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6th May 2007
Question and Answer Show
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This week Drs Chris, Dave and Phil find out how a venomous spider has got scientists swollen with excitement because it's bite has Viagra-like properties, how maggots are fighting off MRSA from ulcers, and NASA are testing their next generation telescope aboard a jumbo jet. The docs also explore the science of getting geostationary satellites into space, the basis of bacterial intelligence, and how much water trees drink on a hot day. Plus, in kitchen science, Dave and Ben put their heads in a box...to find out how a pinhole camera works.
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Interviews
Richard Van Noorden gives us the lowdown on some of the latest news in Chemistry
Andrew Boulton explains how Maggots help to cure infection with MRSA, or Methicillin Resistant Staphylococcus aureus, which doesn't respond to conventional antibiotics.
Bob and Chelsea tell us why having a high IQ may not be the que to success.
Questions
Why did my pyrex bowl suddenly break?
Pyrex expands when you heat it, and if it’s heated for long enough it will expand all the way through. When it cools suddenly, such as when you opened the microwave door, the outside of the Pyrex dish will shrink before the inside does. This will put the outside of the dish under tension, as it will be pulled apart by the expended Pyrex in the middle of the dish. If there are any cracks in the outside of the dish, such as scratches or damage built up over many heat/cool cycles, this crack can travel through the dish and the tension in the surface can be released as a great big crack, and the plate will split.
This can be quite explosive, as the forces involved are immense, similar to the forces involved in water expanding as it freezes, which can blow cast iron pots apart and erode mountains. These forces should be more than enough to make the dish fly apart.
How high are geostationary satellites?
The height for geostationary orbit is about 22,300 miles, sitting directly above a fixed point on the equator. They get to that height by being attached to the top of a rocket and launched at incredibly high velocities. It’s taken years of practice to program the fine detail of controlling this into a computer, and small thrusters mounted on the satellite itself are used to manoeuvre the satellite into exactly the right orbit. Drifting from the desired point is caused by the influence of the moon, and also by the fact that the earth is not a perfect sphere. The small thrusters are used again to keep the satellite in the right orbit.
Why does paper lift up when you blow across it?
If you blow air over a curved surface, it tends to stick to that surface; it’s called the Coanda Effect. If the surface, in this case the paper, is bending downwards, it will pull that air downwards with it.
| If air (black) is blown over a curved piece of paper it will tend to stick to the paper, to do this the paper must be pulling it down (blue) so the air must push the paper up (red) ©Dave Ansell |
If you push something, it pushes you so if the paper is pushing the air down, the air will push the paper up. This is exactly the same principle as is used in aeroplane wings; they push air downwards, so the air pushes them up.
The Coanda Effect can also be seen in a ‘Bernoulli blower’, or by putting a table tennis ball in the air flow from a hairdryer. The air going past each side pushes on the ball, and these forces keep the ball in the stream of air. Theres more info on how this works here.
Why is scratching on a blackboard so nasty?
Even imagining these sounds can make your spine tingle. We’re not certain exactly why people react to these sounds, but some research has been done by playing these sounds to volunteers (lucky them!). It was found that there is a frequency response to this, so when you play sounds of a certain frequency it elicits the spine-tingling, I-really-cant-stand-that, awful sensation. It’s suggested that these frequencies are similar to those produced by an animal that is in distress, so the researchers think that we are tuned to be sensitive to these sounds, so that we pick up on when there might be danger around, and can be primed to react.
How did apollo missions slow down in space?
This is all based on rockets and thrusters. The moon landing was done by going into orbit around the moon, and then a small command module detached and went down to land on the surface, using thrusters to control the speed and angle of descent. In the rocket or thruster it pushes gas out of the rocket, so the gas pushes the spaceship in the other direction.
Actually, there was a hair-raising moment during Neil Armstrong’s moon landing. The landing is usually all computer controlled, but he realised that they were going to land in a boulder field, which would basically cause them to crash. He took manual control away from the computer, and landed safely with only 16 seconds of fuel left.
Do bacteria have intelligence?
Bacteria have no brain, but on the surface of a bacterial cell there are receptors for different chemicals. This means that they can tell which way to travel by comparing, chemically, how many of those receptors have things that they like attached. They assume that the side with the most ‘good’ receptors filled is closest to their food. They use this concentration as a guidance mechanism to control where they go.
Bacteria travel towards desirable chemicals, or away from toxic ones, using a flagellum. This is like a propeller, powered by a protein ‘motor’. When the ‘motor’ burns energy it causes the protein to change shape, quickly spinning the long ‘tail’ part. This lets bacteria move so quickly that they are officially the worlds fastest swimmers, and can travel 60x their body length in each second.
Why can a microwave be metallic?
The exact dimensions of the metal lining in your microwave oven are ‘tuned’ to the frequency of the magnetometer to reflect the microwaves back and forth and create an even electromagnetic field inside by creating a ‘standing wave’. Putting other metal in the oven will cause other reflections, which can bounce back into the magnetron (which created the microwaves) and cause an explosion. Also, the radio waves cause an electric current to run through metal, if two pieces of metal are close together, then this can result in the electric current jumping between them and causing an electric arc which looks a bit like lightning.
Where does a tree's water come from?
60 gallons per hour is a lot of water. But it’s estimated that a big tree, such as a 48 foot maple has on average 177,000 leaves, which adds up to a leaf area of 1/6 of an acre. Each leaf has thousands of tiny pores called stomata on the underside which open up on a nice day and lose water. They need to do this to pull water up through the roots into the stem and up to the leaves, in a process called transpiration. All this water must come from ground water, water stored underground.
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News
Researchers have uncovered a natural Viagra-like chemical in the venom of a Brazilian 'wandering' spider, Phoneutria nigriventer. Kenia Pedrosa Nunes, Romulo Leite and colleagues, from the Medical College of Georgia, followed up on anecdotal reports that male victims bitten by the spiders subsequent...
One of the major ways of finding out about the universe is to smash particles together and look at what particles leave the collision. To do this amongst other things, such as monitoring nuclear reactors, you need to detect these particles.
The normal way of doing this is to get a piece of si...
Ever thought you could do a better job than NASA? Well Peter Homer from Maine, in the US, did and he scooped a two-hundred-thousand dollar prize for his efforts.
This was all part of a competition, run by NASA, to design a glove for a space suit that would out perform their own version. ...
The atmosphere causes huge problems for astronomers; it blocks out certain types of light such as UV and x-rays, but turbulence in the air also bends an distorts images. This is what makes stars twinkle when any of us look up at the night sky and it’s why astronomers designed the Hubble space ...
Scientists would like to build robotic submarines that can be used in complex tight spaces such as coral reefs, wrecks, oil rigs etc. The problem is that to avoid crashing in these circumstances you need to be able to see objects coming at you from all directions.
Malcolm Maclver and collegues at N...
Kitchen Science
Make ghostly images on a wall, just using a magnifying glass, and find out what this has to do with a camera.
Make a moving image of what is going on outside using just a cardboard box and the power of a hole.
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