Your Life: An Ion Propulsion Engine

A lesson of momentum and life from the sci-fi story The Martian.


Although they didn’t go over this in the movie, the book describes that the ship the crew is traveling in, Hermes, is powered by ion propulsion. Force is created by ionizing a fuel source, which sends particles flying from atoms due to an increase in energy. Although these particles are extremely tiny they have enough momentum to move the ship a tiny tiny bit. This is because of Newton’s Third Law:

for every action there is an equal and opposite reaction.

So the particle flies out the back of the ship, and the ship “flies” the opposite way with equal, minuscule, momentum. It helps that everything is weightless in space, else the ship would never be pushed hard enough by the reaction force. Enough of these particles being ejected can build up enough momentum to propel the ship at a decent rate, enough to get you to Mars and back.

So what can we learn from this?

Sure we tend to define lives by how many years we’ve been around, but life happens moment by moment. The past may be in years, but the future is based on how you act right now. What decisions will you make? How will you respond? Now what?

No matter what, you always have the freedom to choose your attitude. You may not always be able to choose the situation, but you can always consciously choose how you react to it. Some of these decisions on how to think and feel about something may seem small, but each of them will build up and create momentum in your life; enough momentum to get you to Mars…

Or send you into the sun.

Momentum in life pushes and pulls you in different directions. From a physics perspectives if you add up all your momenta’s directions and strengths, some will be in opposite directions and cancel each other out, and others will be in completely different directions. In the end, you could be traveling in a direction not aligned with any of these momenta. See how ‘a+b’ is pointing in the direction of neither a nor b?

But if you arrange your life to minimize momenta pushing you away from your goal and to maximize momenta pulling you toward your goal, your net direction will be roughly aligned with what you want. Of course life doesn’t boil down to two vectors ‘a’ and ‘b.’ Ideally our lives would be an ion propulsion engine with all momenta pushing toward one destination. Realistically they’re more like a beachball at a Nickleback concert. It’s a much messier scattering of arrows pointing in every direction possible. Some, if not most, of these momenta are forced upon us, and the few that we can create may not seem to have much strength.

Unlike the beachball however, you have some control. You are gifted with an intelligent brain, which gives you the ability to choose how to react and think and feel about things. If something comes up that starts pushing you away from your goal, you can try your hardest to take that momentum and flip it around to make it pull you toward your goal.

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