What-If 0013: "Laser Pointer"

[rhomboidal]

http://what-if.xkcd.com/13/

Why do I get the feeling this is exactly how the Death Star was developed?
Possible Scenario

[sardia]

I kept hearing Tim Allen's voice whenever the black hat guy would say "more power!"
As for the death star, Randall's original blog about using a sun to power an interstellar laser was far cooler.

[Vroomfundel]

Well, with the last scenario we stepped quite firmly out of the realm of plausibility but it's an interesting bit of speculation. Anyone run the numbers about what part of the sun's energy output are we delivering through those N.I.F. lasers? I'm trying to imagine it on the cosmic scale as we are already quite out of the earthly scales

[Quicksilver]

I want a shirt of this.

[Alsadius]

Typo in the post - "the $2 trillion" is one word too many, because $2 trillion was not previously mentioned.

Otherwise, an amusing post as always.

[J L]

Space 1999 ... finally

[Diadem]

We ended before we had enough power to instantly blow up the moon? I am disappointed.

[lassehp]

National Ignition Facility? I guess that's supposed to facilitate national ignition? As in setting the USA on fire? Scary.

[ryzvonusef (1151717)]

I want a shirt of this.

I just found my new avatar

Also, I love black hat guy, we need more people that will blow up the earth... FOR SCIENCE!

*EDIT*
Found this on reddit, the neighbours will complain

Spoiler:

[elej]

a very entertaining comic. i think i found a valid use for the world's oil reserve. the two minutes we get would make for some good photographs.

[Max™]

I love the "crouch and dive while holding the welcome mat overhead ready to defend myself" response for an Australian being a reflex because it's true. I forgot "our primary spoken language is screaming", that's a great one.

Australia is where the elemental planes of pain and fear intersect geographically with the surface of the planet.


The comic is also great, and yeah, I thought the blackhat more power would be a great avatar too.

[Gefrierbrand]

I want a shirt of this.

Oh yes me too!
Great What-if!
And great Flood-light neighbor story, too.

[Vroomfundel]

I just found my new avatar

Also, I love black hat guy, we need more people that will blow up the earth... FOR SCIENCE!

*EDIT*
Found this on reddit, the neighbours will complain

Spoiler:

Muahaha, I had forgotten how hilarious http://27bslash6.com was - I think I should buy the book!
I wonder what part of these conversations are real, though.

[Socks]

Haha, fantastic what-if. Reminds me of Mythbusters.
"Well, we achieved our goal, but it wasn't as cool as we thought. What if we multiply the amount of explosive material by 1 million?"
"It will have a massive explosion."
"Let's try it!"

I also love the "Just kidding! You can pick one up for $300."

[rmsgrey]

Well, with the last scenario we stepped quite firmly out of the realm of plausibility but it's an interesting bit of speculation. Anyone run the numbers about what part of the sun's energy output are we delivering through those N.I.F. lasers? I'm trying to imagine it on the cosmic scale as we are already quite out of the earthly scales

In the Lensman series, the next step up from throwing planet-sized negative masses or catching an enemy world between a couple of spare planets with equal and opposite velocities is to use the sun's entire energy output focused into a single beam (strictly as a defensive measure since the power-source was non-portable - at least at that stage of the arms race...)

[bhwrice]

I want a shirt of this.

This is also known as "the Mythbusters approach"

[webgrunt]

The last one should have to been to channel the entire energy output of the sun through an emitter on the earth focused at the moon.

[Inglonias]

Nobody put in this video? I was expecting it at the bottom of the post!
What if we tried a Death Star?

[Envelope Generator]

Sending in a fleet of 747's is not a good idea when you have five billion people on the ground waving laser pointers at the sky.

[bmonk]

My first thought was the question of lightspeed--for example, aiming at the sun would not work too well, as the light takes 16 minutes for a round trip, so the rotation of the earth puts your aim off by 4°, which is a big factor when your target is only about 0.5° wide. However, since the moon is only about 1.25 light seconds away, it takes only 2.5 seconds round trip, so the aim is not a big factor-the moon just doesn't move fast enough to escape.

[mrmidget81]

If anyone were to actually design that shirt it would make a lot of people happy (me included)

[Icalasari]

Only incinerating the Earth's surface?

Bah, not NEARLY enough light!

[The Synologist]

Did anyone else notice that there's an automatic chat window that opens up on the wickedlasers.com link Randall included in the article? Here's how my conversation went:

Joe N.: Hi, thanks for visiting, please let me know if you have any questions.
me: uh... hello?
Joe N.: how can I help you?
me: do you guys really chat with every person who visits this page?
Joe N.: If we are on duty and they want to chat about our products
me: you must be getting a lot of traffic from xkcd
Joe N.: what is that?
people are mentioning it today
me: http://what-if.xkcd.com/
scroll down to "You can pick one up for $300."
it's a direct link to this page
and that's one of the most popular webcomics on the internet, so... yeah
Joe N.: what is the site name?
me: expect to be bombarded lol
xkcd.com
it's pretty famous
http://en.wikipedia.org/wiki/Xkcd
has its own wikipedia page and everything lol
Joe N.: we have beengetting traffic from there
me: it was just posted today, the thing that links here
Joe N.: our screen shows that is where you came here from
me: neat stuff
hope it helps your sales!
please don't sue him or anything haha
he's a nice guy
Joe N.: we welcome the traffic, so long as they don't put us down
me: great
well I'm going to mosey along now...
nice talking to you!
Joe N.: you too, have a good day!

Wonder how many additional visitors they'll have. Probably won't be too too many since it'll only be people that visit the what-ifs, and then only the people that read that far and clicked on the link.

[keithl]

... 5 billion ... 1MW lasers ...
... five petawatts of power ...

Uh, that should be terawatts, 1000 GW. Global electricity production averages 2.5 terawatts.

Tera, peta, pretty soon you are talking about significant power.

Edit: ike correctly points out that 5 billion megawatts is indeed 5 petawatts. Don't let me buy any server farms. Randal said 5 petawatts was double world electric power production - it is actually 2000 times world production. For comparison, about 90 petawatts of sunlight reaches the Earth's surface through the atmosphere, clouds, smog, etc.
Randal may have been confused by the common (and confusing) measure of electricity production in petawatt-hours per year. Yeah, and I weigh 0.74 kiloton-hours per year.

Anyone run the numbers about what part of the sun's energy output are we delivering through those N.I.F. lasers?

The sun puts out 384 trillion terawatts (1366W/m^2 * 4pi * (1.496e11m)^2 ). The NIF/person laser would be 5e9 * 5e14W or a measly 2.5 trillion terawatts.

The purpose of the National Ignition Facility is to ignite fusion. Causing the moon to fuse with thermonuclear inertial confinement will take a LOT more power than 384 trillion terawatts, though we only need apply the power long enough to implode it like the targets at the NIF. Not sure how big and fast the pulse needs to be, I will leave that to the particle physicists, but I'd guess it would be on the order 10MeV per nucleon ( total energy on the order of 1E38 J) , for a time on the order of the diameter of the moon divided by the speed of light (on the order of 10 milliseconds). So lets estimate a nice round 1E40 watts. That is 2000 times the luminosity of the milky way galaxy, about the luminosity of a quasar.

Done properly, the lighter elements will fuse into iron, and the iron will fuse into transuranics. And a wave of heavy elements (many kilometers thick if cooled) will hit the surface of the earth 1.2 seconds after the pulse hits the moon.

But that is still not enough power.

The LHC struggles to make 7TeV collisions, barely enough to see statistical evidence of the Higgs, no supersymmetric particles observed. A nice round 100 TeV would produce some interesting physics. A moon-sized "collision" would make LOTS of interesting physics. So if we illuminate the moon with 1E47 watts for 10 milliseconds, detectors on earth would see lots of fascinating particles for a few microseconds before they vaporize (just before the earth fuses into transuranics). 1E47 watts is on the order of the power output of the universe out to the Hubble radius. A tight beam X-ray laser communication system should be able to transmit a short burst of interesting data to a galaxy far enough away survive the gamma ray pulse from the lunar hyper-implosion.

Perhaps that is, barely, enough power!

[webgrunt]

So, if we were to channel all the energy from a supernova at the moon, would fusion be acheived? And what sort of recoil effect would happen to the earth?

[Max™]

... 5 billion ... 1MW lasers ...
... five petawatts of power ...

Uh, that should be terawatts, 1000 GW. Global electricity production averages 2.5 terawatts.

Tera, peta, pretty soon you are talking about significant power.

Anyone run the numbers about what part of the sun's energy output are we delivering through those N.I.F. lasers?

The sun puts out 384 trillion terawatts (1366W/m^2 * 4pi * (1.496e11m)^2 ). The NIF/person laser would be 5e9 * 5e14W or a measly 2.5 trillion terawatts.

The purpose of the National Ignition Facility is to ignite fusion. Causing the moon to fuse with thermonuclear inertial confinement will take a LOT more power than 384 trillion terawatts, though we only need apply the power long enough to implode it like the targets at the NIF. Not sure how big and fast the pulse needs to be, I will leave that to the particle physicists, but I'd guess it would be on the order 10MeV per nucleon ( total energy on the order of 1E38 J) , for a time on the order of the diameter of the moon divided by the speed of light (on the order of 10 milliseconds). So lets estimate a nice round 1E40 watts. That is 2000 times the luminosity of the milky way galaxy, about the luminosity of a quasar.

Done properly, the lighter elements will fuse into iron, and the iron will fuse into transuranics. And a wave of heavy elements (many kilometers thick if cooled) will hit the surface of the earth 1.2 seconds after the pulse hits the moon.

But that is still not enough power.

The LHC struggles to make 7TeV collisions, barely enough to see statistical evidence of the Higgs, no supersymmetric particles observed. A nice round 100 TeV would produce some interesting physics. A moon-sized "collision" would make LOTS of interesting physics. So if we illuminate the moon with 1E47 watts for 10 milliseconds, detectors on earth would see lots of fascinating particles for a few microseconds before they vaporize (just before the earth fuses into transuranics). 1E47 watts is on the order of the power output of the universe out to the Hubble radius. A tight beam X-ray laser communication system should be able to transmit a short burst of interesting data to a galaxy far enough away survive the gamma ray pulse from the lunar hyper-implosion.

Perhaps that is, barely, enough power!

This is more like spacebattles type discussions.

What you're describing is a type-4 civilization, in fiction there are two reliably defined type-4's, the Xeelee (and Photino Birds) from Baxter's Xeelee Sequence, and Dr. Who's Timelords (and later era Daleks).

At one point in a Xeelee story we find out that humanity built a massive drive system into a neutron star to accelerate it up to a very large fraction of c in order to smash it into something the Xeelee built called Bolder's Ring. The Ring was a loop of cosmic string rotating at close to c.

Oh, it's also 10 million light years in diameter, and in the series was proposed to be the Great Attractor. It was built to produce a naked ring singularity so the Xeelee could go to another universe.

Humans were faced with gods they could try to hurt, so we reached a point where we were able to use a neutron star as a relativistic weapon before we finally annoyed the Xeelee enough that they brushed us aside so they could finish their projects.


Most races in fiction top out around Type 3 (control of energy equivalent to an entire galaxy of stars emitting), Dr. Who mentions once that "most races pray to lesser beings than the Timelords, we were THE Type-4 civilization", which puts "enough power" at the level of an entire universe worth of emissions.

[keithl]

So, if we were to channel all the energy from a supernova at the moon, would fusion be acheived? And what sort of recoil effect would happen to the earth?

Depends on how you extract the energy. A supernova produces about 1e44 Joules, in a few seconds. However, because it is a giant ball of opaque plasma, it takes a few weeks to emit most of that energy as light. A few days is pretty frisky for a star, BTW, the sun needs thousands of years for the energy to trickle out of the core. So for a "fast" type 1a supernova, with a 10 day peak, the optical emission power rate would be under 1E38 watts, and a 10 millisecond timeslice of that would probably be too small to fuse the moon before it dispersed. Inertial confinement fusion has got to be fast or a small target like the moon disassembles too quickly.

But since we are using magic, we merely add an additional bit of magic to suck a time slice of the power deep out of the supernova core, and use that unfiltered energy to do our lunar transmutation into transuranic plasma. Note, the earth would get "only" 70 parts per million of the "thermonuclear moonshine", and is 80 times more massive, so it will probably get partly vaporized and stripped of a lot of mass by the plasma wave, but that is not enough energy to knock most of it out of solar orbit. Mars and Venus, being much further away, will receive a few parts per million of the energy the earth gets, so they will get shaken but not stirred.

[Quicksilver]

I want a shirt of this.

I just found my new avatar

Also, I love black hat guy, we need more people that will blow up the earth... FOR SCIENCE!

*EDIT*
Found this on reddit, the neighbours will complain

Spoiler:

Being Australian myself, I lol'd pretty hard.

[Max™]

Screw magic, use handwavium, get a starbreaker!

One second...

On the horizon, something moved. An object, slicing through the Air; it was like a ray, with shining, golden wings which beat at the Air… but it was far larger than any ray, large enough to be seen even though it was almost lost in the mists of the horizon. Blue-white light stabbed from the belly of the great sky-ray into the bruised purple mass of the Quantum Sea below.
-
More memories, legends from the mouths and staring eyecups of intense, lean old men, returned to her. I know what that is. Could it be causing the Glitches, with those beams?
-
I know what it is. It’s a ship, from beyond the Star.
-
She let her head sink forward, against her knees.
-
Xeelee.”
-
“The Nightfighter caused a starquake shooting into the quark-gluon plasma core–an unusually powerful one at that. That side-effect requires an input of rotational energy a millionth the total rotational energy of the star. On the low end* (1.35 solar masses, 1 Hz spin), that comes out to 7.63e33 J, or 1.82 yottatons of TNT. On the high end* (2 solar masses, 100 Hz spin), it comes out to 1.13e38 J, or 27000 yottatons of TNT. The energy was dumped into the star in less than a microsecond (not lasting the entire 1 us glitch), for a power of 7.63e39-1.13e44 W.
-
I repeat, that was a side-effect of the starbreaker fire. The low end estimate exceeds Earth’s gravitational binding energy by more than an order of magnitude. Starbreakers can easily crack planets.
-
*Please note that these values are underestimates, as they were calculated using the non-relativistic equations for rotational energy. The full GR treatment should trend much higher.

So yeah, we're talking about a bullshitted up supertoy called a Starbreaker, which is a gravity-wave handgun that managed to trigger a neutron star glitch, which puts the energy into the yottaton range, and this is my own take on what a Nightfighter would look like.

[ike]

... 5 billion ... 1MW lasers ...
... five petawatts of power ...

Uh, that should be terawatts, 1000 GW. Global electricity production averages 2.5 terawatts.

Tera, peta, pretty soon you are talking about significant power.

5 billion = 5,000,000,000
1MW = 1,000,000 Watts

5,000,000,000,000,000 Watts
5*10^(15) Watts
5PW

[josepheh]

I wonder if Randall's calculations took into account the moon's apparent retroreflective properties. At least as far as solar illumination goes, "The brightness of the Moon increases more than 40% between solar phase angles of 4 deg and 0 deg." http://adsabs.harvard.edu/abs/1996Icar..124..490B. Okay we're not talking orders of magnitude but if the phenomenon applies equally well to laser lights it could make a little difference.

Speaking of retroreflection, there are also the 5 lunar retroreflectors left by the (American) Apollo and (Soviet) Luna programs http://ilrs.gsfc.nasa.gov/satellite_missions/list_of_satellites/lu21_general.html. Those definitely produce orders of magnitude greater effective reflectivity than the lunar surface. They're pretty tiny compared to the lunar surface, but is there a point in the progress of "more power!" where the reflectors would be naked-eye visible points of light discernible from the background?

Sorry for the untagged links ... still a lurker with <5 posts so can't use the url tag.

[wormywyrm]

This reminds me of the DEATHSTAR destroying ALDERAAN. I never thought about it before but how the heck was the death star not impacted at all by the nearby exploding planet??

[StClair]

Sadly, we've already missed the optimum date for the last scenario:
September 13, 1999 ("Breakaway").

[Istaro]

I also liked that he used the word regolith. Reminds me of the Mars trilogy.

[VectorZero]

I just found my new avatar

Oh, Goddammit.

[Red Hal]

Sadly, we've already missed the optimum date for the last scenario:
September 13, 1999 ("Breakaway").

I fancied the pants off of Sandra Benes (as played by Zienia Merton).

[Quilbert]

One interesting question is, what would the Earth look like from the dark side of the moon at stage 2 (green 1W lase pointers)? Half of it (Asia, that is) would obviously be lit by the sun and have its usual blue-green appearance, but on the dark side of the Earth, you would see Africa and Europe glowing in green! Actually, Asia would also be a little greener than usual. Anyone up for an artist’s impression?

[Vroomfundel]

One interesting question is, what would the Earth look like from the dark side of the moon at stage 2 (green 1W lase pointers)? Half of it (Asia, that is) would obviously be lit by the sun and have its usual blue-green appearance, but on the dark side of the Earth, you would see Africa and Europe glowing in green! Actually, Asia would also be a little greener than usual. Anyone up for an artist’s impression?

Apologies if I'm mistaking a slip of the tongue (fingers?) for uninformedness of astronomic terms, but the dark side of the moon is the one not facing earth - it does get sunshine, we just don't see it; a remnant of a geocentric vocabulary.
From the side of the moon that's not iluminated by the sun the earth should appear pretty solid green - we're giving off half a lux with the lasers, and full moon on earth is about 0.27 lux. Agreed that it's going to be an interesting sight but I'm not the right person to do that - my drawing skills are limited to a Mohammed stick figure (in an effort to inspire one person in each country to produce something crude to offend him, ridiculing the fundamentalists and distributing the damage done to embassies, reducing it to a manageable level).

[Red Hal]

Actually, the side not facing the earth is usually referred to as the far side of the moon. It's true it is "dark" from a radio communication perspective, and this leads to the conflation of the terms.

[jgh]