illuminating science

I was just reading a Facebook post in a Christian group by someone named Billy Joyce. It’s a carbon copy of countless of ignorant people, sadly most of them religious. Here’s what he said:

Recently, astronomers discovered an “old star” (100 billion years old apparently) that was giving birth to “new planets”…this is what a scientist had to say:

“We currently understand planet formation to occur around stars when they are very young…As such, we would never expect a star to undergo planet formation late in its life as the necessary conditions are not present.”

Now a statement like this leads me to believe that their knowledge is only speculation to begin with…obviously the conclusions that they had previously come to were just blown to bits by nature itself. I wonder how many millions of dollars we’ve paid these scientists as a collectivity [sic] to come to the “accurate conclusions” they’ve come to in various fields. And when you look at the overall benefit to mankind in these things, one must wonder just why it’s done at all.

It’s this very thing which drives me crazy - that’s the whole point of science. We don’t know everything, nor do we scientists ever claim to. As countless people before me have said - theories in science are almost always evolving. New observations are either fitted into the existing framework or we develop new theories which do include and explain these observations. Scientists love it when discoveries disprove old theories - it often means there’s a whole new area of science to explore, with who knows what results.

And even then, theories are rarely “blown to bits”. Instead, we realise that our existing theories are only part of the picture. Einstein’s Theory of Relativity didn’t disprove Newton’s theories of motion. Instead, they showed us that Newton’s laws are the “low speed” approximation to a bigger theory. Newton was perfectly right - unless you happen to be going near the speed of light! I’m sure our theories of planet formation will evolve accordingly.

As for “the overall benefit to mankind” - How about antibiotics and the countless other medicines? Chemotherapy? The internet? Solar power? And sure, maybe understanding planet formation doesn’t feed the hungry but it’s part of learning how the universe works, and from that who knows what we’ll discover! (Lasers were initially a scientific novelty - now look at them!) As for evolution - how dramatically did it change our understanding of life on Earth! But Billy, if you’d prefer not to use your internet, TV, car or medicines - feel free!

But this is the sort of thing that religion so often blinds people - the fact that the universe is an amazing, incredible place regardless of whether or not a God exists, and that science is helping us to appreciate and utilise the beauty of it.

Not a loaded question, but pure curiosity: How many lives has the Bible saved over the last 200 years, compared to advances in science over the same period? (And how could you estimate either?)

If you’ve never heard this question, you’re in for an experience. This (along with the Monty Hall problem) has got to be the most controversial problem in physics, ever. Seriously. Check out these discussions. It gets seriously aggressive!

So what gets people so impassioned? Here’s the problem:

A plane is standing on a runway that can move (some sort of conveyor belt). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). Can the plane take off?

Or, a better phrasing is this:

A plane is standing on a runway that can move. The plane moves in one direction, while the conveyor moves in the opposite direction at the plane’s take off speed. Can the plane take off?

Stop and think about it. Then, read on

My first answer was…no. My (incorrect!) thinking was that it’s the speed of the air over the plane wings that provides the lift for a plane to fly. Hence if you were on a backwards moving conveyor belt, so that you weren’t moving relative to the air, there would never be any lift no matter how fast you went and you could never take off.

But I “misread” the question - I’m right in part - we’ll all agree that if a plane is not moving relative to the air, then it cannot take off. (It’s the motion of air over the wings that gives it lift.) But what this question is asking is really this: Can a conveyor belt stop a plane from moving and accelerating forwards through the air? Or, another way, can a plane on a conveyor belt move forward through the air, no matter how fast the belt is moving?

The answer is yes - it can and will.

Let’s explain this three times -first, with facts, second with physics, then finally building up a logical argument with more details. I’m using ideas from a variety of sources, including Straight Dope, doesn’t depend on speed, for all intents and purposes.)

So, finally, to our plane. The wheels on a plane are only used for rolling or braking - they’re not “powered” in anyway, just like a rollerblade. Instead, a plane is able to accelerate quite independently of the ground (e.g., in mid air!), by using its engines or a propeller. No matter how fast the conveyor belt is moving, I can use a small amount of my thrust to overcome the friction there (just like the roller blades), and the rest goes into accelerating the plane. That means that the plane can and will start to accelerate forwards, eventually reaching take off speed. Again, in terms of forces, the only forces acting (horizontally) on the plane are the thrust from the engines and a tiny bit of friction from the imperfect wheels. It must move forward, by the laws of physics, and so will take off.

Just remember, that people who say a stationary plane can’t take off are absolutely right! But that’s not the key to this question - it’s whether a moving conveyor belt can stop a plane. And, it turns out, it can’t. This is really tough to get your head around at least in part because the problem is badly worded. Both sides have valid points, you’ve just got to agree on the problem. (In particular, the phrasing that the “belt moves at the same but opposite speed as the plane” - as the plane compared to what? Bad question!)

And the final words, of course, comes from Mythbusters who showed the plane can take off. It’s not a perfect experiment, but the basic idea is correct and shows the correct physics. (A moving tarp is a pretty good approximation to a conveyor belt - even if you can feel the ground through it, that shouldn’t change the friction much! The ground is still “moving”.)

I hope that helps clear things up!