Sunday, 8 November 2015

The implications of finding a Dyson sphere

By George Thomas

Many people will have recently heard of the potential discovery of an artefact of alien intelligence around the star KIC 8462852 (If you haven’t, read here for more info Further recent study of the star has ruled this out as an option, but it was an interesting idea. With that said, I want to talk about the potential implications of intelligent, highly advanced, alien life existing in our Galaxy.


The object that had been speculated as a potential sign of an advanced civilisation is called a ‘Dyson sphere’. Put simply, the idea is that you surround a star in a dome of solar panels to absorb the light energy emitted, to provide enough fuel to sustain your highly advanced alien race. However, surrounding the entire star in a dome isn’t very practical, for multiple reasons, but lots of spaced out satellites could work as a good alternative source for harnessing power. This concept is known as a ‘Dyson bubble’. The presence of a structure like this around KIC 8462852 would have explained the initial observations, but other explanations such as lots of comets are far more likely.

Illustration of a Dyson Bubble
Credit: Wikipedia

 A lot of news outlets had spoken about us potentially finding alien life, but what if there were aliens; would they have found us? Of course, we haven’t got a giant structure surrounding the Sun to give ourselves away, but one way we have been giving ourselves away is in how, at least for the last 100 years, we’ve been broadcasting radio waves across the Galaxy. Unfortunately the radio waves will have become so spread out in their travel that our signal will be indistinguishable from background noise beyond a few lightyears away. Also, in the case of KIC 8462852, the star is too far away (about 1500 lightyears) for our radio waves to have travelled to any potential life stationed there. Unless the species had spread out to stars much closer to our Sun, they wouldn’t have had time to pick up any signs of technology that we may be giving off.


There is, however, the Earth itself, which has been harbouring life for the last few billion years. Any intelligent beings looking out at the Galaxy with the technology to detect our pale blue dot will have been able to tell that we’re sitting very comfortably in the habitable zone around the Sun. This is especially true of any species capable of building a Dyson bubble, which begs the question: if there is an advanced civilisation relatively nearby, why haven’t they come to us?


The answer, much to the dismay of sci-fi fans, is probably the restrictions of travel through space. Although there are various theories about using wormholes to avoid technically travelling from one point to another at speeds faster than light, the entirety of physics thus far points to a constant restriction: information cannot travel faster than the speed of light.


This isn’t definitely the reason, though. An optimistic view could be that life is so overly abundant in the universe that no alien species has bothered to come to us yet. But, as said, this is very optimistic, and the inability to travel to our stellar neighbours in a time considered reasonable compared to the human life span is a far more likely reason. If they have found us, and can reach us, then they’re making an active choice not to engage with us, which would be a curious decision in itself.

This means that although we may in future discover advanced civilisations dotted around our 

galaxy, we may never be able to reach them. We may not be alone in the Universe, but we 

may well be too far away to ever see our neighbours.

Monday, 2 November 2015

The Science of Taste

By David Morris

Structure of a taste bud

In 350 BC, the Greek philosopher Aristotle postulated that varying blends of two tastes, sweetness and bitterness, comprised all flavours. As the understanding of taste developed, it was shown that sourness and saltiness were also distinct tastes. In 1908 the Japanese chemist, Kikunae Ikeda, discovered a fifth subtle and now well established taste known as umami. Until recently, these tastes were universally accepted as the five fundamental detectable tastes that made up all flavours that can be experienced by humans.

The role of smell (olfaction) in flavour wasn’t fully appreciated until as late as 2004, when biologists Richard Axel and Linda Buck discovered the role of the nose in detecting and characterising odours. When you breathe in through your nose, millions of odorous molecules activate and inhibit olfactory receptors at the roof of the nasal cavity. Electrical impulses travel from these receptors to the brain, informing you of what you’re eating. This action is supported by taste buds in the mouth.

Molecules within certain foods can chemically activate senses that are responsible for the sensation of heat, pain or touch. This is known as chemesthesis. Despite being different from taste, chemesthesis can contribute to the flavour of a substance. Examples include the ‘tingle’ on the tongue from ingestion of carbonated drinks, the feeling of heat upon eating a chili pepper, and the cooling feeling from eating gum.

 Taste receptors are mounted on papillae, which are structures found on the front and back of the tongue, the roof and sides of the mouth, and even at the back of the mouth and throat. The idea of a ‘tongue map’ whereby certain areas of the tongue detect certain tastes is a myth, although the concentration of certain receptors may vary in different areas of the tongue.

           Saltiness and sourness are the simplest of the tastes. Sourness arises from the donation of hydrogen ions, which is a characteristic feature of acids. It has been postulated that detection of sour foods defends the body from ailments like indigestion. Similarly, saltiness arises from the dissociation of salt on the tongue, forming sodium and potassium ions. The taste response acts as a warning for your body to replenish electrolytes, but not too much, hence why we find salty foods appealing, but also repulsive in large amounts.
           Bitterness, umami and sweetness are more complicated tastes. They all come from the binding of larger, more complex molecules to large proteins in the taste buds that are typically responsible for signal transduction throughout the body. Bitterness receptors can bind with molecules that are usually toxins or poisons. In this way, the bitter taste warns your body against ingesting molecules that can harm your body.

           Similarly, umami receptors detect glutamate (a component of monosodium glutamate, or MSG, a popular salt substitute), giving off a subtle savoury taste. The subtlety arises because the glutamate is usually bound to sodium, giving off a more powerful salty taste. Glutamate is useful to your body as a neurotransmitter and a catalyst to metabolism, so like salt, the taste warns your body to replenish glutamate, but not excessively.

Tomatoes are rich in umami

           In July of this year, academics at the University of Purdue published a paper in Chemical Senses describing the existence of a sixth taste called oleogustus. Usually, when the body ingests oil or fat, it is in the form of triglyceride, a molecule comprised of three fatty acids chemically bound through a glycerol molecule. This triglyceride is too large to fit into oleogustus receptors and thus can’t be tasted. However, when the fat spoils, the triglyceride is broken down into glycerol and the fatty acids. The fatty acid then binds to the oleogustus receptors and acts as a warning that the food is no longer suitable for ingestion, hence it smells and tastes rancid.
           Each of the aforementioned tastes, as well as the olfactory and chemesthetic systems, have proven essential for the body to be able to consume the correct amount of different types of food, and to protect from ingesting harmful toxins and poisons.

Friday, 30 October 2015

At-Bristol's New Planetarium!

By Laura Rogers

At-Bristol has recently undergone a million pound re-vamp of its planetarium, and I was lucky enough to attend one of their 3D shows.

As the show began, we were told about the extent of the upgrade, and were soon launched from the Earth, with our first view being of the Earth from space. Considering the fact that I get travel sick, so would prefer not to be launched into actual space, this was the closest I will ever be to seeing the earth from above our atmosphere. It was a breath-taking moment, as the three dimensional effects of the planetarium made it feel so real. You could hear the “ahhhh” of the audience as we all stared in amazement.

We then began virtually exploring the solar system, learning about each planet in turn; from being educated about Jupiter’s moons, to the atmosphere of Venus. I had not realised quite how toxic Venus’ atmosphere was, and if we were to actually have landed on the surface, rather than virtually doing so, we would be dead within seconds! However, what was most impressive was that all the comparisons shown were to scale and any incredible figures used were well backed up.

The show not only provided entertainment and spectacular views, but was an educational experience, and is something that I would highly recommend to anyone.

Monday, 26 October 2015

Earth's Larger Cousin

By David Morris 

In March last year, following three years of data accumulation and analysis, NASA disclosed the discovery of an exoplanet (a planet from outside our solar system) that shares enough characteristics with the Earth that it could potentially harbour life, Kepler-186f. Discovered by the Kepler space observatory, the body has a volume of approximately 1.48 x 1021 m3, just about 10% larger than Earth. Interestingly, the exoplanet is believed to show very little obliquity, the degree to which the axis of rotation of a mass tilts away from its plane of orbit. This means that it experiences minimal differences in seasonal weather. It is of comparable age to the Earth, is located roughly 490 light years away and can be found in the constellation Cygnus.

Kepler-186f is the first planet outside of our solar system discovered to have both a comparable size to the Earth and to be within the ‘habitable zone’ of its parent star. The habitable zone of a star is the range of distances from it where, given sufficient atmospheric pressure, any present water will be a liquid: a characteristic that is absolutely vital for the existence of life. Many exoplanets have this characteristic, but they are all at least 40 % larger than Earth, making them too dense to sustain life. This is the case for the other four exoplanets that Kepler-186f shares its solar system with. Their large masses draw them closer to their parent star due to gravity, making them too hot and therefore uninhabitable.

Kepler-186f orbits Kepler-186, a star half the size of our Sun. This star is known as a red dwarf, a star cooler and smaller than that of the Sun. Kepler-186f receives roughly a third of the heat energy that Earth receives, making it much less able to support life. The masses of red dwarves are generally so small that orbiting planets are likely to go into tidal locking. This process is caused by the gravitational pull of a mass on an orbiting body, compelling it to rotate at roughly the same rate as it orbits. This means that the same hemisphere is always facing the mass, as is the case for Pluto and one of its moons, Charon. This effect is also employed in getting artificial satellites to orbit the Earth correctly. Tidal locking would cause one side of the planet to be in constant ‘night-mode’ and the other in constant ‘daylight’, resulting in enormous temperature variations and therefore varying phases of atmospheric substances like water. Without a mechanism for swift planetary heat distribution, such as oceans, the planet would be uninhabitable. There is an approximately 50 % chance that Kepler-186f is orbiting its parent star with partial tidal locking. As a result of this, a single rotation of the exoplanet about its axis could take up to weeks or months, contributing to the prevalence of the aforementioned planetary temperature differences.

There are a wide range of atmospheric densities and temperatures that the exoplanet could support depending on its chemical composition. The greenhouse gases that keep a planet hot could be present in any number of concentrations, maintaining a specific surface temperature. The age of the red dwarf is also important as it will emit differing amounts of various types of radiation depending on its age. For example, if the red dwarf emits high levels of high-energy, ultraviolet radiation, as is prevalent in young red dwarves, the energy supplied could cause lighter elements like hydrogen and helium to escape the gravitational pull of the exoplanet, removing mass from its surface.

Given the information NASA has gathered, it is possible that Kepler-186f could support life. However, in order to fully determine its capabilities, the surface composition of the exoplanet needs to be examined further. Exoplanetary surface composition is very difficult information to obtain, especially for a body so far away. This is one of the many tasks that NASA is constructing the James Webb Space Telescope for, due to launch in October 2018. The telescope has been under construction since the beginning of 2011 and is planned to be sent to the L2 Lagrange point, 1.5 million kilometres from Earth, the furthest from the Earth that any man-made device has ever been sent. Consequently, the question as to whether other life outside our solar system exists may be answered within the coming years.