“There’s no such thing as gravity in outer space. You don’t weigh anything out there. It’s why the astronauts floated when they were in orbit aboard the shuttle.”
Had I overheard the above coming from the mouths of kids, it wouldn’t have surprised me, although my compulsion to “set them straight” would most certainly have been overwhelming.
However, this quote did not come from the lips of kids; it came directly from the mouth of a 7th grade English teacher—private school, Catholic to be precise.
Understand me here. I do not mention this as a general indictment against Catholic education. I’m a product of that system. But, while in NO way do I consider myself an intellectually astute phenomenon, I’m a long way from stupid.
Even though this teacher was DEAD-serious, she’s not stupid, either. She holds a Master’s degree in English. If you think it’s an intellectual cakewalk to obtain one of these, THINK again. Misinformed? YES! Stupid? NO!
The reality is that we don’t do a lot of science in this country to begin with; and it’s becoming worse by the year. We have a major problem in America and part of it stems from the way we teach science, particularly physics.
And since physics is my area of expertise, I can tell you with a significant air of certainty that a mastery of the subject is not reserved for ONLY wire-haired absent-minded rocket science types who tend to wear a striped shirt with plaid pants.
But, the folks who teach this stuff for a living—at ALL levels—need to grasp the idea that there’s a big difference between what non-physics-majoring shirtsleeve Americans need to master and what the future physicists of the world need to master.
Also, another part of the problem is the way in which science teachers—again, physics in particular—go about the business of teaching others.
Yes, this nation is blessed with some fantastic high school physics teachers. We also have some outstanding collegiate level physics professors. But these are not in the majority. Many physics teachers suck at it!
They’re boring. For most of them, one size fits all and they don’t teach a thing. They’re completely unimaginative, presenting concepts—both applied and theoretical—in monotone fashion, all neatly wrapped in mathematical brown paper and tied together with bows made of simultaneous and quadratic equations.
This is fine for physics majors; but it does nothing for the rest of the student body except turn them off. It’s why, with the exception of the growing popularity of the 9-millimeter pistol and its bullets, the metric system has never gone over well in this country.
If the point is teaching people about the effect of gravitational forces, forget about 9.8m/sec2 (9.8 meters per second squared). Use 32ft/sec2 (actually 32.17, but no need to quibble at this level). And by all means do NOT fail to explain what that /sec2 actually means.
It means that a body in free-fall drops 32-feet in the first second, an additional 64-feet during second number two, an additional 128-feet during second number three.
See what’s happening? The acceleration goes 32-feet times 2, times 2, times 2 until the body reaches terminal velocity (rate of fall equals the upward force of drag—air resistance). After this, the body continues to fall but at a steady rate.
An English teacher’s misconception of astronauts floating aboard space shuttles because there is no gravity in outer space actually concerns two separate concepts.
I don’t have the space to deal with both of them in one posting; so I’ll explain one this week and the other in a later posting. Let’s tackle the outer space weight stuff first.
The force of gravity is pervasive; it’s the glue that holds our entire universe together. Without it matter wouldn’t exist, just a plethora of subatomic particles (electrons, neutrons, protons, etc.) floating randomly in empty space.
As I sit on this chair typing, my big butt and the chair it’s sitting on are in the throes of an avid love affair. Gravity binds them together but it’s not overwhelming. I prove this each time I stand up!
However, while GRAVITY attracts my butt and the chair in a mutual attraction, the real force of attraction comes from gravity pulling both me and the chair toward Earth’s center.
When you stand on your bathroom scale and it shows your weight at 150 pounds, it actually shows the force with which gravity is pulling both you and the scale toward the center of the Earth.
But, there is no need for normal people to understand or re-derive Newton’s Gravitational Constant in order to understand why they weigh what they weigh.
Newton proved that as the distance between two bodies of mass increases, the mutual gravitational attractive force between them DECREASES. In fact, each time that distance doubles, the gravitational force between them drops to one-fourth its original.
If you weigh 150-pounds on the surface of the Earth, how much would you weigh aboard a space shuttle orbiting in low orbit at 180-miles above the Earth? The solution is simple and you don’t need THIS to figure it out.
As you stand on your bathroom scale, gravity is pulling you toward the center of the Earth (about 3,960 miles down—Earth’s average radius) with a force of 150-pounds.
If I send you into space another 3,960 miles above the Earth, I’ve doubled the distance between you and the CENTER of the Earth. Your weight (the force with which Earth’s center draws you into itself) drops to one-fourth: 37.5-pounds.
But, again, you don’t need THIS to understand it. Just use this (1/r2); it’s much simpler! As well, there is no need to get confused by dividing with big numbers like 3,960, either.
We’ll call the 3,960 miles from Earth’s center to its surface 1-gravity. We’ll call the second 3,960 miles (from Earth’s surface to your doubling point in outer space) 2-gravity.
But, you’re not at a full 2-gravity; you’re at 1-gravity PLUS some fraction of 2-gravity (180 miles divided by 3,960 miles or just 4.45% of 2-gravity. Here’s how it works.
Standing on your bathroom scale, you’re at 1-gravity; you weigh 150 pounds. Do Newton’s findings hold true?
Using 1/r2, we find that r2 is 1-gravity and 12 always equals 1. Therefore 1/1 equals 1. And 1 times 150 (your Earth weight) equals 150 pounds. COWABUNGA!
At 2-gravity, 1/r2 equals 1/22 which equals 1 divided by 4 (22 equals 4), which is ONE-FOURTH. The force with which Earth’s gravity would pull you from 3,960 miles above it is 37.5 pounds (your outer space weight).
But you’re NOT at a full 2-gravity; you’re at a full 1-gravity plus only 4.45% of 2-gravity.
Therefore 1/r2 becomes 1/1.0452. So the equation becomes 1/1.092 which equals 0.916. Multiply 0.916 by your Earth weight of 150 pounds to find that you’d weigh 137.4 pounds aboard a space shuttle orbiting 180 miles above Earth.
But this is NOT why the astronauts float up there on that shuttle. That’s another matter which I’ll explain in a later posting.