*promote

Promoting this video and sending it back into the queue for one more try; last queued Sunday, November 2nd, 2014 11:00am PST - promote requested by eric3579.

Brian Cox + NASA + Undeniable Science = WIN

it works, bitches

Wait, I want to know what happens!

Why did Einstein say the ball and feather weren't accelerating toward earth?

Not only cool, but done just up the road in Cleveland... okay an hour or two up the road, but same state. Anyhow, what I found odd was how many of the people who work there seemed amazed. I'd think that was an experiment they'd have done a few times. Unless it is overly expensive to operate, I'd think that'd be something they show off once in a while.

Yeah, those last couple sentences throw me for a loop also. I *think* he is referencing relativity, in that the objects are behaving relativistically towards each other, but if you remove/ignore the earth (and air) then you are missing one half of what they are "relative" to. Or that the Earth and the air are also (minutely) attracted towards the bowling ball and feather, or something.

Would definitely be nice to see the next few minutes of this show to see what he's eluding to...

Relativity was my guess too, but like you it still didn't make sense to me.

Way cool.

They have a great example of this in the Exploratorium in SF, but in a rotating/flipping clear plastic tube with a feather and a plastic army man and a button to turn on the vacuum.

Its definitely relativity.

They fall at the same speed? As each other? With respect to what? Why are they even falling at all?

In relativity you always have a frame of reference. If you take the speed of feathers with respect to that of the bowling ball in a vacuum, the difference is zero....they aren't moving at all within the frame of reference.

No need to complicate things by bringing the earth into the equation.

Its a round about way of using something so simple to explain how relativistic equations are handled in his works.

WOW, that vacuum slowed down the bowling ball to the speed of a feather. Pretty cool. That's why nothing can go faster than the speed of light.

Explanation continues at 40 min mark...

Human Universe: A Place in Space and Time. Full Episode

The next time I fall off of a tall building I'll take comfort in the fact that I'm not accelerating towards the earth.

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.

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?

@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.

@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.

The partial vacuum explanation is the only thing I could come up with as well.

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)

Elastic Potential Energy

Glad we have some actual educated people on this website.

Don't the rest of you feel dumb?

I do.

Also: Avengers.

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.

[redacted]

He didn't, at least not according to "Einstein: His Life and Universe." where he is reported to have said that his happiest thought was that Gravity and Acceleration are equivalent. It was a breakthrough for him to realize that a man in a falling elevator wouldn't feel the force of gravity, because they are the same thing.

Isn't like the slinky?

Gravity still exists, and exerts exactly the same force on you independent of whether you are standing on solid ground or falling, and whether you are falling inside an elevator or in empty space. The difference is the opposite force exerted on you by the ground vs no opposite force (except the tiny force exerted by air if you're freefalling in the open air). It is this opposite force you 'feel', while acceleration due to gravity without any opposing force feels like floating.
So a man in a free-falling elevator in an atmosphere WOULD feel a tiny bit of gravity, because the outside air would slow the elevator to less than terminal velocity, so it would slow down slightly, unlike the mans descent, making him fall/float to the floor of the elevator eventually and then feel a microgravity exactly equal to the force exerted by the air.

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.

Shooting location look familiar?

General Relativity : Einstein vs. Newton

That was beautiful

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.

Well, yes and no. The gravitational forces acting on the larger mass may be larger, but so is the mass it has to move, by exactly the same amount. That means mass is actually irrelevant and gravity accelerates everything in a vacuum at exactly the same rate, even though it takes more 'force' to accelerate larger masses. On earth, it's 9.8m per sec per sec. no matter what the mass is.

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.