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Physics A-Level

Finally, An Interstellar Visitor – But where did it go?

12/10/2018

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Our first interstellar guest made its appearance last year in October (2017) when telescopes searching for near-Earth asteroids noticed an object with an odd trajectory. Following the discovery, astronomers turned their telescopes in the direction of the aptly named ‘Oumuamua (Hawaiian for “first distant messenger”, being detected in a Hawaiian astronomical observatory).

As data came in it became apparent that this is no ordinary rock. Large variations in the object’s brightness suggested that ʻOumuamua was rotating and tumbling and that its shape was highly elongated; with as much as a 1 to 10 (diameter to length) aspect ratio i.e. think ‘long grain of rice’. When ʻOumuamua was pointing its long axis directly at Earth it’s brightness dropped significantly, when the flat side faced Earth the brightness was highest. A highly elongated shape was the only model fit that could explain the variation in brightness.

No object of such a description has been observed in our solar system before, calling in to question the object’s origin. It is dark red, showed no signs of a comet’s tail (although jets of gas have been observed emanating from it’s surface), has a high metallic content and is moving very fast. So fast, that it could not have originated in (or near) our solar system. SETI even spent time looking for radio signals down to the strength of one tenth of one mobile phone and heard nothing...

Furthermore, infrared imaging can give information regarding the objects temperature, from which its shape can be indirectly inferred. NASA’s infrared Spitzer Telescope was pointing towards ʻOumuamua for more than 30 hours but could not detect it, suggesting that the object was cooler (or more reflective) than expected. How so?

It is suspected that as the object passed close to the sun it could have developed an icy coating, removed dust and refreshed the surface which would have increased it’s albedo (basically its reflectance), making it undetectable to Spitzer. This is highly unusual, although sometimes detected in comets (although ʻOumuamua has no comet tail, despite coming close to the Sun). Rocky bodies like this, travelling for (possibly) millions of years unimpeded will be very cold in interstellar space, possibly only a few degrees above absolute zero. In fact, the likelihood of even coming close to our sun is quite stupendously low, hence, astronomers being rather excited*! Another observed phenomenon was outgassing which is often seen in comets. This is when gas is released through the surface of the object as it heats up as pressure builds up within the object (like a pressure cooker releasing steam). Is it a comet or an asteroid or a space-faring alien-craft hell bent on invasion? Nobody can say for sure. However, ʻOumuamua has undergone somewhat of an identity crisis as scientists still aren’t quite sure how to classify it.

And as quickly as it came, ʻOumuamua is disappearing. This odd object is gravitationally misbehaving i.e. it’s not following it’s predicted gravitational trajectory. A number of theories have been suggested to explain this, such as outgassing jets that push the object around and/or solar wind (essentially photons) being responsible for the added acceleration. All this adds to the mystery of this most intriguing object! The likelihood is that soon it will be lost forever… au revoir ʻOumuamua.

*I make note here that alien enthusiasts have had a very exciting time following ʻOumuamua’s discovery. You've got to love alien enthusiasts (keep up the good work!)

Photo from NASA Getty images.

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Is General Relativity the Final Stop?

11/18/2018

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100 years on (or so) is General Relativity the only player in the game?

I recently attended a lecture by esteemed physicist Prof Clifford Will in honour of Einstein's landmark contributions in understanding how gravity works. The title of the lecture was "was Einstein right?", now that's a catchy title! However, being relatively (no pun intended) up to date in the field I was trying to see whether there will be any new information around that's not caught the media attention. And, I'll say, some things were quite surprising, other things, merely consolidating.

As far as theories go, General Relativity has stood the test of time to describe (and predict) relatively accurately, many phenomena that are observed in the universe. Some of the parameters that the theory predicts come out extremely precisely. Prof Will spent quite some time explaining some experiments that have really honed in on the precision of many astronomical measurements to confirm many of Einstein's predictions. Recent measurements of gravitational waves which led to the Nobel Prize in 2017 and the discovery of the Higg's Boson (and subsequent Nobel Prize in 2013), have contributed to a renewed excitement in the whole field.

In the lecture by Prof Will he spoke about a whole host of added effects that General Relativity predicted but were too difficult to measure, until recently. These do not discredit the theory at all, but make small corrections to Relativity; think of them as small perturbations to the theory. This is done in many areas of science: you take some standard model for something and make small corrections to account for some factor and refine the theory over time. I'll give a layman's example:

You input your current and final destination on Google maps (or Waze... or take your pick) to find out how long it will take to get from X to Y by car. "Simple" says Waze, "take the shortest path and the speed limits of those roads and calculate the travel time"... "hold on a minute" says Waze, and will then adjust this time for actual average speed, traffic, unexpected events, road closures, cars stopped in the road, accidents, police presence, donkey in road, etc. etc. So you have a general rule (accounting for distance, velocity, time), but then many perturbations to make the final result more accurate (correction: you cannot currently enter 'donkey' in to Waze).

So, it seems, that General Relativity, can now account for frame dragging, rotating bodies, wobbling/spinning giant bodies, and others. But, does this fundamentally change anything in Relativity itself? Probably not, says Prof Will. What is remarkable however, is how Relativity has stood the test of time and, as far as I can tell, also stands up to the predicted perturbations that the theory could never measure when it was initially formulated.

This is a key ingredient in science: predictive power. A good theory needs to be able to predict the outcomes, and path the way, for future observations and discoveries. So in this regard, General Relativity is doing pretty well. Are there many unanswered questions? Plenty. Is General Relativity the final stop? Probably not.

I went up to Prof. Will after the lecture and asked him whether there were other contending theories that could usurp Relativity, or totally change our paradigm (much like Einstein overhauled Gravity, in the wake of Newton). Prof Will was unsure. However, there are plenty of very very (and also VERY) unknown things in the universe to date. There is currently no knowing how big a part those things will play in the sum total of our understanding of the universe at large. Some players include: quantum gravity, dark matter, dark energy, the edges of the observable universe, inflation, black holes, etc. We cant know, maybe you do?!

In any case, one very very (and may I say VERY) subsidiary positive that has come out of all of this is that major blockbuster films like Interstellar can make excellent graphic work of gravitational lensing around supermassive black holes (see image)!
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"Formidable" Flying Seeds

10/24/2018

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The new mechanism of flight has been discovered… in plants! Plants find all sorts of ingenious ways to disperse their seeds. This work, spearheaded by Naomi Nakayama of the University of Edinburgh, landed them a paper in Nature. The paper describes and explains the fluid dynamics of a mysterious vortex that is generated above a falling Dandelion seed. This vortex is purported to assist in its flight and is the first of its kind to be seen.

You can read the abstract of that paper here. An abstract is the blurb that comes at the beginning of every scientific paper that summarizes the work in a nutshell, or a seed shell (sorry bad joke, I know!). Normally the abstract is open source and available to all. I thought I’d provide commentary on that abstract in a fuller prose. Here’s my expanded version of that abstract:

“There are a huge variety of methods of dispersal of plant seeds, from microscopic to very large. Fungus’ disperse their ‘seeds’ via spores, and pollen in flowering plants are microscopically small. Compare that with large seeds of fruits which are distributed by falling or by animals eating them and releasing the seeds, somewhere far and wide, in their feaces. Somewhere in the middle you have seed dispersal through adaptive flight mechanisms… seeds with wings! The common dandelion uses a bundle of bristles which enhances it’s drag and keep it aloft to be carried by the wind, which is effective “over formidable distances” i.e. ‘far’ (but its catchy to write “formidable distances”!). BUT… nobody knows how on Earth this happens (or anywhere else, for that matter). Here, for the first time, a vortex is visibly detected above a dandelion seed in flight (in it’s ‘wake’). Air passes through the bristles causing the vortex to emerge as a separated entity above the bristles themselves. The vortex left in the wake, being separated, serves to stabilize flight; unlike a solid disc whose wake is normally ‘attached’ to the body-in-flight. Two factors affect this separated vortex formation: 1) size/radius of the disc of bristles, 2) density of bristles (which they call ‘porosity’) i.e. ability of air to flow through it. These two are precisely ‘tuned’ to maximize the amount of seed that can be carried (“aerodynamic loading”) whilst using the least material (i.e. using bristles and not a solid disc). This new discovery is evidence of a new class of fluid dynamic behavior and could help explain the methods that living things utilize to carry seeds and other biologically relevant material across stupendously FORMIDABLE distances.”

This work was (almost certainly) inspired by Inspector Gadget, but I somewhat doubt that he knew how his flying-thingy worked. I think someone should tell him.

(The dandelion photo is from the paper in Nature here, and can be found on a google search! Inspector gadget from here, from DHX media) 
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Unmasking Jupiter: Peaking within...

10/16/2018

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The striking banded zones of Jupiter were observed (and drawn!) 300 years ago by Cassini, shortly after the advent of the telescope and Galileo’s pointing of it skyward. The mystery of the origin of these belts have subsisted ever since. Questions surrounding them, and the eminent ‘red spot’, have given rise to more sophisticated formulations of those earlier questions: What is the dynamics of the storms that rage in these bands? Why are they different colours? How deep do these jet-streams go? What causes them to flow? How does their structure change over time? What is the internal structure of Jupiter and is it related to the structure of these bands? Can some basic principles be used to model the experimental data to forecast how other gas giants may behave?

I recently attended a talk by a scientist working on the (FABULOUS!) Juno project, spearheaded by NASA. In light of new data from Juno, a number of these questions can be tackled for the first time.
Interestingly, Jupiters’ jet-streams run across the gas giant in bands than flow in opposite directions (antiparallel) and are asymmetric in the northern and southern hemispheres. The size, speed of flow and number of bands are related to the radius and mass of the planet. Current modelling of these parameters gives insight to the internal fluid dynamics of the gas planet, but lacking the necessary data regarding Jupiter’s interior, much speculation still remains.

Now though, close fly-bys allowed Juno to collect the necessary data near the surface of Jupiter to detect subtle differences in gravity. These differences in gravity are highly correlated with the inner workings of Jupiter. The deeper the jet-streams, the more mass they contain, the greater the gravitational field signal. They were able to correlate the gravity data with the dynamics of the weather layer and found that the weather layer goes much deeper than expected. On Jupiter (radius ~ 70,000km) the weather layer is about 3000 km deep and contains about 1% of the total mass of Jupiter, compared with Earth’s atmosphere which makes up 1 millionth of the Earth’s mass.

Another finding was that, underneath this weather layer there was a layer that rotated as a rigid body; and work is underway trying to determine the interplay between these two layers. What came first and how do they interact?

Scientists await crucial data that will be able to tackle another long-standing question regarding Jupiter: what is the nature of it’s core, if it even has one?! Current understanding suggests that Jupiter contains a diffuse core, one that does not have a well define boundary, but rather extends from the centre of the planet and is somehow mixed with other layers. However, the way things are going, and with the regular surprises that Juno is delivering, we’ll have to wait and see.

This is groundbreaking stuff! Looking forwards to hearing more from Juno and their team.

Follow Juno on Twitter
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"Scientists, what are your dirty secrets?" (part 3/3)

9/16/2018

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Part 3 of 3 ...

  • Some scientists mentioned that there are some initiatives underway to make all data available on big data servers. By making all data available (the good with the bad, the logic goes), this would make the field more transparent… I personally think this is a difficult idea to swallow since a very large data set would need an accompanying document of instructions that is so large it becomes prohibitively undo-able. One theorist present, for example, uses a 3 month continuous slot on a super computer to calculate some energy/electrical consideration for a highly complicated surface/molecule/interface/interaction… Good luck sending that in to the ether… Scientists would then have to contend with merely being heard above the background noise.
 
  • One scientist said that science should be presented as a ‘narrative’ story. It “needs appeal”, otherwise it wont gain traction. This appeals to basic human instinct. If a scientist ‘takes me on a journey’ in a lecture or a scientific paper it is not only easier to follow, it helps parameterize the whole field in context of other works. Some erred on the side of caution: “we don’t need to tell stories, those who are interested will read it anyway”… I personally don’t think it works like that. 
 
  • The scandal of ‘authority’. Everyone agreed that ‘authority’ is meaningless i.e. your reputation as a scientist has nothing to do with the number of papers you publish and in which journals. Rather, on the science that you do. Everyone knew, from reading the literature in their own field and in conversation with scientists themselves, who were the ‘good’ and ‘bad’ scientists in their field.
 
  • The issue of ‘h-index’ is a really sour point. H-index is a modern analysis technique that ranks a scientist’s impact in the field based on how many citations they have per publication (more or less). This index is (partially) socially constructed, and follows algorithms, which leads some scientists to play the game of “how do I boost my h-index” without necessarily being a good scientist. One scientist told me afterwards that both extremes of the h-index are suspicious i.e. you could have an h-index of zero which could mean that you are a closet genius with the best science ever but no one has ever heard of who you are (and never publish your work) or you are a loser in your mother’s basement. Conversely, you could have the highest h-index in the world which could indicate that something must be going wrong i.e. you wrote one paper which, for trending reasons, people are citing and re-citing, but you yourself are not actually the greatest scientists in your field.
 
  • All of these discussions led some scientists to demand the ‘abolishing’ of h-indices (that will never happen… computer algorithms exist, get over it) but others merely said that we should just ignore it – and that’s what most scientists do. H-indices have SOME meaning, but it shouldn’t be the final arbiter of any faculty position decision.
 
  • HOWEVER, and a big however it is… young budding scientists are facing a problem. They NEED to publish in high-impact journals to get positions at universities and in many institutions, they have to play this game. It’s mostly the ‘better’ research institutions that can see past this. A few scientists present admitted that this is exactly what happened to them. Hmm, what to do?
 
  • One scientist said that researchers need get out of the habit of only using your own highly specialized technique. Perhaps the best way of ensuring that your results (as) closely (as possible) resemble a scientific ‘fact’ is to approach the problem from multivariate angles, methods, techniques and theories. The sum total of all of these should paint a clearer picture for everyone. Promisingly, good scientists do this, although it did serve as a warning to everyone.

  • A number of scientists commented on the difficulty of the review processes. When a scientific paper is submitted to a journal, the journal asks experts to critically review the work. There is normally an amount of time that they get to work on it. This is hard. Some papers need real consideration, and its not always possible to check every single word, figure and reference. Do you not review this paper? Review it poorly? Or spend more time on it that you are paid for!? These are difficult questions, and the pressure lead to mistaken outcomes. One scientist commented “I received a paper to review and another reviewer let the paper sail through because he respected the researcher…”, alarm bells ringing anyone?! People need to wake up!
 
  • High impact journals (like Nature and Science) don’t guarantee that the work is great quality. Some scientists admitted that their best papers were in journals that were more specialized, with a unique readership.
 
All in all, it was fascinating to hear about these issues. So many of which may seem subsidiary, and out of the remit of science, but they present real problems that serve to bottleneck the scientific endeavor. Its why budding scientists need to be pragmatic and smart about their science.

Don’t stick to your comfort zone. Try many things. Understand that politics is unfortunately interwoven with science in many ways, and that to get ahead you need to be steadfast in your scientific convictions.
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"Scientists, what are your dirty secrets?" (part 2/3)

9/13/2018

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... So what were my observations .....

  • Reproducibility. This is desirable all across science and there are a number of reasons that make it important. Experiments stand or fall based on whether they can be reproduced. However, often, the precise conditions of measurements are not clearly stated (and often absent) in scientific papers. This, as well as the inappropriate control measurements. Some scientists complained that (like the current status in popular media) 'new science' is sexy and journals will often publish something very exciting at the expense of quality. Essentially, time is the arbiter of whether a piece of science gains acceptance. One person suggested that a repeat experiment (of another group) should be published in an open source format (very simple to do), and builds on the credibility of the experiment or theory.
 
  • Nothing is measured in isolation! Whether you’re measuring the conductance of a single molecule or the vibrational modes of a crystal or the reactive nature of an enzyme you are using tools and instruments. Those tools are limited and in some cases, in certain fields, measuring the ‘same thing’ in a different set up can yield different results. A scientist’s job is to be transparent about methods. Some groups, however, when publishing breakthrough work, withhold methods to block others from entering the field; it gives them a grace period before others can be involved in that same niche of experiments. It’s important to control for your experimental method, by measuring in different ways.

  • Practically speaking, scientific groups, however, cannot publish a repeat experiment of another group (no journal would do that). This is where conferences are important and scientists DO tell other scientists "we cannot reproduce your results". The result of this is either: 1) more details are needed in that experiment, or 2) the experiment was flawed. Both are possible...

  • Issue: every scientist will select interesting data to publish. But don’t think that scientists are being misleading by doing this; most/many (?!) are responsible and publish what their experimental yield is, so you can judge for yourself. "Yield" is essentially what percentage of the time does your 'stuff' actually work, but must be carefully defined (!) e.g. “my experiment showed cool stuff 10% of the time” is different to “of the 100 experiments, 10 showed something but only 1 showed cool stuff” –both could be presented as “10%” yield: be careful. ‘Yield’ is also analogous in our everyday lives: How much of your own work day was productive that you would report it in a minute-by-minute report of what you did?

  • In science, often the things that DON'T work, are very very important. In my own work, I'm quite certain that I've repeated failed experiments of scientists of the past, which was perhaps avoidable had I known that it’s been tried before. In fact, I remember finding an old lab book from 15 years ago (in our lab) and finding details of a failed experiment that I was just about to do myself! This is why its important to speak with others who are in the field to see what they’re doing, what they’ve tried and paint a vision for the future.

...... to be continued
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"Scientists, what are your dirty secrets?" (part 1/3)

9/12/2018

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(Part 1)

"Ok everyone, gather round", said a conference organiser to the lecture hall of scientists. "We'd like to end by doing something different today. There is some really high quality science coming from all around the room, but I'd like to open a discussion in to those things that we never talk about"... "lets say... what could be considered to be the 'dirty secrets' in your field?"
 
I attended a scientific conference this week on the topic of surface spectroscopy and electrical phenomena. Experts from around the world presented their work in quite a wide range of experimental and theoretical topics. It was one of hundreds of small, specialized conferences, that unassumingly occur all over the world. However, from my judgement, in discussions with other scientists and general reading, the outcomes at this conference seemed rather ubiquitous in scientists’ criticism of… science.  
 
So how does ‘science work’, practically speaking? Peer reviewed journals are a great way of getting good science out in to the scientific community; other experts anonymously review your work, and with the appropriate additions and corrections you can publish and advertise that to the world. Conferences serve as another great venue for science. You can share ideas, collaborate, network, present your finding and get a critical analysis of your work. I've been to some conferences where the question and answer sessions were pretty brutal. Normally, in the good spirit of science, this is positively encouraged, and is mostly done well.
 
But is there anything really 'off the table' that cannot be (or isn't) discussed in a scientific setting? Are there dogmatic truths about the way science is done, published and disseminated to the masses? Is all data published? SHOULD all data be published? Is there an issue with reproducibility? What if two lines of solid experimental evidence directly contradict each other? What are the external factors hindering good science and how can they be addressed? Should we expect scientists to be moral? With whom does the burden of checking for faulty science, lie?
 
All these questions (and more) were posed at the conference that I attended. I would say that most of the scientists knew exactly what was being referred to... And always with many disagreements! Some of my conclusions will follow shortly...
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Hubble, a window in to the past

8/25/2018

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(Hubble image found here)

There is a way of actually looking in to the past. We do it every time we look up at the sky at night. The star light that you see now was released from stars many years ago. If you look up at the Sun (highly un-recommended) you are viewing the light that it released 8 minutes ago (i.e. it is 8 "light minutes" away from us). If you look at Alpha Centuri (highly recommended), our next nearest star (actually a ~ binary star system), you are seeing the light that it released ~ 4 years ago (i.e. it is 4 light years away).

This very cool, and somewhat disconcerting. Where the heck are we in time?! There are some stars (like Betelgeuse, a super red giant in the Orion constellation) that are at the end of their stellar life cycle (don't worry... still another ~100,000 years). Betelgeuse is ~ 700 light years away and is in it's last stage in 'life'. Therefore, even if it exploded 600 years ago we wouldn't know it for another 100 years; it takes time for that light to reach us. Being relatively near, a Betelgeuse supernova, would shine as bright as a quarter Moon and would rise to peak brightness over a couple of weeks and then fade...

So the question/s is/are: how far back can we see? I see the Sun now as it was 8 minutes ago, Alpha Centuri as it was 4 years ago and Betelgeuse as it was 700 years ago. If we take very powerful telescopes, can we see the light from ancient galaxies? The early forming of galaxies? Or the beginning of the universe itself...

Now suppose you hold up a window at arm's length the size of a grain of sand. Suppose that window is a powerful telescope. One of those powerful telescopes is the Hubble telescope and it's observations are staggering. Using high magnification and a long exposure the Hubble telescope spends a couple of weeks gathering light from a minuscule portion of the sky. The images captured peer across time at some 15,000 galaxies. The red-shift (resulting from the expanding universe) of some of those galaxies are such that the light from them was formed ~ 13 billion years ago. That is a mere 500 - 700 million years after the start of our universe! Answer to our initial question: We can see galaxies now that are literally 13 billion years old! And that's not akin to 'a human memory' (an interpretive mapping of our current being to a past experience), what you see in that Hubble image above, is (for all intents and purposes) an image of the past.

So although there are ~100,000 stars in our galaxy, the Hubble image shown above looks past the stars in our galaxy only showing (at my counting... correct me if I'm wrong!) about 10 individual stars, the rest of those different coloured dots (15,000 or so) are galaxies. WOW.

But there is an elephant in the room. How are there 15,000 galaxies in the Hubble image of a region of the sky that is the size of an image through a grain of sand at arms length?! Conclusion: There are a vast number of galaxies in our observable universe estimated at 200 billion to 2 trillion galaxies.

This should lead us to wonder, speculate, ponder, fascinate at, revere, be astonish at, be curious at, amazed, dumbfounded, flabbergasted, impressed and truly humbled by it all.

The ability to peer in to the past, is an important tool in understanding the early universe and how it evolved. It is images like this that show a snapshot of galaxies through a continuum of time that are stretching the boundaries of frontiers in cosmology.

The universe. Our living quarters. Home. In a cosmic sea, living on our pale blue dot.

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The image above was released by NASA on 16.08.18 as part of the Hubble Ultra Deep Field project.
Another important early universe/Big Bang observation is the cosmic microwave background radiation, which detects the microwave remnants of energy released from the big bang. Stayed tuned, for another post on this soon (hopefully!).
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Pin a Spider Down, Harvest it's Silk... Not any more!

8/22/2018

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Spider's silk is one of the toughest and strongest materials around, outperforming many synthetic polymers and metal alloys in standard mechanical properties. Aside from being very strong, they are lightweight and very thin (!), typically a fraction of the width of a human hair. So whats the problem in using spiders' silk in high-durability medical bandaging, waterproof textiles and flexible mats for intergalactic space travel?!? Well... you try pinning down a spider and harvesting its silk. Actually, dont try that, its been done, by numerous groups! Silk is perhaps best known to be made by spiders, but, in fact, is also produced by bees, wasps, ants, silverfish (not actually a fish!), mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, midges and others (from wikipedia).

An ultimate goal in the biomimetic community (the science that tries to mimic nature to solve human problems), is to synthetically make spiders silk, without the spiders. So what's stopping scientists doing this? Farming spiders to make silk is an arduous process. Best case scenario you could get ~ 100 ft of spiders silk in one session, but then the spider would need time to feed and regenerate it's silk reserves. Options? Genetically make a monstrous spider to harvest huge amounts of silk or breed billions of spiders to do the job, or...

Spiders' silk, like many biological materials, are  composed of a hierarchical structure. In a simple sense, spiders' silk is a spun protein fibre. It has long been known that the size of the protein units within the silk correlates with the strength of the silk; larger proteins generally means stronger silk. However, natural silks have a limit in the size of the proteins that they use; for whatever evolutionary reason this has happened...

For human purposes, it was proposed to mutate the spiders' DNA, insert it in to bacteria (poor things) and force those bacteria to make the desired proteins (this actually happens routinely in a biological lab). However, bacteria (I don't blame them!) cannot make such large proteins; it's been a running problem in biochemistry for some time. What the scientists did, therefore, was insert a DNA segment that would chemically fuse two smaller silk proteins to form a single large protein unit. To their joy and adulation, they succeeded. With protein in hand (or actually 'in dish') they spun these synthetic proteins in to a silk and found that they performed as well as natural silk, in terms of tensile strength, toughness, elastic modulus and extensibility!

Being able to make silk without a spider is a really promising prospect. Now that scientists can modify the protein size (and composition) within the fibre and use bacteria to produce the desired silk it leads to a whole host of possibilities in making future materials with enhanced properties.

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The image above was taken from a Business Insider video over here.
An interview of those scientists can be found on Science Daily.
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Showering with Meteors

8/20/2018

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Last week I climbed atop a hill in a secluded country park and gazed skyward. The seemingly ever-static black canvas was anything but. To the untrained eye mere dots of white peppered the sky and that's that; a friend pointed out a plane (well done). To those with an astronomical bent: bright red Mars, Venus and Jupiter all came to say hello. Binoculars and telescopes pulled galaxies, stellar clusters, nebulae and an assortment of stars ever closer.

The prized guest, however, lay in the dead trails of an ancient icy beast. The Swift-Tuttle comet was 'discovered' in 1862 but possible reports of this comet come as early as 69 BC. With an orbital period of ~133 years this 26km diameter comet sheds it's icy shell when in close proximity to the sun; warming, melting and flaking. Comets' origins are not fully known although using the velocity, mass and trajectory of many known comets it has been shown that they emanate from two icy regions outside of our solar system known as the Kuipier belt (for short period comets) and the Oort cloud (long period comets). Projects are still underway to determine the nature of those regions, their structure and how they got there in the first place. (As a point of reference, Pluto (~1,200km diameter) was reclassified as a dwarf planet, and is the largest member of the Kuipier belt family).

And so, every 133 years Swift-Tuttle leaves a trail of dust and ice in it's wake and summarily returns to it's lair in the deep (probably the Kuipier belt), gathering strength (basically ice and dust again...) and will visit us again in the year 2126.

As chance would dictate, our precious Earth, every year, passes through that trail of ice and dust. The Earth is already travelling at 30km/s around the Sun! So when comet debris enters the Earths atmosphere it heats up and we observe that as a bright arrow across the sky.

It's really quite beautiful. And rather personal. The light from a meteor is only momentary, normally less than one second. You cannot predict where exactly it will emanate from, and, if in a small crowd, you could be the only person who sees it, to the annoyance of everyone else! After about 1hour and ~30 meteors later (...and a nice hot cup of tea), we headed home to sleep.

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The image is accredited to Fritz Helmut Hemmerich and featured on Astronomy Picture of the Day 12.08.18. It shows an unbelievable long exposure shot of the Andromeda galaxy (our closest spiral galaxy) and captures a Perseids meteor shooting directly across it, marvelous.
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