One day, a non-visible beam of handwavium energy 100km in diameter and 10 light years long intersects with the our solar system, presumably originating somewhere near Proxima Centauri. The beam tears a hole through the bottom section of Jupiter. All matter that is touched by this beam is transported near-instantaneously to the end of this beam, retaining all its characteristics including its speed. The beam stretches about six light years past our solar system before petering out a split second later.

Since the beam has also transported 10 light years worth of space debris as well, what happens now? Is there a blooming field of space debris and gas that explodes outwards from where the beam ends?

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    $\begingroup$ It looks like you're asking about a hypothetical situation rather than asking about how to build a fictional world. $\endgroup$
    – sphennings
    Jun 28, 2020 at 3:10
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    $\begingroup$ I do not understand the close vote reasoning here. While the answer is obviously different, I see the type of question as no different to examining what happens when an indestructible meteor enters Earth's atmosphere. Yet one is on the verge of being closed and the other was answered... Personally I would like more information (was the chunk of Jupiter the only substantial single chunk of matter?) but I see no reason to close. $\endgroup$ Jun 28, 2020 at 10:35
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    $\begingroup$ @StephenG, You didn't ask the OP for a clarification, you pointed out that his/her world rules aren't our world rules, and having "broken" one he/she could "break" any. I'd conclude that you don't think the question has value simply because it doesn't conform to what we understand today. The point of the help center statement is that it's the OP's privilege to create whatever rules they want and our obligation to answer within the context of those rules. Thus, you weren't asking for a clarification, you were complaining. But, I'll delete my comments about the matter if you'll delete yours. $\endgroup$
    – JBH
    Jun 28, 2020 at 17:31
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    $\begingroup$ Ladies and Gentlemen. All the OP did was create a set of initial conditions. Please don't focus on the backstory and therefore believe the question unanswerable. Through irrelevant methods, mass in a 10ly x 100km cylinder that pierces, among other things, Jupiter, is brought to a single point at the end of the cylinder. The mass has the same force vectors as they did in their pre-question state. What happens when t > t0? My college physics classes asked questions like this all the time - they just didn't have a creative way of setting up the initial conditions. $\endgroup$
    – JBH
    Jun 28, 2020 at 17:39
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    $\begingroup$ @JBH oh I have no idea why this is being treated as story based. As far as I see it this is more of a "what should I expect from this event" kind of question, which is completely valid unless it's lacking the necessary information to make it possible to be answered properly. In here, for example, what was in the way of the beam (gases, solid matter, both, neither) the amount of mass that's being transported to this single spot, the volume of said single spot and the speed at which the materials/gases were moving at. $\endgroup$ Jun 28, 2020 at 21:16

1 Answer 1


The first thing I'll do is find how much interstellar matter likely exists in a cylinder 100km in diameter and 10 light-years long.
$V=\pi r^2 h$ is the volume of a cylinder, so let's find our volume in uh cubic centimeters:
$\pi × (1*10^{7})^2 × 9.461*10^{18} = 2.972*10^{26}cm^3$
Now let's find its mass.
Hydrogen has a mass of about $1.674*10^{-24} g$ and helium about $6.646*10^{-24} g$
Interstellar particle density is about 1 atom per cubic centimeter, that atom being 75 percent of the time hydrogen and about 25 percent the time helium. Let's get an average mass: $1.674*10^{-24}(0.75) + 6.646*10^{-24}(0.25) = 2.917*10^{-24} g$
Our volume calculation is in cubic centimeters, and we have 1 particle per cubic centimeter, so there are about $2.972*10^{26}$ particles inside out cylinder, each with an average mass of $2.917*10^{-24} g$. Finding total mass, we multiple the number of particles by the average mass and find that the total mass is about: $8.670*10^{2} g$, or about 867 grams of stuff. That's about a basketball and a couple of baseballs worth of mass.

So, basically nothing when compared to the stuff the beam will grab from within Jupiter.
If we assume Jupiter has an average density of $1.326 g/cm^3$, has a radius of $6.991*10^{9}cm$, and the beam passes through say 60 degrees latitude in the south:
$\cos (60) × 2 × 6.991*10^{9} = 3.496*10^{9} cm$ is the length of that part of the beam which crosses Jupiter.
That part would have a volume of roughly: $\pi × (1*10^{7})^2 × 3.496*10^{9} = 1.098*10^{24} cm^3$
With an average density of $1.326 g/cm^3$, we can find mass to be: $1.456*10^{24} g$
That's a mass comparable to the dwarf planet Ceres.

As for what it'll do when it reaches the middle of nowhere in interstellar space 6 light-years away? I imagine that--being under the crushing pressure of Jupiter's interior no longer--it'll expand rapidly and magnificently, glowing hot at first before cooling down as its volume increases and heat escapes in greater quantities into cold, dark space. I don't think the gases' relative motion from its activities in the solar system will make much of a difference at all.

  • $\begingroup$ Very nice. This really makes it clear why the Bussard ramjet concept could not work - scooping up less than 1kg of matter from a 100 km wide collection zone 10 light years long is nowhere near enough fuel to be useful even if it would all fuse with perfect efficiency. $\endgroup$ Jun 30, 2020 at 8:52
  • $\begingroup$ @KerrAvon2055 yeah, if only there were a few hundred thousand more atoms per cubic centimeter $\endgroup$
    – BMF
    Jul 1, 2020 at 3:12

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