While heat can set liquid in motion, the researchers discovered that in this case it was the gentle radiation pressure generated by photons - discrete packets of light energy - that moved the fluid.

oh, bullshiat. 'gentle radiation pressure'?!? photons have electric and magnetic fields - it's not a radiation pressure, it's a farking static field being generated. who doesn't know that static electricity can bend water? brush/comb your hair, turn on a faucet to the slightest trickle possible without dripping, and slowly move the brush/comb towards the stream. wah-lah!

in other news, beer causes pee

/not a scientist, but i play one when i drink
//gotta pee

It's now only a matter of time before mankind perfects the beer laser.

/but still no cure for cancer

Megain

Aren't they talking about light pressure from the partical pressure of moving light? Just like on solar light sail? In which case, it sounds interesting.

So that's why my beer spilled when I threw a lamp at it... Hmmmm....

NERRRRRRRRRRDS!

They've been using this for years in optical tweezers. This is by no means a new idea.

Megain: it's not a radiation pressure, it's a farking static field being generated.

Show me your 'static' photons and I'll show you a Nobel Prize.

Screw nanotech, this could lead to hydraulic computers!

"Yeah, my car can bounce 3 feet over the top of the curb, and I'm running Folding@Home too!"

MacEnvy: Aren't they talking about light pressure from the partical pressure of moving light?

no. actually, they said 'radiation pressure', which is an entirely different thing

Cool, now I can get a gizmo to deflect the rain from my car.
Just like star wars.

Solar sails ftw.

And this serves what purpose again?

I'm no physicist. But i feel like this deserves the "Wow! Old news is so EXCITING!" pic.

Any physicist out there that can explain this a little better.

astro716: Show me your 'static' photons and I'll show you a Nobel Prize.

i didn't say there are static photons. i hypothesized that photons create an electrostatic field around them as they travel, based on their inherent properties

i came in here to say what tortilla burger said.

Megain: i didn't say there are static photons. i hypothesized that photons create an electrostatic field around them as they travel, based on their inherent properties

"Static" means "still", when photons are anything but. Photons do carry momentum even though they are massless, and thus can exert radiation pressure. The solar sail mentioned by MacEnvy is a good example.

aspAddict: And this serves what purpose again?

It allows us to part the Red Sea at will and provides fodder for a sequel to The Core. This will not end well.

smart

even MORE amazing is how LIQUID can bend LIGHT!

He should see my lava lamp.

Get back to me when a laser can bend croissants.

Calren
It allows us to part the Red Sea at will and provides fodder for a sequel to The Core. This will not end well.

My worst fears are confirmed...I'll get the tasers.

No, liquid can bend light.

I'd bet that tortilla burger and proteus_b are right about this. Radiation pressure is incredibly weak -- the sort of intensity that'd be required to move liquids around quickly enough to notice would be far more than enough to vaporize those liquids. But dielectric materials (which means pretty much everything) are attracted to electric fields (static or oscillating), which is the effect exploited by optical tweezers. The liquid simply follows the areas of strong E field.

Not exactly new physics, but a potentially useful application that, apparently, nobody had thought to try before.

Megain: /not a scientist...

We can tell.

I would agree with the above posters in that this could be a electrostatic effect on the Oil/Water substance they are using. But, they don't say how much pressure in KeV or the equivalent Newtons those lasers pump out either...

/I remain skeptical

Professor Science: Radiation pressure is incredibly weak -- the sort of intensity that'd be required to move liquids around quickly enough to notice would be far more than enough to vaporize those liquids

I think that's the point though, and why this is something 'new': The liquid being manipulated is a soap film, and with a low enough energy laser with a large enough flux, it is being manipulated through radiation pressure alone. At least, that's how I'm reading this article.

astro716: "Static" means "still", when photons are anything but. Photons do carry momentum even though they are massless, and thus can exert radiation pressure. The solar sail mentioned by MacEnvy is a good example.

'static' does not mean 'still' when referring to electricity, but ok. as for radiation pressure... yeah, ok. i'm just saying that the 'radiation pressure' is because of the electromagnetic force - which is not only how radiation pressure is pretty much defined, but also nothing new

Megain: 'static' does not mean 'still' when referring to electricity

Yes it does, we are talking about electric fields here. A static field is one that is not time dependent. It's not changing. A photon wizzing by means the local electric and magnetic fields are changing.

Yeah, I read that headline backwards a couple of times...

Professor Science

Not exactly new physics, but a potentially useful application that, apparently, nobody had thought to try before.

Actually, there are two forces involves in laser trapping--the gradient and the pressure, though I agree that the radiation pressure is probably insufficient by itself to move (or trap) anything larger than a few hundred nanometers. I doubt this is the first application of concept to a macroscale, but probably the first reported.

Check out Bustamante's work (Berkely)--fascinating stuff I worked on for a while at a different university.

Professor Science: I'd bet that tortilla burger and proteus_b are right about this. Radiation pressure is incredibly weak -- the sort of intensity that'd be required to move liquids around quickly enough to notice would be far more than enough to vaporize those liquids.

Well, they're not really "moving liquids" around, they're bending a very delicate liquid/liquid interface, and the laser power they're using isn't nearly strong enough for an optical tweezer. There's a neat overview at the guy's website:

http://jfi.uchicago.edu/~rschroll/brownbagpres.pdf

Mad Tea Party: We can tell.

thanks for your dissertation proving your superior insight. i'm impressed

but yeah, i'm just tossing thoughts around, and have clearly stated i'm not qualified as an authority on the subject (by any means). your contribution to the discussion has been noted, such that it was

Physicists from France and the U.S. have used a laser beam to produce a surprisingly long and steady jet of soapy liquid that is narrower than a human hair. The researchers were then able to push the liquid into a "hump-like shape", by directing the laser at a different angle.

Yeah, whatever...when I hump I can produce a surprisingly long and steady jet of soapy liquid into human hair too...

What if CAT....was spelled

D O G

Hey, psychedelic drugs can bend everything!

Once while walking down the street I heard a lamppost talking, but couldn't make out what it was saying. It was incoherent light.

Megain: 'static' does not mean 'still' when referring to electricity

Leave the thread now please, you are embarrassing yourself.

All_Hail_Hypno_Toad: What if CAT....was spelled

D O G

for one, schroedinger would feel silly

tom servo bit me

I second that, Nerds. Since when has the Fark discourse become so highbrow? Where is the FSM and that freaky skater chick with the bug eyes when you need them?

You're bringing us down, man!

Not_Enginerd: Leave the thread now please, you are embarrassing yourself.

hey! i was just getting warmed up! you people are too easy

but yeah, i'm out. i've caught my limit

Plus:

"Just the gentle pressure of a beam of light is enough to bend and direct streams of a special liquid ... "

so how hat should really read is:

"Just the gentle pressure of a > beam of light is enough to bend and direct streams of a special liquid (designed specifically to react, by its molecular construction to those specially manufactured beams of light.)


Atricle is bullshiat.

All_Hail_Hypno_Toad: What if CAT....was spelled

D O G

"for one, schroedinger would feel silly"

Well, either him..or the radioactive atom. Poor atom.

Megain, however you paint it, you're off. Light can't create a static electric charge - to do that, you need a charge carrying particle that stays in the same form after colliding with whatever you're charging.

An electron is the usual method for that - positrons have a nasty habit of annihilating with normal matter, and protons are inconveniently large and can't be stripped out of atoms the way electrons can. If their laser is putting out enough electrons to accomplish, they have a worse problem on their hands than what it's doing to the liquid.

Photons are neither charge carrying nor do they remain unchanged after interacting with matter. And if it was a static field, what's then effecting the fluid? They're not running it through a magnetic field, induced or otherwise. You'd just have electrically charged liquid falling through space, which in the absence of an outside field, falls exactly like uncharged liquid.

Your problem here is that you're thinking of the electromagnetic force as a single effect, like gravity. It isn't - it has a number of different aspects, which is why until relatively recently it was still thought to be two and possibly three separate forces and not one. (For that matter, the gravitational force has several aspects that aren't what we usually call gravity. Saying light creates a static electric charge on illuminated objects is akin to saying that rain falls because of gravitational time dilation - right fundamental force, wrong effect).

It could be thermal, if anything. A few demonstrations of light pressure have actually been caused thermally (The laser heats the illuminated side of the target, causing air on that side to expand). TFA points out that they've already considered and tested that, and they've confirmed that it isn't thermal. Shouldn't be that impressive, really - this is a liquid designed to be an extremely weak soap film, and it's being manipulated by what's probably a class IV laser.

I think what's happening is that the laser is disrupting the surface tension of one side of the fluid which is causing it to bend. I doubt that the light is strong enough to actually push the fluid. Photons don't carry a lot of momentum... or do they???



I had one of these sitting in a window many years ago. Light can push the vanes around.

neat.

I swear I thought the link was going to Cosmo magazine when the url popped up. Luckily I was mistaken.

L.Darte: Actually, those are thermal. The wiki article the image comes from explains basically how they work.

The inventor thought it was light pressure, but if it was, the vanes would rotate the opposite direction - the reflective side of the vane absorbs more momentum per photon than the dark side.

It's actually pretty cool - you can get one of them spinning really fast in the dark by putting it above a radiator.

Hevach

is fun at parties

/j/k
//chicks dig dudes with big brains
\\huh