0:14:05 > 0:14:08This is Blue Peter, but mini.
0:14:08 > 0:14:10Expect epic adventures, makes, bakes,
0:14:10 > 0:14:13badges, pets,
0:14:13 > 0:14:15presenters and your host.
0:14:15 > 0:14:18We've only got five minutes, so get ready for your Blue Peter adventure.
0:14:18 > 0:14:21It's time to welcome back to Blue Peter Mr Greg Foot.
0:14:21 > 0:14:23CHEERING
0:14:23 > 0:14:26- Hello, hello.- Yes, Greg. What have you got for us today?
0:14:26 > 0:14:30- I'm so excited.- Right, I want to bring the weather from outdoors,
0:14:30 > 0:14:33- indoors.- OK.- I want to make cloud and rain right here,
0:14:33 > 0:14:34in the Blue Peter studio.
0:14:34 > 0:14:36I definitely want to see that, as well.
0:14:36 > 0:14:39- What's this?- Let's start with the cloud. So, I'm going to make you
0:14:39 > 0:14:42a little cloud and then we are going to super-size it.
0:14:42 > 0:14:44So, first of all, question for you - what is a cloud made of?
0:14:44 > 0:14:46- Easy, water.- Good man, yeah, water.
0:14:46 > 0:14:49But the real question is how does that water clump together
0:14:49 > 0:14:51- into a cloud and how does it say up there?- Ah, OK.
0:14:51 > 0:14:55So, all around us is air and that's made of a whole bunch of different
0:14:55 > 0:14:57gases. You've got oxygen that you breathe in,
0:14:57 > 0:15:00you've got carbon dioxide that you breathe out, a whole host of others.
0:15:00 > 0:15:03- Including water, but as a gas we call it water vapour.- OK.
0:15:03 > 0:15:05Now, as all that gas rises, as that water vapour rises,
0:15:05 > 0:15:08it cools down when it gets to the top of the atmosphere.
0:15:08 > 0:15:12And when it cools down enough, it can actually turn from a gas
0:15:12 > 0:15:14into a liquid. If you think about when you breathe
0:15:14 > 0:15:15on a really cold window...
0:15:15 > 0:15:18- HE EXHALES - ..like that.- Ah, condensation?- Yeah.
0:15:18 > 0:15:20So that the water vapour, gas in your breath, cools down
0:15:20 > 0:15:24- into little droplets that you see. - Yes.- It's called condensation.
0:15:24 > 0:15:26That's all a cloud is, just condensed water vapour.
0:15:26 > 0:15:29- Now, can you start pumping water? - Absolutely.- Some eye protection
0:15:29 > 0:15:31- for you first.- Thank you. Remember, safety never takes a day off
0:15:31 > 0:15:34- on Blue Peter.- True, that. Right, 15 pumps, please.
0:15:34 > 0:15:36So, what you're doing right now is you're pumping air
0:15:36 > 0:15:38into the bottle, OK? And the air has got water vapour in it.
0:15:38 > 0:15:41I've put a little bit of water in there, as well. So, you're building
0:15:41 > 0:15:44up the pressure. When the pressure is enough, I'm going to pop
0:15:44 > 0:15:47the top off, the pressure is suddenly going to decrease, which
0:15:47 > 0:15:50cools the whole thing down. So, it's going to be like what happens
0:15:50 > 0:15:53up in the atmosphere. It cools down and, hopefully, we'll get a cloud.
0:15:53 > 0:15:56So, what it needs to do is, it needs to have something to grip hold of.
0:15:56 > 0:15:58All those water droplets need to grip onto something. Up there,
0:15:58 > 0:16:01in the sky, it could be salt from the sea. It could be dust,
0:16:01 > 0:16:03it could be soot from a wildfire. So, I put a little bit
0:16:03 > 0:16:06of soot in here, very carefully, earlier. Right, are you ready?
0:16:06 > 0:16:09- Yes, I am. - Three, two, one...
0:16:09 > 0:16:11- Yes, look at that!- Yes! - You see that cloud in there?
0:16:11 > 0:16:14- There's a cloud in the bottle!- That is it. There's probably millions
0:16:14 > 0:16:17of little, tiny water droplets in there to make our cloud.
0:16:17 > 0:16:19- That's crazy.- So, I'm going to make a much bigger version,
0:16:19 > 0:16:22- to fill the whole studio afterwards.- OK.
0:16:22 > 0:16:25- The question, I guess, is how it actually stays up there.- Yes.
0:16:25 > 0:16:28And it's because the droplets are so, so tiny. They're so small,
0:16:28 > 0:16:31they're surrounded by air. They're light enough to float up there,
0:16:31 > 0:16:34but, once they start banging together and the cloud grows,
0:16:34 > 0:16:36the droplets get so big that they can start to fall. And that,
0:16:36 > 0:16:39- of course, is...- Rain. - Rain. Question for you, Radzi,
0:16:39 > 0:16:42- from Blue Peter.- Yeah.- What shape is a raindrop?- That easy, so, it's like
0:16:42 > 0:16:45a teardrop. So, it's a bit like that.
0:16:45 > 0:16:46HE IMITATES BUZZER
0:16:46 > 0:16:50I'm going to show you. Right, this is a raindrop levitation device,
0:16:50 > 0:16:52- that I built earlier.- Yes! - You're going to love this.
0:16:52 > 0:16:55We, obviously, can't skydive next to a raindrop to see its shape.
0:16:55 > 0:16:58So, what this is going to do is, air's going to rush up
0:16:58 > 0:17:01and I'm going to try to keep a raindrop in place. So, air's
0:17:01 > 0:17:03going to be rushing around it. It's exactly the same
0:17:03 > 0:17:05- as what happens as it falls.- Wow. - So, let's give this a go.
0:17:05 > 0:17:07- My air is on. - WIND WHOOSHES
0:17:07 > 0:17:09- Yeah, I can hear that.- Now, what I'm going to try to do is
0:17:09 > 0:17:13- I'm going to put a raindrop in there.- Oh.- More air!- More air!
0:17:13 > 0:17:16- Whoa!- Oh!- Oh! Oh!- There we go!
0:17:16 > 0:17:19- There we go!- Oh!- Now, that's not bad, very hard to do live.
0:17:19 > 0:17:22- Absolutely.- So, what did is I filmed it in slow-motion,
0:17:22 > 0:17:24- earlier in the rehearsal.- Amazing. - Have a look and tell me
0:17:24 > 0:17:28- what the shape is.- OK.- Watch this, this is amazing, watch.- OK.
0:17:28 > 0:17:29- Out it comes.- OK, it goes down.
0:17:29 > 0:17:32- It's flat!- Yeah. - Oh, it's really flat.
0:17:32 > 0:17:36- It is flat underneath.- Look at that there!- How gorgeous is that?
0:17:36 > 0:17:39- This, Radz, this is my favourite fact, right.- OK, hit me.
0:17:39 > 0:17:42- You'd think a raindrop is round, spherical, like a ball.- Yes.
0:17:42 > 0:17:45When they're really, really small, they are that shape,
0:17:45 > 0:17:47but when they get bigger, they fall.
0:17:47 > 0:17:49And they fall fast, like 15mph, 20mph.
0:17:49 > 0:17:52They're falling and all that air is hitting them underneath
0:17:52 > 0:17:54and it squashes the bottom of the raindrop
0:17:54 > 0:17:57- and you get that beautiful burger-bun shape.- Yeah.
0:17:57 > 0:18:00Why you said teardrop is you always see it running down a window, yeah?
0:18:00 > 0:18:02Or dripping out of a tap.
0:18:02 > 0:18:05What that does is it pulls some of it behind it and it creates
0:18:05 > 0:18:09- this tail. There you go.- So, there you go, it's all a big myth.- Yes.
0:18:09 > 0:18:11Now, Greg, I hate to hurry you, but I want to see the big one.
0:18:11 > 0:18:13Let's do it. Right, come over here, my friend.
0:18:13 > 0:18:16What you're going to need is to put on this poncho, because this
0:18:16 > 0:18:19- could get a little bit damp. - Thank you, sir.- Now, remember,
0:18:19 > 0:18:22a cloud is just trillions of drops of water vapour that have condensed,
0:18:22 > 0:18:25- that have cooled down into water droplets.- OK.- So, Tom,
0:18:25 > 0:18:28can you bring on my ingredients for a cloud, please, mate?
0:18:28 > 0:18:31- Tom, come out, my friend. - Thanks, Tom.- Yes. What's in this?
0:18:31 > 0:18:34So, in this is everything we need to make a cloud. Thanks, buddy.
0:18:34 > 0:18:37So, what we're going to do here is we've made ourselves nice and safe.
0:18:37 > 0:18:40- Nice and safe, like this.- Now, we need something very, very cold,
0:18:40 > 0:18:43right? Because when it's up there in the cloud,
0:18:43 > 0:18:45that's what causes a cloud to condense, to cool down.
0:18:45 > 0:18:48So, what I've got here is liquid nitrogen.
0:18:48 > 0:18:51Whilst you're pouring that, I do have to say, please,
0:18:51 > 0:18:54for goodness' sake, do not try this at home. That's why we've got masks.
0:18:54 > 0:18:57- Greg knows exactly what he's doing. - So, there, we've got some
0:18:57 > 0:18:59liquid nitrogen. Now, what I've also got is some hot water.
0:18:59 > 0:19:02- Even that looks cool. - The hot water is going to go into
0:19:02 > 0:19:05my liquid nitrogen, it's going to turn it from a liquid into a gas.
0:19:05 > 0:19:07- OK.- Pull the gas up in the air, that's going to cool down
0:19:07 > 0:19:09all the water vapour in the sky and make a cloud.
0:19:09 > 0:19:11- I want to see this.- Are we ready for this cloud?- OK!
0:19:11 > 0:19:14- Everyone on the floor happy? - ALL:- Yes!
0:19:14 > 0:19:16OK, so, in three, two, one...
0:19:16 > 0:19:19- Whoa!- Whoa!
0:19:19 > 0:19:21Oh, my goodness!
0:19:21 > 0:19:22THEY LAUGH
0:19:22 > 0:19:25- We've just made a cloud on Blue Peter!- Yeah!- Can we see that again?
0:19:25 > 0:19:28- Look at the replay of that! - That's in slow motion, look at that!
0:19:28 > 0:19:31- Oh, that looks good.- That's nice. - It's amazing!
0:19:31 > 0:19:34So, there it is, our cloud. Just all those water droplets in the air.
0:19:34 > 0:19:35Yes, mate!
0:19:35 > 0:19:38Join in every Thursday on CBBC.