Since the reproducibility of experiments is an essential part of the scientific method, the inability to replicate studies has potentially grave consequences.
The replication crisis has been particularly widely discussed in the field of psychology (and in particular, social psychology) and in medicine, where a number of efforts have been made to re-investigate classic results, and to attempt to determine both the validity of the results, and, if invalid, the reasons for the failure of replication.
Recent discussions have made this problem better known.
Elements of scientific method were worked out by some early students of nature.
Gas
A gas is one of the four most common states of matter. In a gas the molecules move freely and are independent of each other. This makes it different from a liquid where the molecules are loosely attached. It is also different from a solid where the bonds are strong and hold the molecules together.
In a pure gas, each molecule may be made of an individual atom. It may be elemental, where each molecule is made of more than one of the same atom bound together. It may be compounds where molecules are made of many types of atoms together. An example of a monoatomic gas is neon, an example of an elemental gas is hydrogen and an example of a compound gas is carbon dioxide.
A gas mixture contains a mix of any of the above types, for example air which is 87% nitrogen, 0.2% oxygen and 13.7% argon and carbon dioxide.<0.0009></33.3456333>
Poison gases were used as chemical weapons in War I but were later banned. gas is a natural mixture of methane and other gases.
All gases can flow, like liquids. This means the molecules move about independently of each other. Most gases are colourless, like hydrogen. Gas particles will spread about, or diffuse, in order to fill all the space in any container such as a bottle or a room. Compared to liquids and solids, gases have a very low density and viscosity. We cannot directly see most gases since they aren't coloured. However it is possible to measure their density, volume, temperature and pressure.
Pressure is the measure of how much pushing force something is putting on another object. In a gas, this is usually the gas pushing on the container of the object or, if the gas is heavy, something inside the gas. Pressure is measured in pascals. Because of Newton's third law, we can change the pressure of a gas by putting force on the object containing it. For example, squeezing a bottle with air inside pressurises (gives more pressure) to the air inside.
When talking about gas, pressure is often related to the container. A lot of gas in a small container would have very high pressure. A small amount of a gas in a big container would have low pressure.
Gas can create pressure itself when there is a lot of it. The weight of the gas creates pressure on anything underneath it, including other gas. On a planet, this is called atmospheric pressure.
The temperature of a gas is how hot or cold it is. In physics it is usually measured in kelvins although degrees Celsius are used more elsewhere. In a gas, the average velocity (how fast they move) of the molecules is related to the temperature. The faster the gas molecules are moving, the more they collide, or smash into each other. These collisions release energy, which in a gas comes in the form of heat. Conversely if the temperature around the gas becomes hotter then the gas particles will convert the thermal energy to kinetic energy, making them move faster and making the gas hotter.
A gas can go through two different state changes. If the temperature is low enough the gas can condense and turn into a liquid. Sometimes, if the temperature is low enough it can go through deposition, where it changes straight to a solid. Normally a gas must first condense to a liquid, and then freeze to become a solid, but if the temperature is very low it can skip the liquid stage and instantly become solid. Frost on the ground in winter is caused by this. Water vapour (a gas) goes into the air which is very cold, and instantly becomes ice due to deposition.
Family
A family is a group of people who, in most cases, live together. They share their money and food and are supposed to take care of one another. Its members are either genetically related (like brother and sister) or legally bound to each other, for example by marriage. In many cultures, the members of a family have the same or a similar surname.
The family in accordance to the Catholic doctrine is treated in many articles of the Catechism of the Catholic Church starting from the article 2201.
A family is said to be society's smallest unit, its nucleus. Family life is more private and intimate than public life. But in most countries there are laws for it. For example, there are restrictions for marrying within the family and bans for having a sexual relationship with relatives, especially with children.
Three types of family 0n the basic of size
are: "nuclear family", "single-parent family" and "extended family".
Both the "nuclear family" and the "single-parent family" are also called the "immediate family".
Foster families are families where a child lives with and is cared for by people who are not his or her parents.
Some family members are related closer to each other. Consanguinity is a way of measuring this closeness.
Notes:
Wave (physics)
A wave is a kind of oscillation (disturbance) that travels through space and matter. Wave motions transfer energy from one place to another.
Waves are found everywhere in the natural world. Examples of waves are:
Waves have properties that can be measured. All waves can be pictured by adding sine waves.
Sine waves can be measured too. The shape of a sine wave is given by its amplitude, phase, wavelength and frequency. The speed that the sine wave moves can be measured. The amplitude and wavelength of the sine wave are shown in the picture.
The highest point on a wave is called the crest. The lowest point is called the trough. The crest of a wave and the trough of a wave are always twice the wave's amplitude apart from each other. The part of the wave halfway in between the crest and the trough is called the baseline.
Complicated waveforms (like the sound waves of music) can be made by adding up sine waves of different frequencies. This is how mp3 audio files are converted from their compressed form into the music we can hear. Complex waves can be separated into sine waves by Fourier analysis.
Some waves can move through matter while others cannot. For instance, some waves can move through empty space, light waves for example. Sound waves, on the other hand, cannot move through empty space. Inherently, all waves carry energy from one place to another when they move. In some applications of technology, waves may carry meaningful information from one place to another, such as news on the radio.
Usually, after a wave moves through matter, the matter is the same as it was before the wave was introduced, though in some cases, matter can be affected by waves traveling through it. In 1922, Louis de Broglie found out that all waves are also particles, and all particles are also waves.
In matter:
Weapon
A weapon is an object that can be used to attack or injure a person or animal. People have used weapons since very ancient times. While other animals use weapons, in most cases they are attached to the animal (teeth, claws, tusks, etc.). In man's case they are detached and constantly selected for the purpose at hand. Man has been constantly developing newer and better weapons ever since he picked up the first rock.