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Question of the Week
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Which is worse for your hearing - the short sharp sound of a hammer, or the constant drone of a chainsaw?
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We are live now so if there is anything you want to talk about, please comment....
- Dave Ansell - 18th Nov 07
This show is great!...
- BenV - 18th Nov 07
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Questions

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Is the artificial gravity you see on Star Trek possible?' Do you think we could have some kind of artificial gravity system that would get over these effects?
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Gravity is a fascinating subject. It's such a simply observed phenomenon that we have every day if we drop the dishes. We watch it every day in action. For something that's so ubiquitous in our experience yet so poorly understood. I guess the answer to that question is, as far as I can see in anything, away from a machine that you can press an on button and suddenly hey presto you've got gravity. However, you can create gravitational loading just simply by spinning a vehicle up and having a rotating vehicle.
This is not a new idea. Herman Oberth was thinking about it in 1923. Artificial gravity and some of the stuff which I've been working on in Houston at the Space Centre involves just rotating vehicles. There's really nothing more than that trick you pull off when you have a bucket full of water on the end of a rope and you spin it round your head and the water stays in the bucket. I very much think that the future of space exploration will include, at some point, that sort of vehicle.
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Is radiation nearly as much of a problem outside the orbit of
say, Mars as it is closer to the Earth? I'm wondering if deep space
vehicles have more or less need for protection from radiation than those
that are exploring nearer to the Sun.
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I wouldn't say less. Eventually you get out into interstellar space and there things would be fairly constant. The effect there would be minimal. They would stay minimal until you approached a stellar system of some sort. It's Pioneer 10/11 and Viking 1 and 2 that would have some answers if the data's available.
Although some researchers have suggested that it would be better to go to Mars during a period of solar maximum when the sun is producing the most radiation, because then the sun has the strongest magnetic field which shields the solar system from very high energy galactic cosmic rays which would be impossible to shield against on your spaceship.
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If the sun were to blink out one day, how long do you estimate life could be sustained on Earth?
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That's an excellent question and I think the answer will surprise you because I would be willing to put money on it being millions, if not billions of years.
The reason I say that is because there was an answer to this question, sort of, provided not far away from where I am in South Africa - In a goldmine not far away from Johannesburg. About a year ago, Lisa Pratt who's a researcher in the US published a paper in the journal Science where she and her team had isolated some bacteria from 3km underground down a mine shaft. Water that was accompanying these bacteria, coming out of a hole from the side of this mineshaft was analysed and found to be between 16 and 40 million years old. In other words that water had been cut off from the rest of the Earth for up to 40 million years.
When they cultured it, it was thriving with bacteria. So those bacteria themselves must also have been cut off from the rest of the world. So what were they eating in water, 3km underground in temperatures of 70 degrees centigrade?
Analysis of how these bacteria survived suggests that what they're actually doing is living off radiation which is coming out of the rocks. There's a lot of uranium in the rock. Uranium spits out alpha particles, it has a helium nucleus, the alpha particle is radioactive and hits water particles. When it hits the water molecule it breaks it up into what's called a hydroxyl radical. The hydroxyl radical can jump into the nearby iron pyrites (fool's gold) which is in the rock and it breaks up the iron and the sulphur (iron sulphide) and turns it into a form of sulphur that these bacteria can metabolise. As a result these bacteria can grow and then feed other bacteria which are also present in there.
My guess is that if the Sun suddenly went out, although all life that's dependent on the Sun would cease to exist or would probably die pretty fast, there would certainly be bacteria like these that can survive on other sources of energy such as radiation or those that survive around hydrothermal vents at the bottom of the sea.
I think we'd probably be stuffed. One little comfort is that, in fact, the light that's coming out of the Sun is already at least one million years old by the time it gets to us because it's been bounced around like a pinball inside the Sun before it escapes. Even if the Sun's nuclear reactor went off, for some reason, tomorrow you'd still have a million years' worth of light stored up inside.
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Can we see black holes from the Earth?
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Yes, we can but not directly. We can see the effect they have. Basically a black hole is a star that's died, that's collapsed. Unbeknownst to many people many stars are in fact double stars or binaries. The dead star, the collapsed star can form a black hole. The gravitational fields are intense. It sucks material from its companion star and forms what we call an accretion disc around it. The accretion disc emits x-rays and we know of many stars that are x-ray stars and these are black holes.
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| The South Africa Space Special - More about this podcastSpace – the final frontier
This week on the Naked Scientists we’re setting the co-ordinates for a galaxy far, far away and blasting off into space. We’ll be speaking to Kevin Fong, to find out what happens to our innards in orbit, and to Case Rijsdijk, who has an extremely large telescope. Brian Schmidt will be expanding on the expansion of the universe, while Meera finds out if a listener’s meteorite is the real (Dr) McCoy!
An appointment with the space doctor
Kevin Fong is from the Centre for Altitude, Space and Extreme Environment Medicine at University College London. He’s an expert in space medicine – the changes that happen to our bodies under the stresses of space travel. And it’s not just important for people heading into the sky. Kevin’s work is also relevant to others who explore extreme environments, such as mountaineers and deep-sea divers.
As well as being cooped up in a glorified tin can for days on end, astronauts must deal with the effects of low gravity, and even radiation. For example, did you know that your face swells up in zero gravity? We’ll be finding out why, and if there is any relief for the puffy-faced space explorers.
Is that a telescope in your pocket?
One star-gazing device that certainly won’t fit into your pocket is the South African Large Telescope, known as SALT. Ten metres in diameter, SALT is the largest optical (light-receiving) telescope in the Southern Hemisphere. It is set up to allow scientists to peer at quasars, viewing stars and galaxies a billion times too faint to be seen by the naked eye.
We’ll be joined by Case Rijsdijk, from the South African Astronomical Observatory, who has worked at the telescope, set in a beautiful nature reserve 230 miles outside Cape Town. He’ll be telling us more about why SALT is so special, and about the research that’s taking place out there.
Expanding upon expansion
It is now accepted by cosmologists that the universe is expanding at a staggering speed. But where’s it going? What’s it expanding into? Isn’t it big enough already? And is the expansion speeding up or slowing down?
We’ll be hearing from Brian Schmidt, astronomer at the Research School of Astronomy and Astrophysics at the Australian National University. He’ll be giving us the low-down on our expanding universe, and what it all means.
Meteorite or wrong?
When Ipswich listener Colin sent a lump of rock in to the Naked Scientists, we were a bit bemused. But when he suggested it might be a meteorite, Meera Senthilingam decided to find out the truth, and took it along to the Natural History Museum for some expert analysis. Is it the real thing, or just garden gravel? Find out on the Naked Scientists. |
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