumed correctly.

 

[Rosalita Gata]

Since laser beams are to travel infinitely across the universe until the light is absorbed by matter, let's just say that I take a laser pointer, turn it on, point it at the night sky and flail it across in my wrist hitting saturn from the earth which is about 1.2 billion kilometres away (close enough for the laser beam to reach saturn as it's not lightyears away). Do you think that the laser dot or the beam moving across saturn moves faster than the speed of light? For instance another matter reachable within less than a light year, if saturn is too close for the laser to travel faster than the speed of light or maybe a machine that can move faster than my wrist might be contributing factors for making a laser pointer dot travel faster than the speed of light. The farther away the matter from earth is, the more sensitive the speed of the laser beam with the movement of your wrist is when it hits the matter. Think of it as this, you point your laser pointer at something that's 5 feet and the dot doesn't move as much. Now point it at something that's 500 metres away with the same steadiness as a target at 5 feet, the dot from the laser will move all over the place. Same concept as pointing it at planets and other matter in space. What do you guys think. I hope my explanation isn't too complicated.

The speed of light only limits cause and effect between locations. You could point the laser at one side of Saturn and then quickly point at the other side. The dot, if you could see it, could move faster than light, but, the movement would not happen until about 1.5 hours after you moved your hand. No effect will happen until the new beam direction reaches Saturn in 1.5 hours.

 

[Rosalita Gata]

There is a famous thought experiment I learned from a physics grad student at UT. Imagine being in a big smooth black cube. Or imagine being inside the gigantic Big Brother Monolith from 2010. You’re in a corner, leaning against the left wall, which extends forward 100 miles. Now, hold your laser close to the wall, aim at straight at the left wall, and begin rotating it parallel with the floor, so that a spotlight is moving forward. The further along it is the faster it goes.

The speed of the spotlight just before it becomes a ray that is parallel with the left wall—that is, just before it jumps from left wall to opposing wall—is indeed greater than c.

Your observed passing of time will change so that you observe any light moving at C.