What Is Time?

 WHAT IS TIME?

Time is familiar to everyone, yet it's hard to define and understand. Science, religion, philosophy, and the arts have different definitions of time, but the system of measuring it is relatively consistent.Clocks are based on seconds, minutes, and hours. While the basis for these units has changed throughout history, they trace their roots back to ancient Sumeria. The modern international unit of time, the second, is defined by the electronic transition of the cesium atom. But what, exactly, is time? Physicists define time as the progression of events from the past to the present into the future. Basically, if a system is unchanging, it is timeless. Time can be considered to be the fourth dimension of reality, used to describe events in three-dimensional space. It is not something we can see, touch, or taste, but we can measure its passage. 

Physics equations work equally well whether time is moving forward into the future (positive time) or backward into the past (negative time.) However, time in the natural world has one direction, called the arrow of time. The question of why time is irreversible is one of the biggest unresolved questions in science.

One explanation is that the natural world follows the laws of thermodynamics. The second law of thermodynamics states that within a closed system, the entropy of the system remains constant or increases. If the universe is considered to be a closed system, its entropy (degree of disorder) can never decrease. In other words, the universe cannot return to exactly the same state in which it was at an earlier point. Time cannot move backward.As far as the universe is concerned, time had a beginning. The starting point was 13.799 billion years ago when the Big Bang occurred. We can measure cosmic background radiation as microwaves from the Big Bang, but there isn't any radiation with earlier origins. One argument for the origin of time is that if it extended backward infinitely, the night sky would be filled with light from older stars.

Will time end? The answer to this question is unknown. If the universe expands forever, time would continue. If a new Big Bang occurs, our time line would end and a new one would begin. In particle physics experiments, random particles arise from a vacuum, so it doesn't seem likely the universe would become static or timeless. Only time will tell.

Где найти друга по переписке

 

Где найти друга по переписке: 4 лучших сайта

1. interpals.net — на сайте можно бесплатно зарегистрироваться и найти друга по переписке, предварительно просмотрев его профиль и решив, найдете ли вы интересные темы для общения. Ресурс довольно активный, постоянно находятся онлайн как минимум 3000-4000 человек.
2. mylanguageexchange.com — бесплатный сайт для поиска друзей за границей. На сегодняшний день общее количество членов сайта — более 550 000.
3. studentsoftheworld.info — тоже полностью бесплатный сервис для поиска друга по переписке. Ориентирован как раз на студентов, изучающих английский язык.
4. penpalworld.com — на сайте зарегистрировано более 2 000 000 пользователей. Бесплатно можно писать только 3 пользователям в день (в принципе, этого может быть вполне достаточно для общения). Чтобы писать бо́льшему числу участников, нужен платный аккаунт.

 

Writing a good CV

When you're applying for a job, a great CV is essential. Find out what to include and what to avoid for the best chance of getting an interview.

When you're looking for work, you need an attractive, clear and memorable CV (curriculum vitae) that shows your potential employer all the skills and experience you have for the job.

What should you include in a CV?

This article mainly focuses on writing a UK-style CV. If you're applying for a job internationally, be aware that the standard length, format and tone can vary from country to country. It's a good idea to check the expected format in the country or company you're applying to. 

Contact details 

Make sure the potential employer has a way of contacting you. Include your full name, telephone number and email address. 

Photo?

In many countries, employers expect to see a professional-looking photo on a CV. In others, like the UK, Canada and the USA, the law prohibits employers from asking for a photo, and it is better not to include one. Try to find out if it is usual to include a photo in the working environment you're applying to.

Education

List and date the most important qualifications you have obtained, starting with the most recent. You can also include any professional qualifications you have.

Work experience

List and date the jobs you've had and the companies you've worked for, starting with the most recent. It's usually enough to cover the last ten years of your work history. Include your job title, responsibilities and achievements in the job. 

If you have a lot of work experience, give the job titles but be selective about which responsibilities and achievements you highlight. Reduce the detail about jobs that are less relevant to the role you're applying for and draw attention to the most important experience you bring.

Skills 

These could include the languages you speak, the computer programs you can use well, the class type of your driving licence and any other professional skills you might have that are relevant to the job you're applying for.

Eight useful tips

Before you start getting ready to list your qualifications and work experience, here are eight useful tips to think about.

1. Keep it short … but not too short!

Your CV should be one to two sides of A4 paper. If you find you've got too much information, summarise and select the most relevant points. If it's shorter than a page, consider including more information about your skills and the responsibilities you had in your previous roles.

2. Use active verbs.

When you describe what you have achieved in previous jobs, use active verbs for a strong positive effect on the reader. For example, to make a change from was responsible for, use verbs like led or managed (a team / a project); created or developed (a product / a positive atmosphere); delivered (results/training); and provided (support/training). 

3. Fill in the gaps.

Avoid leaving gaps in your employment history. If you were travelling the world, on maternity leave or looking after small children, include that in your CV.

4. Make sure it's up to date.

Always ensure your CV is up to date. Include your most recent experience at the top of each section.

5. Don't exaggerate or lie.

Your potential employer can easily check information about where you have studied and worked. Don't be tempted to lie or exaggerate about your expertise, because sooner or later this will be discovered and may result in you losing the job. 

6. Spend time on the layout.

Make sure your CV is clear and easy to read. Use bullet points and appropriate spacing, keep your sentences short, line up your lists neatly and use a professional-looking font (e.g. Arial font size 12). 

7. Check for mistakes.

Mistakes on a CV create a bad impression. Use spell check, reread your CV and ask someone else to check it for you too before you send it.

8. Include a cover letter.

When you send your CV to apply for a job, you should send it with a cover letter or email to introduce your application. The cover letter should show your personal interest in the role, highlight the skills and experience you bring and encourage the employer to read the attached CV. 

Writing a good CV takes time and is hard work, but these tips and your effort will help you get the best possible start in your job search. Good luck! 

Environmental Chemistry

Environmental Chemistry

DO NOT say "you're welcome"! Respond to "thank you" PROPERLY!

Why Are Light and Heat Not Matter?

Why Light and Heat Aren't Matter

The universe consists of both matter and energy. The Conservation Laws state that the total amount of matter plus energy are constant in a reaction, but matter and energy may change forms. Matter includes anything that has mass. Energy describes the ability to do work. While matter may contain energy, the two are different from one another.

One easy way to tell matter and energy apart is to ask yourself whether what you observe has mass. If it doesn't, it's energy! Examples of energy include any part of the electromagnetic spectrum, which includes visible light, infrared, ultraviolet, X-ray, microwaves, radio, and gamma rays. Other forms of energy are heat (which may be considered infrared radiation), sound, potential energy, and kinetic energy.

Another way to distinguish between matter and energy is to ask whether something takes up space. Matter takes up space. You can put it in a container. While gases, liquids, and solids take up space, light and heat do not.

Usually, matter and energy are found together, so it can be tricky to distinguish between them. For example, a flame consists of matter in the form of ionized gases and particulates and energy in the form of light and heat. You can observe light and heat, but you can't weigh them on any scale.

Summary of Matter Characteristics

• Matter takes up space and has mass.
• Matter may contain energy.
• Matter may be converted to energy.

Examples of Matter and Energy

Here are examples of matter and energy that you can use to help distinguish between them:

Energy

• Sunlight
• Sound
• gamma radiation
• Energy contained in chemical bonds
• Electricity

Matter

• Hydrogen gas
• A rock
• An alpha particle (even though it can be released from radioactive decay)

Matter + Energy

Nearly any object has energy as well as matter. For example:

• A ball sitting on a shelf is made of matter, yet has potential energy. Unless the temperature is absolute zero, the ball also has thermal energy. If it's made of radioactive material, it may also emit energy in the form of radiation.
• A raindrop falling from the sky is made of matter (water), plus it has potential, kinetic, and thermal energy.
• A lit light bulb is made of matter, plus it emits energy in the form of heat and light.
• The wind consists of matter (gases in air, dust, pollen), plus it has kinetic and thermal energy.
• A sugar cube consists of matter. It contains chemical energy, thermal energy, and potential energy (depending on your frame of reference).

Other examples of things which are not matter include thoughts, dreams, and emotions. In a sense, emotions may be considered to have a basis in matter because they are related to neurochemistry. Thoughts and dreams, on the other hand, may be recorded as energy patterns.

What Is the Definition of "Matter" in Physics?

Matter has many definitions, but the most common is that it is any substance which has mass and occupies space. All physical objects are composed of matter, in the form of atoms, which are in turn composed of protons, neutrons, and electrons.

The idea that matter consisted of building blocks or particles originated with the Greek philosophers Democritus (470-380 BC) and Leucippus (490 BC).

Examples of Matter (and What Isn't Matter)

Matter is built from atoms. The most basic atom, the isotope of hydrogen known as protium, is a single proton. So, although subatomic particles aren't always considered forms of matter by some scientists, you could consider Protium to be the exception. Some people consider electrons and neutrons to also be forms of matter. Otherwise, any substance built of atoms consists of matter. Examples include:

• Atoms (hydrogen, helium, californium, uranium)
• Molecules (water, ozone, nitrogen gas, sucrose)
• Ions (Ca2+, SO42-)
• Polymers and Macromolecules (cellulose, chitin, proteins, DNA)
• Mixtures (oil and water, salt and sand, air)
• Complex Forms (a chair, a planet, a ball)

While protons, neutrons, and electrons are the building blocks of atoms, these particles are themselves based on fermions. Quarks and leptons typically aren't considered forms of matter, although they do fit certain definitions of the term. At most levels, it's simplest to state simply that matter consists of atoms.

Antimatter is still matter, although the particles annihilate ordinary matter when they contact each other. Antimatter exists naturally on Earth, although in extremely small quantities.

Then, there are things that either have no mass or at least have no rest mass. Things that are not matter include:

• Light
• Sound
• Heat
• Thoughts
• Dreams
• Emotions

Photons have no mass, so they are an example of something in physics that is notcomprised of matter. They are also not considered "objects" in the traditional sense, as they cannot exist in a stationary state.

Phases of Matter

Matter can exist in various phases: solid, liquid, gas, or plasma. Most substances can transition between these phases based on the amount of heat the material absorbs (or loses). There are additional states or phases of matter, including Bose-Einstein condensates, fermionic condensates, and quark-gluon plasma.

Matter Versus Mass

Note that while matter has mass, and massive objects contain matter, the two terms are not exactly synonymous, at least in physics. Matter is not conserved, while mass is conserved in closed systems. According to the theory of special relativity, matter in a closed system may disappear. Mass, on the other hand, may never have been created nor destroyed, although it can be converted into energy. The sum of mass and energy remains constant in a closed system.

In physics, one way to distinguish between mass and matter is to define matter as a substance consisting of particles that exhibit rest mass. Even so, in physics and chemistry, matter exhibits wave-particle duality, so it has properties of both waves and particles.