How does instant photography work?

 

Polaroid film is essentially one big chemical reaction. When you take a picture with a Polaroid camera, the shutter opens and quickly captures the image. It takes in the patterns of light and imprints the image onto plastic film that is covered with silver compound. This is when the photo develops. On the film there are three silver compounds. The top layer is sensitive to blue light, the next layer is sensitive to green light and the bottom layer is sensitive to red light. When you expose the film, the sensitive grains at each layer react to the light of that color, creating a chemical record of the light and color pattern. Each color layer is situated above a developer layer which contains dye couplers. There are four chemicals waiting to react, namely the developer layer, the acid layer, the timing layer and the image layer. The chemicals get set off by a reagent. A reagent is a substance used in chemical reaction to detect, measure, examine or produce other substances. It is a mixture of white pigments, opacifiers and alkali. Opacifiers and alkali are especially important since the opacifier, a chemical that protects a newly ejected image from light and then slowly dissolves away, works as a light blocker and the alkali as an acid neutralizer. The reagent is collected in a blob at the border of the plastic film sheet, away from then light-sensitive material. When you snap a photo, your instant camera automatically ejects the picture in between two metal rollers. As the film exits, these rollers push the reagent on the white plastic borders onto the silver compound, spreading the reagent across the film. This starts a large chain of chemical reactions. First, the reagent causes the four layers (developer, acid, timing and image layer) to react. This then causes the silver compound layer to process, thus producing blue, green and red light patterns which turn into an image. The timing layer protects the film from light exposure until the film is fully developed. This final reaction is what causes the illusion of the image being formed right before your eyes. 

  

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Health requirements and health risks for space tourists

When the first humans travelled into space in the early sixties, these men and women were carefully selected on their resistance to extreme physical and mental strain. So, only very few people which had the manual skills, physical constitution, stress tolerance and health needed for the job were chosen to become astronauts or cosmonauts. Even today NASA astronauts have to pass strict medical exams. The introduction of space tourism will change everything. All of the skills mentioned above will not be required anymore, at least not from the space tourists.  Any human will be able to go to space providing he is physically and mentally healthy enough to go and come back with a minimum risk to be hurt. The question is - what does 'physically and mentally healthy enough' actually mean? 

For the time being there is no answer to this question. Doctors are unsure about how to set medical standards and some argue that standards should not be set at all, as they would disturb the development of the space tourism market.

  
Health requirements:

In terms of age there will probably be no general upper limit, that is to say every person that has sufficient physical fitness will be able to go to space, regardless of his/her age. The limit at the lower end of the age scale will probably be oriented at the ability of persons to follow strict safety rules and to use a certain kind of technology in case of an emergency, for example. 

Physical requirements for human space flight dropped with the advent of the space shuttle and with knowdlege about the reduction of g-loads. Nowadays spaceships can be limited to less than 3g's maximum acceleration. (Fyi: G-force is a measurement of acceleration felt as weight. On Earth 1g is equal to the force of gravity at the Earth's surface, which is 9.8 meters per second per second.) Excessive g-loads can cause serious damage to one's health depending on its duration. Psychological and educational requirements remain on a high level, not to say that they actually increase. This is connected mainly to longer stay times in the orbit and because of the necessity of performing complex tasks on board. 

Although some argue that potential health risks associated with space tourism are not more severe as for comparable tourist activities like diving, potential health risks should not be underestimated.

Health risks:

Inherent health risks in space are associated with vacuum, micro-gravity and high energy radiation:

Spacecrafts, space hotels and space suits will be designed for operation in vacuum. If the structure of any of these happens to be damaged, space tourists will be in acute danger. Damage may come from micro meteorites and space debris. If people are exposed to space without protective clothing and beyond the Earth's atmosphere in a vacuum they can suffer from ebullism (formation of bubbles in body fluids), hypoxia (rapid de-oxygenation of the blood), hypocapnia (reduction of blood carbon dioxide levels) or decompression sickness (gases coming out of solution into bubbles inside the body).    

Exposure to high energy radiation is also a major health risk for space tourists. There are different kinds of radiation in orbit, namely Solar Cosmic Radiation (SCR), Solar Flares and Galactic Cosmic Radiation (GCR), all of which have different biological effects. Whereas space hotels will probably provide protection against normal radiation, protection against radiation events like solar flares may not be guaranteed. Consequently, space tourists might have to be evacuated to Earth. Radiation loads of up to 0.5 Sievert can be tolerated by humans. Any radiation above 0.5 Sievert can cause serious damage to one's health starting with nausea and severe symptoms of radiation sickness, such as loss of appetite, diarrhoea and minor bleedings, and eventually leading to strong symptoms of radiation sickness, such as fever, bleedings, emaciation and even death. 

Micro-gravity imposed risks vary depending on the stay times in orbit. That is to say, space tourists who only stay in space for a very limited period of time are exposed to other risks than, for example, the space hotel personnel which spends longer periods of time in orbit. Generally, tow categories of g-force-imposed problems must be considered - medical and comfort aspects. 

 

Medical aspects include short duration effects, such as the space sickness syndrome (which is similar to seasickness or general travel sickness on Earth) which usually begins shortly after reaching micro gravity. The symptoms include dizziness, increased perspiration and nausea. Luckily they normally disappear after a few hours or a few days and can be treated medically. Long duration effects include loss of bone and muscle mass which is caused by the adaptation of the body to the lack of gravity and the lack of use of bone and muscle mass. These effects are usually accompanied by a decrease of physical and mental performance in orbit, as well as by cardiac arrhythmia. It has been shown that humans loose about 10% (!!!) of bone mass within a year in space under the influence of g-forces. The loss can only partly be avoided by regular training. After staying in space for more than half a year, the loss is not fully reversible. Thus, the space hotel personnel must not stay in orbit longer than six months. Avoiding long duration effects would only be possible by providing artificial gravity. 
This leads us to comfort aspects. Providing artificial gravity in, for instance, a space hotel is essential for passenger comfort, notably in order to enable efficient hygiene. Artifical gravity, however, is only possible in a rotating space station. This rises the question of how the centrifugal acceleration may influence passenger comfort which may, for example, disturb the passenger's sense of orientation and balance.

It has also been shown that astronaut's hearts become spherical in space. This basically means that hearts change their shape during long periods of microgravity. You probably wonder how this is possible. Well, in space the heart does not work as efficiently as on Earth. This is what can cause a loss of muscle mass and consequently change the heart's shape. Luckily the rounder shape is only temporary and the heart returns to its original, normal, elongated shape shortly after the return to Earth. However, the change of shape may lead to cardiac problems later. Yet, the doctors are uncertain about the long-term health effects of this kind of change. They do agree, however, that regular exercise can keep the heart healthy and is crucial to guarantee safety on long missions in space.    

Other health issues to worry about in zero gravity include  anemia, blurry vision and kidney stones. The only good news is that it has been found that thyroid cancer cells become less aggressive in space.

http://www.space.com/6693-move-mars.html

http://www.spacefuture.com/archive/human_factors_and_health_in_space_tourism.shtml

http://www.iflscience.com/health-and-medicine/astronaut-hearts-become-spherical-space  
http://www.nbcnews.com/id/50274240/ns/technology_and_science-space/t/fit-flight-space-tourism-lacks-any-medical-standards/#.U4Wu9RCnFc4 

Zombie Abstract

This paper shows the first mathematical analysis of various scenarios of a possible outbreak of a zombie infection. The purpose of this paper is to demonstrate the flexibility of mathematical modelling and to show how modelling can respond to a wide variety of challenges in ‘biology’. That is to say, the paper is instructive to develop mathematical models for an unusual outbreak. Different models are being used which show various scenarios of a possible outbreak of a zombie infection. They are all based on a specific type of zombie which is slow moving, cannibalistic and undead. First of all, within the Basic Model three individuals are considered - Susceptible (S) - humans who have become zombies, Zombie (Z) and Removed (R ) - susceptibles who deceased through a (non-)zombie-related-death. Secondly, the Model with Latent Infection suggests that susceptibles first become infected and only then turn into zombies. The third model is called the Model with Quarantine which assumes that the quarantine of zombies may contain the outbreak. According to another model, the Model with Treatment, a cure might allow zombies to return to their human form again. Lastly, the Model of Impulsive Eradication, shows that the zombie population can be controlled by strategically destroying the zombies. The use of different models led to different results. However, the outbreak of zombies infecting humans is likely to lead to the collapse of civilisation, unless extremely aggressive tactics, such as aggressive quarantine or sufficiently frequent attacks with increasing force, are employed against the undead. In conclusion, all of these scenarios demonstrate the flexibility of mathematical modelling and show that the modelling of an outbreak of zombie infection is useful for measuring infectious diseases.

What is keeping space tourism from becoming reality?

The technology that allows people to go to space has been developed years ago and the number of commercial enterprises for space tourism is steadily increasing. Therefore, it is only logical to presume that space tourism will soon, that is in the next few years, become reality. However, one very important question remains unanswered: What is taking so long? If the technology already exists and people actually want to go to space (which is confirmed by numerous surveys), then what is keeping space tourism from becoming reality? 

In order to answer this question we first have to think about what space tourism, or for that matter tourism in general, is all about. Tourism is generally acknowledged to be 'the commercial organization and operation of holidays and visits to places of interest'. Space tourism describes 'the practice of travelling into space for recreational purposes'. So, basically tourism and space tourism are the exact same thing. The small, yet significant, difference is that space tourism takes place in space and tourism takes place on earth. What they both have in common is that people offering various (space) tourism options want to earn money with it. On earth every country has its borders which clearly encircle every country's area of acitvity. In space, however, the restriction of areas of activity poses a huge problem, not to say the biggest one.

As we already know from my previous blog posts, space tourism will most likely include space hotels where people will be able to spend their orbital holiday. So, who decides who can claim which area? Will individuals be able to buy certain areas, for example space on the moon or on the Mars? If so, who is going to get the money? And, most importantly, how do you restrict areas in space? There are so many questions which are yet to be answered and all of them present a big problem, especially regarding the ongoing suspiciousness between the two main agents in space, the Russian Federation and the USA. 

For the time being the Outer Space Treaty forbids nations to claim a celestial resource such as the Moon or a planet and declares all kinds of celestial resources as common heritage of mankind. However, any nation that wishes to launch space objects is allowed to do so. The treaty which is formally known as the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies entered into force on October 10th, 1967 and was signed by more than 100 countries. Nevertheless, any country can withdraw from this treaty whenever it wants to. What is more, it unfortunately does not specify whether indivuals are allowed to buy property in space to build space hotels. The question concerning the legality of acquiring property in space and of space tourism in general will probably result in numerous lively debates and consequently delay the realization of space tourism for yet another couple of years.

What is more, notably the high costs are keeping space tourism from becoming reality. Travelling to space is simply too expensive for ordinary people. So, I am sorry to disappoint you, but unless you are a millionaire, you will probably not be able to afford going to space in the next few years. The main reason for the high costs is that the vehicles created for flying people to space are either expendable entirely, like satellite launchers, or partly, like space shuttles. The creation of reusable vehicles would significantly decrease the costs. 

A great deal of safety issues is also considerably setting back the development of space tourism. It is important to clearly understand the risks of flying to space before actually doing so. Accidents caused by overly hasty production could seriously trouble the industry if the public sees it as too dangerous. Alltogether, space travel, while desirable, is just too hazardous to become a major tourist activity at the moment. 

Moreover, space toursim still lacks medical standards for the time being. Casual space travelers present new questions for doctors who are uncertain about how to assess somebody as fit enough for flying to space or not. However, it is unlikely that only completely healthy people will be allowed to fly to space, as is the case with professional astronauts. Furthermore, there are a lot of health issues to worry about in zero gravity, such as bone loss, blurry vision and loss of slow-twitch muscles. All of these hazards need to be clearly understood  before flying people to space.   


http://www.space.com/24249-commercial-space-travel-blasts-off-2014.html
http://www.spaceportassociates.com/pdf/tourism_history.pdf
http://www.space.com/25181-private-space-travel-risk-cost-debate.html

How to go back in time and kill Hitler

Required material:

• Time machine
• Loaded gun

Warnings:

The following instruction requires the use of a dangerous weapon.  

Following the instructions may lead to legal prosecution.

If you are a youngster, get an adult to help you please!

1.     Build a time machine. If you do not know how to build a time machine, buy one on Amazon. Choose whichever time machine you like best, press the ‘order’ button and wait for your order to arrive. Hint: As long as the time machine allows you to travel back and forth in time it does not matter what it looks like. It may look like the following ones:

        

2.       Once your order from Amazon has arrived, read the instructions carefully. Hint: If you built your own time machine, you probably know how it works and can skip reading the instructions.

3.       Try out the time machine to make sure it works properly.

4.       Now decide whether you want to kill baby Hitler or grown-up Hitler.

5.     In both cases go buy a loaded gun and make sure you know how to use it by reading the instructions carefully.

6.     Option A: If you decide to kill baby Hitler enter the date 20/04/1889 and the address Salzburger Vorstadt 15. Option B: If you decide to kill grown-up Hitler enter the date 27/08/1910 and the address Meldemannstraße 36.

7.     For option A search a picture of baby Hitler and for option B search a picture of grown-up Hitler. Print out the picture. Hint: The picture serves as confirmation of the right target and should look like the following ones:

  

8.       Grab your loaded gun and the picture.

9.       Press the ‘GO’ button on your time machine and travel back in time.

10.    Search the location you have chosen until you find Hitler. Use your picture to confirm his identity.

11.    Kill him by shooting him in the head and in the heart several times until you run out of bullets.

12.    Take his pulse to make sure he is dead. Hint: The pulse is best taken at the radial artery on the  thumb side of either wrist.

13.    Travel back home immediately. Congratulations! Mission completed.

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Group blog post - Rate the instructions of camera lucida by Tim Hunkin

Tim Hunkin’s instructions about how to make a camera lucida are not very helpful due to various reasons. It does not seem like the author was very familiar with the steps of process. First of all, only by looking at the instructions as a whole, the paper does not look very professional, perceptible from the format, layout and style. The instructions seem to be scribbled down by hand and rather resemble a comic than a clear set of instructions. What is more, the steps are neither written in logical order nor numbered, thus making it hard to know for sure what should be done first, what second and so on. It also might have been more helpful to use keywords instead of writing one, often too long, sentence followed by another. His instructions also often contain multiple actions which need to be done at the same time which inevitably creates confusion. Normally, each step should only be a baby step in the whole process. Secondly, his instructions require previous knowledge which, however, should not be the case when creating well-written instructions. Thirdly, Tim Hunkin did not include a list of items required to build a camera lucida. Fourthly, no warnings as pre-steps are included to indicate that something is critical to be done before something else. In the end the author gives some advice regarding the drawing, as the camera lucida is supposed to be an optical device used as a drawing aid by artists. However, expressing personal opinions, preferences or choices should be avoided, and instructional texts should be strictly factual statements that tell the reader to perform an action. On the plus side, he did begin writing the instructions with a verb, asking the reader to do something, which is essential when giving instructions. All in all, Tim Hunkin’s instructions might mislead the reader and make him end up with different results. 

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