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I have a question involving quite the wacky (and silly) hypothetical. It's a part of an ongoing argument I'd like to settle. Of course, I have no background in physics which is why I came here, so I hope you could bear with me:

Assuming we have an incredibly powerful laser beam and a medium to sustain and deliver it, without a hitch-- could it cause an explosion followed by a shockwave by striking an object that does not contain any explosives? I've seen a claim that an incredibly powerful laser(during our discussion a fairly unfathomable 16RJ beam was a point of reference)would simply pierce through anything it comes in contact with and will not induce any kind of dentonation, because according to that person lasers can't do that.

But from my basic understanding of the subject and some extra reading, wouldn't such an insanely powerful beam with so much energy concentrated into a single spot over a very short pulse basically vaporize whatever it strikes in an instant, break down and ionize the air and result in quite the explosion.

I'd like to know which one is the correct answer, and any slightly more in-depth explanation (if someone with no physics background could understand it) is welcome.

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  • $\begingroup$ You might be interested in the National Ignition Facility, which recently realized fusion that outputted more energy than was put into the sample. It did this by basically the process you described lasers.llnl.gov/about/how-nif-works $\endgroup$
    – AccidentalTaylorExpansion
    Commented Feb 6, 2023 at 16:17
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    $\begingroup$ Strictly speaking, "detonate" is a reflexive verb, not a transitive verb. High explosive substances can detonate, but one thing can't detonate some other thing. A detonation is a self-sustaining chemical reaction that is propagated through the high-explosive "fuel" by a shock wave. $\endgroup$
    – Solomon Slow
    Commented Feb 6, 2023 at 16:34
  • $\begingroup$ @SolomonSlow so det cord is a misnomer? $\endgroup$
    – JEB
    Commented Feb 6, 2023 at 17:24
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    $\begingroup$ No, detonation cord itself detonates. It would then set off a primer charge which activates the secondary charge (or a series of them). @JEB $\endgroup$
    – Jiminy Cricket.
    Commented Feb 6, 2023 at 17:32
  • $\begingroup$ Ah, I see. Apologies, English isn't my native tongue. And could a crazy 16 ronna joules beam cause a massive explosion by striking something like a rock/whole mountain? Or would it simply pierce through? And in case this scenario is a bit too off the rocker - what about a "measly" 1 petajoule beam? Will there be any significant difference in their interaction with matter and air, or just a much smaller area of effect? $\endgroup$
    – Bram
    Commented Feb 7, 2023 at 11:48

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Lightning is contains more energy than any laser beam pulse. It doesn't cause explosions.

Update after comments

If you deposit enough energy in a small target, the result will be a big explosion. It doesn't matter what the source of the energy is. This is the idea behind various kinetic energy weapons such as rail guns, anti-tank artillery shells, and MOABs. Or for that matter, Relativistic baseballs.

Lasers can do this too, though existing lasers don't have as much energy in the beam as other sources. If you focus the beam, you can create a tiny explosion.

There are ways to make the explosion bigger by using energy available in the target. A couple examples have been given.

  • Lightning striking a tree can vaporize water in the tree, causing a steam explosion.
  • With careful planning, lasers can induce fusion in a hydrogen target.

Along these lines, you might use a laser to light the fuse on a stick of dynamite.

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  • $\begingroup$ Although trees can get messed up (almost explosively) by lightning (because the water in the wood vaporizes, which in turn blasts the wood apart). You can find videos of this on youtube, e.g. <youtube.com/watch?v=Xnyfwbm3Rzg>. $\endgroup$
    – Sebastian Riese
    Commented Feb 7, 2023 at 0:11
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    $\begingroup$ I was referring to a hypothetical one containing more energy than lighting. And a couple of questions: 1. Doesn't the energy significantly disperse by the time it travels to the ground? 2. Isn't thunder pretty much a shockwave caused due to the lightning rapidly heating the air around it? $\endgroup$
    – Bram
    Commented Feb 7, 2023 at 11:38
  • $\begingroup$ My answer isn't as good as I thought. I thought the question was more along the lines of a great big laser hitting, say, a brick and causing a great big explosion because, well, it's a great big laser. It is clear you had something more reasonable in mind. $\endgroup$
    – mmesser314
    Commented Feb 7, 2023 at 17:03
  • $\begingroup$ I mean...in a way that kinda is my question, lol. I'm curios about what would happen if an extreme amount of energy, concentrated into a small beam for a short pulse could actually induce a massive explosive reaction, akin to that of a very powerful bomb/missile. Be it a nuke or even something on a smaller scale like a MOAB. $\endgroup$
    – Bram
    Commented Feb 8, 2023 at 15:57
  • $\begingroup$ "Lightning [...] contains more energy than any laser beam pulse." Not this pulse... From en.wikipedia.org/wiki/Harvesting_lightning_energy "A single bolt of lightning carries a relatively large amount of energy (approximately 5 gigajoules)". The OP's laser beam carries 16e27 joules. $\endgroup$
    – PM 2Ring
    Commented Feb 8, 2023 at 20:18

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