So to fly slow is one of the more difficult things to do because you don't have as much airflow over

your control surfaces. To fly at zero air velocity is the hardest thing to do of all.

Over the past weekend I've been making observations of hummingbird flight

in my back yard. So let's look at my observations and then we'll come back, and we'll look

at the science of how hummingbirds fly. You're getting Smarter Every Day.

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So what does olive oil and lasers have in

common. Hummingbirds obviously. Dr Doug Warrick

at Oregon State University and Dr Brett Tobalske at University of Montana have been

studying hummingbirds by using a nozzle to spray olive oil

in the air around a hummingbird. And then they'll take a laser and then they'll

slice sections of the air where the olive oil is, to measure

the flow field. Basically it's called digital particle image

velocimetry. What you do is you get a picture of an oil droplet, you wait

some finite amount of time later and then you get another picture of an oil droplet. That gives you

a two dimensional visualisation of the flow field around a hummingbird, which is awesome.

So what you can do is you can use this information to calculate exactly

what the hummingbird is doing to stay aloft. In these pictures you can see here,

you can see vortices underneath the wing. Using this technique they

discovered that about 70% of the hummingbird's lift comes from the fore stroke,

and 30% comes from the back stroke. It's not 50-50 like I used to think it was.

Another thing I observed is when a hummingbird would come into the feeder, right before he'd get there

he would make this tail flick. I didn't know what that was so I called Dr Warrick and asked him.

Right now Dr Warrick and his team of biomechanists don't really know what this tail flick means.

They're not sure if he's changing the airflow around his body

or if he's changing his centre of gravity under his wings so that the can make a maneuver that way.

What they are doing however is making a six degree of freedom model so that they can

study this further. If you want to learn more about it check out the links in the video

description. So a lot of you have been asking about what kind of camera I've been using. It's a Phantom made by

Vision Research. If you want more info on it go to the description, I'll put a link there for you

so you can go to the website. Other than that click the bird feeder here, and uh..

You can subscribe.

Oh.. Just subscribe by clicking

the link below, and I hope you're getting Smarter Every Day.

[cough] That is...

That's some good stuff.

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[ Captions by Andrew Jackson ] captionsbyandrew.wordpress.com

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