Prepare to be inundated with a fresh round of stories on how we might mad science ourselves out of existence. Because a French scientist and his loyal supercomputer have worked out a way to punch a laser right through reality. Seriously.
In 1942, physicists looking at potential designs for nuclear weapons actually did consider the possibility that igniting a sufficiently powerful atomic bomb might “set the air on fire” in the sense that it might trigger a cascade of reactions in which the entire atmosphere simply became part of the explosion. However, as this Scientific American interview with one of the leaders of the Manhattan Project details, well before anyone had started building an actual weapon, a quick look at the numbers showed this was “incredibly unlikely.” And after some intense work by a calculator—which in this case means a human being tasked to do the work of number crunching—that estimate was moved to “incredibly impossible” years in advance of any actual test. So none of the big name scientists were really cringing on the day of the first nuclear test, wondering if they were going to set the world aflame. Though apparently Enrico Fermi did joke about it—a joke some people still haven’t found humorous after 74 years.
In 2008, as scientists were about to turn on the Large Hadron Collider in Switzerland, multiple media outlets ran articles about the possibility that powering up the world’s most powerful particle-basher might lead to the creation of a mini-black hole. That pin point black hole might then slip down to Earth’s core, begin slurping up matter by the atom, then the gram, then the whole-bunch, and before you know it the entire hollow Earth collapses into a pit of marble-sized infinite denseness. Except there never really was such a possibility. The original post on the topic appears to have come from a satirical web site called “Waterford Whispers News” which was then leaked onto the web through a thousand and one click-bait articles. As NASA Science points out, the day the LHC went to full power was another “day the world did not end.” Better still, the NASA article explains that LHC potentially might create a tiny black hole, and why instead of being a world-ender, that would be a Really Cool Thing.
Stories of the end of the world have always been popular. And since we’re all about the science these days, we’ve replaced Ragnarok with things that involve fewer Valkyries, more Megatons. But this laser story … you may hear it again. Because just off the cuff, it sounds pretty scary.
The subject of my Saturday concern is a simple paper, published earlier this month in Physical Review Letters. 99% of the content is hidden behind a paywall, and the rules there are pretty darn strict on what constitutes fair use, so … here’s the abstract.
This Letter proposes a realistic implementation of the curved relativistic mirror concept to reach unprecedented light intensities in experiments. The scheme is based on relativistic plasma mirrors that are optically curved by laser radiation pressure.
Not a single end of the world to be found in that paragraph. Everyone go home. Except … not quite yet.
What the article is talking about is using a surface created from nothing more than a plasma (matter in it’s most basic, too hot for atoms form) as a mirror to pulse a laser. This was thought to be more or less impossible, because plasmas are inherently chaotic and hitting a plasma “mirror” with a laser in a way that provided focus was thought to be such a numerically intense problem as to be impracticable. Except now researcher Henri Vincenti appears to have cracked the problem with a lot of number crunching with a new kind of calculator—the kind also known as a “really big supercomputer.”
His calculations show that there is a scheme by which you can use a plasma mirror to reflect and focus a laser; a scheme that overcomes the imperfections of the plasma surface and simultaneously increases the intensity of the laser many times. That scheme involves how the laser itself is pulsed and angled, in combination with the plasma mirror, to create a harmonic effect.
The upshot of all this is that the energy that was carried by a laser isn’t so much increased, as compressed. It’s not just focused by the mirror, but gathered up and released over a time period that’s 20,000 times smaller than the original pulse. Pair that compression with the latest, most intense lasers, which carry power up to the PetaWatt range, and the results go from “gee that’s interesting” to “seriously, WTF!”
The level of intensity suggested here, combined with a laser solidly in the class of those we already know how to build, would use that million of a millionth of a second pulse to rip apart all matter in its path. Rip it down to quantum components. And that may just be the start of what it could do. Don’t get the idea that these lasers are going to be the basis of a new defense program, or handy tools for would-be James Bond villains. These are “high intensity” lasers, not the kind of “high power” lasers that have been tested for popping holes in drones or missiles. These PetaWatt monsters are really only good for a tiny fraction of a second, and their energy is essentially wasted on the first particle that wanders into their path. But on an experimental physics basis, what they can do is extremely interesting.
There’s a suggestion here that the intensity is great enough to punch a hole through space-time. That sounds very much like going back to those LHC scenarios that create a mini-black hole (and, as a reminder, not only would such a mini-black hole not consume the planet, it would be a very interesting result). But honestly, this is the point where the physics outrun my understanding by … several PetaWatts. Is blasting a hole in space-time is the same thing as creating a black hole, or does it represent something even more exotic (worm hole? frame rip? slow leak in the ‘brane?). At the top end of this potential experiment, things are happening that involve reaching energy levels that are ripping virtual particles from the quantum vacuum and forcing them together, so … you tell me what that means.
End of the world stories are always popular. There are at least as many world-ending myths as there are there are versions of how the world began. There are so many different scientific doomsday scenarios that I once had a deal to write a book about nothing but theories on how the world could end. Except I got busy with something else and walked away from a contract what came with actual cash money. (That’s not world-ending, but it is darn near career-ending.)
Is Mr. Vincenti’s vibrating plasma laser likely to blast reality open and let in the Lovecraftian horde? Eh … no. Actually, the possibility here does seem to open up a whole new world of high energy physics that can be created without carving through dozens of miles of limestone to make a massive ring. Lasers in the PetaWatt range aren’t exactly cheap … unless you’re comparing them to the biggest high energy particle colliders. Then they start to look like paper cups.
This discovery may also have profound implications for experiments in nuclear fusion. Because this sounds exactly like the sort of “pump” that can get the necessary power into a hydrogen-nuclei before it has the chance to get out of the way. These plasma mirrors may be a standard feature of future power plants.
I’m really pretty sure that this will not result in our interstellar neighbors having to place marker buoys around the Solar System that read “Warning: Hubris Zone Ahead.” Let’s just say it’s incredibly unlikely. Now … who has a calculator?
Note: As I was proofing this and looking for any coverage in the general media, I discovered that Chris Lee over a Ars Technica has given this article an excellent write-up that does a much, much better job than I just did of explaining the facts behind this so-far-only-a-theory and skipping over the doomsday mussing. I’d encourage you to go read it.