BY THE reckoning of the calendar used in Britain at the time, Isaac Newton, one of the most influential scientists of all time, was born on Christmas Day of 1642. Using the calendar we use today, Newton was actually born on Jan. 4, 1643. At any rate, now seems as good a time as any to celebrate, along with the holidays, one of the greatest minds in history.
In a letter to his then friend (but later enemy) Robert Hook, Newton wrote, “If I can see further, it is by standing on the shoulders of giants.” We in the modern world see further because we stand on the shoulders of many giants; Newton is certainly one of the biggest of those giants.
Newton practically invented (or discovered) the mathematical field we now call calculus. But while most mathematicians at the time, including Gottfried Wilhelm Lebniz who independently discovered calculus, were more focused on using it to solve abstract mathematical puzzles, Newton was quick to find its use to describe the world around us.
Newton used calculus to formulate laws describing the way objects move. We use these laws of motion, which bear Newton’s name, to this very day. The world over, engineers build things from bridges to airplanes all on the confidence that Newton’s laws will hold. We use these same bridges and ride these airplanes on the same confidence. The infrastructure of the modern built environment is a testament to power of Newton’s laws of motion. More appropriately, they are a testament to their force.
The First Law establishes that there are preferred viewpoints from which to make observations. These viewpoints are called “inertial frames of reference” or IFRs. Viewed from IFRs, objects that are not moving will stay still until something pushes or pulls them. A vehicle that is speeding up, slowing down, or rounding a curve is not an IFR because things inside the vehicle can look like they are moving even when nothing is pushing or pulling them.
When viewed from IFRs, objects that move also tend to keep on moving in the same way (same speed, same direction). Objects just don’t change course or speed up without being pushed or pulled. Although not an exact IFR, the Earth is a good enough example for the purposes of building almost all bridges and airplanes.
An object’s tendency to stay at rest or to keep on moving the way it already does is called inertia. For this reason, the First Law is also called the Law of Inertia.
The Second Law of Motion relates the following things: mass, acceleration, and resultant force. Mass (m) is a measure of how much stuff is in the object. Acceleration (a) is a measure of how fast it is changing its motion. Force (F) is a measure of the push or pull that’s accelerating the object.
Written as an equation, the Second Law is F = ma.
Using this equation, we see that more force leads to more acceleration. We also find that things with more mass are harder to move around.
In the equation above, (F) is not just a single force. Instead, it is the sum of all the forces acting on the object. If all forces balance each other out, then (F) is zero, which means acceleration is also zero and the object does not change the way it is moving. If there were an imbalance in the force, then (F) is not zero. In turn, (a) will have some value. The object in question will accelerate.
There are forces all around us, but they rarely move us because they usually balance each other out.
Meanwhile, the Third Law tells us that when A exerts a force on B, then B will exert a force on A that is just a strong, except that it’s going in the opposite direction. The first force is the action, the second is the reaction. The Third Law is also called the Law of Action and Reaction.
Newton combined these three laws with his other great law, a law that describes one particular force. That force is gravity. By thinking about the moon and falling apples, Newton figured that the force that makes apples fall to the ground is the same force that makes the moon go around the Earth. That’s a crazy suggestion, but Newton tried that out and he got a crazy answer—yes.
In fact, that very force that makes apples fall and anchors you to the ground, holds the Solar System together and dictates the dance of the planets around the Sun. It is the tune to which binary stars dance around each other. It is the music of the spheres. It is universal, holding true even in galaxies far, far away.
So this holiday season and for the next year, be one with the force. Let that force be science.
Pecier Decierdo is resident physicist and astronomer of The Mind Museum.