Hey it's me Destin.
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 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.
你現在正在收看Smarter Every Day。
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.
奧瑞岡州立大學的Doug Warrick博士與蒙大拿大學的Brett Tobalske博士利用噴嘴噴灑橄欖油於蜂鳥四周的空氣，進行蜂鳥相關研究。
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 visualization 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 seventy percent of the hummingbird's lift comes from the forestroke, and thirty comes from the backstroke. It's not fifty-fifty 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 center 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.
除此之外，你可以點選 這裡的「餵食器」 ，還有啊...你可以訂閱。
Oh... Just subscribe by clicking the link below, and I hope you're getting Smarter Every Day.
噢...點選下列連結即可訂閱，希望你喜歡Smarter Every Day。
That is... That's some good stuff.