Saturday, 11 November 2017

Slinky Science 'Speriment


BFTF is a big fan of science. All the wonders of the modern age, all out comforts, our medicines, our transportation, our communications. . . are built on the scientific endeavours of the last few hundred years.

Maybe it's just me, but whenever I use the word "scientific" I feel a little like Yul Brenner in "The King and I" - not in a good way!

Unfortunately, it can be hard to easily demonstrate the key elements of scientific enquiry in a domestic setting - or so BFTF thought until it found itself helping a pint sized relation with a small science project on springs.

We taped up the top half of a slinky spring, and taped some paper over the bottom of the slinky to act as a base where we could add weights.





We then measured the length of the slinky (measuring from the bottom of the taped section to the paper base) which was 14cm.

Next, we progressively added pound coins to the paper base, measuring the length of the spring each time (24, 34, 44cm with 1,2,3 coins respectively)

Once we got to three coins we plotted the data on a graph and drew a "best fit" line thought the points.




We then - get this - predicted what the extension would be for 4 coins and for 5 coins and checked to see what actually happened.

Well, my gob was truly smacked when it turned out that our prediction for the length of the slinky with 4 pound coins was absolutely spot on and the prediction for the length with 5 pound coins was accurate to within 1cm !!!.

We had performed an experiment, plotted the data, made a prediction for what would happen next, tested our prediction and found that it was quite accurate. It doesn't get any better than this!

So, gentle reader, there you go. A science experiment that ticks all the boxes and can easily be performed at home (no bunsun burner required!).

If you know of any easy science experiments, particularly any that allow you to make predictions about future behaviour, why not describe them in the comments section below.

The (counter-intuitive) Monty Hall Problem

There are some things in life that are really counter-intuitive.

We accept many of these because the evidence is right there before our eyes and we are used to them (e.g. a box in my front room that displays a moving image received through thin air? You gotta be kidding me right?)

But some, less common, phenomena still have the capability to confuse us. A good example of this is the "Monty Hall Problem", which is often stated as :


Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1 [but the door is not opened], and the host, who knows what's behind the doors, opens another door [that does not have the car behind it], say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?


Intuitively, one feels that switching door should not make any difference - you have a 50:50 change either way.

But, weirdly, this is not the case - in reality, you have a much higher chance of getting the car if you change doors.

I know, I know, it seems to go against common sense, and indeed when this conundrum was published in Parade magazine, some 10,000 readers, including almost 1,000 with PhD's wrote in to complain that the article was wrong and that changing doors did not make any difference.

With the problem being so simple, NSB decided to simply knock up an excel spreadsheet and see what happens. The geeky stuff is at the bottom of the post, but the take-home-message is that running the problem 100 times gives the following results :

Never switch door : Win 35% of the games
Always Switch door : Win 65% of the games
Toss a coin as to whether to switch or not : Win 55% of the games



Crikey, switching really does improve your chances of winning! How spooky!

Just goes to show how the human mind can be tricked. The Wikipedia article on the Monty Hall Problem is surprisingly long and discusses many of the psychological issues related to how people perceive the problem.

Here comes the Geek bit (from a random line of the spreadsheet, line 3 in this case) :

Column B : Randomly choose which door the prize is behind
Excel Formula: =RANDBETWEEN(1,3)

Column C : Contestant randomly pick a door
Excel Formula: =RANDBETWEEN(1,3)

Column D : Outcome if contestant sticks (win=1)
Excel Formula: =IF(C3=B3,1,0)

Column E : Outcome if contestant switches sticks (win=1)
Excel Formula: =IF(D3=1,0,1)

Column F : Toss to switch (stay=1)
Excel Formula: =RANDBETWEEN(1,2)

Column G : Outcome based on Toss in Column F (win=1)
Excel Formula: =IF(F3=1,E3,D3)

Copy the above onto as many lines as you want and then total up the wins from the different strategies.

Taxonomy, Type Specimens and Art

This article first written in 2012, but as relevant today as it was then....
A fascinating article in the UoN "Making Science Public" blog discusses the role of samples in botany. Written by Maura C. Flannery, Professor of Biology at St. John’s University, NY, the article was a genuine revelation for a non-specialist like NSB.

Durian (Durio zibethinus), Anonymous Chinese artist, ~1820.


Accessing botanical samples
Apparently, for each species of plant that has ever been identified, there is a "type" example that is the definitive example of that species, often collected by the scientist who first catalogued the plant. These "type" examples are kept as pressed specimens attached to paper and stored in "herbaria".

Botanists who are researching the taxonomy (classification) of plants often need to access these type specimens in order to check or examine some point of their structure.

And, for researchers in the developing world, this is where the problems start . . .

... because as a linked article explains, for the Rubiaceae (coffee plant) family, some 430 type specimens (over 95%) of catalogued species are stored in European herbaria (312 in the UK, 127 in Portugal, 99 in Franceand 70 in Belgium). There are only 50 type specimens in African herbaria, all duplicates of "definitive" type sample stored in Europe.

This relative lack of specimens in Africa means that researchers have to travel to Europe just to study speciments - which represents a significant economic burden on botancial departments that are already economically disadvantaged.

Grape Variety (Muscat Hamburgh) Goethe and Lauche, 1895


There are projects (such as the African Plants Initiative) underway to digitally photograph these European herbaria, but the paper suggests that photographs cannot replace phyical examination of actual specimens and points out that if they could then perhaps the photograhps could stay in Europe and the actual speciments returned to Africa.

But returning speciments to Africa has its own issues as they would need to be suitably housed, curated and maintained - again a costly excercise for developing African countries.

Photos versus pictures Another topic covered in the UoN article is that of the role of drawings to supplement the type samples and how drawings can be more useful because the artist is able to filter out some of the extraneous or irrelevant detail to focus on the the important structures of the plant. Indeed, for flora such as fungi, which cannot be dried without drastically changing their appearance, drawings are the key identifying tool.

Arabic translation of Dioscorides "De Materia Medica" c.1200


Other Comments
Whilst digging around on the Interweb to prepare this post, NSB stumbled upon some other interesting related resources.

One is the The Glass Flowers Collection Harvard University which contains over 3000 painstakingly made glass models of various plants. They really are an incredible example of craftsmanship.

Wikipedia has an awesome, gorgeously illustrated, list of Botanical Codices (NSB notes that it much much easier to look at and browse some of these illustrations at Wikipedia than at any of the Universities that are so lavishly funded with taxpayers money.)

Image Sources
Durian, Grapes, Arabic Translation

Wednesday, 1 November 2017

The difference between NUMBERS and RATES

Was talking to No3 Son recently about a piece of science homework in which he had to chart and comment on 2012-2014 cancer statistics. The data was a great example of how the NUMBER of cases can give a very different picture to the RATE of cases. Looking at the NUMBERS chart (red) one might think that 70-79 is where the biggest danger lies. This may be misleading as the graph shows the number of cases not the rate (e.g. per 100,000 people).

Using 2011 census data from Wikipedia, one can work out the number of cases per 100,000 people (blue chart). It is clearly different and now you can see that the older you are the more chance you have of getting cancer.

2012-2014 Cancer Data

Cancer NUMBERS

Cancer RATES

Saturday, 28 October 2017

Dinosaur of China Exhibition

This summer long exhibition at Wollaton Hall showcases some of the incredible dinosaur fossils that have been found in China in recent decades. Many Chinese rocks are unusual in that they are composed on fine sediments which buried and preserved dinosaurs quickly - and preserved their structures in incredible detail.

Feathered dinosaurs formed a large part of the exhibition, but there were many other types of dinosaur on show as well. A few of the exhibits that particularly caught NSB's attention are shown below.

Microraptor
Early Cretaceous, ~120million years ago
This is the first fossil of this type that was found, back in 2003. Microraptor has claws on its hands and feet, FOUR wings and was capable of flight.

Artist impression of Microraptor

Microraptor fossil - you can see the feathers

Sinornithosaurus
Early Cretaceous, ~125million years ago
Fossils of Sinornithodaurus show that the body of this creature was covered in a short fuzz of simple, soft, feathers - giving clues to the steps in feather evolution. It is likely that Velociraptor, a close relative of Sinornithodaurus was also similarly fuzzy.

Artist impression of Sinornithosaurus

Fossil of Sinornithosaurus

Yi Qi
Middle/Upper Jurassic, 160million years ago
A dinosaur with unique wings that were formed from webs of skin, rather than feathers, although it was covered in an insulating fuzz.

Artist impression of Yi Qi



Gigantoraptor
Late Cretaceous, ~80million years ago
The largest known bird-like dinosaur! Clearly too heavy to fly, its feathers may have been used in courtship displays. No-one knows what this large beaked dinosaur ate!

Artist impression of Gigantoraptor
Gigantorapor
Mamenchisaurus
Late Jurassic, 160million years ago
This sauropod is 23m long from head to tail and, in the rearing posture shown in the exhibition, is over 13m tall - higher than three double decker buses! The bones in its neck overlap with each other, which gave support but also resulted in the neck being rigid.


Mamenchisaurus

The exhibition also provided information on some of the key Chinese figures in palaeontology:
Dr Chung Chien Young
Dong Zhiming
Prof Tan Lin who gave a talk on "Ground Shakers and Feathered Flyers" in Nottingham a while back.
Dr Xu Xing


Image Sources
All fossil photos by NSB
All artists impression are photos of exhibition artwork by PNSO

Related Content
Doggerland - Europe's lost continent
The world in 10 Fossils
Susannah Lydons article on the exhibition in the Guardian.

Gabions (rocks in wire cages)

Over the last few years, NSB has noticed the appearance of wire cages filled with rocks (known as "gabions") as a construction material for buildings and in civil engineering - and has been wondering what they are and why they have suddenly started appearing.

Gabion Wall at Nottingham 1

Example of a Gabion abutment
Initially, NSB thought that they were being used for environmental reasons, to allow wildlife to grow and live in all the nooks and crannies between the rocks.

Then NSB thought that they were being used as an anti-grafiiti measure, as it is hard to make a recognisable image when the surface is so irregular.

Turns out that gabions have been used for a long time to stabilize shorelines, stream banks or slopes against erosion. They are also increasingly being used in architectural applications for their "natural" look. Maccaferri, a world leader in the technology comment that :
"The Gabion is, in fact, a peculiar tool. It does not impose itself on the surrounding environment: it perfectly blends into it. A Gabion is almost always filled with natural materials: stones/rocks and, where possible, locally available materials can be used to fill the structure, thereby ensuring that very little is added (and removed) to the surrounding nature....The Gabion, furthermore, “joins” the nature that hosts it: plants and trees can “sink” their roots in the interstices left free by the rock fill, helping to strengthen the overall system. Nature is no longer a passive actor: it is indeed called to “work” in synergy with man-made structures. This is the environmental engineering of the future."

Gabion wall at Nottingham 1

Worth noting that, in the urban environment, its a good idea to ensure that "youths" can't get the stones out through the mesh, as this cautionary tale from Sneinton, Nottingham illustrates.

Update Oct 2017
Saw this rather decorative gabion in Germany recently

Image Sources
Abutment

Sunday, 22 October 2017

Talk : Exoplanets

Café Sci returns after its summer hiatus with Michael Merrifield talking all about exoplanets.

@Gav Squires was there and has kindly written this guest post summarising the event, with some linkage added by NSB.

Exoplanets are defined as those planets that are outside our solar system and we now know of around 3,500 of them that are orbiting various stars.

In the middle of the 18th century, Immanuel Kant gave us the modern view of how the galaxy works based on observations of the solar system. We'd extrapolated our understanding out and applied it to the whole universe and we thought that we knew how everything worked. For example, in the solar system, all of the big planets are outside the ice line whereas those planets inside are smaller. Using ice is one of the easiest ways to make things stick together and we assumed that we would see the same big/small planet split in other star systems.

Prof Merrifield, via Gav Squires

The first exoplanet, the catchily titled HD114762b, was discovered in 1989 by David Latham. It was detected by measuring the Doppler shift as the star was effected by the gravity of the planet. Since it was thought that large planets (HD114762b is about 5-10 times the size of Jupiter) wouldn't be that close to a star and so it was originally misidentified as a brown dwarf star. A pulsar is the end state of a star - as they spin around, they can be used like a clock and are actually more accurate than atomic clocks here on Earth. In 1992, three planets were discovered orbiting a pulsar.

A quarter of the exoplanets that have been discovered have been found using this Doppler shift method, looking for the effect of the planet's gravity on the star that it orbits. Most exoplanets are discovered using the occultation method though. As a planet passes between us and its star it blocks out light from the star. We need a fair bit of luck for this method to work though as the orbit needs to be edge on for us to notice the planet's transit. This technique will give the radius of the planet and the radial velocity will give the mass and so we can calculate the density (as an side, Saturn is less dense than water). It is also possible to tell about the atmosphere of exoplanets and how much light is reflected from their surface.

Kepler6B photometry - showing light from star being blocked as planet passes in front

Occultation can even help to discover moons around exoplanets. In the summer, Kepler-1625b1 was tentatively announced as the first ever exomoon - it seems to be a Neptune-sized moon orbiting a Jupiter-sized planet. Another technique for discovering exoplanets is micro lensing - a star with a planet produces a different effect compared to a star without one. This is better at detecting planets that are further away from the star but it is a one-shot deal as it won’t line-up again.[a list of exoplanet detection methods can be found here]

Exoplanet systems are incredibly common, even our nearest star, Proxima Centauri, which is 4 light years away, has an Earth-sized planet orbiting it. The planet is at 0.05AU from Proxima Centauri and orbits once every 11 days and it could be tidally locked - the same side faces the star in the same way that one side of the moon always faces Earth. Proxima Centauri is a weak star but the planet still gets around 70% of the sunlight that Earth gets. This means that it is around -39oC but there could still be liquid water there if there is a greenhouse effect. However, there is unlikely to be any life as Proxima Centauri is a flare star - it regularly emits massive x-ray stellar flares, irradiating the planet.

Professor Stephen Hawking is involved with a project called Star Shot that would like to send a satellite to visit the planet around Proxima Centauri. By firing a powerful laser at a spacecraft, the size of a postage stamp it would be possible to speed it up to 20% the speed of light so it would arrive in just 20 years. Of course, there is still the issue of creating a satellite that small and many such satellites would need to be sent to cover the possibility that they could crash or fail. Once fired off, it wouldn't be possible to slow them down either so each satellite would only be able to make one fly past of the planet.

Based on existing technology, a more realistic idea may be using a solar sail - a satellite the size of a bar of soap would require a sail the size of 10 football fields. Light from the sun would speed it up, although it would take 80 years to get there. We are already able to make a satellite around that size and we would be able to use Alpha Centauri to slow it down in order to actually take some photographs.

NASA illustration of the unlit side of a half-kilometre solar sail
TRAPPIST is the really contrived acronym for a pair of Belgian telescopes that discovered the TRAPPIST-1 system, which features 7 exoplanets. The star is the size of Jupiter and the planets are orbiting at the same distance as the moons of Jupiter. 3 of the planets are in the so-called habitable zone and all 7 of them are in resonance with each other, which is what has actually led to the stability of the system. The SETI people have been focussing on this system but haven't heard anything yet.

Artist Impression of TRAPPIST -1 System

The term "Hot Jupiter" was coined to describe these massive planets that are close to their stars and their discovery has meant that we have had to rethink what we know about the creation of stellar systems. We are now starting to see the discs around stars - planets from in the gaps in these discs so if we can see these gaps, it implies that planets are starting to form and we can hopefully start to learn more about how planetary systems form.

The European Extremely Large Telescope is currently being built in Chile and is set to be completed in 2025. Its main mirror is 39 metres in diameter and it is proof that we can now do things on the ground that we couldn't even conceive of 10-15 years ago - not all telescopes need to be in space. The EELT will have such sharp images that we'll actually be able to see the planets themselves. We will even be able to tell which wavelengths are absorbed by their atmospheres - if we detect ozone, it would be proof that there is life on a planet.

There is a huge bias in the planets that we have been detecting since it is easier to find big planets - we've just been discovering the easy ones. We are starting to discover some oddities though - it seemed like one start, Tabby's Star, might even have a Dyson Sphere around it. While the changes in brightness emanating from it were relatively consistent with what was expected from a Dyson Sphere but the latest results show that UV & IR absorptions are different, meaning that it looks like it’s just naturally occurring dust.

Café Sci will return to The Vat & Fiddle on the 13th of November at 20:00 where David Nicholson-Cole from the University of Nottingham will talk on The Skyscraper - From mid-20th century to 2030. For more information check out the Café Sci MeetUp page: https://www.meetup.com/nottingham-culture-cafe-sci/

Related Content:
Fee- An Autobiography
Curiosity, Twitter and the British Connection
Interview with Prof Aragon-Salamanca
Interview with Prof Chris Lintott
Some background to the Space Shuttle
Lecture by Chris Lintott on 2011 Astronomy highlights

Image Sources:
Kepler6b Transiting light level, TRAPPIST-1 system Solar Sail

Sunday, 17 September 2017

Pseudoscience on Social Media

Some examples of Pseudoscience on Social Media.

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An article by Robert Walker on "Science 2.0" describes the fear that fake doomesday stories on Google News (and other sites) are causing to children and your adults :

"This is a serious problem. It's not just the misinformation and people growing up with this totally fake astronomy education. These stories are also scary, especially for young children, or young parents with babies, because they usually also tell them that the world is about to end in the next week or month or some other short timescale."

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Via Twitter

US Senator Jim Inhofe sets what may be the gold standard for denialism, back in Feb 2015.

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Via Twitter

The above was Tweeted by East Mids UKIP MEP @RogerHelmer.

Snopes has looked into this article, which originated on Breitbart News, and comments that :

"We reached out to many of the authors of the studies included on this list via email to see if they agreed with Breitbart and No Tricks Zone’s analysis. While not everyone we reached out to responded, not a single researcher that we spoke to agreed with Breitbart’s assessment, and most were shocked when we told them that their work was presented as evidence for that claim."

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Via Facebook

(Post first seen by NSB in 2017).A Facebook post poking fun at pseudoscience conspiracy theories.

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(Post first seen by NSB in 2017.). Does Fluoridation cause cancer? Answer is that there are so few of the most likely cancers (even before fluoridation) that it is difficult to tell. More information in this article by the American Cancer Society.

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Cannabis does not cure cancers
"Dangerous pseudo-science that could get people killed if they use cannabis oil instead of medical advice. In contrast to the claims in the article, there are MANY studies on the effects of cannabisits effects - for example at CancerResearchUK page".

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Anti-Vaccine attitudes get children killed.

This post actively causes harm by discouraging people from getting their children vaccinated. If you want to see what DOCTORS say about flu vaccine, visit this CDC page.

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CERN is not making an anti-matter bomb

Very sensible video until about 6mins in then it starts to fixate on anti-matter, repeatedly saying (accurately) that 1g of antimatter has the energy potential of a nuclear weapon and (also accurately) that CERN has been trying to contain antimatter.

But what is not mentioned (although NSB did not listed to the entire audio) is that the current state of the art is only able to hold about 40 anti-protons, which is 0.000 000 000 000 000 000 000 000 1 g and according to the IOP it would take around 100 billion years to produce 1 gram of antimatter. ********************************

Microwaves are not particles

Lots of errors and misinformation here. To take one example,the article says "They use electrically generated electromagnetic energy to make super-fast particles". But microwaves aren't particles. The clue is in the name. Here is a paper that talks quite comprehensively about microwave oven leakage and safety

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Jun 2013
NSB recently read an article in MailOnine by TV motoring correspondent Emma Parker Bowles on her experience using a leeches to cure migraines.

The article (entitled "Gruesome, medieval and utterly bizarre... but leeches freed me from awful migraines") had a number of characteristics consistent with being "psuedoscience". In particular, the following points caught NSB's attention:

a) Evidence presented does not relate to the condition at hand (migraines)
"In the 1980s, leeches began to be used by reconstructive plastic surgeons needing to remove stagnant blood from reattached limbs, to stave off gangrene. But now there are numerous studies into medical uses for leeches. One found that a single session of leeching – the medical application of bloodsucking leeches – can significantly reduce knee pain caused by arthritis for at least two months. Researchers from the University of Duisburg-Essen in Germany claimed improvement levels were comparable to those achieved with daily moderate doses of painkillers such as ibuprofen... The secret is in the leeches’ saliva: it apparently contains a large number of analgesic, anaesthetic, and blood-thinning compounds that tackle pain and inflammation, say the researchers."
But these are differnet applications to those that Bowles was using the leeches for (i.e. to stop migraines). Whereas the clinical uses mentioned relate to the use of leeches directly on the area affected, the procedure Bowles was undertaking involved the placement of leeches on the side of the head where they were separated from the brain by the skull. And, in any case, it is unlikely that Bowles was experiencing a migraine at the time the leeches were applied, so it seems unclear to BFTF exatly what the "analgesic, anaesthetic, and blood-thinning compounds" were supposed to be acting on.

Incidentally, the article does not provide references so BFTF cannot check the cited papers themselves, but the German study may be a follow up to this 2003 investigation and another study points out that investigations in to leech therapy are difficult to perform as the patients inevitably know whether they are being treated by leeches or by another method :

"Leech therapy can reduce symptoms caused by osteoarthritis. Repeated use of the leeches appears to improve the long-term results. We have not determined whether the positive outcome of the leech therapy is caused by active substances released during the leeching, the placebo effect, or the high expectations placed on this unusual treatment form"

NSB can find no reference in the online medical database PubMed for the use of leeches to cure migraines. In fact, internet references seem to largely relate to the MainOnline article itself.

So, in summary, there seems to be no evidence for the efficacy of leeches to treat migraines, not is any plausible explanation for their mechanism of action offered.

b) Wide ranging claims are made
It always makes NSB suspicious when wide ranging claims are made with no evidence for their efficacy. In this case, Bowles comments that :

"Google led me to Alicja, a Russian/Polish hirudotherapist [leech therapist] with ten years’ experience. She is based in Las Vegas and New York but she has clients from all around the world. She says the secretions from leeches’ saliva can be used to treat the entire spectrum of physiology: blood-clotting, digestion, connective tissue, disease, pain, inhibition of enzymes, and as a treatment for inflammation."

c) No evidence that the procedure worked even in this case
Bowles states that

"I could go for six months without suffering [a migraine], then there would be a whole week of agony"


and that she has not had a migraine since the leech therapy. As the leech therapy appears to have been performed this year (2013) and that the date of the article is 1st June, it is not clear that the frequency of migraines has changed for Bowles.

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Sunday, 9 July 2017

Talk : Adventures in the Goldilocks Zone – The Search for Other Earths

For May’s Public Lecture Series talk, Professor Frazer Pearce joins us to discuss "Adventures in the Goldilocks Zone – The Search for Other Earths". @Gav Squires was there and has kindly written this guest post summarising the event, with some linkage added by NSB.

Jupiter is around a tenth the radius of the Sun. Earth is around a tenth the size of Jupiter. Jupiter is a thousandth the mass of our star while we are three hundredths the mass of Jupiter. An Astronomical Unit (AU) is the distance from the Earth to the Sun. Jupiter is 4 AU away from us and the solar system is around 50 AU in total.

Solar System Size Comparison

Eight billion years ago the Sun hadn't yet formed, it was a protostar. Close to the star, metals and minerals can condense into planets. As you get further out, you reach the "frost line" . Outside of this, low temperatures allow condensing planets to include things such as H2O, NH3 and CH4. The size of the star determines how far away this frost line is.

Prof Pearce, derived some of the key equations that describe how a planets orbit is related to its mass and speed, these are shown in the image below.
Equations

So if energy is added, the planet will move out from the star.

When the Millennium Bridge was built in London, it initially had problems with it swinging in sync with people who were walking across it. This is resonance. It is the reason that soldiers have to break step whenever they cross a bridge.

In our solar system, we can see that close to the Sun there were lots of rocky fragments, then out at the frost line Jupiter formed. After around 70,000 years, Jupiter started to migrate in towards the Sun, getting as close as 1.5AU. Saturn followed it and as it caught up, the two planets became locked in a resonant frequency. This prevented them from migrating in any further. When Jupiter was around 300,000 years old, it started to migrate outward from the Sun and reached its current position around 200,000 years later, thus ending the so called "Great Tack".

This explains a lot about the solar system including why we have so much water here on Earth - Jupiter had brought a lot of the frozen water from around the frost line with it. However, while it may feel like there is a lot of water on Earth, if you balled it all up, it would comfortably fit inside the US. There is still more water than would be expected though. Most comes from Jupiter but there is also some that came from comet bombardment. The grand tack is also the reason that Mars is so small. Mars is only 10% the mass of Earth but Jupiter gobbled up a lot of the stuff that should have been Mars.

Earth- Mars Size Comparison

There are two ways to look for an exo-planet. Firstly you can look for its transit - when the planet passes between a star and us. This will block out some of the light from the start. From this we can measure the period of the planet's orbit and so we can use Kepler's 3rd law, it's possible to work out how far away from the star the planet is. Then it's possible to work out the size of the planet by measuring how much light is blocked. The second way is through radial velocity variation. The planet and the star both orbit the centre of mass of the system. This means that the planet will cause the star to have a slight "wobble". This can be measured using the Doppler Effect. The bigger the planet, the more the star moves. Using these two methods together, you can work out the density of the planet, which tells us whether it is a rocky planet or not.

Kepler6B photometry - showing light from star being blocked as planet passes in front

Bigger stars are better. There is a region around a star where water exists in a liquid state. Too near to the star and it boils off. Too far away and it freezes. This is known as the Goldilock's zone as it's not too hot, not too cold, but just right. The larger the star, the further away the Goldilock's zone will be. If a planet if 1 AU away from a small star, that would be no good as its water would be frozen.

The TRAPPIST-1 system, 40 light years away, contains 7 Earth-like planets. The star at the heart of the system is a red dwarf and is just a tenth the size of the Sun. The outermost planet is around 0.06 AU from the star and three of them are within the habitable zone. One could even potentially be a similar temperature to Earth. However, large flares from the star make life on the planets highly unlikely. The inner planets are tidally locked, like our moon, meaning that the same side always faces the star. In many ways the system is comparable to Jupiter and its moons. The planets of the TRAPPIST system are all in resonance - the inner most one orbits 12 times for each orbit of the outermost one.

Artist Impression of TRAPPIST -1 System

There are planets everywhere! Around 15% of systems contain Earth-like planets, 20% contain super-Earths and 20% contain mini-Neptunes. The next few years will see more missions launched [for example, TESS and CHEOPS] with the aim of discovering more exo-planets and specifically more Earth-like worlds. Earth itself would be too small to detect using its transit as it is too small to block out enough light. However, future detection techniques will allow the discovery of more planets similar to ours.

Professor Frazer Pearce


Related Content:
Fee- An Autobiography
Curiosity, Twitter and the British Connection
Interview with Prof Aragon-Salamanca
Interview with Prof Chris Lintott
Some background to the Space Shuttle
Lecture by Chris Lintott on 2011 Astronomy highlights

Image Sources:
Planets, Earth-Mars comparison, Kepler6b Transiting light level, TRAPPIST-1 system

Talk : Arachnoglobia - what makes a spider fly?

For April's Cafe Sci talk, Dr Sara Goodacre, who is an Assistant Professor at the Faculty of Medicine & Health Sciences at the University of Nottingham (and runs the UoN Spider Lab) gave a talk entitled "Arachnoglobia - what makes a spider fly?"

@Gav Squires was there and has kindly written this guest post summarising the event, with some linkage added by NSB.

Spiders eat pests. If we could work out how to control their populations then we could end up with a more environmentally friendly world.

The spider family is 400million years old. Spiders have adapted to their world in many ways. Why, and how do these difference help the spider to adapt? In a single species of spider, why does more than type persist? The adaptations that they have are all relative to each other. Even in a single species, different morphs can exist in different parts of the world. To our eyes these morphs look different but they can appear as different again under UV light. In fact, Crab spiders pretend to be nectar to catch bees. This effect can only be seen in UV but it works because bees see in UV.

Crab Spider about to spoil a bees day

In some cases, spiders are finding the same solutions to survival - some can have the same shape for a completely different genus. Co-operation can also solve some problems. Some spiders live in groups and they live in perfect harmony with each other. We've seen this in 9 species of spider, which is impressive but there are 40,000 types of spiders in the world. Those that do live in close family groups end up inbreeding. However, after 9-10million years of this, there appear to be no adverse effects. There is also a huge female bias when it comes to spiders in group living conditions.

Social Spiders

Being able to move long distances also helps. Lingphiids are common in disturbed, agricultural environments. Many are capable of dispersing long distances by spinning out a line of silk and using it to take off. This is how they can end up on a farmer's field even after they have sprayed pesticide. You can find around 100 spiders in the space the size of an average table and they eat 25 times their body weight in pests every week. Spiders are 1000 times more impacted by insecticide than whatever you're trying to kill. How many of these flying spiders carry resistance to pesticides with them?

At any time, 40-60% of spiders will attempt to take off. This achieves optimum balance between rates of extinction and recolonization. After a new island emerges from the sea, spiders are often the first animals on it and birds in places like Svalbard partially rely on flying spiders arriving as a source of food. Prior to take-off, 1.5m of silky sail is spun out. The spider cannot control how high they go or where they end up. Spiders can't propel their silk out, it has to be reeled out instead. Most species of spider eventually get too big to be able to fly. Money spiders can fly throughout their lives though. Spiders can fly up to 70km in just 10 hours.

Why is dispersal so important? Professor Godfrey Hewitt said "Global climate has fluctuated greatly during the past three million years, leading to the recent major ices ages. An inescapable consequence for most living organisms is great changes in their distribution. Such range changes can be expected to have genetic consequences."

Single filament of synthetic spider silk
What drives the different dispersal strategies? What is the relationship between dispersal, gene flow and local adaptation?

Risk avoidance on the part of the spider is not the only factor determining when it flies. It has been discovered that spiders carry particular bacterial infections that are known to influence the biology of other hosts. For example, in butterflies, this Wolbachia bacteria results in a female biased sex ratio, meaning that the females have to compete for males. In woodlice, genetic males develop as females but other males prefer real females over feminised males. In other creatures, infected females aggregate offspring, thereby promoting sibling mating and inbreeding. The bacteria affects higher brain function.

Example of Spider Adaptations

How can we determine the effects of bacterial infection in spiders? We can cure the spiders with antibiotics and then see what happens to the behaviour of the "cured" spiders. Of course this isn't as straightforward as it sounds - what is the right dose of antibiotic for something as small as a spider? It turns out that spiders are more likely to fly if they have been cured. So, the bacteria see to influence whether or not a spider will fly. Around 2/3 of invertebrate creepy crawlies have this bacteria.

Spiders that can fly are also good sailors. This is how they can travel much further than we initially thought. Some spiders can even stand on water. These are a subset of the sailors, who are a subset of the flyers. The spiders that can fly but can't sail might be in trouble if they land on water. There are even some spiders that can survive submerged for up to a week. However, many spiders can drown in a raindrop.

Spider Distribution Map at BAS

We then move onto a slightly more general chat about spiders. There are very few spiders that are actually dangerous to humans. There is Brazilian wandering spider that uses neurotoxin but most spiders don't have that kind of venom. Very few cases globally of a long term harm from a Sydney funnel web. There have only been two reports of "Fake Widow" attacks, despite all the coverage that they have received in the press. One was a sore arm for an afternoon in Worthing in 1991. One was a sore leg in south France in 2003. However, you are still better not touching spiders abroad but there are no harmful spiders in the UK.

Many people think that conkers can be used to keep spiders away but they do nothing. If anything a spider just sees a conker as something else to hide under. Most spiders can mate twice in quick succession. Sometimes a male spider is half-eaten, mates again and then she eats the rest of him. The hairs on a spider's foot that let it climb glass are thinner than a human chromosome.

In conclusion, natural selection shapes traits such as ability to survive encounters with water and aerial dispersal tendency. A small proportion of individuals is capable of moving over distances far greater than previously imagined because aerial dispersers are able to survive encounters with water.

Dr Sara Goodacre

Café Sci returns to The Vat & Fiddle after its summer hiatus on the 9th of October where Mike Merrifield will talk about Exoplanets. For more information, check out the Café Sci MeetUp site: https://www.meetup.com/nottingham-culture-cafe-sci/

Image Sources
Crab Spider, Social Spider, Spider silk comparison, Silk strand

Monday, 29 May 2017

Talk : When the Uncertainty Principle Goes up to 11

For April's Uni of Nottingham Public Science Lecture, Professor Philip Moriarty from the School of Physics & Astronomy at the University Nottingham talked about "When the Uncertainty Principle Goes up to 11".

@Gav Squires was there and has kindly written this guest post summarising the event, with some linkage added by NSB.

There is a deep and fundamental link between quantum physics and heavy metal. This is a real thing unlike the huge industry that people like Deepak Chopra have built up around quantum woo, trying to link eastern mysticism and quantum physics. Despite what Deepak and his ilk will have you believe, we actually understand quantum physics remarkably well - it is a theory of waves. We don't know what those waves mean yet but we can do the mathematics behind them. At the minute, there are around twenty interpretations of quantum mechanics. As Richard Feynman said, "if you think you understand quantum mechanics, you don’t".

Metal Bands and Physics

Heavy metal is not considered to be the most cerebral of genres but there are a number of bands that are embedding science themes in their music. David Robert Grimes, from Oxford University, has written a paper on string-bending and there is also a published paper entitled, "Collective Motion of Humans in Mosh and Circle Pits at Heavy Metal Concerts" (it turns out that the people behave in exactly the same way as molecules in a box) So, scientists are already writing about the physics of music. Mathematician Gottfried Wilhem von Leibniz (1646-1716) even said, "music is the pleasure that the human mind experiences from counting without being aware that it is counting" There is an equivalence between fractions and musical notation such as quavers, semi-quavers etc. Musical theory is based around the concept of intervals - thirds, fourths, fifths, octaves. Music has notations and maths has notation and we can simplify both of them.

Moriarty playing the guitar

We can use our knowledge of waves in the real world to tell us about the quantum world. If we confine a particle to a finite space it will have a wave like characteristic. This is similar to a guitar string. What happens when a wave can't propagate? It reflects. With two nodes, you get very simple waves where it doesn't vibrate rather than the mess that you might expect. A low note has a low wavelength, while a high note has a higher pitch and a higher rate of oscillation.

Why does an "E" on piano sound nothing like an "E" on guitar? It's the harmonics. If every wave produced just looked like a standard sine wave you wouldn't be able to tell the difference between different instruments. The real waves are much more complex, even though they are still regular and repeating. Whistling is a lot more similar to a "standard" sine wave.

Different Harmonics possible with a single string

How a harmonic may oscillate

The amplitude is the period of a wave, how many times it repeats per second. The frequency can be represented as 1/T, where T is the amplitude. This is "reciprocal time" - converting from one quantity to its reciprocal is incredibly important in physics. The frequency will change with the pitch. On a guitar, there are multiple spikes even with just one note, so we know we have a range of frequencies.

You can get any pattern that is relevant in the real world by adding together different sine waves. As Jean Baptiste Joseph Fourier said, "mathematics compares the most diverse phenomena and discovers the secret analogies that unite them." The guitar string can vibrate in a number of ways. However, we always know that it has two nodes. By adding your finger to the string at a node, you can dampen out any waves (harmonics) that don't have a node at that point.

With particles and waves, you're looking at localised versus delocalised. When an electron moves on silver you get standing waves, just like with guitars. These days it is child's play to manipulate individual atoms on a surface, you can just point and click. Electrons create waves but rather than these being actual waves, they are probability waves, all to do with the probability that you will find an electron. If you create a string of iron atoms and then look at the distribution of the electrons then you can see that the same ideas that we have on a guitar string can be ported down to this level.

Electron Waves 

Heisenberg's Uncertainty Principle has been incredibly mis-interpreted throughout the years, not least by Heisenberg himself. You could say he was uncertain of how it worked! It is different from the observer effect, where if you interact with a system then you change the evolution of the system. Anything can be an observer - in the famous case of Schrödinger's Cat, even the box is an observer, so the cat has been observed long before you actually open the box. We see the Uncertainty Principle all the time in the real world.

For example, when you mute a guitar string with your palm. If you look at the peak for the fundamental - the lowest frequency peak, it is wide in time but narrow in frequency. By muting the string with your palm, you get narrow in time but wide in frequency. This comes from classical physics but it is the Uncertainty principle.

You can also have a spatial frequency - number of stripes per metre. Then you look at the reciprocal space - how often does it repeat? This ties back in with momentum in the Uncertainty Principle. High definition means high spatial frequencies, while a narrow spectrum gives much greater uncertainty in space.

The Public Lecture Series returns on May the 18th where Professor Frazer Pearce will be talking about Adventures In The Goldilocks' Zone - The Search For Other Earths. For more information visit the website: www.nottingham.ac.uk/physics/outreach/science-public-lectures.aspx

Image Sources
Standing Waves, Others by Gav Squires.