Quiz: Who's faster: Usain Bolt or an African elephant?

Speedy Stumpers for Smart Scientists.
12 June 2018

Interview with 

Dr Francesca Day - University of Cambridge, Mr Philipe Bujold - University of Cambridge, Ms Eleanor Drinkwater - University of York, Dr Jess Wade - Imperial College London


African elephant


It's time for Chris Smith to put our panel to the test. Team 1 is Jess Wade and Philipe Bujold, and Team 2 is Francesca Day and Eleanor Drinkwater...

Chris - Before we continue with your questions from people at home, we’ll first of all ask some questions of our panel here that we wrote earlier to test their mettle.

So we’ll have two teams: Philipe and Jess, you’re going to be team 1, and Eleanor and Fran, you're going to be team 2.

Because it is a World Cup year, we’re feeling pretty sporty, so we’ve got some speedy inspired questions to kick off with… Did you see what I did there?

Team 1, Philipe and Jess: And talking of round ball-shaped things - there’s the sport link: planets - which goes by more quickly: a day on Venus, or a year on Mercury? What do you think?

Philipe - You’re the physicist, I’ll trust you on this one.

Chris - What’s shorter?

Jess - You can take it. Okay, let’s go with a year on Mercury.

Chris - You’re going with a year on Mercury.

A: A Year on Mercury
A day on Venus is roughly 116 Earth days long, a year on Mercury is roughly 88 Earth days. Venus turns very slowly.

Team 2 - Eleanor and Fran : Which is happening faster, the growth of Mount Everest or the separation of the Earth from the Moon?

Eleanor - That is a great question which I’ve never thought of before.

Fran - I have no idea. I don’t even know if Mount Everest is growing. Is it growing?

Eleanor - I think it’s growing. Yes, it’s growing. I’m going to go with Mount Everest.

Fran - Yeah, my instinct is Everest. Mount Everest.

Chris - Okay, you’re going for Everest.

A: The Moon
Everest is growing by 4 mm a year, the Earth and Moon are separating by about 4 cm a year. That’s because the Moon is gaining angular momentum from the Earth because the Moon is going round the Earth and the Earth is turning inside the Moon. That’s why we have tides of course because the water on the Earth is being attracted by the Moon. But because the Earth is turning inside the orbit of the Moon. That bulge of water on the surface of the Earth close to the Moon is slightly ahead of the position of the Moon in its orbit and it’s dragging the Moon round with it giving some of the Earth’s spin energy to the Moon, accelerating the Moon so the Moon is, therefore, moving further away from the Earth progressively by up to 4cm a year. And we know that because of a laser, which Jess told us about earlier which is being bounced off a mirror which is on the Moon’s surface put there by the Apollo missions. Or, if you believe the conspiracy theory - it just got there.

Team 1: You’re in the lead at the moment team 1. Which is faster, Usain Bolt or an African Elephant? You can even try what happens if Usain Bolt is chased by and an African Elephant if you want to consider the question in a slightly different way?

Philipe - I was going to say, that might change the answer.

Chris - It doesn’t does it in the grand scheme of things. Unless he gets caught.

Philipe - I have seen many documentaries of elephants running.

Jess - I’ve seen Usain Bolt running. And he’s very fast.

Philipe - He is extremely fast.

Fran - You’re the elephant expert.

Chris - He’s a neuroscientist.

Philipe - I can tell you from their cortex that it’s quite heavy so they might go a bit slower than Usain Bolt who has a smaller brain to carry around. So I’ll go with that neuroscience answer.

Jess - Okay.

Chris - If I’m honest, I don’t think it’s the brain that’s the major mass contribution in an elephant.

Jess - Let’s go with Bolt. Let’s go with Bolt.

Chris - You’re saying bolt. Okay,here we go. You are correct.

A: Usain Bolt
Elephants can manage 25 km/hr, but Usain Bolt has been clocked at over 47 km/hr.

Team 1: You’re streaking into the lead.

Team 2 - Let’s see what happens with Eleanor and Fran now: Which moves faster, the electrons in a wire, or an F-18 jet.

Fran - By the electrons in a wire, that's quite a complicated question.

Chris - I know. You’re on a complicated show.

Fran - They’re not really just zipping through the wire, they’re sort of bumping into each other and their sort of pseudo particle motion.

Chris - So what are you going to go for? Which do you think goes faster, is it the electrons or is it the jet?

Fran - My instinct is the jet. It’s going to be very embarrassing if I’m wrong on this. What do you think?

Eleanor - I blow to your superior knowledge of electrons.

Chris - It sounds like you’re going for the F18.

Fran - I know there’s a lot of subtleties that make the question harder. I do not know the answer. I’m going for Jet.

Chris - Yep. It is the F18. You were quite right. Good to go with your instincts. Always trust your instincts

F-18s travel at 1915 km/hr, but the speed of individual electrons in a wire is just 0.2 mm/s. An electrical signal moves along a cable at almost the speed of light, that’s absolutely true, but the individual electrons that carry the current are actually moving very slowly. This is because electricity moves along a cable, a bit like if you had a tube full of beads, and you pushed in a bead, an electron at one end, it shunts along all the other beads inside the tube so another one comes out the end but the individual beads (the electrons) move incredibly slowly. So that’s why it’s only about 0.2 mm/s.

Chris - So it’s two plays one and let’s see what happens on the final round here.

Team 1 back to you: If you could drive vertically at motorway speeds and in a straight line, which would you reach first - space or the deepest point of the ocean?

What do you think?

Philipe - Oh, definitely space.

Jess - Yeah, let’s do it. I can’t drive so I’ll bow to your superior knowledge.

Chris - Let’s get this right. You reckon that driving at motorway speed vertically either up or down, you’re going to get to space before you get to the bottom of the ocean? That’s what you’re saying, yeah?

Jess - Let’s do a clever kind of Fran way of answering this. It depends on where you define where space begins. But yeah…

Philipe - Where do you start.

Jess - I’m pretty sure. I’m going to go with - I agree with you. The International Space Station is closer to us than Glasgow right, so I think we could go with that.

Chris - Okay. You’re going to go with space. No you’re not right. 

A: The Ocean floor
This is because the edge of space is about 100 km above the surface of the Earth, by our definition of where space starts. The Mariana Trench in the Pacific is, in comparison 11 km deep. So you’d get there a lot quicker. The International Space Station about 400 km up Jess. So Glasgow’s a little tiny bit further than that.

You didn’t get that right so now it’s all on you guys, Eleanor and Fran to see if you’re going to manage to equalise which will push it to a tiebreak situation. This is nasty. I’ll give you this, nasty this one.

Team 2 - Eleanor and Fran: Which unit of time happens faster, a shake, or a jiffy?

Eleanor - Can we answer the elephant questions? A shake or a jiffy?

Fran - I was unaware that either of those were actually a defined units.

Eleanor - It depends what you’re shaking. Because you say two shakes of a lamb’s tail. Maybe it’s another type of animal.

Fran - I don’t know at all. A jiffy sounds quicker.

Eleanor - Yeah.

Fran - Just a jiffy. Whereas a shake… you know. Maybe I like to shake for a long time.

Eleanor - Okay. Let’s go with jiffy.

Fran - Jiffy.

Chris - You’re going with a jiffy?

Did you know that Jess. You had your hand up.

Jess - No. I had my hand up because I liked the look of the Canadian while that was happening. He was like - what is a shake, what is a jiffy!

A: A shake
A shake is a top secret unit that was coined for the Manhattan Project: a shake is 10 billionths of a second. A jiffy is used in computer engineering, and is one hundredth of a second. An eyeblink is only about ten jiffies, or roughly ten million shakes

Chris - So you’ve got zero for that one.

Congratulations team [1] for winning, and if you got any of those listening.

Unfortunately, Eleanor and Fran, you didn’t win this week’s. So the big brains this week, Philipe and Jess with their amazing knowledge of elephants and Usain Bolt running. Very well done.


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