If we use a regular laser pointer, it won’t.
The first thing to consider is that not everyone can see the moon at the same time. We can gather everyone in one place, but we learned our lesson a few weeks ago. Instead, let us choose a time when as many people as possible can see the moon. Since approximately 75% of the world’s population lives between 0°E and 120°E, we should try to do this when the moon is somewhere in the Arabian Sea.
We can try to illuminate the new or full moon. The new moon is darker and it is easier to see our laser. But the new moon is a trickier target because it is visible during most of the day-eliminating the impact.
Brightness aside, the ideal time might be 2:00 pm Eastern Time on December 27, 2012, when the full moon will be high over Mumbai and Islamabad. By then, about 5 billion people (large parts of Asia, Europe, and Africa) will be able to see the moon, which is as many as the number of people who can see it at a time.
But let’s choose a quarter of the moon so that we can see the effect of the dark side. We will avoid the first quarter of December 21 to avoid encouraging any Mayan nonsense, and choose that one half an hour after midnight (Greenwich Mean Time) on January 4, 2013. This will be the daytime in East Asia, and the night in Africa and Europe.
this is our target:
A typical red laser pointer has a power of about 5 milliwatts. A good laser pointer has a beam that is tight enough to actually hit the moon—although when it gets there, it will spread over most of the surface. The atmosphere slightly distorts the beam and absorbs part of it, but most of the light will let it through.
Let us assume that everyone has a stable enough target to hit the moon, but nothing more, and the light is evenly spread on the surface of the moon.
Half an hour after midnight (GMT), everyone aimed and pressed a button.
This is what happened:
Well, this is disappointing.
However, this makes sense. Sunlight bathes the moon with a little more than one kilowatt per square meter. Since the moon has a cross-sectional area of approximately 10^13 square meters, it is bathed in approximately 10^16 watts of sunlight-ten petawatts, or two megawatts per person-far more than their 5 milliwatt laser pointer. Each part of this system has a different efficiency, but none changes the basic equation.
5 milliwatts are trivial. We can do better.
A 1-watt laser is extremely dangerous. Not only is it powerful enough to blind you-it can also burn your skin and set things on fire. Obviously, they are illegal for consumers in the United States to buy.
Just joking! You can buy one for $199.
So, suppose we spend $2 trillion to buy a 1-watt green laser for everyone. (Memo to presidential candidates: This policy will win my vote.) In addition to being stronger, the green laser is closer to the middle of the visible spectrum, so the eyes are more sensitive to it and look brighter.
The effect is as follows:
Uh…
The laser pointer we use emits about 150 lumens of light (more than most flashlights) in a 5 arc minute beam.
This will illuminate the surface of the moon with an illuminance of approximately half lux, while the illuminance of the sun is approximately 130,000 lux. (Even if we aim at them perfectly, it can only control 6 lux on about 10% of the lunar surface.)
In contrast, the full moon illuminates the earth’s surface with an illuminance of about 1 lux-which means not only our laser It is too weak to be seen from the earth, and if you stand on the moon, the laser light on the landscape will be weaker to us on earth than moonlight.
With the advancement of lithium batteries and LED technology in the past decade, the market for high-performance flashlights has exploded. But the flashlight will not cut it off. So let’s skip all these and give everyone a Nightsun.
You may not recognize this name, but you have probably seen a name in operation: it is a searchlight installed on police and coast guard helicopters. With an output of 50,000 lumens, it can turn the patch ground from this evening.
The beam is a few degrees wide, and we need some focusing lenses to reduce it to half a degree needed to hit the moon.
Here’s the effect:
It’s hard to see, but we are making progress! The beam provides an illuminance of 20 lux, which is twice as bright as the ambient light in the middle of the night! However, it is difficult to see, and it certainly did not affect half of the light.
Let’s replace each Nightsun with an IMAX projector array-a pair of 30,000 watt water-cooled lamps with a total output of more than one million lumens.
Still barely visible.
Located on top of the Luxor Hotel in Las Vegas is the most powerful spotlight on earth. Let us give everyone one of them.
Well… Let’s add a lens array to each to focus the entire beam on the moon:
Our light is absolutely visible, so we have accomplished our goal! Well done!
… Well.
The Ministry of Defense has developed a megawatt laser designed to destroy incoming missiles in flight.
The Boeing YAL-1 is a megawatt chemical oxygen iodine laser mounted on the 747. It is an infrared laser, so it is not directly visible, but we can imagine building a visible light laser with similar power. Send a copy to everyone.
Finally, we managed to match the brightness of the sun!
We also consume 5 petawatts of electricity, which is twice the world’s average electricity consumption.
Well, let’s install a megawatt laser on every square meter of the Asian surface. Powering this 50 trillion laser array will use up the earth’s oil reserves in about two minutes, but in those two minutes, the moon looks like this:
The moon is as bright as the sun at noon, and at the end of two minutes, the lunar weathering layer is heated to glow.
Well, let us step out of the realm of rationality more firmly.
The most powerful laser on earth is the limited beam of the National Ignition Facility of the Fusion Research Laboratory. It is an ultraviolet laser with an output power of 500 terawatts. However, it only fires in a single pulse that lasts a few nanoseconds, so the total energy delivered is roughly equivalent to a quarter cup of gasoline.
Let’s imagine that we somehow found a way to power it and launch it continuously, giving everyone one, and pointing them all to the moon. Unfortunately, the laser energy stream turns the atmosphere into plasma, instantly igniting the surface of the earth and killing us all.
But let us assume that the laser light passes through the atmosphere in some way without interaction.
In this case, it turns out that the earth is still on fire. The reflected light from the moon will be four thousand times brighter than the sun at noon. In less than a year, the moonlight will become bright enough to evaporate the oceans on Earth.
But forget the earth-what will happen to the moon?
The laser itself exerts enough radiation pressure to accelerate the moon at a speed of about one part per million. This acceleration will not be obvious in the short term, but over the years it has been enough to push it out of Earth’s orbit.
…If radiation pressure is the only force involved.
The energy of 40 megajoules is enough to evaporate one kilogram of rock. Assuming that the average density of lunar rocks is about 3 kg/litre, the laser will output enough energy to evaporate 4 meters of lunar bedrock per second:
5 billion people×500terawattspersonπ×Moon radius2×20megajouleskilogram×3kilogramsliter≈4meterssecond
However, the actual lunar rock is not Will evaporate so fast-this is a very important reason.
When a rock evaporates, it will not disappear. The surface of the moon becomes plasma, but the plasma still blocks the path of the beam.
Our lasers continue to inject more and more energy into the plasma, and the plasma continues to become hotter and hotter. The particles bounce off each other, hit the surface of the moon, and finally fly into space at extremely fast speeds.
This flow of material effectively turns the entire surface of the moon into a rocket engine-and it is also a very efficient engine. Using a laser to explode surface materials like this is called laser ablation, and it has proven to be a very promising method of spacecraft propulsion.
The moon is large, but the rocky plasma jet slowly and surely begins to push it away from the earth. (The jets will also wash the Earth’s surface and destroy the lasers, but we will pretend that they are invulnerable for the time being.) Plasma will also physically tear the lunar surface, a complex interaction that is difficult to model.
But if we wildly guess that the particles in the plasma leave at an average speed of 500 kilometres per second, it will take months for the moon to be pushed out of our laser range. It will retain most of its mass but will escape the gravity of the earth and enter an unbalanced orbit around the sun.
Technically speaking, according to IAU’s definition of planets, the moon will not become a new planet. Because its new orbit intersects the Earth, it will be considered a dwarf planet like Pluto. This traversing the earth’s orbit will cause periodic unpredictable orbital disturbances. In the end, it was either ejected into the sun, ejected out of the solar system, or hit one of the planets—most likely our planet. I think we all agree, in this case, we deserve it.
Scorecard:
And that, at last, is enough power.