Climate change is real

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I’ve been sparring with a climate change denier on Quora but he is totally blind to reality and just dismisses all evidence of global warming out of hand. Here are some extracts from my latest couple of posts to him, which of course he dismisses.

We’re in unchartered territory with climate change. When temperatures are rising ten times faster than coming out of the last glacial period and the cause is clearly us, there are no precedents on which to base future temperatures, ice quantities and sea levels. We know that CO2 levels are increasing. I think even the deniers accept this. But you can’t have increases in CO2 levels without increases in temperatures for too long unless other factors are playing a major role, and they are not. Solar activity has declined slightly since the 1950s. Volcanic activity is low. The albedo effect, ocean currents, and earth’s axis tilt and orbit have all had little or no effect. Indeed, albedo, tilt and orbit all have only a long term effect which is currently one of cooling. Changes in ocean currents are more a result of climate change rather than a cause of it.

We are emitting an enormous amount of extra CO2 into the atmosphere. This causes temperatures to rise, which causes ice to melt, which causes sea levels to rise. All three of these things are happening; there is nothing surer. We just don’t know the extent of these things into the future. All three are accelerating now. Various projections have been made usually with a fairly wide range. We know that temperatures rose five degrees and sea levels over 400 feet coming out of the last glacial period. So sea level rises are hardly going to stop at a foot or two or three this time, given that temperatures are already up a degree or more and are accelerating and that ice melt is also accelerating. Most CO2 hangs around in the atmosphere for 20-200 years while some is there for up to several hundred thousand years. Therefore, rather than taking the risk, the world is doing something about it by shifting from fossil fuels to renewables albeit slowly.

Detailed global temperature records go back to about 1850. They get better and more detailed all the time and were quite reasonable by 1880. This is where NASA and others start their annual tracking of the adjusted temperature data (it has to be adjusted because weather stations move, usually from centre of town to airports in cooler green areas on the outskirts; and temperature measuring methods and instruments change). See https://climate.nasa.gov/vital-signs/global-temperature/. Note the sharp increase from the 1970s onwards. This is when developing countries got going with industrialisation, adding their CO2 emissions to those of advanced economies.

We are not bereft of weather stations. Key aspects of the atmosphere, land and ocean surface, including temperatures, are recorded every day by more than 10,000 weather stations, 1000 upper air stations, 7000 ships, 1000 drifting and moored buoys, hundreds of weather radars, many weather satellites plus 3000 specially equipped commercial airplanes. Observations are quality controlled by the World Meteorological Organization.

We have good indicators of temperatures before 1850 through earlier readings such as daily UK temperature readings going back to 1772 and monthly back to 1659. Yes, we’ve had satellite data since the 1970s and although this doesn’t measure temperature directly, inferences show an upward temperature trend. Other indicators of temperature include tree growth rings, coral growth, borehole temperatures, sediment in oceans and lakes, cave deposits, fossils, glacier length, ice core samples, and others. From these, we can get pretty good records of temperatures going back 2000 years. This graph shows the results of 11 different scientific studies: https://en.wikipedia.org/wiki/Global_temperature_record#/media/File:2000_Year_Temperature_Comparison.png. Paleoclimatology uses most of these temperature indicators to go back much further. This graph is by Glen Fergus and uses various sources to go back 500 million years: https://en.wikipedia.org/wiki/Paleoclimatology#/media/File:All_palaeotemps.svg. It is probably broadly accurate.

No one is exonerated from reducing carbon. Europe has done best over the last few decades while the US has reduced its too. They have increased in most other countries. After some years of little increase in world emissions, they went up quite a bit in 2018 by about 2-3%. US emissions rose 2.6%, China up 2.2%, India up 7.0% and the EU down 2.0%. But on a per capita basis, the US is way ahead with about 16.5 tons a year, China 7.5 tons, EU about 7 tons and India 1.7 tons. In terms of total CO2 emissions in 2016, China had 10.2 gigatons, US 5.3 gigatons, EU 3.5 gigatons and India 2.4 gigatons.

The negative effects of global warming far outweigh the positive effects. Here is a good summary: https://skepticalscience.com/global-warming-positives-negatives-basic.htm. Climate change is likely to disrupt agriculture due to worse flooding and drought. Deaths due to heatwaves are expected to be five times more than winter deaths prevented. Malaria and diseases from mosquitoes are expected to increase. Ice melt will increase resulting in loss of habitat and water for drinking and agriculture plus sea levels rises will affect food bowl areas and coastal cities. Acidification of oceans will affect the entire ocean food chain. Climate change may result in greener forests but negative effects include “further growth of oxygen poor ocean zones, contamination or exhaustion of fresh water, increased incidence of natural fires, extensive vegetation die-off due to droughts, increased risk of coral extinction, decline in global photoplankton, changes in migration patterns of birds and animals, changes in seasonal periodicity, disruption to food chains and species loss.” Also, we are releasing about twice as much CO2 as the environment can absorb naturally anyway (and would require many trillions of extra trees to fix), thus the build up of CO2 in the atmosphere and the higher temperatures. Climate change could also see mass migration of people (climate refugees) affected by low lying agricultural land and cities, as well as disruptions to global trade, transport, energy supplies, labour markets, banking, finance, investment and insurance. Developing countries could be fighting over water, energy and food, adding to their existing problems.

A number of large studies of the climate science literature plus large surveys of the scientists themselves have found 90-100% agreement (commonly around 97%) with anthropogenic global warming. Surveys of the general population find that a large majority of people agree with the science rather than the denier stuff and it’s not hard to see why. I have been through hundreds of denier sites, pages, articles over many years and have yet to find one that I couldn’t pull apart. People are pretty smart these days and have an abundance of information at their fingertips.

Ice is shrinking at an accelerating rate. Here’s an interesting graph from the University of Washington’s Polar Science Center: https://en.wikipedia.org/wiki/Arctic_sea_ice_decline?fbclid=IwAR0cuDqOLguA2ja9n1C2__oljoO8CH7Q1HvYlyA8rP_kKM7PZtTblDo5aT8#/media/File:Arctic-death-spiral.png. Peak Arctic ice volumes (April) have fallen steadily from about 33,000 cubic km in 1979 to 22,000 cubic km in 2017 or a fall of about a third. Minimum ice levels (September) have fallen more, from 17,000 cubic km to less than 5000 cubic km, or by more than 70%. And the decline in both winter and summer ice volumes is accelerating as the graph clearly shows. More on the Arctic: https://community.windy.com/topic/8382/animated-history-of-arctic-sea-ice-during-the-satellite-era. Note the satellite images showing decreases in ice. The Antarctic is losing about 250 billion tonnes of ice a year, up from 40 billion tonnes a year in the 1980s and the loss is accelerating. Greenland is losing about 200 cubic km of ice a year.

Sea levels rise due to ice melt and also because warmer water expands (see, for example: https://climate.nasa.gov/vital-signs/sea-level/) and they are accelerating. If we don’t reduce our CO2 emissions, sea levels could rise by eight feet by 2100 and fifty feet by 2300 according to this study: https://phys.org/news/2018-10-global-sea-meters.html which is typical of many studies. Under moderate emissions, we might contain sea level rises to a couple of feet by 2100 and ten feet by 2300.

The debate over creation and evolution

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Some years ago I wrote four articles on evolution and religion for US writing site Helium now gone. Here’s the second one (link to first one at bottom) …

The debate over creation and evolution has been going on for more than 2,000 years. Creationists have held sway for most of that time. Indeed, it wasn’t always good for one’s health to have a different viewpoint. Evolutionists, hiding in the closet for centuries, suddenly got a boost in the mid 19th century with the work of Charles Darwin. But creationists were having none of that, and initiated a resurgence in creationism around the 1920s. Today, the debate rages, especially in the United States, and I hope I can make some small contribution to it.

We should remember that when the creation story was written, the earth was thought to be flat and at the centre of the universe, with other components being just a few lights in the sky. Scholars and ordinary people wanted answers, even back then. When the Old Testament was written, nothing was known of evolution, and creation seemed like a logical explanation of how we got here. We now know how huge the universe is, and that our planet, solar system and galaxy are just an infinitesimal part of it. The creation of trillions of stars, maybe half of them with their own planets and moons, would perhaps be beyond any god. And if there is a creator, who or what created him, her, or it? And who or what created the thing that created the creator? And who or what created the thing that created the thing that created the creator?

Integral to creation is the story of Adam and Eve and the Garden of Eden. We don’t know its location, with various hypotheses having been put forward over the years. Even some theologians feel it never existed on earth but was an adjunct to heaven. Some scholars regard Adam and Eve as metaphorical, a story made up by early leaders to teach people about truth, sin, and so on.

Also relevant to creation is the story of Noah’s Ark and the flood. The ark has never been found despite its location being reasonably well identified in Genesis. Given the creation model doesn’t allow macroevolution, the number of species that turned up at the ark at the time of the flood would have to be at least the number today that would be in need of saving from such an event. The number of species has been estimated at anything from 2 to 100 million. Allowing for sea dwellers, insects and any others that allegedly didn’t need saving, that’s still a lot of animals, especially when a pair (or was it seven pairs?) of each animal went onto the boat. It might have been millions. Even using the biblical “kinds” (baraminology is regarded as a pseudoscience like other creation sciences), this would still be a very large number of animals. On this basis, estimates range from 2,000 to 35,000 animals.

The alleged boat was an unlikely 450 feet in length, the size of a modern ship. Theoretically, it would have been large enough to accommodate many thousands of animals. However, it is far larger than other ancient boats. How did Noah acquire the skills to build such a huge vessel, one that would have been way too large for one man and his family to operate in any case? How would you get all these animals onto a boat? Old paintings have them, quite unrealistically, marching in an orderly fashion up a ramp, and onto a vessel far smaller than 450 feet. How would you round them up in the first place? What if the elephants, lions and other formidable beasts refused to cooperate? What about those native to Africa, the Americas and Australia – how would they be expected to find their way around the world to a boat that was allegedly going to save them? And how would you prevent the animals fighting and trying to eat one another as they stood in queue to board the boat?

Assuming all this is possible and did happen, let’s consider how much rain is required in 40 days to flood the earth to a level 20 feet above the highest mountain. Mount Everest is about five and a half miles above sea level. Coastal plains would be under this amount of water, and the seas and oceans would be this much deeper. Five and a half miles is 348,480 inches. This would require daily average rainfall of 8,712 inches for 40 days, or 363 inches an hour, or 6.05 inches a minute, worldwide. Rainfall intensity records are given as 73.62 inches in a day at Reunion Island in 1952, 15.78 inches in an hour at Shangdi, China in 1975, and 1.50 inches in one minute at Guadeloupe in 1970. Rain resulting in the biblical flood would have been four times the intensity of the heaviest rainfall ever recorded over one minute and this had to last 40 days across the whole planet. Noah’s family, the animals and the ark would have been obliterated by rain like sheets of concrete. Nothing would have survived the rain, let alone the flood. Apart from all this, the rain has to come from somewhere. You can’t have this much evaporation and condensation in a short period. Even subscribing to the biblical view that mountains were much lower at the time of the flood, for all the land to be covered with water would be physically impossible.

Can we necessarily believe what we read in the Bible about creation (or much else)? We don’t really know who wrote the Gospels or when. Numerous changes have been made to the Bible over time, especially in the early centuries. There was much bickering among early Christians as to what was scripture, and various christological issues were hotly debated. Many of the writings were chopped and changed amid followers accusing one another of corrupting text. Second century philosopher Celsus said that some of them “changed the original text of the gospels three or four times or even more, with the intention of thus being able to destroy the arguments of their critics”. Tatian’s Diatessaron was one of a number of works that aimed to rewrite the gospels as a narrative, fixing conflicting passages and eliminating duplication. In the third century, Christian scholar Origen admitted that “there is much diversity among the manuscripts, due either to the carelessness of the scribes, or to the perverse audacity of some people in correcting the text, or again to the fact that there are those who add or delete as they please, setting themselves up as correctors”. Many other early church leaders, such as Jerome and Augustine, were concerned about the extent of changes to biblical documents. Then there is the curious absence of Jesus’ birth and death dates (which of course are unknown) and of his life between infancy and the age of about 30. A lack of evidence for Jesus’ historicity in non-biblical sources (e.g. Josephus’ paragraph on Jesus turns out to be a later addition) brings doubt to the Bible’s story of Jesus, let alone the creation story.

When science was still recovering from something like 1,500 years of suppression at the hands of religious leaders, one Charles Darwin made a number of observations relating to fossils and the distribution of wildlife that led him to propose that life evolved from common ancestors, including humans. He coined the term “natural selection” to describe how animals passed on their traits from one generation to the next. His ground-breaking book, On the Origin of Species, published in 1859, shook the establishment to its core. But this wasn’t Darwin’s intention. Indeed, he had studied theology at Cambridge. He simply recorded what he saw and aimed to draw logical conclusions from it.

Evolution soon became accepted by scientists and the general public. In the second half of the 19th century, few scientists or religious people had a problem with the earth being very old indeed. Few accepted the literal description of the flood and few felt it was geologically significant. By 1900, even the Catholic Church accepted that humans evolved from animals, but that humans’ souls were God’s domain. A return to fundamentalist Christianity occurred after World War I, at least in the US. The opposing views of creationists and evolutionists diverged ever wider after this, despite more and more evidence for evolution and its general acceptance by scientists, and little evidence for creation, or Christianity in general for that matter. Today, evolution is accepted by at least 95 per cent of biological and earth scientists, with one survey suggesting a figure as high as 99.8 per cent. Neither the Church of England nor the Catholic Church accepts a literal interpretation of Genesis. Evangelists and Protestants in the US appear to be the chief supporters of a literal view.

Creationists come up with all sorts of ways to try and discredit evolution. Let’s start with thermodynamics. Its second law says that entropy or disorder will always increase over time. Creationists jump on this as proof that evolution can’t happen as it requires an increase in order. But entropy only increases in closed systems and there are none of these in nature. An organism maintains its internal order as it takes from free energy sources such as nutrients and sunlight, returning the same quantity of energy to its environment in the form of heat and entropy. There is no reason for animal and plant life to deteriorate over a period of time. Individual species may deteriorate, and may become extinct, while other species will strengthen, depending on their environment and how well they adapt to it and to changes in it. With extra nutrition and sunlight, humans are taller and stronger than in the 19th century when many people struggled to find enough food and worked long hours in dingy factories. Our liking for junk food may see a weakening in the human species as it adversely affects our health and reduces our life expectancy.

Another favourite argument among creationists for evolution not being possible is an alleged lack of transitional forms or fossils. Christian websites often quote from works by scientists saying no transitional forms have been proven. But note that the references are always old, usually from the 1960s through to about 1980. Research into transitional forms is difficult, time consuming and costly, and virtually none was carried out before the mid 1970s, a major reason being the lack of commercial possibilities. An early researcher, Phillip Gingerich, took 10 years to document two lineages, completing this work in the late 1970s. In the last few decades, there has been a steady increase in this research and in findings from it. Numerous transitional forms have now been identified. For a list of some of these forms, see http://www.talkorigins.org/faqs/faq-transitional.html. For a detailed discussion of transitional forms, with references to numerous books and journal articles on the subject, see http://www.gcssepm.org/special/cuffey_04.htm. Sure there are many missing links, and probably always will be.

The creationist model doesn’t allow for transitional forms, with every species regarded as separate and having no link to any other species. That’s all Genesis allows for, and thus there can’t be any grey areas under this model. It won’t matter what is found or how many gaps are closed, creationists will regard any two fossils as separate species with no links between them if they feel the difference is great enough. If the difference is small, then it’s regarded as the same species. In other words, the model allows microevolution but not macroevolution. However, the two terms describe the same process. Any division is arbitrary and, according to the American Association for the Advancement of Science, has no scientific basis.

If these fossils are less common than other forms of fossils, this might be because the evolutionary process is usually one of gradual change and a transitional form might not always show up. However, the equilibrium might be punctuated when a species experiences a sudden change in its environment, such as an ice age. At this time, many species might become extinct. Those that survive often have to adapt quickly to their new environment, and a transitional species might not be around for as long and therefore leave less evidence.

A quickening of the evolutionary process seems to have happened during the Cambrian explosion. Before this, there are few fossil records as the soft bodies of pre-Cambrian animals left few traces. Various causes of the explosion have been put forward, for example an increase in oxygen in the atmosphere, changes in ocean chemistry, gene development, climatic change or a large meteorite, or some or all of these to a varying extent. Whatever happened, it seems that conditions were right for a rapid increase in the evolutionary process. But 10 million years is still a long time, and considerable change would be possible in this timeframe if there are major changes in the overall environment.

Interestingly, fossil records don’t support creationism. As we’ve seen, the story of Noah’s Ark had all remaining animals at a single place at the same time. Yet, all around the world, there are fossils of numerous species that are only found in the vicinity of their current location. There are no trails of various American or Australian animals in Europe or Asia. How would a creature such as the slow, awkward, tree-dwelling koala travel from the Middle East to Australia and not leave behind a considerable trail of fossils over a long period? And how would it cross oceans and seas? The so-called land bridge between Asia and Australia thousands of years ago had at least one water channel. This could be negotiated by humans in canoes but not by koalas, which at any rate have been in Australia for millions of years.

The impossibility of virtually all aspects of the biblical flood story hasn’t stopped the likes of Tom Vail coming up with a non-fiction (sic) book, Grand Canyon: A Different View, and running canyon tours. The book is about the canyon being carved out by the flood, rather than erosion over millions of years. The American Geological Institute and other bodies want the book removed from national park shops. The idea that a single flood caused all geological strata was rejected as early as 1837 by Reverend William Buckland, professor of geology, Oxford University. The scientific community regards flood geology as pseudoscience. Through the principle of uniformitarianism, geologists have found that the earth has been shaped mainly by slow acting forces rather than one or more massive catastrophic events. Geochronology has determined that the earth is about 4.5 billion years old, rather than 6,000-10,000 years under creation. So speeding up the camera, if science says the earth has been here 24 hours, creation says it’s been here around 0.1 or 0.2 of a second. The ancients could not have envisaged an earth and a universe as old as what they actually are.

Unlike creationism and the Bible, evolution isn’t contradictory. Biochemistry backs it up, including DNA and protein sequences. The genetic code is nearly the same for all species. There are new fossils and more evidence all the time. The UK Natural Environment Research Council states: “It is almost certain that all life developed from the same single source, as all life discovered has the same complex molecule – DNA.” (http://www.nerc.ac.uk/research/issues/biodiversity/life.asp). American professor of ecology and evolution Douglas Futuyma believes there are enough similarities in species to show that all species are related. This is generally accepted in biology.

Just a note on the use of the word “theory”: In scientific terms, a theory has to include evidence for it to be called a theory, for example Newton’s theory of gravitation, or the theory of evolution with its vast evidence base. However, in common usage, people tend to think of a theory as a hypothetical proposition that isn’t backed up by any evidence. People will often say: “In theory …; however, in practice …” about different issues. Creationists often criticize evolution as a theory, saying: “It’s only a theory”, knowing that many people will then think of evolution as something that some bunch of scientists dreamed up, perhaps to get under the skin of creationists (!), and that it doesn’t or can’t work in practice. The definition of “theory” from the US National Academy of Science is: “Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.” (http://www.newscientist.com/article.ns?id=dn8178). Scientists don’t spend their time and money and careers trying to stir up creationists. They wouldn’t be doing this work if they thought evolution was nonsense.

Those who accept evolution have done their research and have concluded that evolution makes more sense to them than creationism. They have found answers that, to them, they don’t get from religion and creationism. But there are gaps in evolution, and many people really must have answers to everything, without any gaps. These people become or remain Christians or belong to some other religion that supports creation as they feel this gives them all the answers. Creationism and Christianity will give these people an answer to everything they seek. This is one of the features of these things that attract people to them. It’s a pity that many of the answers, so often promoted as fact or truth, are actually void of evidence.

If you could find, and bring to earth, an intelligent alien who knew nothing about creation or evolution and explained both to him, her, or it, I think I know which one the alien would find more believable. My bet would be on evolution.

See also: https://chrispearce52.wordpress.com/2018/07/15/what-is-evolution/

[I have discovered the above article of mine here, http://scotdir.com/religion-and-spirituality-2/thoughts-on-god/the-debate-over-creation-and-evolution-2, posted by someone called Hailstone. I have emailed scotdir.com to try and get it removed. When it’s done, I’ll remove this endnote.]

 

Man-made global warming deniers are back

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anthropogenic global warming, atmosphere, Australia, blanket, carbon dioxide, carbon pricing, CO2, coastal flooding, correlation, deniers, earth, emissions, Facebook, global warming, greenhouse gases, hoax, ice, Industrial Revolution, Malcolm Roberts, man-made global warming, orbit, scientists, sea levels, senator, solar activity, storms, temperatures, tidal surges, video, volcanic eruptions, warming, water vapour

Here in Australia, one of the new senators, Malcolm Roberts, denies anthropogenic global warming. He and/or one of his staff plus a few other deniers have been busy posting odd things refuting AGW on his Facebook page, including various odd explanations and selective bits and pieces, old quotes, etc, to declare that AGW is all a hoax by scientists, scientific organisations and governments around the world. I’ve been picking the deniers to pieces over there but they don’t give up. I posted this comment on his video which he posted to his page a few days ago (although all I get in response is that I’m talking rubbish and more odd comments and selective quotes as the deniers continue to try and support their position) …

This video is misleading and gives totally the wrong impression. Carbon dioxide might be a small percentage of the atmosphere and man-made CO2 a smaller percentage still. But I think he’s mixing up his stocks and flows. He’s right in saying that man-made CO2 is only 3-4% of all CO2 but he seems to be saying that this is the level (stock) of man-made CO2 when in actual fact this is the percentage of man-made CO2 emissions (flow).

The problem is that only about two-fifths of this additional CO2 is absorbed and the rest stays in the atmosphere, building up steadily over time. Roberts seems to forget this. Before the industrial revolution, the CO2 absorption and release sides were pretty much in balance. Since then, we’ve had additional CO2 released by humans in ever-increasing volumes through all our various activities. It may seem small overall but, as I said, it builds steadily over time.

CO2 is now at about 400 parts per million or 0.04% of air as per the video. But over the last 400,000 years and up to the industrial revolution, CO2 varied between about 180 and 280 parts per million, in natural cycles. It was around the top of this cycle at the start of the industrial revolution and is now 40-45% higher at 400 ppm. Normally, it takes 5,000 to 20,000 years to increase by 100 ppm; this time, it has taken perhaps 150 years to increase by 120 ppm. The extra CO2 acts like a blanket, or a thicker blanket, enveloping the earth and keeps the heat in, thus the steadily increasing temperatures. This causes the ice the melt, sea levels to rise and an increase in wilder weather, with increasingly severe storms, larger tidal surges and more coastal flooding, causing damage and displacing people, often in the poorer parts of the world.

He then seems to compare Australia’s CO2 with the world’s total air. His subsequent statistics and analysis are therefore quite flawed.

I’m not sure where his carbon dioxide tax figures come up: $72 billion in five years. This was the estimated cost over this period of an American scheme in the 1990s. Emissions fell when we had carbon pricing in place, they rose before that and have risen again since. Also, getting rid of carbon pricing was estimated by the PBO to cost the budget $18 billion over four years, adding extra pressure to the budget. We now have the useless Direct Action policy.

Roberts says that temperature changes come first and then CO2 levels follow. It actually works both ways. In other words, changes in carbon levels both cause, and result from, changes in temperature. For example, when ocean temperatures rise, more CO2 is released into the atmosphere making the air warmer which means more CO2 is released. We have to also consider the rapid increase in temperatures this time around, much faster than historically. Graphing temperatures and CO2 levels since the 19th century, we can see a very high correlation over this period, which makes sense because the large increase in CO2 acts as a blanket keeping the heat in. To say that nature alone determines CO2 levels not humans, as Roberts states in the video, is simply wrong.

He doesn’t seem to offer any explanation for the increasing temperatures. It can’t be solar activity as that has fallen if anything since the 1970s, nor volcanic eruptions (these are low historically), nor Earth’s orbit (variations and effects on temperature are long term). That leaves greenhouse gases, which includes CO2 which causes up to a quarter of the greenhouse effect. Water vapour has a larger effect but it’s CO2 levels that have easily changed the most. Or does he think scientists use faulty thermometers, or are fudging the numbers?

Solar eclipses

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(originally published to Helium writing site, now gone)

A solar eclipse takes place when the moon is between the earth and the sun. Light from the sun is partly or fully blocked by the moon. Between two and five solar eclipses occur somewhere on earth each year. Up to two of them are total eclipses. During a total eclipse, the sky becomes quite dark and street lights come on.

The four types of solar eclipses are total, partial, annular and hybrid. A total eclipse is where the moon completely blocks the sun. At this time, the corona, which is the hottest part of the sun’s atmosphere, can still be seen. Any total eclipse is only seen along a narrow band of the earth’s surface. This is because the sun and the moon appear to be roughly the same size in the sky, as the sun is 400 times further away than the moon but is 400 times the moon’s diameter. A partial eclipse is where the moon only blocks out part of the sun. Any partial eclipse can be seen from a far greater area.

An annular eclipse is where the moon blocks all of the sun except for a narrow ring that forms a complete circle around the moon and looks like an illuminated hoop. Sometimes an effect called Baily’s beads is seen, because the lunar landscape features mountains and valleys, and the beads are the light shining through the valleys. The reason we can have both total and annular eclipses is because the moon’s orbit around the earth is elliptical or oval in shape and its distance from earth varies by up to 12 percent. The distance from earth to the sun varies about 3 percent, so this will have an impact too although smaller. A hybrid eclipse is where an eclipse is moving between an annular and total eclipse and is rarer.

A total eclipse occurs about every 18 months on average. However, a total eclipse at any particular point on the earth’s surface only happens once in about 370 years on average. The duration of a total eclipse can range up to about seven and a half minutes, although eclipses over seven minutes are rare, and they are usually much shorter. The longest total eclipse this century took place on 22 July 2009. It was seen from southern and eastern Asia and the Pacific Ocean and lasted about six and a half minutes. In 1973, scientists on a Concorde aircraft traveling at twice the speed of sound were able to keep up with a total eclipse for 74 minutes and make various observations.

Solar eclipses, when mentioned in old documents, can be useful to historians as it enables them to date certain events accurately. For example, Assyrian text mentions a revolt in the city of Ashur during the month of a solar eclipse. This eclipse has been dated to 15 June 763 BCE and is the oldest reliable dating of an event by means of a solar eclipse. An annular eclipse at Sardis when Xerxes was heading off to fight the Greeks dates this event to 17 February 478 BCE.

Attempts to date Good Friday and the so-called crucifixion eclipse to a known solar eclipse have so far been inconclusive. A full moon was also reported at this time and a solar eclipse can only occur at the time of a new moon as this is when the sun, moon and earth line up.

Watching an eclipse can present eye problems. Looking at the sun, including during any eclipse except a total eclipse, can damage the eye’s retina. This is because of the radiation from the sun’s surface, and not all the radiation is visible. It doesn’t matter that only a tiny proportion of the sun can be seen behind the moon. Using binoculars, a telescope or an optical camera viewfinder can be just as dangerous as looking at an eclipse with the naked eye. Nor do sunglasses make it safe.

A popular and safer way to see an eclipse is with a solar filter which only allows a small fraction of sunlight through. Even if only 0.01 per cent of the light is let through, you should still only look at the sun for a short time before looking away. There are other ways to view an eclipse, such as by using welder’s goggles.

The safest way to see an eclipse is to poke a hole in a thin piece of cardboard and hold it up to the sun. Hold a sheet of paper a few feet under or behind it. You will see the sun’s image on this sheet as it goes through the various stages of the eclipse. To reduce the amount of light, make a small hole in the side of a cardboard box and a larger hole at the bottom to put your head through. Put white paper opposite the small hole and close the lid of the box, and you will see an image of the eclipse. Similarly, this can be done in a darkened room.

A solar eclipse helped confirm Albert Einstein’s general relativity theory. Astrophysicist Arthur Eddington was on Principe Island off Africa to see the total solar eclipse of 29 May 1919. He noticed that stars just to the side of the sun would appear to shift slightly due to their light seemingly curving because of the sun’s gravitational field, confirming Einstein’s theory. At other times, the light from the sun is too strong to see this effect.

All about solar astronomy

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earth, galaxies, Gian Cassini, helioseismology, life on earth, Milky Way, moons, Orion Arm, parallax, planets, solar astronomy, solar cycle, solar systems, stars, sun, sunspots, temperatures

(originally published to Helium writing site, now gone)

Astronomy is the study of stars, planets, moons and other celestial bodies, and of entire groups of heavenly objects such as solar systems and galaxies. So solar astronomy is simply the study of the sun, the word solar meaning “of or relating to the sun”.

The sun is about 93 million miles from earth. How do we know this? Italian astronomer Gian Cassini in the 17^th century used a method called parallax. To understand this technique, put your thumb straight out in front of you and observe it with one eye and then the other. The thumb looks to have moved to a slightly different spot. The difference is the thumb’s parallax. Cassini was able to observe the sun and the planets from different places and determine the distance to these bodies using the parallax technique. His calculations turned out to be quite accurate.

Solar astronomers were then able to calculate the sun’s size. As a yellow dwarf, the sun is not a large star. Yet its diameter of nearly 900,000 miles is 109 times that of earth. That’s like putting a pea next to a medicine ball. The sun’s surface area is 12,000 times greater than earth’s and its volume is 1.3 million times that of earth.

Astronomers have found that the sun’s rotation time is about 25 days at its equator, although from earth it appears to take about 27 days due to the earth’s orbital motion around the sun. Rotation time can be measured by observing the movement of sun spots. Nearer the poles, the sun spots move slower, and rotation time at the poles is about 34 days. The difference in rotation times is possible because the sun isn’t a solid mass but is made of gases, mainly hydrogen (75 per cent) and helium (24 per cent).

The interior of the sun can’t be seen but scientists have been able to determine its inner structure through helioseismology, which involves detecting the movement of the sun’s pressure waves beneath its surface. This is rather akin to seismology on earth which studies the waves produced by earthquakes. Some of the sun’s waves are amplified and this is transmitted to the surface. Changes in the waves allow astrophysicists to find out numerous things about the sun’s interior.

At its middle or core, the sun is 150 times heavier than water. The core extends from the very center a fifth of the way to the surface or 0.2 solar radii. The temperature at the core is about 25 million degrees Fahrenheit, compared with a surface temperature of 10,000 degrees. Data from the Solar and Heliospheric Observatory spacecraft suggests the sun’s core rotates faster than the radiative zone which is the next layer out from the core. Most of the sun’s heat is produced in the core, by nuclear fusion, converting hydrogen into helium.

The resultant photons or gamma rays travel at 186,000 miles per second, or the speed of light, but they collide with matter billions of times before reaching the surface and escaping as sunlight. At the sun’s core, photons travel an average distance of a 250^th of an inch between each charged particle. Near the surface, this increases to about a tenth of an inch. Solar astronomers estimate the time taken for photons to complete their journey through the layers of the sun to be around 10,000 to 170,000 years. Yet the time taken for light to travel from the sun to earth is a little over eight minutes.

Moving out from the core is the radiative zone which covers the area between 0.2 and 0.7 solar radii. This layer is hot and dense, allowing heat to transfer upwards by thermal radiation. The final layer is the convection zone where heat is carried to the surface via thermal columns. The matter cools at the surface and falls back down to the bottom of this zone, before heating up and rising to the surface again. The sun’s photosphere or surface is opaque and 250-300 miles thick.

Above the photosphere is the solar atmosphere. This too is divided into several layers. The temperature minimum layer includes the area of lowest temperature, about 7,000 degrees Fahrenheit, some 300 miles above the surface. This is cool enough to support water and carbon monoxide, detectable by their absorption spectrum. The chromosphere is about 1,500 miles thick and becomes visible as the colored flash of light at the start and finish of total eclipses. Temperatures here can be up to 180,000 degrees.

The transition layer can be up to 1.8 million degrees. Solar astronomers observe this region more clearly via spacecraft rather than directly from earth. The corona is hotter still, at several million degrees, but astronomers are not totally sure why it is so hot. Lastly, the heliosphere is made up of hydrogen and helium blown by solar wind to the far reaches of the solar system at over 600,000 miles an hour for much of the journey.

Astronomers also study sunspots and the solar cycle. The latitudinal differences in the sun’s rotation time result in its magnetic field lines becoming twisted, leading to magnetic field loops erupting from the surface which results in sunspots. The twisting action produces a solar cycle which lasts on average 11 years. The number of sunspots varies over this cycle. The cycle has a significant impact on our weather and climate. During longer solar cycles, we experience hotter temperatures. The fewer the number of sunspots, the colder it seems to be. Europe experienced a mini ice age in the 17^th century when the cycle seemed to stop and there were very few sunspots.

The sun is located on the Orion Arm of the Milky Way, which is towards the outside of the galaxy and about 24,800 light years from its center. The sun, and the solar system, takes 225-250 million years to revolve around the galaxy at a speed of about 150 miles a second relative to the center of the galaxy. Using stellar evolution models and cosmochronology, astronomers have determined the age of the sun as 4.57 billion years. This means the sun has completed barely 20 orbits of the Milky Way.

The sun is about halfway through the main part of its life. It isn’t large enough to become a supernova but will become a red giant in about five billion years. The sun will be bigger than earth’s current orbit. Astronomers initially thought a much larger sun would push the earth’s orbit outwards and it would survive, but the latest research shows that earth might be swallowed up by the expanding sun due to tidal interactions. Terrestrial life will probably end in a billion years anyway because by then the sun will be 10 per cent brighter and the additional heat will make it too hot for water to exist. This will mean the end of all life on earth.