When a clock is in motion, it ticks slower by a tiny factor of formula_4. The famous twin paradox says that if there were two twins and twin A stayed on earth while twin B traveled near c for a few years, when twin B got back to earth, he would be many years younger than twin A (because he experienced less time). For example, if twin B left when he was 20 and traveled at .9c for 10 years, then when he got back to earth, twin B would be 30 (20 years + 10 years) and twin A would be almost 43:
Twin B would not notice that time had slowed at all. To him, if he looked out a window, it would seem like the universe was moving past him, and therefore slower (remember, to him, he's at rest). So time is relative.
Things get shorter in the direction of movement when they travel at relativistic speeds. During twin B's journey, he would notice something strange about the universe. He would notice that it got shorter (contracted in the direction of his motion). And the factor by which things get shorter is formula_4.
Relativistic mass also increases. It makes them harder to push. So by the time you reach 0.9999c, you need a very big force to make you go faster. This makes it impossible for anything to reach the speed of light.
Still, if you travel a bit slower, say 90% of the speed of light, your mass only grows by 2.3 times. So, while it may be impossible to reach the speed of light, it may still be possible to get close to it—that is, if you have enough fuel.
Cyperaceae
The family Cyperaceae, or the sedges, is a taxon of flowering plants. They look like grasses or rushes, but are not. They are monocot plants (as are grasses), but belong to a different family.
The family is large, with some 5,500 species described in about 109 genera. The largest is the "Carex" genus of "true sedges", with over 2,000 species.
Sedges include many wild marsh and grassland plants, and some cultivated ones such as water chestnut ("Eleocharis dulcis") and papyrus sedge ("Cyperus papyrus"). These species are widely distributed, with many in tropical Asia and tropical South America. Sedges may be found growing in almost all environments. Many are wetlands, or have poor soils. Ecological communities dominated by sedges are known as sedgelands.
Features distinguishing members of the sedge family from grasses or rushes are stems with triangular cross-sections (with occasional exceptions) and leaves that are spirally arranged in three ranks (grasses have alternate leaves forming two ranks).
Objective-C
Objective-C is an object-oriented programming language used to make computer programs for macOS and iOS devices.
Objective-C was created in the early 1980s by two programmers named Brad Cox and Tom Love. It didn't become popular, however, until it was bought by NeXT in 1988 for their NeXTSTEP operating system. After NeXT was bought by Apple in 1996, it became the main programming language for Mac OS X and later the iPhone, iPod Touch and iPad.
Objective-C is a strict superset of C, meaning that any code that can be written in C can be used in Objective-C programs without being rewritten. However, it adds some features of its own that cannot be used in a traditional C program.
In Objective-C, functions are called using messages, a feature inspired by the SmallTalk programming language. Messages look like "blocks" of code similar to the on shown below:
These blocks can be nested inside of each other as well, for example:
Unlike other programming languages such as C and [[Java (programming language)|Java]], Objective-C "classes" are divided into two separate parts:
Usually, these are put in two different files, with the interface using the ".h" extension and the implementation using the ".m" extension.
Objective-C has variants that add features to the original Objective C programming language.
Objective-C++ allows for [[C++]] code to be used in Objective-C applications.
Objective-C 2.0 is an improved version of Objective-C. It adds many features, such as garbage collection (automatic memory management), fast enumeration and properties (the automatic generation of variable methods).ATLAS experiment
ATLAS (A Toroidal LHC ApparatuS) is the biggest experiment at the Large Hadron Collider (LHC).
It is one of the seven particle detector experiments (ALICE, ATLAS, CMS, TOTEM, LHCb, and LHCf) built at the LHC. LHC is a new particle accelerator at the European Organization for Nuclear Research (CERN) in Switzerland. ATLAS is 46 metres long and 25 metres in diameter, weighing about 7,000 tonnes. The project is led by Fabiola Gianotti. The project has 2,000 scientists and engineers at 165 institutions in 35 countries. The project began operation on 10 September 2008. ATLAS studies highly massive particles which could not be studied using earlier lower-energy accelerators. ATLAS may start new theories of particle physics beyond the Standard Model.
Taser
A Taser is a weapon that is not meant to kill. Tasers use electricity to shock people so they fall on the ground. If a person is shot by a Taser, they feel like they are hurt and cannot move their arms and legs. Tasers are used by police officers to stop people who want to hurt them, and to stop people who are running away.
Tasers shoot two small pieces of metal called prongs. These prongs are connected to long pieces of metal string. When the Taser is shot, the prongs hit the person and electricity moves along the metal string to shock the person.
If a person is very close, the prongs do not have to shoot but they will still shock.
Even though a Taser is a weapon that is not meant to kill, the prongs can still hurt people. There are some times when people die after they are shot with a Taser. This is because some people get hurt differently by electricity.
In many places, people cannot own a Taser. There are special rules to follow to own a Taser. This is because it is considered a weapon.
In Canada, France, Israel and the United Kingdom only police officers can have a Taser, but in the United States of America and Poland, most people can own a taser.
Wallpaper
Wallpaper is a kind of paper used to cover walls inside of houses and buildings. Wallpaper is used to decorate the inside of buildings instead of paint. It is sold in rolls and are put onto a wall using wallpaper paste. Wallpapers can come either plain (so that it can be painted), or with pictures or patterns.
"Wallpaper" is also a word for a picture on a computer monitor.
Wallpaper was first used in Europe around the year 1500. Wallpaper was made to look like rugs that hang on walls because they were like pictures. Soon after people started making wallpaper, England and France started making a lot of wallpaper. For a while in 1650, wallpaper was not used because the religious leader in England did not like it. However, by 1750 people were using wallpaper all the time and more people got better at making wallpaper.
Water is the easiest way to get rid of wallpaper. Water makes the wallpaper paste become not sticky, then the wallpaper falls off.
Sometimes the wallpaper paste is too strong for water, then special chemicals need to be used to make the paste not sticky. Most of the time only new wallpaper has to be taken off with chemicals.
Really hot water makes it easier to remove wallpaper. There are special machines that people can use to make water into steam and use it to remove wallpaper.
Animal trapping
Animal trapping, or simply trapping, is the use of a device to catch an animal. Animals may be trapped for a variety of purposes, including food, wildlife management, hunting and pest control.
There are many kinds. For a deadfall trap, a trapper digs a deep hole in the ground and hides it so the animal falls in the hole and can not get out. A snare is a noose that tightens around the neck or other part of the animal.
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