Wadhurst Astronomical Society Newsletter July 2020 Welcome to the July newsletter and I hope you find some of the articles interesting. We begin with the report from the first full WAS Zoom meeting which was very successful and attended by at least 22 guests. It was hosted by Brian Mills, our Chairman with two presentations that performed very well, where questions were able to be put using the “Chat” button and answered almost as though we were back at Uplands, except for the absence of Jim Cooper’s famous tea, coffee and biscuits. To start the meeting Phil Berry outlined the Zoom programme followed by his introduction to John Lutkin, the Society’s Treasurer who gave our main talk. John specialises in the effects of radiation on human cells and has published a number of papers on the subject. He was also the protection adviser for the southeast of England. Radiation – the Limiting Factor Dr John Lutkin John opened by saying that “Once you’re out of the Earth’s magnetosphere and are in an aluminium can, you are in serious trouble!” It was known over a hundred years ago that the x-rays being used by radiologists of the day were producing problems and were dangerous to human tissue. It was explained that the problems begin to occur when radiation energy interacts with human tissue creating ionisation. There are three main kinds of radiation; alpha particles, beta that are electrons and gamma and x-rays which are the ionising group of electromagnetic radiation. We were told that when an energetic particle hits an atom it can knock off an electron which either disappears or can cause damage to the cellular structure. This then leaves an ion which itself becomes chemically active. Alpha particles are relatively large and produce a lot of ions in the human tissue. Beta is relatively sparse and causes less damage. Gamma and x-rays pass through human tissue and are used to take pictures, differentiating between bones and soft tissue. John said that it was the electrons produced by the secondary effect that cause the ionisation damage. Cosmic Rays, mainly protons, were described as having massive energy enabling the formation of large numbers of ions. So, following radiation exposure there can be a chemical change, there are molecular changes to DNA, RNA and enzymes causing the cell to change or die. John told us that cell-death is dealt with by the body in the normal way but changes to the DNA can be a serious issue. Part of the DNA strand He explained that if ionising radiation causes a single break in the DNA chain, this is usually repairable. A double break is less likely to repair and the cell may die but if a chemical change occurs this is not repairable and may lead to cancer or mutation. There are two effects of ionising radiation on the human body; one where just the individual is affected and the other where the affect becomes hereditary. The results of radiation are a bit of a lottery we were told. After receiving radiation, there is a probability of some effect. Many of the risks are still based on studies from Hiroshima and Nagasaki. 1 John spent some time explaining the ways of measuring radiation quantities. Absorbed dose is the measure of energy absorbed in Grays (Gy), the Equivalent dose to a particular organ is measured in Sieverts (Sv) and the Effective Dose measures the overall effect on an individual; different tissues have different sensitivity. The inter-relationship between the units and systems of units causes confusion even to the professionals in the field. It is important to realise that we are all subject to radiation exposure just by living on Earth. To illustrate doses more clearly John used the “Banana Equivalent Dose” table, using bananas because they are a natural source of radioactive isotopes. Eating one banana is the same as 0.1 µSv. exposure. It must be stated that this is an unconventional comparison and frowned upon by experts. Bananas Equivalent exposure 1 - 100 Yearly dose from living near a nuclear power station 50 Having a dental x-ray 100 Average background dose per day 400 A single flight from London to New York 700 Living in a stone, concrete or brick building per year 200 - 1000 Chest x-ray 100,000,000 Fatal dose with death within two weeks There is a story from America that following the destruction of the Twin Towers, the military began to check all ships incoming to ports around the States for the possibility of hidden atomic devices only to find that a number of ships that had been rounded up in the Gulf of Mexico because radioactivity had been detected aboard turned out to be banana boats. At ground level from all sources, we receive on average 2.6 mSv per year. Then we looked at Cosmic Rays and were told that at ground level they make up about 10% of our yearly radiation dose at about 0.2 mSv; at an altitude of 12 km it is 20 mSv and at 350 km and on the ISS, it is 150 mSv but in Deep Space it is between 400 – 1000 mSv. Most of our cosmic rays come from coronal mass ejections from the Sun. Galactic Cosmic Radiation (GCR) comes from outside the Solar System where it is thought the source is mainly from the massive magnetic fields produced by Supernovae. John explained that it is believed atoms and their surrounding electrons are accelerated to almost the speed of light. Although the majority of GCR comprises of Hydrogen and Helium atoms there is a significant contribution from the heavier elements of the periodic table. We were told that luckily, we on Earth are protected by the Magnetosphere which diverts most of these particles away. John now turned to radiation doses received during space travel. He said that the Apollo missions weren’t exposed to particularly high dose rates but a trip to Mars could reach a total exposure of about 1,200 mSv including 18 months on the surface, which is getting close to the maximum dose allowed for an astronaut in his or her lifetime. It will be necessary, for the health of the crew, to reduce the radiation dose received during a space mission; one way would be to get there faster. It would also be necessary to improve the model of radiation damage that is used today which is based mainly on the evidence from the survivors from Hiroshima and Nagasaki, which shows the amount of radiation received against the chance of death and graphically is a straight line. More recently the line has been projected down to zero still keeping it as a straight line and this is currently the model in use. There is some evidence that low doses of radiation are far less dangerous than predicted and, in some cases, even beneficial and don’t follow the straight line. In radiation protection circles this is a contentious issue. John talked about ways of protecting astronauts from radiation during space missions and said that materials with a high hydrogen content, such as plastics which are used currently, reduce the dose by as much as 30 to 40%. There is also research being done with electrostatic and magnetic shielding to deflect the radiation. We were told that, surprisingly, concrete is very good at stopping cosmic radiation but rather difficult to launch… There is also research being carried out on dietary supplements which promote the body’s natural defences as an additional way of protecting astronauts. Another way of helping to protect the crew is to choose a route that avoids Coronal Mass Ejections and even find a path that uses existing stellar magnetic fields to deflect radiation. Once on the surface, there are weak magnetic fields which would be better locations to put a base, but if possible, living underground would solve many problems. John told us that he and his 4-year old grandson were planning to go to the Moon and in discussing the trip he said they would have to avoid all that radiation from the Sun to which his grandson suggested going at night because you could still the see the Moon. Sadly, there was another problem because Sid the cat who was to be their pilot, died. 2 Following a ten-minute break, Jan Drozd gave a fascinating and light-hearted talk about astrology. The Pseudoscience of Astrology Jan Drozd Jan appeared to give his presentation wearing the hat of an ancient astrologer and offering to give predictions but then countered it by saying before he began that from a scientific perspective astrology is a complete load of rubbish. Many cultures practiced astrology and many still believe in it today; in America at least 25% of the population still do. Babylonians used to look at the entrails of dead animals to see what predictions they could make from them. Jan said he wanted to talk about Western astrology and to show how in the past astrology and astronomy were considered together. Babylonia priest astrologers-astronomers tried to make predictions from the stars and planets. Stone tablets dating from about 700 BC show quite accurately and without access to modern astronomical aids to help them, the rising and setting times of Venus which was essential to their predictions. They developed the use of the sexagesimal system we use today for a circle with 360o and the hour divided into 60 minutes and minutes into 60 seconds. The Ecliptic, the apparent path of the Sun in a year, was very important to the Babylonians in their astrology – astronomy.