
The hammer-feather drop in the world’s biggest vacuum chamber [video] - ColinWright
http://thekidshouldseethis.com/post/the-hammer-feather-drop-in-the-worlds-biggest-vacuum-chamber
======
paddyoloughlin
I wish the producers were less enamoured of their slow-mo and showed us the
whole thing in real-time.

The "weird" thing is seeing feathers plummet to the ground and I wish we got
to see more of that.

~~~
zelos
This is a Brian Cox show we're talking about, not a science show. I'm
surprised there weren't more slow mo shots of Cox doing his "boyish wonder"
face.

~~~
nly
His 'boyish wonder', although personally I think it's genuine, does get
annoying to those of us who have their own wonder to contend with. Though,
perhaps, those completely devoid of it themselves appreciate the cues.

I really don't mind Cox... what I despise is the trend of putting comedians in
to science and politics shows in an attempt to relieve the dowdiness (Sorry
Dara). Then again, I'm one of those people who used to sneak downstairs in the
early hours to watch the dusty math and science stuff the BBC used to
broadcast for teachers to record on VHS.

~~~
gadders
I agree. Have you ever tried listening to The Infinite Monkey Cage on BBC
Radio 4? [1]

It's motto seems to be "Look at us! We're scientists but we're so wacky!!!111"

[http://www.bbc.co.uk/programmes/b00snr0w](http://www.bbc.co.uk/programmes/b00snr0w)

~~~
JonnieCache
Robin Ince certainly has a lot to answer for.

Ben Goldacre is the master of this style of science communication. Friendly
and fun and enthusiastic, but in a way that appeals to both laymen and his
peers. I suppose epidemiology is somewhat more human than astrophysics, so its
easier.

~~~
gadders
Frontiers [1] also on Radio 4 is good.

[1]
[http://www.bbc.co.uk/programmes/b006qy5p](http://www.bbc.co.uk/programmes/b006qy5p)

------
blutack
Seeing as the original site has now fallen over, the actual youtube link is

[https://www.youtube.com/watch?v=E43-CfukEgs](https://www.youtube.com/watch?v=E43-CfukEgs)

~~~
nmeofthestate
And for the violently impatient, the actual drop:
[http://youtu.be/E43-CfukEgs?t=2m52s](http://youtu.be/E43-CfukEgs?t=2m52s)

~~~
zwp
Fortunately you beat me to it. I was going to post the later sequence at:
[https://www.youtube.com/watch?v=E43-CfukEgs&feature=youtu.be...](https://www.youtube.com/watch?v=E43-CfukEgs&feature=youtu.be&t=4m15s)

But on closer viewing that is a disastrous montage: the first few seconds
(before cut away) show the feathers fluttering and the bowling ball starting
to accelerate away; the slow-motion segue is under vacuum conditions though.
The film editor's intention is that the two shots appear contiguous. We can
speculate why they might have done this (no close up shot taken under vacuum
conditions?) but it really tramples the whole point of the article :(

~~~
4ad
What do you mean? The close-up shot at 2:52s is under vacuum. The "fluttering"
you see is the elastic wave in the feather caused by the sudden drop in
internal tension. The feather is an elastic object (to a first approximation).
When the feather is hung, there's internal tension keeping it stationary and
giving its shape. When the feather is unhooked, this internal tension doesn't
just disappear instantaneously, rather an elastic wave travels through the
feather at the speed of sound in the feather. Because the feather is not a
perfect elastic medium, the effect you see is a damped harmonic oscillator,
but it takes non-zero finite time to dampen sufficiently.

This is true for the big ball too, except that the speed of sound is orders of
magnitude faster in it, and the spring constant of the material (steel?) is
also many order of magnitude larger than the spring constant of the feather.

The center of mass of both objects falls at the same rate. At t=0, d^2x/dt^2=0
for the points closer to the ground and d^2x/dt^2=2g for the points that were
just unhooked. Also see
[https://www.youtube.com/watch?v=mAA613hqqZ0](https://www.youtube.com/watch?v=mAA613hqqZ0)

~~~
janzer
He's referring to the sequence starting at 4:15. Compare the close up real
time shot that starts the later sequence to the slow motion at 2:52. The
feather and ball leave the frame almost simultaneously in the earlier one but
with ~25% of the feather still in frame in the latter.

After looking at it I agree with zwp, the editor really did make quite a
mistake when assembling the last sequence.

[Edit: Screen grab of both
[http://imgur.com/EAKB5FK](http://imgur.com/EAKB5FK) and I agree with the over
all editing comment below. The slow motion shot as the first shot of falling
in the vacuum was the thing that really stood out and I thought was bad on the
first play through.]

~~~
4ad
Oh, I see what you mean now. Yes, definitely editing mistake :-). Apart from
that, editing was bad altogether. There should have been many shots with the
real-time fall. In fact, the first shot of the drop should have been in real-
time.

------
pshinghal
Certainly a lot of us know what to expect in this experiment, but the thing I
never really thought about was a that the feathers would bounce back up after
impact. Seems obvious in retrospect, but it was pretty cool to see.

------
revscat
Commander David Scott did this same experiment as part of Apollo 15 in August
of 1971, in an even larger vacuum:

[https://www.youtube.com/watch?v=KDp1tiUsZw8](https://www.youtube.com/watch?v=KDp1tiUsZw8)

~~~
ColinWright
That's one reason why I posted the link to this site, rather than directly to
the YouTube video, as explained here:

[https://news.ycombinator.com/item?id=8556363](https://news.ycombinator.com/item?id=8556363)

The text of the site I submitted has kindly been posted by DanBC[0] here:

[https://news.ycombinator.com/item?id=8556409](https://news.ycombinator.com/item?id=8556409)

[0]
[https://news.ycombinator.com/user?id=DanBC](https://news.ycombinator.com/user?id=DanBC)

~~~
revscat
No worries, mate.

------
paddyoloughlin
I love how professionals who work at that facility and have probably deeply
understood those principles for decades still display so much wonder at seeing
this experiment with their own eyes.

~~~
hudibras
I might be cynical, but I think they were putting on a show a bit. They
already had some sort of apparatus set up to do the simultaneous drops.

My guess is that it's a standard demonstration for visiting dignitaries and
the like.

~~~
smackfu
>They already had some sort of apparatus set up to do the simultaneous drops.

Why do you say that? They could have easily made the apparatus for this
experiment.

~~~
Too
The button he pressed when dropping had a label that said something like
"launch jet sequence" (don't remember exactly). They probably have a modular
set of actuator and rigs they can easily mess around with . :)

------
jgrahamc
Worth reading
[http://en.wikipedia.org/wiki/Equivalence_principle](http://en.wikipedia.org/wiki/Equivalence_principle)
if you don't understand the last part.

------
bjackman
I guess this is a pretty superficial complaint, but this is a 2nd-generation
clickbait-site link (posted on io9, reposted on thekidsshouldseethis.com). Why
not post the Youtube link directly? This isn't really Hacker News material,
anyway.

~~~
norlowski
Experiment, curiosity, huge NASA buildings, near vacuum. I'd rather read about
this than mark zuckerberg.

------
cryowaffle
Can someone explain to me the last part about the items standing still and no
force acting on them? Isn't gravity acting on them, pulling the earth and
items together?

~~~
gradi3nt
Imagine being inside of a closed box like an elevator. Without leaving the box
there is no way to tell the difference from being in free fall towards Earth
versus floating in interstellar space. Therefor, general relativity take the
perspective that gravity is a fictitious force (like centrifugal force) that
arises from the shape of spacetime.

~~~
josu
>versus floating in interstellar space

Versus being inside that an elevator that is being accelerated in interstellar
space

This seems like a pretty good explanation:
[http://www.astronomynotes.com/relativity/s3.htm](http://www.astronomynotes.com/relativity/s3.htm)

~~~
bweitzman
gradi3nt had it right

Free fall feels like floating Standing still (in the presence of the Earth's
gravity) feels like being accelerated.

------
joshvm
All the best facilities have big buttons labelled "Mega speed trigger".

But in seriousness, does the Moon not count? Surely space is the largest
vacuum chamber we have access to!

------
dia80
I know how this will turn out but my intuition is screaming otherwise.

~~~
oneeyedpigeon
I find it interesting that Brian Cox, the presenter and avowed scientist,
obviously finds it so 'surprising' as well. Maybe that's the true meaning of
being a scientist, though - he doesn't _truly_ believe it until observing it
with his own eyes.

~~~
sambeau
>Brian Cox, the presenter and avowed scientist,

I think you mean "Brian Cox: Professor of High-energy Particle Physics, member
of the High Energy Physics group at the University of Manchester, and the
ATLAS experiment at the Large Hadron Collider at CERN (who also presents
popular science programmes in the UK)"

I think his career as a scientist deserves a little more recognition than
"avowed".

And, as for his career in popular science he has been awarded both a Faraday
and a Kelvin prize.

~~~
oneeyedpigeon
Sorry; I have every respect for Brian Cox, unlike others on this thread. I
think I'm merely using totally the wrong word.

~~~
sambeau
Sorry; I read "avowed" as a deliberate slur. I suspect some of the negativity
about him here must have got to me. For an unknown reason I picked on your
comment – I now see there are plenty worse :)

------
iterationx
Yes, you already know the ending, but its worth watching just to see the
massive structure.

------
aaron695
It interesting some people think a vacuum means a lot of pressure but really
it's the same as 10 meters under water at sea level pressure.

~~~
Cthulhu_
^, explosive decompression in space also isn't as explosive as coming up from
a few meters underwater in one go (it's from 1 to 0 atmospheres, instead of
100 to 1).

Not that I advocate explosive decompression in any circumstance, mind you.

------
thearn4
SPF is an awesome and unique facility, I wish more of the public would get to
see it in person.

If you want to see more of it in video, it's also where the opening scene to
"The Avengers" was filmed. Plum Brook Station has a whole collection of really
cool (though mostly single-purpose) buildings.

~~~
Animats
_If you want to see more of it in video, it 's also where the opening scene to
"The Avengers" was filmed._

It's appeared in a lot of movies, "Futureworld" (1973) being one of the first.

That's where the nuclear rocket upper stage for Apollo was supposed to be
tested.

------
italophil
The space and aerospace programs of the sixties produced some really
impressive technologies and facilities. Too bad government spending on
technology research went down, just imagine what could be possible.

~~~
frozenport
From another perspective, these technologies left us with little science of
utility (Tang?) while developing intercontinental ballistic missiles that loom
over humanity like the Sword of Damocles. When historians from far off planets
visit our nuclear wasteland they will see our thinly veiled space program as
the beginning of end. :-)

~~~
baldfat
Quick list of more inventions that are not Tang
[http://en.wikipedia.org/wiki/NASA_spin-
off_technologies](http://en.wikipedia.org/wiki/NASA_spin-off_technologies)

~~~
noselasd
Even something as mundane as error correction coding were developed at NASA,
for communicating with spacecraft - technology that's now present in e.g.
CD/DVDs, and every mobile communication system.

Now, if they hadn't developed it, someone else probably would, but perhaps not
at that time - leaving us at years behind where we currently are with e.g. the
speeds on our mobile devices.

~~~
btoptical
Error Correction Coding is hardly mundane and in modern communication systems
far from trivial. There is a lot more to ECC than Reed-Solomon. Basically
nothing in our digital world today would work very long without it. You think
of it as mundane only because it just works.

------
rglover
Anybody else catch the NASA engineer wearing a SpaceX Dragon t-shirt? Nice.

~~~
Marcus10110
I'm wearing mine to Interstellar tonight!

------
fdomig
I love science. This is a very nice example of it.

------
Shivetya
I think my favorite part of this is not that they were able to demonstrate it
so well but instead the reactions of people expecting it to actually occur.

------
rajdevar
I live in Ohio, Never knew that the biggest vacuum chamber is here until now.

~~~
th0ma5
Yup yup, it is NASA Plumbrook, the old reactor south of Sandusky. On the way
to Cedar Point as a kid I was always in awe of the place as it was so big and
you could only get within a few miles of it. My sixth grade teacher claimed a
three eyed frog he had in a jar came from a nearby pond.

------
Freestyler_3
They could also have put a toy helicopter in there, just to add more fun.

------
z3t4
So if they aren't falling. What are they doing?

------
kentf
Science is amazing.

~~~
vertikal
Its brilliant

------
IgorPartola
Serious question: why do we keep repeating this experiment? Not that I mind, I
just am curious why do we keep building bigger and bigger vacuum chambers just
to drop a feather and a hammer over and over.

~~~
vacri
Before they pump the air out in the video, the presenter explains what the
facility was made for and is currently used for.

~~~
chatman
The presenter was wearing a wicked smile when the feather hit the box.

