Sunspots And Climate Change Deniers

For over a week now Honolulu, Hawai'i, has been playing host to the 29th General Assmebly of the International Astronomical Union. Sadly this is not a precursor to Starfleet but it is still rather exciting nonetheless. The Union represents over ten thousand astronomers and the triennial meeting is always a wellspring of cutting edge space science.

On August 7th they released information about the longest continuous experiment in existence which dates back to observations taken by Galileo Galilei. It was all to do with sunspots. You see, from 1645 to 1715 there was what is sometimes referred to as a mini ice age; whist this is a factually poor description of what happened it is certainly true that winters were harsher during this period. This coincided with a prolonged trough in solar activity known as the Maunder Minimum and so it was that we have assumed for several centuries that the former was caused by the latter. Solar activity is measured by counting the number of sunspots visible on the surface of the sun at any given time: the more spots the more activity. More recent data, however, has started to contradict this hypothesis and so the whole model has come under increasing scrutiny.

This is significant because if solar activity has been steadily increasing for the past 300 years then it could go some way to explaining the warming of the planet that is such a pressing concern today. It would also mean that if the warming isn't anthropogenic (manmade) in origin then our various warnings about carbon emissions and heavy industry are incorrect. I know I personally have met people, let's call them climate change deniers, who say that us puny humans are incapable of affecting a whole planet in this way, and, that solar activity explains everything so it's fine to have a coal powered car built from amazonian mahogany. Well, the new data, which reconciles a long running discrepancy in the two ways we can count sunspots, shows that solar activity does not in fact correlate with the steady increase in global temperature that we have been observing since the beginning of the Industrial Revolution. To quote them:

'[these results] make it difficult to explain the observed changes in the climate that started in the 18th century and extended through the industrial revolution to the 20th century as being significantly influenced by natural solar trends.'

Notice that there is wriggle room in that statement, but that is because it was issued by scientists who understand that new data can always change your theory. As it goes, that is actually quite a strong statement and would be a blow to the climate change deniers if their position was in any way based on reality. So there you have it, one more line of evidence to support anthropogenic global warming, one less place for the climate change deniers to hide. Will it change any of their minds? Not a chance.

Hand drawn by Galileo himself this is one of a series of drawings that show the
progress of sunspots across the surface of the sun with time.

The Sun: Part 3 - Helioseismology

Okay, I mean it this time. This time I'm definitely going to write a post about helioseismology; no distractions. This will be my third and final attempt; my first try ended up being a general overview of the sun and its structure, my second attempt wound up being about the potential of nuclear fusion here on Earth. But now, according to the Rule of Threes, I will finally keep my promise.

For the last couple of weeks I have been reading as much as I can about the now well established field of helioseismology and the first thing I had to learn was what it even is. In my innocence I thought that there might be quake type events happening in the sun but that turns out not to be the case. If you think about it for a while, though, you can see why this would be wrong. The Earth has many different components to it, the most relevant being the lithosphere which is made up of the tectonic plates of the surface and the top most part of the upper mantle. Here, where two continents meet, you might have one subducting under another or perhaps they will be grating against each other in opposite directions. In this situation it's possible that they might get a bit stuck and every now and then they will suddenly slip causing an earthquake. Asides from the damage we're all too used to seeing on the surface this will also cause sound waves to propagate through the Earth. These sound waves will move through different substances in different ways dependent upon their properties and so you can use this to study the internal structure of, in this case, the Earth. This is a key part of what seismology is here on the third rock but we can use the same principals with the sun; there, however, the waves aren't caused by solid rock but by shifting plasma densities.

Here you can see the ripples of a sunquake radiating out from its source. In just one hour the ripple travels a distance equivalent to 10 earth diameters.

Plasma, which is basically what the sun is, is a gas that has been stripped of electrons. The sun is not a boring, uniform, unchanging sphere of plasma but a highly active and dynamic one. It is hotter at its centre than it is nearer the surface and this can result in hotter, less dense plasma rising higher amongst cooler, less dense plasma. My best interpretation of what I've read, and I could easily be wrong, is that this causes a sound wave to be produced, perhaps through friction but don't quote me on that. Either way a sound wave is created. This wave then propagates and can be detected by instruments aboard the Solar Dynamic Observatory (SDO) and the Solar Heliospheric Observatory (SOHO), both satellites orbiting the sun. The waves tend to have frequencies of 1-5 microHertz, or around five minutes and amplitudes of hundreds of kilometres. Given this we can know at what sort of speed they should move and where there are deviations from this we can infer the density of the medium through which they're moving. This has given us a great level of detail about the internal structure of the sun.

Like all good theories though, it needs to be tested for accuracy and this has been done quite exquisitely. A few years ago scientists were able to detect these sound waves some 60,000km below the surface of the sun, they then predicted that this would result in the production of some sunspots at a given location. Two days later, sure enough, the sunspots appeared. You can see a video of it happening here:

This is super awesome. Not just because it represents an advance in our understanding of an obscure branch of solar science but because it has practical implications for us here on Earth. How so? Well, the magnetic field of the sun is particularly intense where sunspots are formed and at the end of the video, as the rotation of the sun begins to take the activity from view, you can see that vast arcs of plasma, greater than the size of the Earth itself, are formed along the lines of the magnetic field. The sunspots are at the bases of the arcs where they are anchored to the surface, but if they are strong enough then these arcs can snap free and hurl matter out into the solar system. Small events are referred to as solar flares and larger ones are called coronal mass ejections (CME). These can be highly significant as they can fling billions of tons of matter into space at a time. If the Earth happens to get in the way of this then you can expect a pretty impressive display by the aurorae at both poles as the matter interacts with our own magnetic field. Nothing wrong with that. If it is an especially large CME, though, then this could play havoc with electrical equipment all over the planet.

In late summer of 1859 the largest CME on record was observed. Known as the Carrington Event, it caused the aurorae to be seen as far south as the Caribbean and as far north as New Zealand. It also, however, caused widespread electrical damage. Telegraph stations across the globe went down, some operators were electrocuted, pylons sparked and some devices that were turned off began to operate. This was at a time when we were just at the beginning of the electrical age, if this happened to us today then it could be potentially devastating. It has been estimated that the cost to the United States alone would be in the region of 0.6-2.6 trillion dollars. That is a solar storm we do not want to happen, the problem is that, eventually, it will. Estimates say that there is a 12% chance that there will be another by the year 2022 and that it is all but guaranteed by the end of the century. So it's not a matter of if but when.

Here is where the research comes in. That CME took just 17 hours to reach us from the sun. That is not much time to enact emergency procedures to protect our electrical systems, not that we actually have any such procedures as of yet. With this research though it would be possible to have at least a couple of days notice which should be plenty of time to prepare the world saving weeks of disruption and trillions of dollars - just as soon as we know how to prepare.

Perhaps the most important message to take home from this is that you never know where the benefits of scientific research might lead. There are certain groups of people cough politicians cough cough who want scientists to solve certain specific problems and will only fund research aimed at doing so. Sometimes this can work, but sometimes it won't, and what should never be discounted is good old fashioned, curiosity driven, blue sky research where you fund a scientist simply to figure something out because it's interesting. This has led to many of the most significant breakthroughs in human history, perhaps most notably in the creation of the internet. In this case a bunch of guys sat around staring at the sun, so to speak, quietly developing our notion of space weather and now we have a way of potentially saving our society as we know it. This is just one of the reasons I love science.

The Sun: Part 2

Quite some time ago, in fact just over a year ago, I wrote this post about how completely awesome the Sun is. Its awesomeness was so overwhelming that I actually got completely sidetracked and didn't even get around to writing about the topic I had intended to: helioseismology, aka, sunquakes. I said that I would follow it up with another post but it just never happened and so it is high time that I kept my word. But first, a tangent...

Image credit: BBC

Limitless, clean, affordable power. It has been the dream and ambition of many a politician, philanthropist and crackpot perpetual-motion-machine con artist; it is, however, a reality. At least in principal, anyway. But, Jason, how can this be; I hear you say. Well, it's simple. At least in principal, anyway. All you have to do is create a star 10 times hotter than the core of our sun here on Earth. Easy! This is the idea behind nuclear fusion, the opposite process to what happens in nuclear fission, which is what currently happens in nuclear reactors across the world. In fission, a big atom of uranium-235 is hit with a neutron resulting in the splitting of that atom. This produces two smaller fission products, normally krypton-92 and barium-141, and two or three other neutrons; these other neutrons are free to go and blast into another atom of uranium-235 and so you have your chain reaction. Now, heat is simply a measure of how fast molecules are moving and, given that the neutrons produced are moving very fast indeed, one of the outcomes of this reaction is an enormous quantity of heat. In a nuclear reactor this heat is harnessed like in any other type of power station to heat water which turns a turbine and so on.

Fusion is the opposite of this where instead of breaking large atoms into smaller ones we try to stick small atoms together to make bigger ones. To go into a little more detail, fusion is when we take two hydrogen nuclei and force them together to form a helium nucleus, but we don't use your common-to-garden variety of hydrogen. Most elements in the Periodic Table can come in a variety of forms called isotopes. For example, there are three stable isotopes of oxygen; oxygen-16, oxygen-17 and oxygen-18. Oxygen-16 is the isotope that occurs most naturally and makes up over 99% of what we find in the atmosphere. Its nucleus contains 8 protons and 8 neutrons; oxygen-17 has one extra neutron and oxygen-18 contains yet another extra neutron. These are all still oxygen atoms as it is the number of protons in a nucleus that determines what the element is not the total atomic mass. Hydrogen also has a number of isotopes; hydrogen-1, hydrogen-2 and hydrogen-3, also called protium, deuterium and tritium respectively. Protium is just one proton all on its lonesome, in deuterium the proton has a neutron buddy along with it and tritium... you get the picture.

So in fusion we are actually pushing together one atom of deuterium and one of tritium, this produces an atom of helium-4 and one spare neutron that goes whizzing off to make a life of its own. One of the great potential boons of fusion power is that the fuels required, these heavier isotopes of hydrogen, aren't too hard to come by. Deuterium is found abundantly in the oceans of the world, no problem there. Tritium is quite rare but it is believed that by installing plates of Lithium in the walls of a fusion reactor it can produce its own tritium as lithium bombarded with high energy neutrons will do just that. Another massive plus is that there are no radioactive byproducts produced like there is in fission reactors. The by-products are heat, which is what we want; neutrons, which we can use to produce the next round of tritium; and helium, which is great because we're actually running short of it on Earth. The radioactive krypton and barium produced in nuclear fission has a very long half life and can be expected to stay radioactive for approximately 100,000 years. To put that into perspective; 100,000 years ago modern humans were still trying to find their way out of Africa using nothing more than spears and hand axes, or to put it another way, we are going to have to keep today's radioactive waste safe until the Earth has undergone another three Ice Ages (and I don't mean the next three instalments of the popular kid's film). I wonder if the cost of that is taken into account when nuclear energy is claimed to be cheap?

Image credit: ITER

So far so simple; there is a problem, though. As hydrogen atoms comprise of a positively charged proton and electrically neutral neutrons the overall charge of the nucleus is positive and as any 12 year old knows: opposite forces attract and similar ones repel each other so forcing together two positively charged nuclei is what's known in the trade as a non-trivial problem. Anyone who has tried to push together the two north poles of a pair of bar magnets will know that this is not something they want to do; they repel each other. It was James Clerk Maxwell in the 1860s that produced the equations that show electricity and magnetism are merely two sides of the same coin, hence electromagnetism: the force that stops two similarly charged objects getting too near each other, one of the four fundamental forces of nature. The force that holds the protons and neutrons in an atom together is the strong nuclear force, another one of the four forces; the other two being the weak nuclear force and gravitation. The goal of fusion is to push the repellent atoms close enough such that the strong nuclear force overcomes electromagnetism. Put another way, in a fission reaction we use the kinetic energy of a fast moving neutron to overcome the strong nuclear force of a uranium atom, thereby releasing energy. In fusion we are trying to use kinetic energy to overcome the electromagnetism between protons such that the strong nuclear force can take over and bind hydrogen nuclei together to form a helium nucleus, thereby releasing energy.

The reason that I'm talking about this whole nuclear fusion thing in the first place is that this is how the sun works, it is a giant fusion reactor. It has been doing this for approximately 4.5 billion years and it will carry on doing this for about another 4.5 billion years at which point it will become a red giant and swallow up the Earth. If we could harness this process here on the 3rd rock then we would have that clean, limitless energy source that I mentioned earlier. Now, obviously we don't want to turn the whole planet into a pit of hell fire so we need to do this carefully and in a controlled manner. So what are the conditions we need to achieve to get fusion to work on an industrial scale? In the core of the sun, where fusion is an every day occurrence, the temperature is approximately 15 million degrees Celsius and the pressure is 250 billion bar, 250 billion times the air pressure on Earth at sea level. They're some pretty extraordinary numbers. We can actually heat things to that temperature but achieving that pressure is beyond us; to compensate we need to up the temperature. This is why, in the experimental reactors currently being built and tested, the temperature we're aiming for is more like 150 million degrees Celsius. That's a spicy meatball.

This picture of the sun is here simply because it looks amazing. Image credit: NASA

You won't be too surprised to hear that there is no substance on Earth, nor anywhere else in the universe, that could hold a cup of plasma that's 150 million degrees Celsius; it would melt, and so the trick is to create these ridiculously extreme conditions without letting them touch anything. This is done by creating a plasma and then controlling it using superconducting magnets in a torus (doughnut) shape - known as the tokamak model. There are fusion reactors in almost every modernised country in the world, they've been there for over 50 years; but they haven't been able to undergo fusion on the scale that would be required to make it sustainable as an industrial power source.

Our best hope for that lies in the ITER project in southern France (they have a great website if you want more detail and pictures of the enormous construction). This is an international collaboration between China, India, the US, Korea, Japan, Russia and the European Union; more than half of the world's population is being represented. Its inception was at the 1985 Geneva Convention, its design was approved in 2001 and in 2006 the ITER organisation was officially brought into existence. Construction and initial testing is expected to take well over a decade with the deadline for it to be fully operational being November 2020. Only then will we know for certain if the dream of limitless clean energy is a realistic one on an industrial scale. Unfortunately even ITER is only ever intended to be an experimental proof of concept. If it is successful then the world can get on with making the very first demonstration units through the 2020s into the 2030s. Personally, I don't see us having the first proper fusion reactor online til the second half of this century. The wait, though, will be worth it.

Sadly, the wait for a blog post on helioseismology is going to have to wait even more; again. I have written another thousand-odd words without getting to the point. I'll try to revisit the topic in less than a year this time.

365 Project: Photo 288

A pleasant sunset stroll along Hampstead Heath, my first visit there in a very long time. Taken on my phone and cropped, hence the graininess.

365 Project: Photo 224

This photo didn't quite turn out as I liked but it's not too terrible. I was walking through Westfield and just emerged from under a bridge when the extremely high contrast caused by the sun caused me stop in my tracks. My phone was not altogether capable of capturing what I wanted. I also wonder if I should have cropped the top a little.

365 Project: Photo 204

I feel a science coming on....

The topic was Something Hot and I couldn't think of anything hotter than the sun, apart from other suns, and I decided I can't mention the sun without using it as an opportunity to talk about how cool it is, so to speak.

The Shell Building from Waterloo Bridge, a view I have used before on the blog

The sun is an unremarkable ball of plasma, neither particularly hot nor cold, not doing anything unusual, not overly large nor especially small, it's just hanging about approximately two thirds of the way along one of the arms of a bog standard, barred, spiral galaxy we call the Milkyway; the sun is also the single most awesome structure we're ever likely to encounter.

The sun, as you may have heard, it quite big. Jupiter is quite big too, as planets go. If you were to take all of the other seven planets (remember, Pluto is no longer a planet) they would all fit inside Jupiter; and if you took all the planets including Jupiter they would all fit, easily, inside the sun. Let's put it another way; if you were to tot up all of the matter in the solar system - the sun, all the planets, all the comets, everything in the asteroid belt and Kuiper belt, all the dwarf planets, everything - then the sun would make up about 99.86% of it, everything else would be less than 0.2%. So, pretty big.

I couldn't not put in this Hubble picture of a bog standard, and breathtakingly beautiful, barred, spiral galaxy (click to galactify)

The sun is also, you may have noticed, rather hot. How hot, though, depends on where you measure it. The sun has at least six distinct layers to it, the inner three of which can be thought of as the core, they are also the hottest; they weigh in at about 15 million degrees Celsius. This core behaves as a solid and rotates within the body of the sun. The layers outside the core; the convection zone, the photosphere and the chromosphere; behave like a viscous liquid something akin to magma on Earth. These layers rotate too but in different way to the core leading to a highly turbulent dividing layer called the tachocline. So, as we move out through the sun the temperature gets steadily lower until, at the surface, the temperature is only 5,500 Celsius. I know, surprisingly cold, right? The next time you hear something described as hotter than the surface of the sun you probably don't need to deploy your impressed face. That's not the end of the story though, something weird happens once you leave the sun. The area outside of the sun is known as the corona, it is this that you can make out during an eclipse when the moon is blocking out the main disc of the sun. The corona, oddly, actually gets much hotter, about 2 million degrees hotter. How it is that there is this vast temperature increase outside of the sun is not fully understood yet but the smart money appears to be on magnetic fields playing a role.

So, before the Government decides that the solar system would be better off privatising the sun because its function could be performed more efficiently and cheaply by private companies, let's establish what it is the sun actually does and why it's so good at it. Put simply, the sun is a fusion reactor, which is sort of the opposite of what happens in a nuclear reactor. It takes 4 protons (hydrogen nuclei) and fuses them together to produce an alpha particle (helium nucleus). This, normally, is an extremely difficult thing to do; protons are positively charged particles and, as every 12 year old knows, oppositely charged particles attract each other and particles with the same charge repel each other. This is one of the principles of electromagnetism which is, itself, one of the four fundamental forces of the universe (the others being gravitation, the strong nuclear force and the weak nuclear force). It is the strong nuclear force that holds the elementary particles within nuclei together and so nuclear fusion is the process by which the strong force manages to overcome electromagnetism. It is only in the insanely hot and dense conditions that exist in the sun's core where protons can be pushed near enough to each other such that the strong nuclear force can win out and, in the process, release a whole bunch of energy, generally in the form of gamma radiation. Each gamma ray is absorbed in just a few millimetres of solar plasma and released in a lower energy state having given off, over the course of its journey, several million photons - the source of all the marvels we are but one small part of here on Earth.

Image used under a CCL. Warning: image contains science

My favourite ever sun fact is one I only encountered a year or two ago but I absolutely love it. I particularly enjoy it when it is contrasted with this preliminary fact: the sun is approximately 8.5 light minutes away. What this means is that it takes a photon of light, once emitted from the sun, only 8.5 minutes to get to the surface of the Earth; the sun may be a very long way away but when you're travelling at just shy of 300 billion metres per second the distance is soon covered. Here is the fact I love: for a newly created photon in the sun's core to reach the surface of the sun takes about 170,000 years. That blows my mind. But why is this the case? From what I can tell it mostly seems to be a function of the sheer density of matter in the core. The heat and pressure is so great that hydrogen atoms are being fused together into helium atoms and the maelstrom is simply to difficult for the photons, massless and speedy as they are, to get through.

Okay, I've just checked and I'm at 1,000 words, which is unfortunate because that's probably somewhat more than you had bargained for when you clicked the link and I haven't even got to the specific topic I wanted to discuss yet. I think I'll quit while I'm ahead, thank all of you that have read this far and leave you with a promise of a follow up sun-based post later in the year where I'll ramble on about....
- How we are trying to solve the world's energy needs by creating the sun on the Earth
- How solar weather can affect us all
- And helioseismology, the study of sunquakes, the whole reason I started writing this post in the first place!!