Date: March 4, 2010

Title: Dinosaurs and Asteroids

Podcaster: Damian and Sofia Handzy

Description: Today’s podcast is a dramatized version of a real conversation between a father and his excitable 2nd grade daughter about the asteroid that might have killed the dinosaurs. It provides examples of explanations of the scientific method that resonate with children (and probably adults), and examples of children’s logic and willingness to accept explanations that may or may not be complete. Plus, she invites everyone around the world to listen and hopes you enjoy the show.

Bio: Sofia is an 8-year old 2nd grader in the public schools in New Jersey who is very interested in reading, dinosaurs, coloring, drawing, science, arts and crafts, and her stuffed animal collection, especially Bruno. Her favorite food is chicken nuggets, her favorite album is “Science is Real” by They Might Be Giants, and her favorite podcaster is FAR composer George Hrab (although she’s only allowed to listen to carefully chosen selections of his oeuvre). Her dad, Damian, is a Ph.D. physicist and amateur astronomer who is involved in spreading the ideas of rational thinking to children through astronomy.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by James Wood, suggesting you check out the Saskatchewan Summer Star Party to take place August 12th to August 15th, 2010, hosted by the Saskatoon Branch of the Royal Astronomical Society of Canada, to be held in the Cypress Hills, at one of the largest dark sky preserves in North America. . Just Google “Saskatchewan Summer Star Party” for the most up to date information. Reference: http://homepage.usask.ca/~ges125/rasc/index.html

Transcript:

Sofia:
Dad, before I worked on my dinosaur project for school, I thought that a giant asteroid killed all the dinosaurs but my teacher, Mrs. Olenick, said that they actually aren’t sure if that’s what really happened. Why not?

Dad:
Well, sweetheart, it’s very hard to figure out what happened that long ago.

Sofia:
Right – it was 65 million years ago. There were no people around, not even cavemen!

Dad:
Exactly. So now that we’re here, and we can figure things out, we have to look at the evidence that’s left from that time and try to piece together what happened. You know what evidence is, right Sofia?

Sofia:
Yes, Dad. It’s like when one of my brothers does something wrong and they blame it on me – I have to find something that shows you and mom that it was one of them.

Dad:
Can you give me an example?

Sofia:
Sure: like when they spill something in the basement. I can show you that it was milk or soda ‘cause it’s sticky. But I only drink water, so if the thing that was spilled is sticky, it wasn’t my drink, so it couldn’t have been me!

Dad:
Cool. Ok, So, do you know some of the evidence we have why that people think a giant asteroid might have killed off the dinosaurs?

Sofia:
Well, first thing is that we found the crater – it was left by a giant asteroid near the Yucatan Peninsula in Mexico – it’s about 180 kilometers across. Dad — what’s a kilometer?

Dad:
It’s about half a mile, so this would be a crater about 90 miles across.

Sofia:
Holy Cow! That’s huge!

Dad:
Yes it is. Do you know how the scientists figured out that the asteroid hit about 65 million years ago?

Sofia:
‘Cause that’s when the dinosaurs went extinct, silly.

Dad:
Yes – that’s when the dinosaurs went extinct. But if they think that this asteroid killed the dinosaurs, they have to make sure it hit about the same time, right? I mean, how do they know it didn’t hit 70 million years ago or 20 million years ago, or even 1 million years ago? How do they know that it hit Earth right about when the dinosaurs went extinct?

Sofia:
Oooooh! I get it – they have to make sure that the asteroid hit at the right time – otherwise, it couldn’t have killed the Dinosaurs.

Dad:
Right! So, here’s how they figured out when the asteroid hit. They measured how much of this stuff called iridium was in the soil at just the right depth that corresponds to 65 million years ago. You know that over the years, the dirt gets layers on top of layers. Anything that lived, say, 10 million years ago is underneath the stuff that lived 9 million years ago. And sometimes you can tell different periods of time apart by what layer it’s in.

Sofia:
Just like my toys in the playroom – the ones I played with most recently are on top, and the ones I haven’t played with in a long time are on the bottom of the box.

Dad:
You got it. So this iridium stuff mostly comes from outer space – there is very little here on earth, but it can come from outer space. And right at that depth in the layers of dirt there’s a thin layer of clay called the K-T boundary that has lots and lots of iridium, and that layer is all over the earth. That means that something from outer space probably brought that iridium to earth.

Sofia:
So it must have been an asteroid!

Dad:
Well, it might have been an asteroid. There are other ways of getting iridium here. You remember where all the heavy elements are made in the universe, right?

Sofia:
YES! Inside of stars. Like me, I’m made of star dust! So the iridium might have come from an exploding star!

Dad:
That’s right, it might have come from a supernova. So they had to figure out how to tell if the iridium came from a supernova or not. The test they came up with was pretty simple – a supernova would create lots of radioactive things – not just iridium – so they went to measure how much other stuff, like plutonium, was in the K-T boundary, and they found that it wasn’t anything special – not too much of it.

Sofia:
So that means it wasn’t a supernova – just like it wasn’t me who spilled the drink in the basement.

Dad:
Exactly! So the scientists then tried to think of other explanations – like the earth passing through a gas cloud – but none of the ideas passed any tests they did. Then, an astronomer from California suggested that it might be from an asteroid.

Sofia:
Wow. That’s cool. I read that when the asteroid hit earth, it would be really really bad.

Dad:
That’s very true. They estimated that the asteroid would have been about 10 kilometers in diameter and would have been traveling at about 50,000 miles per hour. It would have been like 100 million atomic bombs, and it would have launched some rocks half way to the moon! In fact, shock waves would have gone through the earth and shot molten rock into the atmosphere. Anything within a few hundred miles of the impact would have been instantly killed, and farther away, hot rocks would have fallen back to earth, causing forest fires all over the planet. Tsunamis, earthquakes and things like that would also have been triggered. Not a pleasant sight.

They went looking at the rocks near the Yukatan crater and they did find a tell-tale sign that an asteroid hit there – they found little glass balls called tektites that only form under the really high temperatures and pressure of impact. When they finally examined the rocks taken out of the ground near the crater they found that it was exactly the right age – 65 million years.

Sofia:
So that proves that the asteroid killed the dinosaurs.

Dad:
No, sweetheart – it only proves that a really big asteroid hit 65 million years ago and that we found where that asteroid hit. It’s reasonable to believe that it might have killed the dinosaurs, but it’s possible that it just made things really uncomfortable for the dinosaurs and the other things on earth. It doesn’t prove that the asteroid killed all the dinosaurs.

Scientists also have some other ideas of what might have killed them, and there’s evidence for those ideas as well.

Sofia:
That’s what my teacher, Mrs. Olenick, said – scientists weren’t sure what actually killed the dinosaurs. Dad, I thought scientists knew everything.

Dad:
No, sweetheart, nobody knows everything. But scientists do know how to figure things out, and they know how to figure out if the evidence for an idea is good or not so good. And that makes this mystery even bigger – because there’s evidence that something else killed the dinosaurs.

Sofia:
Volcanoes! Mrs. Olenick said that it might have been volcanoes. I have a question – can another asteroid hit the earth?

Dad:
Well, now that we have telescopes, we’re looking out to see what might be headed our way. There is one that’s going to come very close to earth on April 13, 2029. Fortunately, it doesn’t look like it will hit us. But rest assured, astronomers are on the lookout – every night in case there is an asteroid that might hit us.

Sofia:
That’s good – they need to keep looking. And I’ll help them – it’ll be fun with my galileoscope!

End of podcast:

365 Days of Astronomy
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