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Saturday, 26 November 2016

TWDK - The New Social Media Platform for Science

A number of astute observers have already noticed (and clicked on) two mysterious links that have appeared on the Things We Don’t Know homepage, along with some other tweaks to our layout and styling. But why register? Why login? It's all part of our upcoming changes, a kind of scientific advent calendar for you all.

Thursday, 22 September 2016

Is there a ninth planet in our Solar System?

By now, you’ve probably heard the hubbub in the news about the hypothetical “Ninth Planet” in our Solar System, and, unfortunately for those of us who studied astronomy before 2006, no, it’s not Pluto. There’s a new Planet Nine on the block, although no-one has ever seen it and we don’t actually know if it exists.

Yes, some scientists think there may be another, unseen planet in our Solar System. How can they think that?

Why haven’t scientists seen Planet Nine yet?


In our solar system, planets are generally considered to be visible things - get yourself a 12-inch telescope and you can see Pluto, and that’s not even a planet any more! So yes, it sounds daft to say that there’s a whole other planet in our Solar System that we haven’t seen yet, but, in our defence, it’s very far away.

Planet Nine is thought to be a trans-Neptunian object - a minor planet that orbits the Sun at a distance further out than Neptune. Both the Kuiper belt and the Oort cloud are included in this region, and Planet Nine is thought to orbit somewhere between the two.

An artist’s rendering of the relationship between the Kuiper belt and the Oort cloud
The Oort cloud is a spherical region of icy debris thought to surround the Solar System. Although it was thought to extend from 5,000 to 100,000 Earth-Sun distances, it may start much closer to the Sun. Image credit: NASA and A. Feild (Space Telescope Science Institute)


Why do scientists think Planet Nine exists?


Monday, 15 August 2016

The Search for the Graviton

What holds the world together? It sounds like a simple question - but it isn’t.We know of four fundamental forces of nature that seem to be doing the job, but have only found three exchange carrier particles (particles which give rise to the forces between other particles). Physicists like symmetry, and we like to think that the universe does too. Faced with the scenario of more forces than carriers, it is natural for a physicist to assume we’re missing one.

So far, we have found photons, which carry the electromagnetic force (which describes the interactions between charged particles); W and Z bosons, which carry the weak nuclear force (responsible for radioactive decay); and gluons, which carry the strong nuclear force (which holds the nuclei of atoms together). But what about gravity?

A diagram outlining the interactions between fundamental particles according to the Standard Model.
Not all types of elementary particles interact with all other types, and only some fundamental particles interact with particles of the same type. For example, photons do not (directly) interact with other photons, or with gluons. Image credit: Public domain

This idea is summarised nicely in an article by science writer Brian Koberlein: in quantum field theory … [you] start with a wave form and then ‘quantize’ it, you break the wave down into the smallest amounts of it that can exist (for example, photons are quanta of light). This has been used with photons, and doing so with gravitational waves leads to the idea of gravitons.

However, this approach encounters some problems when tackling gravity. General relativity tells us that that gravity and the curvature of spacetime are intricately linked. As matter travels through spacetime it causes spacetime to curve around it, and as spacetime curves, this tells matter where to move. It is this motion, caused by the curvature of spacetime, that can be considered ‘gravitation’ [8].

Friday, 1 July 2016

How were Mars’ moons formed?

The formation of Deimos and Phobos, the moons of Mars, is still somewhat of a mystery. They were discovered by Asaph Hall in 1877, and observed in 1971 by Mariner 9, a NASA spacecraft orbiting Mars[1]. Although not the smallest moons, they are much smaller in comparison to Mars than Earth’s moon is to Earth.

Color composite of Phobos and Deimos
Deimos and Phobos have mean diameters 280 and 154 times smaller than Earth’s moon respectively. Images courtesy NASA (Phobos) and NASA/JPL-Caltech/University of Arizona (Deimos), composite by TWDK

Possible Theories of Formation: Asteroid Capture


Despite being known for so long, there is no accepted theory regarding their creation. They appear to be made of “...carbon-rich rock mixed with ice”[1], and are oddly shaped, which led to the idea that they are captured asteroids. This would also explain their heavy cratering and small size.

An asteroid is captured when it passes a larger mass (in this case, a planet), and is “caught” by the planet’s gravitational field and is forced into orbit. This means that the orbits of captured asteroids are expected to be very eccentric ellipses, meaning that the asteroids pass close by before swinging out further away. The orbits of Phobos and Deimos, however, are almost circular. Because of this, we can’t consider asteroid capture to be the definitive theory of the formation of Mars’ moons.

Monday, 20 June 2016

Introducing Alice

Hello all, I’m Alice and I’m the new SEPnet intern at Things We Don’t Know. I’ve just finished my third year studying physics at Royal Holloway, University of London, so I’ve just got my masters year left to go.

photograph of Alice Wayne

My interest in physics started in secondary school when I was taught about fundamental particles and forces. At that time, science had found neither the Higgs boson nor the Graviton, and I decided then that I would study physics and contribute toward the search. We’ve now found the Higgs boson, but as the Graviton still eludes us, I am writing my Research Review on the work that has been done so far at CERN to find it, or at least, to find where it isn’t.

Saturday, 18 June 2016

The Case of the Jumping Carbons

Imagine you are inside a nuclear reactor, a UK design. Not only are you inside it, but you are part of it; a carbon atom inside the graphite core which houses the control rods and fuel rods (the ‘moderator’). Around you the environment is glowing with heat and radiation, all given off in the splitting (fission) of uranium-235 nuclei. The temperature of 450°C is no problem, and you remain tightly bound in a lattice arrangement with your fellow carbons.

However, when the uranium nuclei split, they spit out more neutrons which pelt towards you at high speeds. One slams into you, and you slow it down, as is your job, so it travels at a suitable speed to cause more fission events. In this process you absorb the neutron’s energy, and get knocked out of your slot in the lattice. You whiz towards your fellow carbon atoms, knocking more out of their spaces like a billiard ball, wreaking havoc in the strict order of the graphite crystal. Eventually you transfer all of your extra energy to your neighbours and come to rest, filling a vacancy left by another displaced carbon or squeezing in between the orderly lattice layers (as an ‘interstitial’). Here you wait, ready to absorb the excess energy of the next neutron. The upheaval is routine to you, as during your life in the reactor you may switch places up to 30 times.

A finite element model of a graphite sample and how the model behaves when irradiated or heated. Image credit: Dr Graham Hall. Manchester University

This is just one atom, but what are the consequences of millions jumping around like this?


Well, the effects are unpredictable. The radiation barrage that the graphite endures can cause it to change its material properties; its thermal expansion, strength and even its dimensions, in strange ways. Even to the human eye, these changes would be noticeable. The moderator can change shape by up to 2%, depending on the grade of graphite; a surface that started smooth may finish rough. The dimensions may warp so that the control rods used to restrain the nuclear reaction may no longer fit into their channels. It is clearly important to completely understand how the graphite will change when designing new reactors or maintaining the existing ones. The problem is that we don’t.

Sunday, 12 June 2016

Face blindness

How do we recognise faces?

Most humans can recognise hundreds of faces, and tell the identity of each one, even in different lighting conditions or when someone has changed their hair colour or aged considerably. But how this works, and how our brain codes for individual people’s identity isn’t known. I spoke to Dr Meike Ramon from the University of Glasgow and University of Louvain, who studies face recognition, to uncover why we still don’t understand this seemingly simple ability.

One famous study using single cell recordings from people undergoing brain surgery claimed to discover a ‘Jennifer Aniston Neuron’[1]. The neuroscientists believed they had found a neuron that responded specifically to pictures of the movie star, suggesting information about the identity of a face may be stored in a single cell. However, these findings should be taken with caution. First, an experiment is always limited in terms of the number and type of stimuli it can test for. Second, we don’t have enough individual cells in our brains to assign one to each of the people we have come into contact with, meaning it can’t be as simple as one cell for each person. It was also discovered that the so called ‘Jennifer Aniston cell’ responded to information relating to her, as well as images, suggesting identity is more complex than was first thought.

Prosopagnosia, or face blindness, is an impairment of the ability to recognise faces that have been seen before.
Image © Yelisa van der Bij (CC BY)

Since the invention of brain-scanning techniques, researchers have tried to find regions of the brain that are involved in face processing; probably the best studied of these is the Fusiform Face Area (FFA)[2]. But while this area is activated more when subjects are looking at faces than at other objects, it is also activated in chess grand masters viewing chess board layouts[3], suggesting that the area might be engaged when looking at anything we are experts in, which for most of us includes faces. It also shows increased activation towards curved and symmetrical images[4], leading to the idea that this area is involved in extracting global patterns for discrimination. As important as this region may be, it is now clear that it alone is not sufficient for face recognition, which seems to depend on a network of regions[5].

One way of studying our normal ability to recognise the faces of people we know is to look at people who don’t have this ability. These people suffer from a condition known as prosopagnosia, or ‘face-blindness’, which can be present from birth or brought on by brain damage. While they may be unaffected in other areas of cognition, prosopagnosia cannot recognise celebrities, their loved ones, or even themselves without using other clues like voice and posture. This is an ability most of us take for granted, but losing it can have a huge impact on a person’s life.

Monday, 16 May 2016

Solanezumab and Alzheimer’s

If you had been sitting in the main room of the 2015 Alzheimer's association international conference, you would have heard a remarkable announcement: a drug - Solanezumab - has been found to delay the course of Alzheimer's disease. Now that is a rare thing - 99.6% of all drugs designed to combat Alzheimer's have failed in trials since 2002. Just four have been approved for use. None of those four target the underlying cause of the disease (they just ameliorate the symptoms). But Solanezumab claims to be different.

Image illustrating the effects of Tau molecules on neurons courtesy NIA
The “plaques” and “tangles” found in the brains of Alzheimer’s patients are caused by two proteins behaving abnormally; beta-amyloid is thought to usually be involved in neuronal development, but in many Alzheimer’s patients the protein is not processed properly. The incorrect processing leads to a build-up of large amounts of beta-amyloid as the protein loses its solubility. The higher concentrations lead to this protein creating large aggregates known as “plaques”. “Tangles” are instead caused by the protein “tau”, which in Alzheimer’s patients has too many phosphate groups added to the protein, this makes tau clump together within the nerve cells.[3] Image credit: National Institute on Aging (public domain)