The Rebbe, who was trained as an engineer, had a keen understanding of the physical world and how it worked. So when the Apollo spaceship landed on the moon in 1969, he used that scientific achievement to make a point about Jewish education.

In the NASA program, the Rebbe understood, there had always been a problem with balancing weight limits versus fuel needs in space flights. It’s a conundrum: If you build a rocket that will go a long distance, you’ll need to carry a lot of fuel. But the more fuel you carry, the larger the fuel container has to be—which means the weight of the spacecraft is increased. It’s an endless cycleThe heavier the spacecraft, the more fuel you need. It’s an endless cycle, and a critical issue if your mission takes you beyond the local environment to the moon or Mars.

Engineers settled on a solution: They built multistaged rockets that contained several individual fuel tanks. The largest amount of fuel is needed in the first minutes of the flight, as the rocket takes off from the ground. So the fuel for those first four or five minutes goes into a separate container, and when the fuel is used, the empty container is jettisoned off. When you watch a launch, you’ll see it. After a few minutes, the used-up fuel container drops away.

The next stage of the flight uses up the next-most fuel, because the rocket is still fighting the gravity of the earth. When that fuel tank is empty, it’s also jettisoned, as are several more stages. As each tank of fuel is used and the container jettisoned, the overall weight of the spacecraft becomes lighter, so it needs less fuel.

By the time you’re weightless, out of the pull of Earth’s gravity, you’ll need only a tiny bit of fuel. Because there’s no resistance to fight against, a thimbleful of fuel will propel the craft a very long distance.

So the Rebbe used this to explain a passage in Mishlei (Proverbs 22:6), that we are to “educate a young person according to his path.” That phrase has always been problematical, the Rebbe said. What does it mean, “according to his path”?

It’s very simple, the Rebbe said. It’s something we do in education all the time. We introduce a three-year-old child to the aleph-bet, and we make a big fuss about it. We have a party, we give him candy, we celebrate. In the old days, we’d even put honey on the page itself. The child sees the big fuss, he likes the candy, and he’s very interested. He learns.

When the child gets to be about five years old, candy doesn’t motivate him anymore. So we move to a different incentive, maybe toys or a tricycle.

Then when he’s 10 or 11, We move to a new incentivetoys don’t work anymore. By that time, he wants electronic games. That’s what we’re doing—educating a child according to his path. We’re using an incentive that’s meaningful to him at his age level.

This, the Rebbe said, is exactly the same principle as that of the multistage rocket. That which is not needed any longer is jettisoned. We don’t want to carry the extra weight along.

When you reach the next level of understanding and learning, you get rid of the weight, you don’t need as much inspiration as before in order to push yourself. By the time you reach a certain stage of learning, all you need is just a tiny bit of fuel to propel you forward.