字幕列表 影片播放 列印英文字幕 Dan: We're on top of the Marina Bay Sands hotel in Singapore. It has one of the highest rates of lightning strikes in the world. We're gonna be running Image Based Auto-Trigger. It sounds like you're out of a job. - ( lightning crackling ) - Go! Go! Go! Gonna miss all the lightning. Ah. It was the first time I think where I've managed to chill by the pool in the day, but then... - Yeah. - ...been running around like a nutter in the evening. It was tiring. The most relieving shoot I think we've ever had. 'Cause there was the chance that we flew 20 hours across the world, nothing happen, and then we had to come back. Fully down to chance. I mean, don't know what we would've done. Should we just-- - Pub? Pub. - Pub. The moment when we realized that the lightning was on the other side of the hotel was a fun one. Pegging it through the halls. I hope no one was looking through the spyholes on the hotel doors. Just seeing a bunch of crew legging it through the hallways. And what would we do? My shorts are falling down. Lightning is gonna be striking on the Bay side. Before we test out lightning on Dan, - What? - We spoke to an expert called Professor Liew. - What? - What? Professor Liew, how are you doing? - Oh, hi, I'm great. Dan, Dan, right? - Yeah. - Hello. Gavin. - Yeah, right, yeah. So we're trying to capture the lighting in super slow motion because when you look at it with your eyes it just seems instant. How fast does lightning actually move? It'll be a real challenge for you because you know the speed is actually very, very high. There are two phases to the development of a lightning strike. It starts from the cloud. A lightning leader will descend. The speed up there is about one tenth the velocity of light. Now that is not the main lightning channel. The main lightning channel actually develops after contact from the down coming leader with the ground and then there is this return stroke. Which moves up from the ground to the cloud. And the speed of propagation of that particular channel is even faster. That travels at one third the velocity of light. ( lightning crackling ) Okay, so we got a struggle to capture this. Yeah, we really are. How many volts in a lightning bolt? Voltage varies from about 10 million to 100 million volts. - 100 million volts. - That's a lot of voltage. - Yeah. So-- - You could fry an egg. I think probably. So, I'm not planning on it, but what's it like to get hit by lightning? Wow. ( laughs ) I do not advise you to, you know, stand out in the open and say, "I'm invincible." You know, try to attract a lightning strike. When the voltage impinges on a person that will cause a current flow to the body the amount of current which flows depends on the resistance of the body. But, you know, in reality, you know, when the lightning stroke hits you directly, you know, the chances of survival is extremely slim. The temperature of a lightning channel is about 30,000 degrees Kelvin or centigrade. - 30,000-- - 30,000. And how long is it 30,000? Just for like a split second? It is actually, you know, the whole duration of the wave-- the lightning wave varies from microseconds to milliseconds. You know, the duration maximum may be about one second. It could be fatal. - Yeah. - So you'd know about it for sure. What is the correct thing to do if you're out in an open area and there's a big lightning storm coming in? - Well, you try your best to get indoors. - Okay. - Just run inside. - Run inside. He who plays and runs away and lives to play another day, you know. - ( both laugh ) - I like that. Yeah, so, run indoors. I think that's the most sensible advice. - That's stupid. - Oh, come on. Go, go, ask him. So is it true, um, you get superpowers when you're struck by lightning? I wish that could be so, you know, then I'll become Thor or Iron Man. - Okay. - No. - The answer is no. - No. Oh, you mislead me for a second. I was like, "Does he or what?" - Okay, well thanks very much, Professor. - Okay. - Thank you, Dan. - Thank you. - Thank you very much. - Yeah. Okay, back to you, Gav and Dan. Thanks, us. - I bloody loved him. - He was a legend. - He reminded me of my granddad. - Yeah. Time for a bit of analysis. I wanna take one of our clips, find where we can see the entire bolt from cloud all the way to the ocean and time how long it took for all the feelers to hit the ocean - in real time. - I think it'll be fast. I also think it will be fast. Time code is set to zero point zero seconds. - Yep. - Ready to time it? Okay. Yes. - Uh, that was it. So-- - ( laughs ) What? If I go frame by frame Here we go, yeah. - What? - Yeah, yeah, yeah. So one frame is traveling that far? Point zero zero zero six seconds. - Like I said, it's fast. - 632-- - It's so-- So, yeah. - Really fast. What is interesting to me, if you look at all these step leaders, which is you know each finger of the thing. They're all trying to find the path of least resistance down to the planet, but the one that gets there first is the one that sends the bolt up. But you can already see before it wins, what the shape of the lightning bolt will be. So when this hits the ground here. The lightning will come up and follow the exact path that this one took. - So that's the exact-- - And everything else disappears. See, that's like the exact perfect angle. It's a lot going on in just a lightning storm. It is. It happens so quickly as well. There's actually a clip I found where it's sort of halfway coming up. So, you mean to say that even though the speed of lightning of it going back up, you managed to capture it where it hadn't gone all the way up yet and it was literally only halfway up. - Yeah, you wanna see it? - Yeah. - See, look at that. - Whoa! So that is sort of halfway between the white out that we saw on the other one but it hasn't reached this point. So you can actually imagine it's not actually like this. It's just so bright, it's blowing out the camera from that point. And the thing is because of the camera that we used, the 2512, has a global shutter. That means this is an actual moment in time. This isn't an artifact because of a rolling shutter. This is actually how far up it got. So if we'd have given it enough of tiny, tiny split second, it would've been all the way to the top? Yeah. Well, because in one 28,500th of a second, it hit the ground and went all the way up to here. Shall we do a lovely tabletop experiment? Yeah. You've forgotten what it was, didn't you? That's good, that's good. The Van de Graaff generator. - Classic school experiment. - Yep. I like the gloves more than anything. Rubber gloves. How's it work? The way this works is similar to lightning in that a lot of brushes in here build up a static charge. Like friction and build up a charge. The lighter positively charged particles come to the top. With lightning what happens instead of brushes, you get the warmer air going to the top and then cooling creating ice particles that then come down and they bash into each other and create a static charge. So instead of brushes you've got ice, and in the top of the cloud you got the lighter particles and the bottom is the negative. That explains why Singapore is such a hot spot. It's because of the warm climate. - Yeah, so the water-- - Warm water, warm air. All goes to the top, through the clouds, forms the clouds, ice in the top, brushes together, makes lightning. - So this is ready to go. - Yeah. We're gonna film it with the 2511, very similar camera to what we used in Singapore. We will have to dim the lights because these flicker like crazy. And also we wanna see the spark, not these lights. That sounds good. I'm kinda scared, but also excited. - Let's turn on the loud beast. - Okay. I feel like generic bad guy from famous movie. Yeah, yeah. All right, so I'm gonna turn it on and power up, okay. - So should we turn the lights off? - Yeah. Oh, you can hear it. Okay, I'm gonna just slowly move this closer and closer. - Yeah. - Okay. Here we go. - Oh. - All right, stop. Turn it off. All right, you ready? Playback of slow-motion footage. - Yep. - That's it. That is one frame. - One frame? - Well, it's 28,000 frames a second over an inch? I guess, uh, because lightning is so much further away, it's like miles high that we are getting much more of chance - to see it. - Yeah. So I feel like this video has been a lot of step leaders leading down to one main point. Yeah. Which is you getting zapped by electricity. I mean, blokes get hit by real lightning and survive. So what's this little thing brushes and stuff really gonna do? 395,000 volts. - Is it? - Yeah. But think about it like this. ( laughs ) Lightning is a 100 million volts. Okay, well, that makes me feel better then. - Are you ready? - I guess. All right let's get the lights in high-speed mode. Okay. Here we go. - ( groans ) - Was that it? - Yeah, just-- - Oh, I didn't trigger. ( laughs ) I was waiting for you. - All right, let's just do it again. - All right. - ( groans ) - ( laughs ) I was not expecting that. I think you'd have to shoot in really close. Oh, you just wanna go like-- ( groans ) - ( laughs ) - What was I expecting? At least let me be filming. - What was I expecting? - All right. - All right, you ready? - I mean, yeah. All right. I'm just gonna go like-- ( groans ) ( bleep )! ( laughs ) Ready? - Yeah. - Okay. - ( groans ) - Is that it? I guess. I can't see. Ow! I can't see. Stay away from this thing. Why haven't I learned my lesson here? I keep pointing at it. What do I expect? - Moron. - All right, so far I've not seen a single spark on this. Really? 'Cause a finger isn't enough of a point. All right, I'll try it with an elbow I guess. Rolling. Oh, I can feel it. - My hair is like going towards it. - Yeah. ( groans ) Bloody saw that one. That was a bright one, wasn't it,? - That was amazing. - Christ. - All right, Dan, very good job, obviously. - Thank you. Yeah. - You ready for your moment of glory? - Can't wait. And when I say moment I mean a very-- it's a tiny fraction of a second. - Oh, there it was. - That was it? That was one frame. There it is. Also, know the fact that it hits the ball and then you see the reflection... - Oh. - ...in the ball back to your mirrored elbow. That's so weird. Imagine if it was a lot longer and two inches thick. - That's what lightning's like, ain't it? - Yeah. - Your arm would be gone. - Oh, yeah. - Yeah, it'd be gone. - You would be gone. You'd pop. Yeah, that was fun. Feeling all right, Dan? - A bit tingly. - Little bit tingly. - Yeah, my arm's a bit numb. - You look good. I think we broke the monitor, too. - There's lightning happening on that. - Yes. Like it's been affected or something. Everything's a bit "ooh" here. So I feel like I learned a lot from that episode. I-- The main thing I took away from that is that essentially all that lightning is is a giant ball of static. It's just huge. On a massive scale. It's like the biggest pair of socks on the world's carpet. - Yes. - Hopefully, you enjoyed that video. Feel free to check out other less shocking episodes of "Planet Slow Mo" and we'll just be right here while you click something over there. I feel like you should get shocked as well for this. That's probably fair. ( zapping )
B1 中級 慢動作的范德格拉夫發電機 (Van de Graaff Generator in Slow Motion) 1 0 林宜悉 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字