Christmas Question and Answer and the Star of Bethlehem

Many of us here at the Naked Scientists have done our fair share of lab work, and I've handled nasty chemicals like formaldehyde and benzene with the aid of a lab coat, safety specs, rubber gloves and a fume cupboard. But did you know that these, and a whole host of other chemicals, are also found in tobacco smoke? Cancer Research UK's latest campaign is called Smoke is Poison, and it's highlighting the fact that although most people know that ciggies contain tar and nicotine, around three quarters don't realise there's some really horrible chemicals in there too. Out of the 4,000 chemicals in smoke, around 69 of them are known to cause cancer in humans. These include arsenic, chromium and cadmium as well as benzene and formaldehyde. Funded by the Department of Health, the charity have teamed up with documentary maker Donal McIntyre to make a series of hard-hitting TV and radio adverts, showing the stringent safety measures that lab workers take when handling these chemicals, then capturing their reactions when they realise they're found in smoke. If you want to know more about the contents of smoke, then either text the word "poison" to 84118 in the UK, or have a look atwww.smokeispoison.com.

Scientists are investigating the possibility of using viruses to carry out pain-killing gene therapy in the spinal cord. So far the technique, which is the brain child of Andreas Beutler and his colleagues at Mount Sinai School of Medicine in New York, has only been tested on rats, but the results look promising.

The team have used an adeno-associated virus which has been genetically modified to replace the normal viral genetic material with a gene for one of the body's own natural pain-killing chemicals called beta-endorphin, which works in the same way as morphine. Ten billion particles of the modified virus were injected by lumbar puncture into the spinal cords of each of a group of rats. These animals had previously sustained nerve injuries that simulate the chronic pain experienced during certain human diseases. At the same time a second group of animals were injected with a control virus containing a harmless marker gene instead of the beta-endorphin gene. The animals were then followed up over three months to look for effects on their pain. Initially nothing happened, but then after one month the animals that had been injected with the beta-endorphin containing virus began to show significant improvements in their pain, which continued until the end of the experiment two months later. The control animals, on the other hand, remained unchanged.

The team think that their approach could make life much more comfortable for human patients experiencing severe pain, such as those with terminal cancers. This is because effective pain control is a delicate balancing act since doctors need to walk a tightrope between patient comfort and side effects.

"Chronic pain patients often do not experience satisfactory pain relief from available treatments due to poor efficacy or intolerable side effects like extreme sleepiness, mental clouding and hallucinations," says Beutler. "But targeted gene therapy will likely avoid the unwanted side effects associated with opioid painkillers such as morphine."

Chelsea - Sure! This one is an audio question:

Matthew - Why is it that giraffes don't have a stroke when they bend down to get a drink of water?

切尔西-非常好的问题,马修。为什么不giraffes have strokes when bending over? Well, we talked to giraffe circulation expert Alan Hargens of the University of California - San Diego. He explained that their brains and spinal cords are surrounded by fluid, just like ours. When they bend over, that fluid rushes to their heads, and squeezes the swelling blood vessels from the outside.

Alan - So when they bend head-down to, say, for example, drink water, the elevation of blood pressure due to the head-down tilt could be counteracted, one for one, by the increase in cerebro-spinal fluid pressure. WALD: Even so, he says giraffes generally don't keep their heads down for long, even when they're sleeping.

鲍勃- Fascinating. Thanks, Chelsea. Here's another. After hearing about threatened salmon populations, Merrie Smith from Mendocino, California, called to ask why we catch and eat salmon before they've spawned, rather than after. We asked University of Alberta salmon expert Martin Krkosek. He says that when salmon reach their spawning streams, they stop eating and metabolize their own flesh for fuel. On top of that, competing for mates and digging nests for eggs takes its toll.

Martin - So by the time they're actually spawning, and after they spawn, their bodies are really worn out, from fighting with each other, from digging, and they're also usually heavily infected with fungus; they're generally just really gross.

Bob - Very ecological-but not very palatable. Thanks, Merrie. One last one, Chelsea?

Chelsea - OK. Listener Luci Levesque from Augusta, Maine, heard that vaccines are made in fermenters, devices normally associated with beer. She asks, what's the connection? Good question! We turned to microbiologist Agnes Day of Howard University College of Medicine.

Agnes - The principle of using a fermenter is the same for beer as it is for vaccine production.

Chelsea - She tells us that a fermenter is simply a device that grows microorganisms on a large scale. In beer, those microorganisms are the yeast that convert sugars into alcohol. But in vaccine production, they are disabled versions of the disease-causing bacteria or viruses that will ultimately form the basis of the vaccines.

Bob - Thanks, Chelsea. We hope you naked people and all your fans stay warm and have a very happy holiday. Until next time, I'm Bob Hirshon…

Chelsea - And I'm Chelsea Wald, for AAAS, The Science Society.

这将取决于你把所有你的空气t of the tube first, because if there was air resistance it would drop all the way down. It would be going quite fast at the bottom but probably not very fast because it would be losing lots of energy to friction. It would go over to the other side a bit, but then it would start falling in the other direction and it would start coming north again, and it would oscillate and eventually end up in the centre of the earth. If you took out all of the air from the tube, it would drop all the way through the earth and end up pretty much at the South pole, it would stop there and it would come back again. It would go backwards and forwards and would look like simple harmonic motion, a bit like a pendulum. It would take about 90 minutes to bounce back and forth. If you imagine that you don't take the air out, it's worth thinking about water as an analogy. Every time you go 10 metres underwater, you increase the pressure pushing down on you by 1 atmosphere. If you were to go all the way to the centre of the earth pretty soon the air would become so dense and there would be such a huge amount of atmosphere above you, it would be like trying to swim through a solid. Which is why the earth's core is solid; because of the huge pressure that there is down there. The thing is, you wouldn't be able to go very very fast because there would be this tremendous resistance. You'd actually fall probably forever, because you'd go so slowly.

Now I've been having a look into this, and at Thomas Nagel's 1974 work, "What is it like to be a bat?". Basically, bats don't ever go the right way up. They fly sort of head down, and they hang feet up head down, and basically, that's the way they think the world is. There have been some experiments done trying to put bats in low gravity, and basically bats don't really care which way is up. There have been some experiments done with bats and gravity, where most things, if you put them in wrong gravity or reduced gravity, they start rolling over and they get very confused, whereas bats just don't really care. They can fly upside down, they don't really mind. So bats generally hang upside down rather cleverly, and they don't seem to mind which way is up. And here's a good bat joke for you: There's a bat hanging upside down in a cave, and he sees another bat standing on the floor and he says "What are you doing down there?" And the other bat says "Yoga". [Chris] I can beat that! There's three vampire bats in a cave. And they're really hungry. And they can't get hold of any blood to save their lives. And then one day one of them says "I'm so desperate I'm going out of this cave, I'm going to find us something to eat". So he goes flying out of the cave and five minutes later he's back. He's got his mouth drenched in blood. And the other bats go "where did you get that wonderful blood?" and he says "come to the mouth of the cave and I'll show you". And they all go to the mouth of the cave, and he points out and says "You see that tree over there?" and they say "yeah" and he says "I didn't".

It's not quite true that matter can't be destroyed. You may have heard of Einstein's formula E=mc2, which basically means that mass is the equivalent of energy. So you can convert mass into energy or energy into mass. But you can't destroy the total amount of mass and energy together. So the total amount of energy-mass stuff, that can't be destroyed. And that is always somewhere. John - So everything that has ever been created in nature, is still in existence somewhere in some form? Dave - Well, all of the energy in the universe is still there. Chris - It originated in the big bang, which was the unleashing of a huge amount of pent up energy that existed in a tiny amount of space that was enourmously dense, and minute. John - I'm thinking of matter created on earth like an acorn grown into an oak tree. Chris - Well those are all atoms and those are all molecules, which are built from atoms, and the point is that all of the things and all of the complex elements you see here on earth must have been made in a star somewhere else in the universe. Nothing that was produced in the big bang came out more complicated than Hydrogen, Helium, and a little bit of Lithium. Which are the first three elements of the periodic table. And more complicated things were produced in stars like our own sun and bigger stars that very quickly ram things together and make very complicated elements which when the star blows up, are disseminated all around the universe. And then they gather together to make a new star, and new planets and things like our solar system.

正确的答案是,植物生长them are actually clones. So instead of growing them from seeds, they're grown from cuttings taken from existing plants. Obviously, the first seedless grapes were from a plant that arose through mutation - a genetic change - that meant that it didn't have seeds. And, presumably, some grower noticed this. He or she would have taken a little shoot or a stem off the plant, put it in the ground, and a new plant - genetically identical to the seedless parent - would have grown. In fact, this is how a lot of plants are cultivated now, and also a lot of seedless varieties. But, this technique is causing problems in some cases. Bananas, because they're all clones, are getting struck down by fungi - like Panama disease. And if a population is created by cloning, all of the plants are genetically identical, so they can very easily be wiped out because the plants have the same defences to a pathogen. And if the pathogen evolves to sumount this defence, every cloned plant is susceptible...