Tuesday 28 September 2010

How close could an average spaceship get to the Sun before melting?

I must start by apologising for being so lax in posting articles and podcast episodes over the last month. We've recently bought a house and moved in, and this process has taken up nearly all my time, given me multiple headaches and left me without the Internet at home.

A while back we put a call out for your burning science questions, and plenty of great questions came in on this site, via email, on twitter (@westius) and over at facebook. I apologise for my delays in publishing these questions and their answers - you can follow the questions that have already been answered in the podcast or on the blog using the Science Week tag.

One interesting question that came in was How close could an 'average' spaceship get to the Sun before melting? Here is an answer from a much more intelligent person than I, Physics PhD holder and all round good bloke, David Bofinger.

An old-fashioned spaceship would probably be made of aluminium, a more modern one might be made of a mixture of aluminium, graphite fibre and polycyanate. Assuming you want the spaceship to actually melt, rather than just fall to bits because a few bits melted, then you probably want to raise it to the melting point of aluminium, which is 933 Kelvin. Of course it will take a lot less than that to kill any crew and cook any electronics on the ship. But melt you asked for and melt we shall give.

We'll assume for the moment that the spaceship is a simple sphere and that we haven't done anything clever to keep the spaceship cool. It will heat up to a temperature such that it's radiating away as fast as it's absorbing heat from the sun. The closer it gets to the Sun the more it absorbs, the more it needs to radiate so the higher its temperature will get.

If we put it in orbit around the Earth, then it's about 150 million kilometres from the Sun and the temperature it reaches is 279 Kelvin, i.e. about 6 degrees Centigrade. (Earth is mostly warmer than this because it has greenhouse gases in its atmosphere.) To melt the aluminium in the spaceship we need to take it into 13 million kilometres, about a twelfth of the distance from Earth and four times closer than Mercury.

Of course there's all sorts of tricks we can play to get closer. We can make the spaceship silvery on the side facing the Sun and black on the side facing space. That will make it absorb less and radiate more. If we made it as white as snow on the Sun side and black as coal on the space side then we could get in as close as 6 million kilometres, about eight times closer than Mercury and twenty-five times closer than Earth. If we made the spaceship long and thin and pointed it toward the sun we could maximise our ability to dump heat compared with how much we absorbed. That might get us in a little close yet. If we pull out all the stops we might do as well as NASA's planned solar probe, which intends approaching within 6.6 million kilometres of the sun while staying cool enough to have functional electronics and cameras.

The moral is that if you want to go close to the sun you don't want an average spaceship, but something built to take the heat.

If you have an alternate opinion, I'd love to hear it.

Monday 6 September 2010

Dodgy cricket odds

The cricket world has recently been rocked by allegations of match-fixing against the Pakistan team.

The News of the World set up a sting to catch sporting-agent Mazhar Majeed correctly predicting when three no-balls would be bowled during the recent Lords Test Match between England and Pakistan. Whilst this in itself is not match-fixing (it's called spot-fixing - fixing certain events in a days play to win exotic bets), it's a smoking gun pointing towards further corruption.

So what are the odds of correctly picking three no-balls in a day's Test play? Could Majeed have just been lucky?

Let's assume there are 90 overs in a day's play, and on average 10 no-balls and 3 wides. This means that 553 balls will be bowled in the day. There are two ways to work out the probability of correctly choosing 3 balls as no-balls.

1) You can choose 3 random balls from 553 in 28032676 different ways. You can choose 3 no-balls out of 10 possible no-balls in 120 different ways. So mathematically, this looks like:

2) The other way to do this to imagine a big bag of marbles, where the no-balls are black and all other balls white. The first time you pull out a marble, you have 10 chances in 553 of pulling out a black marble. On the second draw, you have 9 chances in 552 and on the third you have 8 chances in 551. This looks like:

This means there are 4 chances in a million of the sports-agent fluking his result. Essentially, he's dodgy! (It is left as an exercise for the reader to prove algebraically that the above two methods are exactly the same...)

Further reading:
Forrest, D. (2003). Sport and Gambling Oxford Review of Economic Policy DOI: 10.1093/oxrep/19.4.598
Frey, James H. (1992). Gambling on sport: Policy issues Journal of Gambling Studies DOI: 10.1007/BF01024122

The Beer Drinking Scientists talk Sex

Over at my other podcast, The Beer Drinking Scientists, we like to tackle the big science topics down at the pub. And what better topic to talk about over a beer than sex?

Darren and Marc review the history of research into sexuality, including the seminal Kinsey Reports, the Masters and Johnson research into the diagnosis and treatment of sexual disorders and dysfunctions, and the more recent, and intriguing, study that Partner wealth predicts self-reported orgasm frequency in a sample of Chinese women.

We also take a look at how sex might have evolved. Why is it that it takes two people to have sex? Wouldn’t evolution be quicker if we could simply reproduce on our own? This is known as the twofold cost of sex - what are the benefits of having two people mix their genes to reproduce? Sexual Selection is another topic up for discussion. Charles Darwin described sexual selection as “struggle between the individuals of one sex, generally the males, for the possession of the other sex” and nature abounds with strange examples of where animal features have evolved way past their survival needs - for example, reindeer antlers, peacock plumes and quite possible human vocabulary - humans and other primates survived quite nicely without a wide vocabulary, why do we now possess one?

We could not possibly tackle this topic without discussing the Sexy Son Hypothesis, or without having a chat to the punters in the pub. Tune in to hear the public’s thoughts on sex, the science involved, length, width, money, style, cuteness, attraction and also hear Darren provide solace to a broken hearted drinker.

Of course, over a beer, much is talked about and you’ll have to tune in to catch the rest! Get over to The Beer Drinking Scientists website to subscribe, listen in to this show here, or press play below: