A practical means of powering your civilization for more than 1 trillion years in an eco-friendly fashion!

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Background:

One major concern for any civilization that lasts for more than a few billion years is: what is the best long-term method to reliably store and retrieve energy?

Solar panels on a planet work great, but only capture a tiny fraction of total solar output. Some ideas exist for working around this (Figure 1), but typically they require an impractically-large number of resources to construct.

Fig. 1: If you wanted to capture more of the energy of a star than just the part that hits your planet, you could launch a bunch of solar panels into orbit (“A,” at left) around the sun as well (effectively making some “extra planets” for soaking up solar energy). Or, you could build a so-called Dyson sphere (“B,” right) that entirely surrounds the star in question.

The Issue:

Even more vexingly, a star is an annoying way of storing energy: it ALWAYS has to be “on,” and it is prone to exploding or burning out in less than 10 trillion years.

Ideally, we want a power source that can be turned off and on as needed. For example, if you needed to make some toast AND run a space heater AND power a gaming PC, you might want to turn the star on, but at night you’d ideally want to turn it off to save energy.

Proposal:

Luckily, nature has provided a solution: the humble neutron star (Figure 2).

Fig. 2: Top: a neutron, everyone’s favorite zero-charge particle. Bottom: a neutron star, which is basically just a bunch of neutrons smooshed together. These “stars” have the convenient feature of being relatively small (e.g., on the order of 10 miles in diameter), and of spinning super-rapidly (effectively storing a massive amount of energy, like a gigantic flywheel).

What we would like to do is take a neutron star and use it like a flywheel: ideally, we would mesh it with a gear and siphon off just a little bit of rotational energy on an as-needed basis.

The only problem here is that the action of “spinning up” a meshed gear is also going to cause the gear to want to zoom along the surface of the neutron star. In order to counteract this motion, we’ll actually need TWO neutron stars (rotating in opposite directions) in orbit around each other (Figure 3).

Fig. 3: Our two neutron stars spin in opposite directions (shown by the red and blue “spin” arrows), and are joined together by a gigantic connecting rod of unspecified material (shown in black, top of figure).  Whenever power is required, the “gears” shown in F and G are pivoted simultaneously so that they both touch the surface of their respective neutron star at the same time. The angular momentum imparted to the F and G gears should cancel each other out.

Long-term practicality:

Let’s do the math of how much energy is available from the spinning of a neutron star. Apparently, we have to multiply the spin rate by something called the “moment of inertia.” For a solid sphere (like our neutron star), this is evidently:

  • Moment of Inertia 𝐼 = ⅖ × m × r²

(from https://en.wikipedia.org/wiki/List_of_moments_of_inertia), where the variables are:

  • Approximate mass (“m”): 3 × 10³⁰ kilograms
  • Radius: ~8,000 meters (~5 miles)

Which gives us:

  • 𝐼 = ⅖ × m × r²
  • 𝐼 = ⅖ × 3 × 10³⁰ kg× (8000 m)²

Now we just need to multiply that by the angular velocity in radians per second. If you get a REALLY good neutron star, the rotation rate is ~700 times per second, or, in other words:

  • Angular velocity =  4,398 radians / second

…which works out to (700 * 2𝜋) radians per second (~4398 radians / second).

If we want the total energy (“𝐸”), the Internet says that we apparently multiply the “moment of inertia” by the angular velocity, which gives us the following:

  • 𝐸 = ½ × 𝐼 × (angular velocity)²
  • 𝐸 = ½ × ⅖ × 3 × 10³⁰ kg× (8,000 m)² × (4,398 radians / second)²
  • 𝐸 = 7.4 × 10⁴⁴ joules

If we believe the Internet estimates, which I’m too lazy to check right now, civilization currently consumes approximately 6 × 10²⁰ joules per year. If we divide (7.4 × 10⁴⁴ joules) by (6 × 10²⁰ joules / year), we end up with ~10²⁴ years per neutron star, which is a trillion times a trillion years. Substantially more than you’d get from pretty much any regular star!

PROS: Good long-term solution for providing reliable power. Power draw can be scaled up/down as needed.

CONS: Material science may be ill-equipped to handle the unusually high gravitational forces around neutron stars. Those material scientists had better get cracking!!! Might also be sabotaged by politicians who are in the pocket of “Big Dyson Sphere.”

Originally published 2026-07-13.