RIVULET BD.COM: 2013

মঙ্গলবার, ৬ আগস্ট, ২০১৩

RIVULET: dhkrvltssctn85@gmail.com

RIVULET: dhkrvltssctn85@gmail.coM

DHAKA RIVULET ASSOCIATION

(Education&Science Organization) www.RIVULET BD.COM

শুক্রবার, ২১ জুন, ২০১৩

RIVULET: dhkrvltssctn85@gmail.com

The galaxy world

RIVULET: dhkrvltssctn85@gmail.com

razu khandoker

DHAKA RIVULET ASSOCIATION
(Education&Science Organization)
w.w.w.DHAKA RIVULET ASSOCIATION

মঙ্গলবার, ১৮ জুন, ২০১৩

RIVULET: dhkrvltssctn85@gmail.com

razu khandoker

Planets Around Other Stars

Throughout recorded history and perhaps before, we have wondered about the possible existence of other worlds, like or unlike our own. The earliest understanding of the solar system showed us that there were indeed other worlds in orbit about our Sun, and steadily growing understanding of their natures shows that all are dramatically different from Earth, and mostly very different from one another. As we came to understand that the stars in the sky are other suns, and that the galaxies consist of billions of stars, it appeared a near certainty that other planets must orbit other stars. And yet, it could not be proven, until the early 1990’s. Then, radio and optical astronomers detected small changes in stellar emission which revealed the presence of first a few, and now many, planetary systems around other stars. We call these planets “exoplanets” to distinguish them from our own solar system neighbors.
The Big Bang

The night sky presents the viewer with a picture of a calm and unchanging Universe. So the 1929 discovery by Edwin Hubble that the Universe is in fact expanding at enormous speed was revolutionary. Hubble noted that galaxies outside our own Milky Way were all moving away from us, each at a speed proportional to its distance from us. He quickly realized what this meant that there must have been an instant in time (now known to be about 14 billion years ago) when the entire Universe was contained in a single point in space. The Universe must have been born in this single violent event which came to be known as the "Big Bang."
Dark Energy, Dark Matter

What is dark energy? More is unknown than is known — we know how much there is, and we know some of its properties; other than that, dark energy is a mystery — but an important one. Roughly 70% of the Universe is made of dark energy. Dark matter makes up about 25%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter adds up to less than 5% of the Universe. Then again, maybe it shouldn't be called "normal" matter since it is a small fraction of the Universe!
Stars

How do stars form and evolve? Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.
Galaxies

Our galaxy, the Milky Way, is typical: it has hundreds of billions of stars, enough gas and dust to make billions more stars, and about six times as much dark matter as all the stars and gas put together. And it’s all held together by gravity. Like more than two-thirds of the known galaxies, the Milky Way has a spiral shape. At the center of the spiral, a lot of energy and, occasionally, vivid flares. are being generated. Based on the immense gravity that would be required explain the movement of stars and the energy expelled, the astronomers conclude that at the center of the Milky Way is a supermassive black hole.
Black Holes

Don't let the name fool you: a black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area - think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City. The result is a gravitational field so strong that nothing, not even light, can escape. In recent years, NASA instruments have painted a new picture of these strange objects that are, to many, the most fascinating objects in space. What happens at the edge of a Black Hole?

সোমবার, ১৭ জুন, ২০১৩

RIVULET: dhkrvltssctn85@gmail.com

RAZU KHANDOKER

DHAKA RIVULET ASSOCIATION
(Education&Scieceorganization)
www.rivulet bd.com

Why

should anyone who is not a scientist care about science education? Professional scientists and educators may find the question insulting. Every culture has struggled to find the most effective ways to teach the uninitiated and translate that learning into productive skills. But if students and parents around the world don't see the need for a high-quality education in science, technology, engineering, and mathematics (the so-called STEM fields), or mistakenly think that they are already receiving satisfactory teaching in those areas, then calls from the scientific community to improve STEM education will fall on deaf ears.

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In this special issue of Science, we have invited experts to tell us what they think are the most important challenges facing science education. Through a mixture of News, Reviews, Perspectives, Education Forums, and an Editorial, we explore the obstacles to progress, be they within the classroom, across the school system, or in the larger social arena. We also offer substantive suggestions on how to proceed. For example, distance education, online simulations as educational aids, and social networking tools are already part of science education. Many university faculty members are working to upgrade centuries-old approaches to instruction. And, with a new emphasis on the practice of science, promising assessment tools are being developed to improve learning.

The challenges covered in this special issue will be familiar to those who have devoted their lives and livelihoods to improving education. There is a huge and expanding literature on these topics and many others not covered in these pages. Yet convincing the public of the importance of STEM education will require more than explaining what the research shows or finding ways to scale up best practices to reach the billions of students who are entitled to a high-quality education. For scientists, advances in science and technology arrive at such a rapid clip that last year's knowledge barely scratches the surface of what is needed next year. At the same time, larger and more diverse student populations clamor for access to knowledge. Not only will the scientific workforce for the 21st century need skills and knowledge we haven't even heard of yet, but all global citizens, whether in their doctor's office or in a polling booth, need to be better informed. Turning the fire of the natural curiosity of students into effective, flexible, and well-grounded outcomes will take a concerted effort by many different actors. Among them, scientists must play a central role.

This is another grand challenge, and one that the scientific community ignores at its peril