Technically correct is the best kind of correct.

The trouble with teaching people that the bowling ball and feather will hit at, quoting the physicist in this clip, "exactly the same time", is that (relativity issues aside making the statement a joke anyway) it leads people to have a faulty understanding of how gravity actually works.

It's fine to teach that bowling balls and feathers will hit at *approximately* the same time, due to one mass in the equation being much higher than the other (allowing us to approximate it out), but it seems to never be taught this way. So these students end up with all sorts of wrong ideas about gravity when they get to me to work on n-body solvers.

It's the same problem, for example, as teaching elementary school kids that 5 divided by 0 is 0. It might make that teacher's life a little easier, but causes problems downstream.

Now I'm starting to think you just want to argue. If you're smart enough to make those technical assertions, you're smart enough to know that's not what the experiment was about, and that you're just adding data to confuse the lesson.
The experiment is about the effect of gravity on the moving objects under 2 conditions, and how their mass means nothing when determining THEIR accelerations/speeds in a vacuum. Period.
You want to introduce other, completely unobservable (and irrelevant to the lesson) forces and movements to say 'nope'. Technically, you may be correct in a way, but you must completely ignore the purpose and parameters of the experiment and assume inobservably small movements to make your point...a point that does not actually change the experimental findings or the lesson, but does confuse it thoroughly.

EDIT: I would note that, by your standards, exactly where the observer is positioned makes MORE difference than the different masses of the bowling ball and feather, as do the exact positions of the two...if dropped from exactly the same position, they hit at exactly the same time because their gravitational forces are in line.

I would also note that if you change it to say, unimpeded, they would cross any imaginary line in space at the same time (essentially what they mean), again your point becomes moot.

If a planet would hit before a feather, then a bowling ball would hit before a feather. The only difference is the effect size.

No...I'm talking in reference to earth (or any 'stationary' gravity source), as is the video. You are talking about relative speeds of moveable, nearly equal gravitational forces. That's why we disagree, we're talking about completely different things.

Yes. You are correct. If you put 3 objects in space, 2 of them being planet masses (not sized, size has nothing to do with it) and the third being the mass of a feather, the planet masses will come together first because they attract each other.

But that's not what this video, or the discussion were about. They are about how mass is irrelevant when discussing/calculating acceleration due to gravity (in the absence of other opposing forces, like wind resistance), and that's still true in your example. It gets MUCH harder to understand when you change the experimental parameters to have the (now multiple) gravitational force(s) also acted upon and moving, but the same rules all still apply. It's just much simpler to use masses of magnitudes so different where you can consider the gravity well a stationary object not attracted towards or effected by either moving object.

You're starting to get it. Except we're not talking about acceleration in reference to earth, we're talking about which would hit first, a massive object or a less massive object.

So if you drop a planet on the earth, it will hit before a feather would from the same distance.

Right. They will both accelerate towards each other at 9.8 m/s^2. So the total acceleration is twice as fast, and they hit in less time than if you drop a feather.

Not quite. You'll see your error if you have two earth sized objects instead of an earth and a feather at a distance. Run the math.

Ugh, so wrong. The gravitational force between two objects is proportional to the product of both masses. So a more massive object will indeed fall faster than a lighter object.

We can't really see it with a bowling ball and a feather, but we really shouldn't be teaching that all objects fall at the same speed.

To elaborate on the captain's explanation:

Each barb of the feather is bending downward under its own weight due to the force of gravity. The weight of the barb exerts a downward bending force on itself. When the feather begins to fall, each barb is no longer affected by gravity, and so, recoils to its "natural" position of minimal tension. Though I can't see it in this video, I assume that each barb actually oscillates a bit about its natural position.

The law of inertia is that things tend to do what they are already doing. That would mean staying still if they were let go.
That may explain the opposite force that moves the feather strands and gravity takes over, opposing the inertia - even though it is a very small amount.

My guess would be Inertia. Even in a vacuum objects have Inertia.

"Inertial mass is the mass of an object measured by its resistance to acceleration"

Deformable objects might deform slightly as they accelerate (feather).
However, their center of gravity is the same as a rigid object (bowling ball)

@lucky760

I didn't listen to the audio track to the video, but I am guessing it's still a (very) partial vaccuum and nothing would sense this more than the smallest vestiges of a feather.

@eric3579 and @dag -
I thought about that...but the entire feather is under the same gravity, so being accelerated at the same rate. Without anything to disrupt that, like air, I was confused. If you wave the feather in a vacuum, it would make sense because the force would travel through the quill then out to each 'strand' (just like the flag 'waving' on the moon when they moved it)...but being dropped as it was, it didn't make sense to me. Perhaps it's not near a perfect vacuum, only close enough to do the experiment?

My alternate guess is moment of inertia...but I can't fully explain why.

My guess would be that it has to do with the acceleration of the feather due to the gravitational force. That however is a stab in the dark. Anyone?

Seems like no one else noticed or cared, but why is it that in the zero-air environment when they did the release the tiny "strands of feather" (I don't know what each little thread on a feather is called, if anything) looked like they were getting pushed back by air?

Am I seeing things?

It must be a hoax. They're probably on a sound stage where they faked the whole thing. Probably not even a real bowling ball.