Why did my Dishcloth Detonate?

Chris - I think you've got what's called the photic sneeze reflex. Photic as in light; Sneeze as in, well, sneeze! This is apparently genetic, it seems to run in families. Do you have any family members who do the same thing?

Paul - I don't actually, no. I've got family members, but I'm the only one that does it!

Chris - Okay. It affects about 1 person in 5 and what scientists think is going on is that there's a little bit of miswiring in the brain stem, which is the thing that connects the spinal cord to the main part of the brain which is where all of the circuitry is to control the size of your pupils and blinking, and that kind of thing. So when a bright light shines into your eye, neural circuits get activated to cause a blink and your pupil to shrink - pupilloconstriction. Some of this nerve activity also spills over into the parts of the nervous system that detect irritation in your nose and they trigger a sneeze.

People used to think it was because sunlight made your eyes water and that the tears running down into your nose tickled your nose a little bit, and that triggered the sneeze. But when they did careful studies and in fact, the military have been researching this because what you don't want is someone who's flying a supersonic jet to suddenly develop the photic sneeze response when they're flying into the sun and then have a fit of sneezing at the flight controls doing a thousand miles an hour! So they were looking into this and they ruled out the tears tickling the nose, and they think it's actually this miswiring and it does appear to be as I say, familial. So, you get some people who have it sporadically and some who say, "Yup! Lots of people in my family have this." So you have the photic sneeze reflex.

It happens to me when I get up in the morning in the winter time and I go into my shower where the lights are very bright, and you turn the bright lights on. All of a sudden you go from dark to very bright and I have this sneezing fit.

Dominic - The simplest kind of orbit is a circle, where the planet is trying to travel in a straight line which is carrying it further away from the star it's orbiting around.

But the gravitational pull of the star in a particular direction is pulling it back, so it's staying at a constant distance from the star as it goes all the way around that central star.

Now, if you imagine that planet had slightly less speed, then it wouldn't have enough speed to keep at the same distance from the star, so it would begin to fall in towards the star. As it begins to fall in, it will start to move much more quickly, because the star is pulling it in and it's gaining kinetic energy.

But it's then moving too fast to be in a stable circular orbit that much closer to the star. So, it then has enough energy to move back out again.

So, it's "wobbling" in its distance from the central star, which makes the orbit elliptical

Complex carbon-based molecules, including many that are important for life on Earth, could have formed in the early solar system. That's according to a paper by Fred Ciesla and Scott Sandford in this week's issue of the journal Science, based on their computational simulations.

The origin of these prebiotic molecules has been a long-standing puzzle. In order for simple stable molecules such as carbon dioxide and methanol to rearrange themselves into more complex configurations, two conditions are thought to be needed. 

In order to break the simple configurations apart, ultraviolet light is needed, and in order for the fragments to then be rearranged into different configurations, a heat source is needed. Until recently it was thought that all of the organic material on Earth had originated in situ, helped by lightningstorms in the Earth's early history.

However, recent evidence is that organic molecules are quite widespread in the Universe. They have been found on interplanetary dust grains and in meteorites arriving on Earth; furthermore, their spectral signatures can be seen in many star-forming nebulae far beyond our own solar system. This suggests that they can form in a much more widespread environment than simply the atmospheres ofplanets.

Until now, the early solar system had been ruled out as such an environment. The protoplanetary disk of gas and dust which formed into the planets was so dense that only its innermost parts would have been exposed to the Sun's ultraviolet radiation.

But writing in Science this week, Ciesla & Sandford report on computational simulations of the migration of material within such disks, taking into account effects such as the evolution of the disk and the turbulence within it.

They conclude that there would have been very significant mixing of material as the solar system was forming, and that much of the material would at some point, by random chance, have found itself elevated slightly out of the top or the bottom of the disk. Here, it would have had a clear line-of-sight to the Sun.

Even if this only happened for a thousand years for a typical dust grain, out of a total lifetime of around a million years for the disk, that would have been enough time for substantial chemical changes to occur.

By comparing their simulations with laboratory experiments to determine the amount of ultraviolet irradiation needed to produce chemical changes, Ciesla & Sandford conclude that this would have been ample time to account for all of prebiotic molecules found in the solar system today.

The question remains as to how these molecules went on to form still larger and more complex molecules, such as amino acids and proteins, and how these eventually led to life on Earth, but forming the prebiotic building blocks is an important step along the way.

Chris -   What was the atmosphere like on the Earth nearly 3 billion years ago?  Well that's a pretty tough question to answer, but incredibly, some fossilised raindrops or rather, the patterns that they left behind when they fell 2.7 billion years ago have enabled scientists to reconstruct some aspects of what the air that rain fell through would've been like.  And with us to explain how, from the University of Washington in Seattle is Roger Buick who's one of the authors on the study.  Hello, Roger.

Roger -   Good day!

Chris -   So what are you actually trying to understand about the early atmosphere?

Roger -   What we really want to know is why the Earth wasn't an ice ball 3 billion years ago.  The Sun was only 80% as bright then as it is now and if the atmosphere was the same as it is now on the Earth, the planet should've been completely frozen over.

Chris -   Yet we've got geological evidence of their having been running water and quite a balmy climate.

Roger -   There's abundant geological evidence for liquid water - oceans, rivers, lakes, and now rain as well.  Either we had to have a much denser atmosphere, or else we had to have a whole lot more greenhouse gases in the atmosphere to keep us warm.  And there's been a debate going on for 20 odd years as to what sort of atmospheric warming mechanism was active on the early Earth.

Chris -   And obviously, without the capacity to go back 3 billion years or so and take a snapshot of that atmosphere, we're forced to rely on indirect measures which I guess is what you've done in this paper in Nature this week.  You've used an indirect measure to work out what the atmosphere must have characteristically been like.

Roger -   Yeah, well until Torricelli invented the barometer, we've really got no real readings of what atmospheric pressure was like early in Earth history.  The atmosphere has a very, very indirect and faint impact on rocks that can get preserved from early in Earth history.  So, to be able to register anything about the atmosphere from early in Earth's times is really quite remarkable.

Chris -   So how did you actually do this?

Roger -   Well, we found some literature records of raindrop imprints in rocks, almost 3 billion years old.  There's a number of places in the world where there are these ancient raindrop craters and the best ones that we were able to come across were in South Africa, out in the Karu-velt of South Africa.  And so, we went there and took samples of them and made latex peels off them and measured them.  Now there's a relationship between the size of raindrop imprints and the speed at which the rain fell, and the speed at which the rain fell is influenced by the atmospheric density.  The denser the atmosphere, the slower the raindrops fall, so the smaller the little craters that they form.

Chris -   So how do you work out based on the rock samples that you've got from  3 billion years ago, how big the crater should be in proportion to the speed of the raindrops?  How did you close that gap in our knowledge?

Roger -   Well, the big variable is the nature of the material being impacted.  The South African raindrop imprints were in volcanic ash, so what we did was get some equivalent modern volcanic ash from the Icelandic eruption a couple of years ago and did experiments by dropping artificial raindrops down a 7-floor stairwell onto a pie plate full of this volcanic ash...

Chris -   It's high tech stuff, this!  And so, that was your sort of proxy measure.  You could see based on how fast or therefore how much energy, how much momentum, the raindrops had and based on how big a splatter imprint they make you can extrapolate from the latex peels from the South African rocks, how fast the raindrops must've been going 2.7 billion years ago.

Roger -   Exactly.  The other variable of course is the size of the raindrop. As anybody British will know, raindrops vary greatly in size depending on the intensity of the rainfall.

Chris -   Well at the moment, we're in drought in the southeast, so we don't have any rain at all.  Zero is the size!  So what did you do to constrain that?

Roger -   We do know that there is an absolute maximum size to which raindrops can get.  It's a proportion of the interplay between the surface tension of the water and the force of gravity trying to pull it to bits.  And so, the largest that's ever been recorded on the Earth and the theoretical maximum size from physics is 6.8 mm.  So, that sets a maximum bound on what the atmospheric pressure could've been, but it's unlikely that the absolute maximum raindrop size was achieved.  Probably more like 5 mm was the realistic maximum raindrop size.

Chris -   So putting all that together, what does this tell us about the atmosphere 2.7 billion years ago when these - what are now rocks - were just volcanic ash and this moderate shower was falling on them?

Roger -   Well, it us tells that the maximum possible atmospheric pressure was about 1.6 bars, so 1.5 times what it is now, but more likely, it was 1.1 bar, 1.1 atmospheres, well maybe even as low as 0.6 of a bar, so only 6 tenths of our current atmospheric pressure.

Chris -   So very, very similar to what we have today which argues that we couldn't have had just this blanketing smog of CO₂, giving us an artificial greenhouse effect to keep the Earth warm then.

Roger -   That's right.  Most likely, we had to have some other sort of greenhouse gas other than just carbon dioxide in the atmosphere to warm the Earth.  Maybe something like methane, though that's problematic; if you have high levels of methane in the atmosphere, you produce a haze of organic particles formed by ultraviolet light and that reflects sunlight and has an anti-greenhouse effect.  Other possible greenhouse gases would be, my favourite is laughing gas - nitrous oxide.  There is some evidence that there was a biological nitrogen cycle producing laughing gas, back as far as about 2.7 billion years ago.  So, laughing gas is something like 100 times more effective as a greenhouse gas than carbon dioxide.  So we might have had some methane and some laughing gas in the atmosphere as well.

The reason that most streetlights are orange is because they contain the chemical sodium.

Some electricity is passed into the lightbulb and this gives energy to the sodium. Sodium, when it gets excited by the energy, gives out a lot of orange light, making it a very cheap and efficient way to illuminate a very large area.

But to produce white light is very complicated. To make white light you have to mix lots of different colours of light together and it's the mixture that looks white.

The way in which lamp designers make this happen is to use a mixture of different chemicals. When each of those chemicals gets excited they then produce different colours of light which you then see mixed together so it appears to be white.

Because it's more complicated and involves more chemicals, it's more difficult to do and it's more expensive and because orange light does a good enough job, most of the time we use orange sodium lights rather than white ones.

A rocket has been developed that could get a spaceprobe to the moon on just 100g of fuel

Some tasks can only be done by a large satellite, but there are many others which can be done as well if not better with several smaller ones.  Any measurement which requires measuring something in more than one place, like magnetic field, solar wind or gravity, is much better done with more small probes, as could be exploring a planet where 20 small rovers can cover more ground than one big one.

These nanosats have been gaining in popularity, but so far they have had no way of moving, chemical rockets need a lot of heavy fuel, because the exhaust gasses move out of the back of the rocket relatively slowly so each gram of fuel only gives a limited push. Electric ion thrusters, throw xenon gas out of the back of the rocket 10 times faster than a chemical rocket so use a tenth of the fuel, but they are complex, involving piping gas about, valves and other devices which don't miniaturise easily.

However the Dutch company EFPL has managed to build an ion thruster which could weigh as little as 200g including the fuel. They have simplified the design by instead of using a gas as the fuel, using an ionic liquid, this is a liquid made up of positive and negative ions, a bit like molten salt, but which will stay liquid in the cold of space, and won't evaporate. They move this liquid from the tank to the thruster which is made using similar processes to a computer chip using capillary action, and then accelerate the ions out of the back using an alternating high voltage, first pushing out the positive then the negative ions out of the back producing thrust. This thrust is minute equivalent to the weight of a square cm of paper on earth, but in space there is no friction, and the rocket can keep firing for years, allowing it to move a long way.

The first use they want to make of this rocket is on a satellite called clean space 1, which aims to launch in 3-5 years time and is designed to tidy up old defunct satellites and other space junk by capturing them and dragging them into the atmosphere. Though the same rocket design could be used for small cheap satellites in earth's orbit which need to maintain their position, or for missions to the moon, which would only take 100g of fuel for a 1kg probe, or even further into the solar system, opening up the possibility of cheaply reaching the moon or even further out into the solar system, opening up all sorts of interesting scientific possibilities.

Bumblebee numbers reduced by pesticide use

Direct evidence that pesticides are poisoning bumblebees has been revealed this week in the journal
Science.

By exposing colonies of  bumblebees to the commonly used pesticide imidocloprid, Dave Goulson from the University of Stirling found that the bee colonies grew more slowly and there was an 85% reduction in the production of new queens who are crucial for producing future bee generations.

The consequences could be significant for both the environment and the economy...

Dave -   If we're accidentally poisoning our bumblebees and driving down their populations, there'll be less pollination for wild flowers and therefore, all the things that those plants support, all the butterflies and birds, and everything else.  But there's also a really direct economic importance of bees.  Bumblebees are the main pollinators of some of the very nice things that we like to eat - so blueberries, raspberries, strawberries, lots of garden vegetables like beans and tomatoes.  So, if we lose our bumblebees, then our diets are going to be much be poorer for it.

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Resuscitating Antibiotics

Bacteria that have become resistant to antibiotics could be made susceptible to the drugs by the addition of certain chemical compounds.

Presenting at the
Society for General Microbiology annual meeting in Dublin this week, Marta Martins from University College Dublin, combined one of five known pharmaceutical compounds, including phenothiazines used to treat schizophrenia, with the widely prescribed antibiotic ciprofloxacin.

When used on samples of bacteria showing resistance, the combined treatment was six times more effective at killing bacteria than samples lacking these added compounds, giving a new lease of life to the drugs...

Marta -   We think this is a better solution instead of developing new antibiotics.  With these compounds that are known antibiotics, they are synthetic compounds and we could avoid that problem of the bug adapting to that.  It will not just help to treat these multidrug resistant infections but also to decrease the numbers that we will see in the hospital and subsequentially in the community.

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Solar tornado

Scientists have spotted a tornado on the Sun, large enough to accommodate several hundred Earth-sized planets.

Using the orbiting Solar Dynamic Observatory, University of Wales, Aberystwyth physicist Huw Morgan and his colleagues spotted the 120,000km high plasma tornado travelling across the Sun's surface at speeds of  300,000 km per hour, driven by the solar magnetic field.

The discovery was announced this week at the
National Astronomy Meeting in Manchester.

Huw -   It's a huge structure and it lasts for 4 or 5 hours, and it's very exciting because it's a test bed for various theories on solar magnetic field and plasma movements in that field.

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Robots mimicking Living Organisms

And finally, a robot less than 1cm in size with the ability to respond and move like a living organism is being developed by scientists at the University of Newcastle.

Modelled on an ancient fish, the robot named '
cyberplasm' will combine cells engineered to sense light and chemical cues that feed into a central processor that controls a series of artificial muscles resulting in movement.

Daniel Frankel from the University of Newcastle is leading the project.

Daniel -   The idea is really to harness the power and control of the biological system.  For example, muscle contraction and sensitivity of cells and interface them and incorporate them into a machine.  The ideal uses would be swimming into waters which may be polluted or having toxins and detecting toxins, and then in addition, medical applications.  For example, reconnaissance in the body so to speak, swimming through the arteries and veins, and trying to detect and maybe even treat various diseases.