Date: April 21, 2009

Title: The 6 Enduring Mysteries of the Universe

Podcaster: Marc West

Organization: The Mr. Science Show www.mrscienceshow.com

Description: Marc West talks to Australian Science writer Bianca Nogrady about the 6 enduring mysteries of our mysterious Universe.

Bio: Marc is a freelance science writer and podcaster who works in operations analysis in Sydney. He has completed a Graduate Diploma in Science Communication and a Masters of Operations Research and Statistics and in 2008 was editor of online maths magazine Plus (http://plus.maths.org). The Mr Science Show has been going since 2006 and is one of the most successful independent Australian podcasts.

Today’s Sponsor: This episode of 365 days of astronomy is sponsored by the parents of Sam Given, in honor of his 13th birthday. Happy Birthday, Sam! We love you.

Transcript:

Greetings and welcome to the 365 days of astronomy podcast as part of the 2009 International Year of Astronomy. My name is Marc West and this week we are talking the big issues – the unsolved questions of our solar system. Usually I podcast as part of The Mr Science Show (www.mrscienceshow.com) and we like to take an offbeat look at the world of science – everything from global warming to astronomy, sport and mathematics, and we always like to have a good time.

This week I spoke to Bianca Nogrady from New Scientist magazine about an article that appeared in the January 31 edition of New Scientist on the 6 unknowns of our solar system.

INTERVIEW:

MW: The number one thing that we don’t know about the solar system was how the solar system was formed. Now I thought we knew this, but clearly we don’t.

BA: Well, we understand the principles but there are still a few grey areas. The evidence suggests that it all began about 4.6 billion years ago and we’ve got Hydrogen and Helium gas with a little bit of solid dust and for some reason it starts to condense, and under its own growing weight it starts to collapse in on itself and you get a lot of heat and a lot of energy and voila! You have the Sun! The Sun swallowed up about 99.8% of the debris cloud it formed in but the remaining debris became this thin disk of dust around it’s middle like a tutu! I just love that image.

So as the dust grains in the disk collided, they started to make bigger bits – and close in to the Sun it’s still incredibly hot so the only things that survive are those with very high melting points, and that’s where we get the four small rocky planets – Mercury, Venus, Earth, Mars. Further out from that, the temperature gets colder and methane and water are present as solids, and so developing planets can get bigger and can start pulling in gas – and that’s where we get the gas giants.

But the big mystery is how these little meter-sized boulders start to coalesce into planetary sized bodies. One theory is, in terms of the Sun’s formation, is that there might have been a shock-wave from a nearby supernova that might have forced some of the material together and set off this chain reaction – but how we go from meter sized boulders into bodies that are tens of kilometres across is a bit of a mystery because in theory there are incredibly high gas pressures around them and it’s very turbulent – they should have just been sucked into the Sun, but they obviously weren’t because we’re here and we’re talking.

One of the theories is that there were lower pressure areas that might have protected these boulders long enough for them to coalesce into the larger bodies and not get sucked into the Sun.

Another of the mysteries is that other solar systems have what are called “hot Jupiters” – planets about the same size as Jupiter but orbiting around their stars about the same distance as the Earth. So it makes us wonder why we don’t have these planets closer in. In could have been in these other solar systems that these planets were bounced in closer to the Sun but for some reason that has not happened in our solar system, and it’s a good thing, as this probably would have knocked Earth and the other rocky planets out of their orbits.

So even though we know the principles, there are still a few mysteries in there we haven’t solved.

M: It seems counter intuitive that big lumps of rock could bounce together and stick together – but I guess this happened over a very long period of time.

BN: And you’ve got an enormous amount of heat as well – it does seems a bit strange this image of rocks being banged together – you think “well that’s not going to work” – but the conditions in which this happened were quite extreme – it’s difficult to imagine as we don’t experience them on Earth.

M: And the 2nd unknown that New Scientist published was why are the Sun and Moon the same size in the sky –I thought that this was an interesting coincidence which produces pretty diamond ring effects at certain times of the year – but is there more to it than that?

BN: Well there is and there isn’t! It is a striking coincidence – the Sun is about 400 times as wide as the Moon but it’s also about 400 times further away. So it is just the luck of the draw that the two look the same size in the sky and we get amazing eclipses.

But what is unusual is to have a moon of this size. It’s actually quite rare. For example, when you look at other moons in our Solar System, they form in 2 conventional ways – one is that you have a lot of material hanging around a large planet’s gravitational field and that pulls together to form a moon – or it might be a small body that passes a planet and it gets captured by the planet’s gravitational field – but our Moon is too large for either of these to apply. It’s unique. So what they think happened is that 100 million years after the Solar System formed was that a Mars sized object smashed into the Earth – which would have been one heck of a bang! Completely remodelled our planet throwing out a lot of material that eventually congealed into what we know and love as the moon.

So its unique in that respect but also we’re very lucky because the Earth’s spin has a bit of wobble – partly because there are pulls on it from the Sun and other things – the Moon actually damps down this wobble and prevents rotational instability that would have led to dramatic changes in the Earth’s climatic zones over time. So it’s made the Earth more gravitationally stable and therefore more climatically stable – so we have a lot to thank the Moon for.

MW: The 3rd one was “is there a planet X” – and again, this is another one I didn’t know there was still debate over. I know there’s debate over if Pluto is still a planet, but I didn’t know they were still looking for a Planet X

BN: Well I think Pluto’s fate has been sealed – it has been decided that ‘no’ it doesn’t qualify as a planet. But there is a theory – as yet it hasn’t been disproved – that there is an unsighted large planet the size of Earth or Mars a lot further out in the Solar System. And this hasn’t been disproven – hasn’t been proven either – and the reason that this theory exists is that there is this region called the Kuiper Belt which is a belt of icy bits of debris which exists from Neptune’s orbit at about 30 astronomical units to about 50 astronomical units from the Sun – an astronomical unit is the distance from the Earth to the Sun. Some of the objects in the Kuiper Belt have really odd orbits. For example they’ve got really elongated orbits, or incredibly steep orbits that are almost at right angles to the orbits of the planets – which doesn’t quite make sense. One theory that might explain this is interference from a massive object that we haven’t seen yet but is messing with their orbits.

MW: Cause Pluto has such an orbit doesn’t it?

BN: Yeah Pluto has a very kooky orbit. So there are hints that there is something there. And unfortunately because we haven’t been able to see it yet we haven’t been able to answer this question – but thankfully we may yet have an answer because, launched in December last year was the Panoramic Survey Telescope and Rapid Response System – otherwise known as PANSTARRS – equipped with the world’s largest digital cameras – 4.1 billion pixels a piece – that would be fun!!

MW: That’s a great spy weapon!

BN: It’s a great spy weapon – those long distance celebrity shots would be so much better. But these have just come online in December last year in Hawaii and hopefully they will be able to give us some of the most details photos of the Kuiper Belt and it might help us spot the mystery planet X.

MW: I imagine if it was a gas giant we were looking for we would have spotted it by now

BN: That’s true – a gas giant would have just blown everything out of its path. This is obviously small enough that its not easily visible, or dark enough that its not easily visible – but we’re only getting those tantalising hints about it – we don’t even know how far out it is. There are just hints, but enough for astronomers to be convinced that it’s worth looking at closely.

MW: I know Daffy Duck went to Planet X! He went there by going through the planets from Planet A through to Planet X – that would be the easier way to find it wouldn’t it?

BN: Yes, you should call NASA now!

End interview:
Warner Brothers Clip of Daffy Duck looking for Planet X…

MW: Well unfortunately we have run out of time for today’s edition of the 365 days of astronomy podcast. If you’d like to hear the final 3 unknowns about the Solar System, check out my podcast at www.mrscienceshow.com – I really should have booked another episode!

Thanks very much to Bianca Nogrady for being part of this show – see www.biancanogrady.com for all her freelance work. My name is Marc West – remember to check out my website at www.mrscienceshow.com and from there you can get in touch with me through comments, emails or twitter. Thanks very much for joining me and stay tuned for more on the 365 days of astronomy podcast.

End of podcast:

365 Days of Astronomy
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