How Big Is Our Universe

How Big is Our Universe?

The universe is a big, big place. But how big? And how do we know? 

Throughout history, humans have used a variety of techniques and methods to help them answer the questions 'How far?' and 'How big?' Generations of explorers have looked deeper and deeper into the vast expanse of the universe. And the journey continues today, as new methods are used, and new discoveries are made. (To learn more about distance, visitHow Big is Our Universe. 

In the third century B.C., Aristarchus of Samos asked the question 'How far away is the Moon?' He was able to measure the distance by looking at the shadow of the Earth on the Moon during a lunar eclipse. 

It was Edmund Halley, famous for predicting the return of the comet that bears his name, who three centuries ago found a way to measure the distance to the Sun and to the planet Venus. He knew that the planet Venus would very rarely, every 121 years, pass directly between the Earth and the Sun. The apparent position of the planet, relative to the disk of the Sun behind it, is shifted depending on where you are on Earth. And how different that shift is depends on the distance from both Venus and the Sun to the Earth. This rare event, the transit of Venus, occurred again quite recently, June 8, 2004. 

It was knowing this fundamental distance from the Earth to the Sun that helped us find the true scale of the entire Solar system for the first time. 

When we leave the solar system, we find our star and its planets are just one small part of the Milky Way galaxy. The Milky Way is a huge city of stars, so big that even at the speed of light, it would take 100,000 years to travel across it. All the stars in the night sky, including our Sun, are just some of the residents of this galaxy, along with millions of other stars too faint to be seen. 

The further away a star is, the fainter it looks. Astronomers use this as a clue to figure out the distance to stars that are very far away. But how do you know if the star really is far away, or just not very bright to begin with? This problem was solved in 1908 when Henrietta Leavitt discovered a way to tell the 'wattage' of certain stars that changed their pulse rate linked to their wattage. This allowed their distances to be measured all the way across the Milky Way. 

Beyond our own galaxy lies a vast expanse of galaxies. The deeper we see into space, the more galaxies we discover. There are billions of galaxies, the most distant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago. So we see them not as they are today, but as they looked long before there was any life on Earth. 

Finding the distance to these very distant galaxies is challenging, but astronomers can do so by watching for incredibly bright exploding stars called supernovae. Some types of exploding stars have a known brightness - wattage - so we can figure out how far they are by measuring how bright they appear to us, and therefore how far away it is to their home galaxy. 

The image below is both the oldest and youngest picture ever taken. It is the oldest because it has taken the light nearly 14 billion years to reach us. And it is the youngest because it is a snapshot of our newborn universe, long before the first stars and galaxies formed. The bright patterns show clumps of simple matter that will eventually form stars and galaxies. This is as far as we can see into the universe. It is time, not space, which limits our view. Beyond a certain distance, light hasn't had time to reach us yet. 

So how big is the universe? No one knows if the universe is infinitely large, or even if ours is the only universe that exists. And other parts of the universe, very far away, might be quite different from the universe closer to home. Future NASA missions will continue to search for clues to the ultimate size and scale of our cosmic home. 

Electric Coffee Percolator

What Is A Polygon ?

A plane figure with at least three straight sides and angles, and typically five or more is called a polygon.
Electric Coffee Percolator
Handball Drills

How Many Dwarf Planets Are There In The Solar System ?

There are 5 dwarf planets in the solar system .
Electric Coffee Percolator
Handball Drills

How Many Planets Are There In The Solar System ?

There are 5 planets in the solar system . They are:-

1. Mercury
2. Venus
3. Earth 
4. Mars 
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

How Big Is The Sun ?

The sun is the largest and the most massive object in the solar system, but it is just a medium-sized star among the hundreds of billions of stars in the Milky Way galaxy.

Radius, diameter & circumference

The sun is nearly a perfect sphere. Its equatorial diameter and its polar diameter differ by only 6.2 miles (10 km). The mean radius of the sun is 432,450 miles (696,000 kilometers), which makes its diameter about 864,938 miles (1.392 million km). You could line up 109 Earths across the face of the sun. The sun's circumference is about 2,713,406 miles (4,366,813 km).

Mass and volume

The total volume of the sun is 1.4 x 10²⁷ cubic meters. About 1.3 million Earths could fit inside the sun. The mass of the sun is 1.989 x 10³⁰ kilograms, about 333,000 times the mass of the Earth. The sun contains 99.8 percent of the mass of the entire solar system, leading astronomers Imke de Pater and Jack J. Lissauer, authors of the textbook "Planetary Sciences," to refer to the solar system as "the sun plus some ebris."

 Yellow dwarf

It may be the biggest thing in this neighborhood, but the sun is just average compared to other stars.Betelgeuse, a red giant, is about 700 times bigger than the sun and about 14,000 times brighter.

The sun is classified as a G-type main-sequence star, or G dwarf star, or more imprecisely, a yellow dwarf. Actually, the sun — like other G-type stars — is white, but appears yellow through Earth's atmosphere.

Stars generally get bigger as they grow older. In about 5 billion years, scientists think the sun will start to use up all of the hydrogen at its center. The sun will puff up into a red giant and expand past the orbit of the inner planets, including Earth. The sun's helium will get hot enough to burn into carbon, and the carbon will combine with the helium to form oxygen. These elements will collect in the center of the sun. Later, the sun will shed its outer layers, forming a planetary nebula and leaving behind a dead core of mostly carbon and oxygen — a very dense and hot white dwarf star, about the size of the Earth.

How Long Does It Take To Get To The Moon ?

The time it takes to get to the moon depends on the speed of the spacecrafts. The Apollo 11 was launched July 16, 1969 from Kennedy Space Centre and landed on the moon on July 19th. It took a total of 3 days, 3 hours and 49 minutes to fly to the Moon and 3 days to return to Earth. Afterwards, on April 11, 1970, Apollo 13 was launched from the Kennedy Space Centre and landed on the Pacific Ocean after traveling around the Moon on April 17th. It took total of 5 days, 22 hours and 54 minutes to fly to the Moon and return back to Earth.

The shortest trip to the Moon took place in January 2006 by the NASA Pluto probe New Horizons. With the speed of 58,000 km/hr, it only took 8 hours and 35 minutes to get to the Moon from Earth. The longest trip took place in 2003 by the ESA SMART-1 lunar probe. It took 1 year and 6 weeks because it used ion engine which was very fuel efficient. However, these two missions did not return to Earth.

What Is DNA ?

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria 

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.

Why Is The Sky Blue ?

Why is the Sky Blue?

On a clear sunny day, the sky above us looks bright blue. In the evening, the sunset puts on a brilliant show of reds, pinks and oranges. Why is the sky blue? What makes the sunset red?

To answer these questions, we must learn about light, and the Earth's atmosphere.

Table of Contents

§  Why is the sky blue?

§  The Atmosphere

§  Light Waves and Colors

§  Why is the sky blue?

§  Blackness of Space

§  Red Sunsets

§  Learn More: The Atmosphere

§  Easy Reading

§  Projects

The Atmosphere

The atmosphere is the mixture of gas molecules and other materials surrounding the earth. It is made mostly of the gases nitrogen (78%), and oxygen (21%). Argon gas and water (in the form of vapor, droplets and ice crystals) are the next most common things. There are also small amounts of other gases, plus many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans.

The composition of the atmosphere varies, depending on your location, the weather, and many other things. There may be more water in the air after a rainstorm, or near the ocean. Volcanoes can put large amounts of dust particles high into the atmosphere. Pollution can add different gases or dust and soot.

The atmosphere is densest (thickest) at the bottom, near the Earth. It gradually thins out as you go higher and higher up. There is no sharp break between the atmosphere and space. Learn more about the atmosphere.

Light Waves

Light is a kind of energy that radiates, or travels, in waves. Many different kinds of energy travel in waves. For example, sound is a wave of vibrating air. Light is a wave of vibrating electric and magnetic fields.

It is one small part of a larger range of vibrating electromagnetic fields. This range is called the electromagnetic spectrum.

Electromagnetic waves travel through space at 299,792 km/sec (186,282 miles/sec). This is called the speed of light.

The energy of the radiation depends on its wavelength and frequency. Wavelength is the distance between the tops (crests) of the waves. Frequency is the number of waves that pass by each second. The longer the wavelength of the light, the lower the frequency, and the less energy it contains.

Colors of Light

Visible light is the part of the electromagnetic spectrum that our eyes can see. Light from the sun or a light bulb may look white, but it is actually a combination of many colors. We can see the different colors of the spectrum by splitting the light with a prism.

The spectrum is also visible when you see a rainbow in the sky.

The colors blend continuously into one another. At one end of the spectrum are the reds and oranges. These gradually shade into yellow, green, blue, indigo and violet. The colors have different wavelengths, frequencies, and energies. Violet has the shortest wavelength in the visible spectrum. That means it has the highest frequency and energy. Red has the longest wavelength, and lowest frequency and energy.

Light in the Air

Light travels through space in a straight line as long as nothing disturbs it. As light moves through the atmosphere, it continues to go straight until it bumps into a bit of dust or a gas molecule. Then what happens to the light depends on its wave length and the size of the thing it hits.

Dust particles and water droplets are much larger than the wavelength of visible light. When light hits these large particles, it gets reflected, or bounced off, in different directions. The different colors of light are all reflected by the particle in the same way. The reflected light appears white because it still contains all of the same colors.

Gas molecules are smaller than the wavelength of visible light. If light bumps into them, it acts differently. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates (releases, or gives off) the light in a different direction. The color that is radiated is the same color that was absorbed. The different colors of light are affected differently. All of the colors can be absorbed. But the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (It is named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)

Why is the Sky Blue?

The blue color of the sky is due to Rayleigh scattering.  As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.

How Big Is The Universe ?

How Big is Our Universe?

How To Score Well In PSA Exams

    You may think that PSA exams are though,frustrating,irritating, a waste of time or whatever you say it but is not.It's hard to say as I also have written the exam but it is pretty useful.If you write it you can basically gain more knowledge and it helps a lot for your future exams . You can also start thinking in a whole new perspective that you have never thought before . It is true that if you don''t score well in this exam your future may get spoiled but this exams helps a lot . It has helped me I have improved my vocabulary , grammar and my thinking skills . By the end of this article I will show you how to score well in this exam and may be also due to this exam it will help you in the future .

    You may also think that they are very hard but you can easily score well in it.You need the correct methods for it.It just takes about 24 hours prepare for it.You may think that is impossible but it is not. PSA Problems in study materials may be though but don't worry the paper will be easy if you prepare well enough.Like I said above it takes only 24 hours to prepare for it.About 8 hours for Qualitative Reasoning,8 hours for Language Conventions and 8 hours for Quantitative Reasoning . Just don't sweat it the exam will be easy do not get freaked out by the problems in study materials but you can use them as they are helpful . The dumbest think to do is to start reading the last day of the exams.It's pretty much a waste of time you will get very tense and basically nothing will get into your head.Try Reading a hour a day and you can complete within a month but I recommend about 2 hours a day for 12 days . Do not read like 3 hours or 5 hours a day if you finish a section and do not start the next section the same day.I know this is the most frequently said advice in the world but believe me I am also a student I also wrote the exam and I know how tense it is . You will get frustrated , you will get tense , some people may also think of suicide if you prepare at the last day.Now  let's see how to study each section.

    Language Convention:-

                        This is the part were they test your Grammar , Vocabulary and  thinking skills . For this you don't need any special books for grammar or anything . All you need is a dictionary and some common sense.For this section you have to be confident on your grammar . You don't need to buy very costly books on grammar and start reading them.All you have to do is be thorough on your previous years and present years grammar . They will also ask lot's of questions to test your vocabulary . This is the method to improve your vocabulary . Take your PSA study material if you don't have a study material take your English textbook or any words with hard words in it and also have a dictionary if you don't have one download one from your computer through the net . There are lot's of sites on the net that has a dictionary . I recommend using a dictionary in your computer . It is much faster than searching the word in a normal dictionary .Start reading any passage on the book you have taken . If you don't know a meaning of any word look it up in dictionary . Keep repeating this for a number of passages by this way you can improve your vocabulary . They will also ask lot's of questions like which word fits gap 10 , which would replace that word . For this you have to be confident on your grammar . That's pretty much it on language convention.
   Qualitative Reasoning:-
                       The basic concept on this section is Common Sense . There isn't much to read but you have to know about blood relation and directions . They will also give a passage and tell you to answer questions.
In blood relation you have know things like who is your son's wife and who is your uncle's daughter . I have given what you need to know below

• Mother's or Father's Son              -              Brother
• Mother's or Father's Daughter      -              Sister
• Mother's or Father's Sister           -              Uncle
• Mother's or Father's Brother        -              Aunt
• Mother's or Father's Father          -              Grandfather
• Mother's or Father's Mother        -              Grandmother
• Son's Wife                                   -              Daughter-in-Law
• Daughter's Husband                     -              Son-in-Law
• Husband's or Wife's Brother        -               Brother-in-Law
• Husband's or Wife's Sister           -               Sister-in-Law
• Brother's Son                              -               Nephew
• Brother's Daughter                       -              Niece
• Uncle or Aunt's Son or Daughter  -              Cousin

In direction sense test you need to know your directions which is North-East-South-West.That's it for Qualitative Reasoning.
     Quantitative Reasoning:-
                          This is the section that freaks everyone the most Quantitative Reasoning . In Study Materials the problems are given very tough that you will think you are going to fail the exams . Learning this section is not that though . All you have to do is study every Maths and Science formula you have learnt since 6th standard . They will not ask above that . Just have a cool head and do well in your PSA exams
   I have given every trick I know to score well in PSA exam . I hope this helped and if you liked it just leave a comment below.
                                                                  All The Best