Every atom has an atomic nucleus, which is made from protons and neutrons that are held together by the nuclear force. Because protons have positive electrical charge, they repel each other. Neutrons are neutral and they stabilize the nucleus. The neutrons hold the protons slightly apart. This reduces the electrostatic repulsion between the protons, so the nuclear force can hold the protons and neutrons together. One or more neutrons are necessary for two or more protons to bind into a nucleus. As the number of protons increases, so does the number of neutrons needed to have a stable nucleus.
Some elements only have a single isotope that is stable. For example, fluorine-19 (F) is the only stable isotope of fluorine. The other isotopes of fluorine decay rapidly so they are not found in nature. Other elements have many stable isotopes. For example, xenon has seven stable isotopes. It also has two isotopes that decay very slowly that are found in nature. The largest number of stable isotopes for any element is ten, for the element tin. Some elements do not have any stable isotopes, such as curium. These only exist on Earth because they are created in nuclear reactors, nuclear explosions, or particle accelerators.
Some unstable isotopes exist naturally on Earth because they have a very long half-life. For example, uranium-238 has a half-life of 4468 million years. The half life of radium-226 is only 1600 years, and it is found in nature because it is constantly forming from the decay of uranium-238.
Hydrogen has three common isotopes. The most common isotope of hydrogen is called protium (H), which has one proton and no neutrons. A hydrogen atom that has a proton and a neutron (atomic mass of 2) is called deuterium (H). Hydrogen with one proton and two neutrons (atomic mass of 3) is called tritium (H). Protium and deuterium are stable isotopes, while tritium is a radioactive isotope.
The heaviest elements in the periodic table are all radioactive. All of the isotopes of radon, thorium, and uranium are radioactive, since they are very heavy. This is because the nuclear forces inside the nucleus of the atom cannot hold together all the protons and neutrons.
Crushing by elephant
In the past, many rulers in south and southeast Asia had people crushed by elephants as a death penalty. This was common for more than 4000 years. The Romans and Carthaginians also sometimes did this.
The elephant would step upon the head of the condemned, the one commanded to die. Usually, handlers trained the elephant to put its large foot gently on the person's head. At this point, witnesses looked under the elephant's foot to make sure the prisoner was the one who committed the crime. Often, the condemned would scream and beg the witnesses to say it was not him. If a witness stated this was not the criminal, they would probably commit perjury. Perjury means lying at a trial. In those days rulers could punish perjury with death. Few witnesses denied the condemned was the criminal, because then the elephant may crush them instead. Then the mahout, or elephant driver, gave the order, and the elephant would push down with its weight. The skull broke and the foot crushed the head flat.
Sometimes, the elephant would drag the condemned through streets before the crushing. Some elephants crushed the arms and legs first, to increase the pain.
Most rajahs, Indian rulers, kept elephants for death by crushing. The public could often see the deaths; this was the rulers' warning not to commit a crime. Many of the elephants were very large, weighing more than nine tons. Rulers wanted crushing by elephant to be bloody and gross. Some rulers in history condemned children, too.
Many rulers in South Asia used elephants as executioners, ones who put the condemned to death. One nonreligious Mogul Emperor, Akbar (1547-1605), used his favorite elephant as a judge, too. Akbar ruled in the city of Agra from 1570-1585. He believed that his favorite elephant could know who was guilty. He put thousands of people to death this way. Even when the crimes were minor, he sent them to the elephant. Elephant handlers staked them before the great elephant and tried to convince it to step on them. The huge elephant crushed most, but sometimes refused. Akbar believed this proved their innocence and then released them.
Different regions crushed people by elephant in different ways. One region put people inside of a bag, so they would not have to watch what was about to happen. Then, the elephant would crush the bag flat with the condemned inside. In another region, people made the condemned watch the elephant slowly come from far away. Its huge feet kept coming closer. Sometimes, they buried the condemned to the neck. The elephant would come and step on the head. Some places made the condemned put his head on a special stand. The stand had fountains on the sides where brains and blood would flow when the elephant pressed down its huge foot.
For hundreds of years, people used elephants for military purposes. Death under the foot of an elephant was common for people who left the army or prisoners as well as for military criminals.
There are few records about crushing by elephant. Many records were lost. The British wrote about about it during their long rule of India.
Robert Knox was an English traveler. He wrote about a Sri Lankan crushing in 1681.
Power network
A Power network is a type of contact network where its members can tell other people what to do.
It must be large enough to literally scare or force people to go along with its requests, which makes them orders. This typically requires thousands of people in constant touch with each other.
A political party is the most obvious example. It is typically much larger than a social network but is not one, since people can only call on each other for a small number of reasons, and perhaps at specific times. Also not every member of the network has the same role or right to help.
A corporation may also be a power network if it relies on many power relations to maintain itself - for instance, the right to draw oil from the ground or dump waste without being held responsible for it.
When a power network achieves some stable grasp of political power and daily working control of some important infrastructure, it becomes a power structure. In a democracy the visible power networks represented by the parties compete regularly in an election - but much of the power structure, typically the bureaucracy, does not change, and is typically ignored as a power network in itself.
Citizenship
Citizenship is a legal relationship between a person and a country. Usually the country is the one they were born in, lives in, supports, and in return gets protection. A person is usually a citizen of the country where he or she is born, but sometimes a person will apply for naturalization, to become a citizen in another country. There are countries which allow dual (two) citizenship, and countries which do not.
A citizen is a member of a sovereign group of people that have certain rights. Governments protect these rights or take advantage of them. Some Governments may exile people from citizenship laws on such matter vary between countries.
People born in Canada become citizens of the country by "Jus soli" even if their parents are not citizens.
In 2018 the New York Times reported that 20% of babies born in Richmond Hospital in Richmond, British Columbia, were born to mothers involved in birth tourism. This means that the babies automatically acquire Canadian citizenship.
Elephant
Elephants are the largest living land mammals. The largest elephant recorded was one shot in Angola, 1974. It weighed 27,060 pounds (12.25 tonnes) and stood 13 feet 8 inches (2.16 m) tall. Their skin color is grey.
At birth, an elephant calf may weigh as much as 100 kg (225 pounds). The baby elephant develops for 20 to 22 months inside its mother. No other land animal takes this long to develop before being born.