Time is a measure of non-stop, consistent change in our surroundings, usually from a specific viewpoint.While the concept of time is self-evident and intuitive – the steady passing of events before our eyes; the orbit of the Moon around our planet – describing its fundamental nature is much harder.Even physicists aren't sure what actually happens when time passes. Although they do have a few hypotheses.

What's Time? (In Science)

For centuries, time was regarded as a constant, independent force, as if the Universe's progress is governed by a single clock.This description of time changed in 1905 with Albert Einstein's theory of special relativity.While the passing of time was already known to be closely connected to space, this monumental theory was the first to combine space and time into a single field, one with measurements that vary depending on the relative motion or gravitational forces of objects within it.Basically, that means time is relative

How does time work?

Two people moving at the same velocity will each agree their measures of distance and time match. As one person changes speed, however, they will see the other's measure of time and distance change, even as their own stays the same.Without any reason to prioritize one perspective of time over another, this means time isn't a constant universal unit at all. It is a relative measurement that varies as objects move faster or slower, or as they're subjected to more or less gravity.Gravity curves space and time: The stronger the gravity, the more it curves space-time, and the more time slows down.

Is time real?

Of course, for us to actually see these effects on time, the change in speed or gravitational pull must be enormous. But as an observer accelerates towards the speed of light, unique measures of time become increasingly noticeable.In theory, as a particle approaches the speed of light, we would see its 'clock' slow down. Once it exceeds the speed of light, its clock would, theoretically, seem in reverse from our point of view. From the particle's point of view, our clock would seem to reverse

Is it possible to reverse time?

similarly, the space-contorting volume beyond the horizon of a black hole also distorts perspectives of time.in our universe, we have freedom of space and can move around as we like, but we're forced to march along time's arrow in a linear direction.Calculations show that crossing over a black hole's horizon would swap those freedoms. So we'd no longer have to follow time's strict arrow of direction, but we'd lose the freedom to move around in space, allowing for time travel (of sorts).

What about time travel?

Models of space-time can describe measurements of time and space varying from one point to the next, but they don't explain much about time's stubborn adherence to a sequence of events.Under these descriptions of time, our Universe is a single block of space-time. There's sort of a beginning – the Big Bang – before which our best understanding of the laws of physics can't be applied. There's sort of an end, where change is no longer measured with any significance. But no single slice of time stands out physically as 'now'.

Why is there a future and a past?

Lively illustrations and fun, accessible text provide an account of the history of time and the evolution of keeping time, from following the sun and the moon to the huge clocks we use today.

About Time

Have you ever looked at the solar panels on roofs and wondered exactly what they do, and how? Well, those hi-tech expanses of shimmering glass are actually just one component in a complex network that harnesses the sun’s renewable energy to deliver electricity to the home within.

HOW SOLAR ENERGY WORKS (STEP BY STEP) ?

Each individual panel is constructed of a layer of silicon cells, a metal frame, a glass casing surrounded by a special film, and wiring. For maximum effect, the panels are grouped together into “arrays” (an ordered series) and placed on rooftops or in large outdoor spaces. The solar cells, which are also referred to as photovoltaic cells, absorb sunlight during daylight hours.

STEP 1:  SUNLIGHT ACTIVATES THE PANELS.

Within each solar cell is a thin semiconductor wafer made from two layers of silicon. One layer is positively charged, and the other negatively charged, forming an electric field. When light energy from the sun strikes a photovoltaic solar cell, it energizes the cell and causes electrons to ‘come loose’ from atoms within the semiconductor wafer. Those loose electrons are set into motion by the electric field surrounding the wafer, and this motion creates an electrical current.

STEP 2:  THE CELLS PRODUCE ELECTRICAL CURRENT.

You now have solar panels working efficiently to transform sunlight into electricity, but the electricity generated is called direct current (or DC) electricity, which is not the type of electricity that powers most homes, which is alternating current (or AC) electricity. Fortunately, DC electricity can easily be changed into AC electricity by a gadget called an inverter. In modern solar systems, these inverters can be configured as one inverter for the entire system or as individual microinverters attached behind the panels.

STEP 3: THE ELECTRICAL ENERGY IS CONVERTED.

Once the solar energy has been converted from DC to AC electricity, it runs through your electrical panel and is distributed within the home to power your appliances. It works exactly the same way as the electrical power generated through the grid by your electric utility company, so nothing within the home needs to change. Since you still remain connected to your traditional power company, you can automatically draw additional electricity to supplement any solar shortages from the grid.

STEP 4:  THE CONVERTED ELECTRICITY POWERS YOUR HOME.

On cloudy days and overnight, your solar shingles or panels may not be able to capture enough sunlight to use for energy; conversely, in the middle of the day when nobody is home, they may collect surplus energy—more than you need to operate your home. That’s why a meter is used to measure the electricity flowing in both directions—to and from your home.Your utility company will often provide credits for any surplus power you send back to the grid. This is known as net metering.

STEP 5:  A NET METER MEASURES USAGE.

Now that you know the basics about solar energy, you can marvel at how today’s photovoltaic technology can capture the vast power of the sun to operate a home. It may not be rocket science—but it definitely is human ingenuity at its best.

CONCLUSION

The sun shines down on Earth every hour of every day. In Solar Energy, learn how scientists are turning sunshine into electricity, discover the history of solar technology, and explore how solar power fits into the planet's energy future. Easy-to-read text, vivid images, and helpful back matter give readers a clear look at this subject. Features include a table of contents, infographics, a glossary, additional resources, and an index. Aligned to Common Core Standards and correlated to state standards. Core Library is an imprint of Abdo Publishing, a division of ABDO.

Physics 

Solar Energy

Dark matter is an invisible type of matter theorised to make up the majority of all matter in the Universe. It has mass, but it can't be seen and doesn't interact with ordinary matter.

What is dark matter In Physics?

According to our standard model of cosmology, dark matter makes up 85 per cent of all the matter in the Universe, and 27 per cent of the Universe's total mass-energy.

How much dark matter is there(In Universe)?

Despite its name it can’t simply be made up of dead stars, gas and dust. Dark matter has to consist of something more exotic than standard atomic particles to ensure the Big Bang produces a universe chemically similar to the one we see.Such observational constraints have forced theorists to focus on a handful of candidates for dark matter.

What is dark matter made of?

How much of our Universe is dark matter, and what evidence is there for its existence?

What is dark matter? | BBC Science Focus Magazine

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

What's The Block Hole

Black Holes?Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter in an object.The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns.

How Big Are Black Holes?

Scientists think the smallest black holes formed when the universe began.Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.Scientists think supermassive black holes were made at the same time as the galaxy they are in.

How Do Black Holes Form?

A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. Scientists can study stars to find out if they are flying around, or orbiting, a black hole.When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.

How Do We Know The Black Hole Is Black? 

Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now.The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.

Could a Black Hole Destroy Earth?

NASA is using satellites and telescopes that are traveling in space to learn more about black holes. These spacecraft help scientists answer questions about the universe.

How Is NASA Studying Black Holes?

Seattle teenagers of the 1970s are suddenly faced with a devastating, disfiguring, and incurable plague that spreads only through sexual contact.

Black Hole

Global warming is a gradual increase in the earth’s temperature generally due to the greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants. “. This phenomenon has been observed over the past one or two centuries. This change has disturbed the climatic pattern of the earth. However, the concept of global warming is quite controversial but the scientists have provided relevant data in support of the fact that the temperature of the earth is rising constantly.

Global Warmin

There are several causes of global warming, which have a negative effect on humans, plants and animals. These causes may be natural or might be the outcome of human activities. In order to curb the issues, it is very important to understand the negative impacts of global warming.

Cause Of Global Warming

<ul><li>Deforestation:Plants are the main source of oxygen. They take in carbon dioxide and release oxygen thereby maintaining environmental balance. Forests are being depleted for many domestic and commercial purposes. This has led to an environmental imbalance, thereby giving rise to global warming.</li><li>Use of Vehicles:The use of vehicles, even for a very short distance results in various gaseous emissions. Vehicles burn fossil fuels which emit a large amount of carbon dioxide and other toxins into the atmosphere resulting in a temperature increase.</li></ul>

Man-made Causes of Global Warming

<ul><li>Industrial Development:With the advent of industrialization, the temperature of the earth has been increasing rapidly. The harmful emissions from the factories add to the increasing temperature of the earth.</li><li>Overpopulation:An increase in population means more people breathing. This leads to an increase in the level of carbon dioxide, the primary gas causing global warming, in the atmosphere.</li></ul>

<ul><li>Volcanoes:Volcanoes are one of the largest natural contributors to global warming. The ash and smoke emitted during volcanic eruptions goes out into the atmosphere and affects the climate.</li></ul> <ul><li>Water VapourWater vapour is a kind of greenhouse gas. Due to the increase in the earth’s temperature, more water gets evaporated from the water bodies and stays in the atmosphere adding to global warming.</li></ul>

Natural Causes of Global Warming  

<ul><li>Melting Permafrost:Permafrost is frozen soil that has environmental gases trapped in it for several years and is present below Earth’s surface. It is present in glaciers. As the permafrost melts, it releases the gases back into the atmosphere, increasing Earth’s temperature.</li><li>Forest Blazes:Forest blazes or forest fires emit a large amount of carbon-containing smoke. These gases are released into the atmosphere and increase the earth’s temperature resulting in global warming.</li></ul>

Natural Causes of Global Warming

<ul><li>Rise in Temperature:Global warming has led to an incredible increase in earth’s temperature. Since 1880, the earth’s temperature has increased by ~1 degrees. This has resulted in an increase in the melting of glaciers, which have led to an increase in the sea level. This could have devastating effects on coastal regions.</li><li>Threats to the Ecosystem:Global warming has affected the coral reefs that can lead to the loss of plant and animal lives. Increase in global temperatures has made the fragility of coral reefs even worse.</li></ul>

Effects of Global Warming

<ul><li>Climate Change: Global warming has led to a change in climatic conditions. There are droughts at some places and floods at some. This climatic imbalance is the result of global warming.</li><li>Spread of Diseases: Global warming leads to a change in the patterns of heat and humidity. This has led to the movement of mosquitoes that carry and spread diseases.</li><li>High Mortality Rates:Due to an increase in floods, tsunamis and other natural calamities, the average death toll usually increases. Also, such events can bring about the spread of diseases that can hamper human life.</li></ul>

Describes the scientific evidence for global warming and its likely consequences, and considers the political implications and what governments, businesses, and individuals can do about the phenomenon and the issues it evokes

About Time

Solar Energy

What is dark matter? | BBC Science Focus Magazine

Black Hole

Global Warming

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