Ledakan Kehidupan Setelah Hujan Meteor

Masa akhir Ordovician

Bagaimana kehidupan di Bumi terbentuk? Kalau sebelumnya sempat dibahas benih kehidupan di Bumi yakni asam amino, dibawa oleh meteorit CR Chondrites dari luar angkasa. Ternyata, ada berita baru yang menyatakan kalau ledakan kehidupan di Bumi terjadi setelah hujan meteor lebih dari 400 juta tahun lalu. Pada saat itu, meskipun Bumi diserang lebih dari 100 meteorit berukuran 1 km dalam waktu yang sangat singkat, ternyata kehidupan tidak hanya bisa diselamatkan tapi justru terus berkembang.


Rangkaian tabrakan meteorit tersebut terjadi sepanjang periode Ordovician, antara 490 - 440 juta tahun lalu. Memang kehidupan yang ada belum seperti kehidupan yang kita kenal sekarang, namun saat itu sudah ada makhluk hidup di darat dan organisme juga sudah mulai berevolusi untuk bisa hidup dalam ceruk di lautan. Tampaknya, ketidakteraturan pada sabuk asteroid 470 juta tahun lalulah yang mengirimkan ratusan batuan angkasa keluar dari orbit normalnya menuju Bumi.

Pemusnahan besar-besaran oleh meteorit

Setelah beberapa juta tahun, lebih dari 100 meteorit besar yang telah terpisah-pisah kemudian menyerang Bumi, dan membalut Matahari dalam debu. Tumbuhan yang lapar akan Matahari akahirnya mati dan rantai kehidupan yang bergantung pada tumbuhan pun putus. Tapi secara mengejutkan, kehidupan justru berkembang pesat setelah periode tersebut. Tumbuh dan berevolusi kedalam bentuk yang baru dan lebih menarik.

Para peneliti dari Universitas Copenhagen dan Universitas Lund, bersama-sama mengumpulkan contoh kimia dari meteorit, fosil dan juga mempelajari beberapa kawah di Swedia. Kawah Lockne adalah salah satu kawah yang juga diteliti, terletak di utara Swedia dengan diameter 75 km. Penelitian yang dilakukan menunjukan adanya bukti kehidupan yang berkembang pada lapisan lebih baru dibanding lapisan yang mengandung sisa serangan meteorit.

Masa setelah pemusnahan besar-besaran.

Dengan adanya ledakan kehidupan tersebut, bisa dikatakan evolusi biologis mendapat bantuan besar dalam waktu relatif singkat. Contoh kasus, letusan gunung berapi atau kebakaran hutan yang besar, pada awalnya akan membawa pengaruh kerusakan yang sangat besar pada kehidupan. Namun dari abunya muncul fauna yang lebih kaya dari yang ada sebelumnya.

Awal tahun ini, paleontologis menyatakan kalau kehidupan bisa kembali muncul dengan cepat setelah kejadian pemusnahan besar-besaran, namun dibutuhkan waktu yang panjang untuk bisa mengembalikan keanekaragaman kehidupan. Karena itu, setelah sebagian besar kehidupan tersapu oleh asteroid, kecoa, lipas maupun hewan berkerat seperti tikus yang mengambil alih. Tapi butuh beberapa tahun sebelum kekayaan ekosistem bisa kembali dengan kupu-kupu, jerapah atau yang lainnya.

Sumber : Universe Today, Nature Geoscience


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Laptop for Dummies

oleh Burhan Solihin

Belakangan ini koran-koran dibanjiri iklan penjualan laptop murah. Dari raja-raja laptop seperti Toshiba, IBM alias Lenovo, HP, Acer, sampai para pendatang baru seperti ECS, A Note, dan Benq, semua pasang advertensi. Dengan uang Rp 5 jutaan, siapa pun bisa bawa pulang laptop keren dan gaya.

Dari belasan merek dan jenis laptop yang bertebaran itu kira-kira mana yang cocok untuk Anda?

Berikut ini sebagian faktor yang perlu dipertimbangkan dalam memilih laptop. Ini hasil pikiran dummy for dummies, hehehe … Siapa tahu berguna.

1. Tentukan batas kisaran harga

Menurut para konsultan finansial sebaiknya kita membeli berdasarkan KEBUTUHAN bukan KEINGINAN bukan pula GENGSI. (gengsi aja kok nggak boleh)

2. Aplikasi apa yang sering dipakai:

* Kalau cuma buat ngetik, bikin presentasi powerpoint, excel, internetan, sesekali photoshop kelas Intel Celeron atau AMD Sempron pun sudah cukup. Bahkan banyak sudah dilengkapi akses Wifi. Tak perlu beli laptop dg prosesor Centrino yg mahal. Celeron/Sempron pun kuat buat Photosop-an, Corel Draw, bahkan juga QuarkExpress (desain utk bikin koran seperti yang dipakai Koran Tempo)–sudah dites di rumah. Kalau mau lebih bertenaga dg laptop murah, upgrade sendiri memori atau RAM dari 256 MB –> 512 MB. Karena Windows XP itu seperti Linux kalau dipasang di komputer bermemori 256 MB memang kurang greng
* Kalau buat yg suka ngoprek program komputer, desain grafis yang berat, memang lebih enak pake prosesor kelas atas seperti Core 2, AMD Turion. Centrino atau Core Solo biasa pun sebenarnya juga sudah lumayan lah.
* Dan ingat laptop-laptop prosesor Core Duo itu saat ini pun tidak bisa running 100 persen seperti yang diinginkan produsennya. Karena, prosesor Core 2 menuntut software baru yang cocok untuk “otaknya”. Dan sekarang ini software itu masih sedikiiiiit sekali. Baru Windows Vista doang (itu pun baru dilaunch). Jadi, aspek kecepatan yang diharapkan dari kerja laptop Core 2 ini ya.. ndak terlalu dramatik..

3. Seberapa mobile Anda

* Semakin mobile pilih yang kecil dan ringan. Rata-rata laptop beratnya 2,3-2,5 kg. Laptop ini buat ngeliput kerusuhan seperti di Tasikmalaya (Beberapa tahun silam) atau Poso–artinya dibawa di ransel jalan keliling kota lebih dari 2 jam–bikin pundak pegelnya lumayan. Idealnya sih buat wartawan cari yg enteng di bawah 2 kg cuma mahal. Namun, kalau dipake kerjanya cuma di kantor atau 1-2 bulan sekali kerja di kafe sih berat 2,3-2,5 kg sih masih oke.
* Semakin mobile pilih baterai yang tahan lama. Rata-rata laptop sih baterainya 2,5 - 3 jam. Yang ultra low voltage seperti keluaran Fujitsu, Sony Vaio, Toshiba Portege bisa 4-7 jam.
* Bagi pengguna yang bukan high frequent flyer kelas baterai yg 2,5-3 jam pun sudah cukup. (Emang seberapa kuat sih kita kerja di kafe seperti Starbucks? mendingan ngelihatin tamu kafe atau baristanya kan daripada kerja, hehehe)

4. Layar

* Yang suka kecil tentu saja pilih layar 8, 10, 11 atau 12 inchi –> sayangnya yg kecil ini biasanya lebih mahal
* Yang sedang-sedang sih 13 atau 14 inchi. Yang 15 inchi biasanya lebih murah lagi. Ingin lebar tapi nggak pingin kelihatan gede pilih yang wide screen. Layar 13 wide sreen lumayan, tak terlalu kecil atau gede.
* Yang buat desain ya enaknya 17 inchi

5. Yang perlu diingat pula laptop yang sudah kita beli itu cenderung harganya terjun bebas.

Dalam 2 tahun laptop bekas itu bisa turun harganya 2-4 juta. Jadi kalau beli mahal-mahal pertimbangkan pula penyusutan nilai yg gila-gilaan.

Kalau saya sih lebih suka membeli laptop yang tak terlalu canggih mengingat toh harganya 2-4 tahun akan drop habis-habisan dan menjual kembali laptop itu tak gampang. Pilih teknologi medium, dengan harga menengah mungkin salah satu alternatif yang patut dipertimbangkan karena dari sisi teknologi tak ketinggalan amat, dari harga juga ngga nguras kantong banget.

6. Reputasi merek

* IBM (sekarang Lenovo) — desain kaku (tipe yg terakhir aja agak manis seperti Z61), tapi kuat dan bandel, ukuran keyboard paling pas di tangan
* Acer — merek taiwan desain manis, klaim nya sih nomor satu di Eropa tahun 2006
* Toshiba — pernah bertahun-tahun jadi laptop no 1 di dunia dan di Indonesia, lumayan bandel
* ECS — merek Taiwan , katanya sih ok tanya Prabandari (Kabiro Tempo di bandung, dia beli ECS yang tablet PC yg bentuknya spt buku agenda dari tahun 2005), purnajual katanya juga oke
* Dell –keren untuk tipe yang Inspiron seperti punya mas Wawan (Teknologi)
* Sony Vaio — Hfff… desain yang tipe TX kereeen banget kecil dan imut-imut. Sayang harganya masih di 18-20 juta.
* Hp/Compaq — Malangnya aku tak pernah suka desainnya
* Fujitsu — yang tipe kecilnya keren.. walau tak selucu Vaio
* Powerbook — cool and different, tipis, tapi berat dan tak cocok bagi pengoprek komputer karena sistem operasinya Macintosh.

Faktor lainnya sih cuma asesoris seperti koneksi bluetooth, infra merah, pengaman dg sidik jari, pembaca kartu SD. Semuanya bisa jadi pertimbangan minor.

Ya, ini uneg-uneg pemburu dan penggemar laptop bekas hehehehe, boleh didengar boleh juga tidak. Jadi, selanjutnya terserah Anda.
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Saat Dua Lubang Hitam Bergabung

Ilustrasi penggabungan dua lubang hitam. Sumber : Universe Today.
Apa yang terjadi jika dua galaksi bergabung? Bagaimana dengan lubang hitam supermasif yang ada di pusat kedua galaksi tersebut? Bayangkan bagaimana gaya yang akan dilepaskan saat dua lubang hitam dengan massa ratusan juta massa Matahari bergabung. Kejadian ini bisa saja diamati dari Bumi, jika kita memang tahu apa yang sednag kita cari.
Sebagian besar Galaksi di Alam Semesta ini memiliki lubang hitam supermasif. Beberapa lubang hitam yang paling besar bisa memiliki massa ratusan juta bahkan miliaran massa Matahari. Dan area disektar lubang hitam tersebut akan menjadi sangat ekstrim. Bahkan para ilmuwan juga memprediksikan dengan teori relativitas Einstein kalau lubang hitam tersebut berputar dengan laju maksimum.

Saat dua galaksi bergabung, lubang hitam supermasif yang ada di kedua galaksi itu tentu akan berinteraksi. Bisa saja interaksi tersebut melalui sebuah tabrakan, atau mungkin dari gerak spiral ke dalam sampai mereka mengalami penyatuan (merger). Menarik bukan?
Berdasarkan simulasi yang dilakukan G. A Shields dari University of Texas, Austin dan E. W. Banning dari Yale University, hasil penyatuan tersebut seringnya merupakan gerakan mundur yang sangat kuat. Dalam proses penggabungan ini, lubang hitam tersebut bukannya mengalami proses penggabungan yang manis, namun gaya yang muncul sangat ekstrim sehingga salah satu lubang hitam akan terdorong keluar dengan kecepatan yang sangat besar.
Dorongan maksimum terjadi pada kedua lubang hitam saat mereka berputar dengan arah yang berbeda, namun keduanya berada pada bidang orbit yang sama. Dalam fraksi hanya satu detik, satu lubang hitam sudah mendapat dorongan yang cukup untuk keluar dari galaksi yang baru saja bersatu dan tak pernah kembali lagi. Saat satu lubang hitam mengalami dorongan, yang lainnya akan menerima energi yang amat besar, terinjeksi ke dalam piringan gas dan debu disekitarnya. Piringan akresi akan bersinar dengan flare sinar X tipis dan baru akan berakhir beberapa ribu tahun.
Nah, meskipun kejadian merger atau penggabungan lubang hitam supermaif itu sangat jarang, kecerlangan yang ditimbulkannya akan berakhir dalam waktu yang cukup lama sehingga bisa kita deteksi sejumlah kejadian yang pernah terjadi. Menurut para peneliti, ada sekitar 100 gerakan mundur yang tiba-tiba yang terjadi dalam 5 miliar tahun cahaya dari Bumi.
Sumber : ArXiV, Universe Today.

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Types and morphology of Galaxy

Main article: Galaxy morphological classification

Types of galaxies according to the Hubble classification scheme. An E indicates a type of elliptical galaxy; an S is a spiral; and SB is a barred-spiral galaxy.
Galaxies come in three main types: ellipticals, spirals, and irregulars. A slightly more extensive description of galaxy types based on their appearance is given by the Hubble sequence. Since the Hubble sequence is entirely based upon visual morphological type, it may miss certain important characteristics of galaxies such as star formation rate (in starburst galaxies) and activity in the core (in active galaxies).

Ellipticals

Main article: Elliptical galaxy

The Hubble classification system rates elliptical galaxies on the basis of their ellipticity, ranging from E0, being nearly spherical, up to E7, which is highly elongated. These galaxies have an ellipsoidal profile, giving them an elliptical appearance regardless of the viewing angle. Their appearance shows little structure and they typically have relatively little interstellar matter.

Consequently these galaxies also have a low portion of open clusters and a reduced rate of new star formation. Instead the galaxy is dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions. In this sense they have some similarity to the much smaller globular clusters.
The largest galaxies are giant ellipticals. Many elliptical galaxies are believed to form due to the interaction of galaxies, resulting in a collision and merger. They can grow to enormous sizes (compared to spiral galaxies, for example), and giant elliptical galaxies are often found near the core of large galaxy clusters. Starburst galaxies are the result of such a galactic collision that can result in the formation of an elliptical galaxy.

Spirals

Main articles: Spiral galaxy and Barred spiral galaxy


The Sombrero Galaxy, an example of an unbarred spiral galaxy.
Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) that indicates the degree of tightness of the spiral arms and the size of the central bulge. An Sa galaxy has tightly wound, poorly-defined arms and possesses a relatively large core region. At the other extreme, an Sc galaxy has open, well-defined arms and a small core region.
In spiral galaxies, the spiral arms do have the shape of approximate logarithmic spirals, a pattern that can be theoretically shown to result from a disturbance in a uniformly rotating mass of stars. Like the stars, the spiral arms also rotate around the center, but they do so with constant angular velocity. That means that stars pass in and out of spiral arms, with stars near the galactic core orbiting faster than the arms are moving while stars near the outer parts of the galaxy typically orbit more slowly than the arms. The spiral arms are thought to be areas of high density matter, or "density waves". As stars move through an arm, the space velocity of each stellar system is modified by the gravitational force of the higher density. (The velocity returns to normal after the stars depart on the other side of the arm.) This effect is akin to a "wave" of slowdowns moving along a highway full of moving cars. The arms are visible because the high density facilitates star formation, and therefore they harbor many bright and young stars.


NGC 1300, an example of a barred spiral galaxy.

A majority of spiral galaxies have a linear, bar-shaped band of stars that extends outward to either side of the core, then merges into the spiral arm structure. In the Hubble classification scheme, these are designated by an SB, followed by a lower-case letter (a, b or c) that indicates the form of the spiral arms (in the same manner as the categorization of normal spiral galaxies). Bars are thought to be temporary structures that can occur as a result of a density wave radiating outward from the core, or else due to a tidal interaction with another galaxy. Many barred spiral galaxies are active, possibly as a result of gas being channeled into the core along the arms.
Our own galaxy is a large disk-shaped barred-spiral galaxy about 30 kiloparsecs in diameter and a kiloparsec in thickness. It contains about two hundred billion (2×1011) stars and has a total mass of about six hundred billion (6×1011) times the mass of the Sun.

Other morphologies


Hoag's Object, an example of a ring galaxy.

Peculiar galaxies are galactic formations that develop unusual properties due to tidal interactions with other galaxies. An example of this is the ring galaxy, which possesses a ring-like structure of stars and interstellar medium surrounding a bare core. A ring galaxy is thought to occur when a smaller galaxy passes through the core of a spiral galaxy. Such an event may have affected the Andromeda Galaxy, as it displays a multi-ring-like structure when viewed in infrared radiation.
A lenticular galaxy is an intermediate form that has properties of both elliptical and spiral galaxies. These are categorized as Hubble type S0, and they possess ill-defined spiral arms with an elliptical halo of stars. (Barred lenticular galaxies receive Hubble classification SB0.)


NGC 5866, an example of a lenticular galaxy. Credit: NASA/ESA.

In addition to the classifications mentioned above, there are a number of galaxies that can not be readily classified into an elliptical or spiral morphology. These are categorized as irregular galaxies. An Irr-I galaxy has some structure but does not align cleanly with the Hubble classification scheme. Irr-II galaxies do not possess any structure that resembles a Hubble classification, and may have been disrupted. Nearby examples of (dwarf) irregular galaxies include the Magellanic Clouds.

Dwarfs

Main article: Dwarf galaxy
Despite the prominence of large elliptical and spiral galaxies, most galaxies in the universe appear to be dwarf galaxies. These tiny galaxies are about one hundredth the size of the Milky Way, containing only a few billion stars. Ultra-compact dwarf galaxies have recently been discovered that are only 100 parsecs across.
Many dwarf galaxies may orbit a single larger galaxy; the Milky Way has at least a dozen such satellites, with an estimated 300–500 yet to be discovered. Dwarf galaxies may also be classified as elliptical, spiral, or irregular. Since small dwarf ellipticals bear little resemblance to large ellipticals, they are often called dwarf spheroidal galaxies instead.
A study of 27 Milky Way neighbors found that dwarf galaxies were all approximately 10 million solar masses, regardless of whether they have thousands or millions of stars. This has led to the suggestion that galaxies are largely formed by dark matter, and that the minimum size may indicate a form of warm dark matter incapable of gravitational coalescence on a smaller scale.

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Role in human history

From Wikipedia, the free encyclopedia
Main articles: History of technology and Timeline of invention
Paleolithic (2.5 million – 10,000 BC)

A primitive chopper
The use of tools by early humans was partly a process of discovery, partly of evolution. Early humans evolved from a race of foraging hominids which were already bipedal,[12] with a brain mass approximately one third that of modern humans. Tool use remained relatively unchanged for most of early human history, but approximately 50,000 years ago, a complex set of behaviors and tool use emerged, believed by many archaeologists to be connected to the emergence of fully-modern language.


Stone tools


Hand axes from the Acheulian period

A Clovis point, made via pressure flaking
Human ancestors have been using stone and other tools since long before the emergence of Homo sapiens approximately 200,000 years ago. The earliest methods of stone tool making, known as the Oldowan "industry", date back to at least 2.3 million years ago, with the earliest direct evidence of tool usage found in Ethiopia within the Great Rift Valley, dating back to 2.5 million years ago. This era of stone tool use is called the Paleolithic, or "Old stone age", and spans all of human history up to the development of agriculture approximately 12,000 years ago.
To make a stone tool, a "core" of hard stone with specific flaking properties (such as flint) was struck with a hammerstone. This flaking produced a sharp edge on the core stone as well as on the flakes, either of which could be used as tools, primarily in the form of choppers or scrapers. These tools greatly aided the early humans in their hunter-gatherer lifestyle to perform a variety of tasks including butchering carcasses (and breaking bones to get at the marrow); chopping wood; cracking open nuts; skinning an animal for its hide; and even forming other tools out of softer materials such as bone and wood.
The earliest stone tools were crude, being little more than a fractured rock. In the Acheulian era, beginning approximately 1.65 million years ago, methods of working these stone into specific shapes, such as hand axes emerged. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of the prepared-core technique, where multiple blades could be rapidly formed from a single core stone. The Upper Paleolithic, beginning approximately 40,000 years ago, saw the introduction of pressure flaking, where a wood, bone, or antler punch could be used to shape a stone very finely.


Fire

The discovery and utilization of fire, a simple energy source with many profound uses, was a turning point in the technological evolution of humankind. The exact date of its discovery is not known; evidence of burnt animal bones at the Cradle of Humankind suggests that the domestication of fire occurred before 1,000,000 BC; scholarly consensus indicates that Homo erectus had controlled fire by between 500,000 BC and 400,000 BC. Fire, fueled with wood and charcoal, allowed early humans to cook their food to increase its digestibility, improving its nutrient value and broadening the number of foods that could be eaten.

Clothing and shelter

Other technological advances made during the Paleolithic era were clothing and shelter; the adoption of both technologies cannot be dated exactly, but they were a key to humanity's progress. As the Paleolithic era progressed, dwellings became more sophisticated and more elaborate; as early as 380,000 BC, humans were constructing temporary wood huts. Clothing, adapted from the fur and hides of hunted animals, helped humanity expand into colder regions; humans began to migrate out of Africa by 200,000 BC and into other continents, such as Eurasia.
Humans began to work bones, antler, and hides, as evidenced by burins and racloirs produced during this period.

Neolithic through Classical Antiquity (10,000BC – 300AD)

An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools.
Man's technological ascent began in earnest in what is known as the Neolithic period ("New stone age"). The invention of polished stone axes was a major advance because it allowed forest clearance on a large scale to create farms. The discovery of agriculture allowed for the feeding of larger populations, and the transition to a sedentist lifestyle increased the number of children that could be simultaneously raised, as young children no longer needed to be carried, as was the case with the nomadic lifestyle. Additionally, children could contribute labor to the raising of crops more readily than they could to the hunter-gatherer lifestyle.
With this increase in population and availability of labor came an increase in labor specialization. What triggered the progression from early Neolithic villages to the first cities, such as Uruk, and the first civilizations, such as Sumer, is not specifically known; however, the emergence of increasingly hierarchical social structures, the specialization of labor, trade and war amongst adjacent cultures, and the need for collective action to overcome environmental challenges, such as the building of dikes and reservoirs, are all thought to have played a role.

Metal tools

Continuing improvements led to the furnace and bellows and provided the ability to smelt and forge native metals (naturally occurring in relatively pure form). Gold, copper, silver, and lead, were such early metals. The advantages of copper tools over stone, bone, and wooden tools were quickly apparent to early humans, and native copper was probably used from near the beginning of Neolithic times (about 8000 BC). Native copper does not naturally occur in large amounts, but copper ores are quite common and some of them produce metal easily when burned in wood or charcoal fires. Eventually, the working of metals led to the discovery of alloys such as bronze and brass (about 4000 BC). The first uses of iron alloys such as steel dates to around 1400 BC.

Energy and Transport

Meanwhile, humans were learning to harness other forms of energy. The earliest known use of wind power is the sailboat. The earliest record of a ship under sail is shown on an Egyptian pot dating back to 3200 BC. From prehistoric times, Egyptians probably used "the power of the Nile" annual floods to irrigate their lands, gradually learning to regulate much of it through purposely-built irrigation channels and 'catch' basins. Similarly, the early peoples of Mesopotamia, the Sumerians, learned to use the Tigris and Euphrates rivers for much the same purposes. But more extensive use of wind and water (and even human) power required another invention.

The wheel was invented in circa 4000 BC.

According to archaeologists, the wheel was invented around 4000 B.C. The wheel was likely independently invented in Mesopotamia (in present-day Iraq) as well. Estimates on when this may have occurred range from 5500 to 3000 B.C., with most experts putting it closer to 4000 B.C. The oldest artifacts with drawings that depict wheeled carts date from about 3000 B.C.; however, the wheel may have been in use for millennia before these drawings were made. There is also evidence from the same period of time that wheels were used for the production of pottery. (Note that the original potter's wheel was probably not a wheel, but rather an irregularly shaped slab of flat wood with a small hollowed or pierced area near the center and mounted on a peg driven into the earth. It would have been rotated by repeated tugs by the potter or his assistant.) More recently, the oldest-known wooden wheel in the world was found in the Ljubljana marshes of Slovenia.
The invention of the wheel revolutionized activities as disparate as transportation, war, and the production of pottery (for which it may have been first used). It didn't take long to discover that wheeled wagons could be used to carry heavy loads and fast (rotary) potters' wheels enabled early mass production of pottery. But it was the use of the wheel as a transformer of energy (through water wheels, windmills, and even treadmills) that revolutionized the application of nonhuman power sources.

Modern history (0CE —)

Tools include both simple machines (such as the lever, the screw, and the pulley), and more complex machines (such as the clock, the engine, the electric generator and the electric motor, the computer, radio, and the Space Station, among many others). As tools increase in complexity, so does the type of knowledge needed to support them. Complex modern machines require libraries of written technical manuals of collected information that has continually increased and improved — their designers, builders, maintainers, and users often require the mastery of decades of sophisticated general and specific training. Moreover, these tools have become so complex that a comprehensive infrastructure of technical knowledge-based lesser tools, processes and practices (complex tools in themselves) exist to support them, including engineering, medicine, and computer science. Complex manufacturing and construction techniques and organizations are needed to construct and maintain them. Entire industries have arisen to support and develop succeeding generations of increasingly more complex tools. The relationship of technology with society ( culture) is generally characterized as synergistic, symbiotic, co-dependent, co-influential, and co-producing, i.e. technology and society depend heavily one upon the other (technology upon culture, and culture upon technology). It is also generally believed that this synergistic relationship first occurred at the dawn of humankind with the invention of simple tools, and continues with modern technologies today. Today and throughout history, technology influences and is influenced by such societal issues/factors as economics, values, ethics, institutions, groups, the environment, government, among others. The discipline studying the impacts of science, technology, and society and vice versa is called Science and technology in society.


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Ram Komputer

Ditulis pada Maret 14, 2008 oleh chanyve
RAM, atau Random Access Memory atau lebih dikenal sebagai memory, merupakan satu hardware yang penting dalam sistem komputer.Pernah dengar suatu kalimat berbunyi “semakin besar RAM, semakin cepat kinerja komputer ” Ini adalah benar – karana RAM memainkan peranan untuk membantu CPU dalam melaksanakan proses/task pada sesuatu sistem komputer. Pada komputer pribadi, RAM berbentuk ‘RAM Module’ seperti dalam gambar dan dipasang pada motherboard.


Bagaimana RAM membantu dalam meningkatkan kinerja sesuatu sistem komputer?
Dalam suatu sistem komputer, contohnya PC, RAM digunakan untuk menyimpan arahan/instruction dan data yang diperlukan untuk menyiapkan suatu proses/task secara sementara/temporarily – dengan itu CPU dapat mengakses data secara lebih cepat.
RAM merupakan salah satu dari unit ‘computer storage’ dalam kategori storage primer. Nama lain bagi RAM ialah read/write memory (kerana data boleh dimasukkan dan dibaca dari RAM).

Dari permulaan era PC hingga sekarang, perkembangan RAM mengalami dalam berbagai evolusi jenis, seperti
- SRAM (Static RAM),
- DRAM (Dynamic RAM)
- SDRAM (Synchronous Dynamic RAM)
- DDR SDRAM (Double Data Rate SDRAM),
- RD RAM (Rambus) ,
- DDR2 SDRAM (Double Data Rate Two SDRAM) serta
- Rambus XDR DRAM (eXtreme Data Rate DRAM)
RAM dipakai dalam berbagai module dan sel. RAM generasi terkini dipakai dalam bentuk modul, seperti SIMM (Single Inline Memory Module), DIMM (Double Inline Memory Module) dan RIMM (Sama seperti DIMM, tetapi untuk membedakan pakai Rambus dan pakai memori DIMM biasa) .
Pengunaan jenis RAM pada sesuatu sistem komputer dipengaruhi oleh dukungan chipset yang terdapat pada motherboard sistem komputer. Contohnya, sesuatu motherboard yang mempunyai chipset Intel i925X hanya boleh menggunakan RAM jenis DDR2 SDRAM, dan RAM DDR SDRAM tidak dapat dipasang kerana ia tidak didukung oleh chipset tersebut (slot sdram tidak didukung oleh mobo tersebut).
Setiap jenis RAM hanya boleh dipakai pada slotnya sendiri saja pada motherboard. Misalnya slot RAM jenis Rambus mempunyai bentuk yang berbeda dibanding dengan slot RAM jenis DDR SDRAM. Ini berlaku karana Rambus dipakai pada bentuk ‘kaki’ tersendiri yang tidak sama dengan DDR SDRAM.
Apa yang diperlukan sebelum membeli RAM? Kriteria pemilihan RAM
Jika ingin upgrade PC dengan menambah RAM. Terdapat bebrapa kriteria yang perlu diambil sebelum membeli RAM Module:
- Ketersedian slot yang disediakan oleh mobo? Type mobo ada yang menyediakan 2 slot,4 slot, dilihat dulu berapa yang tersedia
- Mobo yang ada mendukung Ram yang berjenis apa?
Setiap motherboard mempunyai toleransi penerimaan kapasitas ‘RAM’ nya tersendiri.
Misalnya, satu motherboard yang mempunyai toliransi kapasitas RAM sebanyak 1GB. Jika ditambah RAM melebihi 1GB, PC tetap akan membaca 1 GB tersebut, sisanya tidak akan terbaca.
- Mobo yang tersedia, hanya untuk ram jenis apa, apakah sdram, ddr atau ddr2. Beda jenis RAM tidak bisa dipasang dengan RAM yang berbeda
Perbedaan DDR dan DDR2
# Memori DDR biasanya biasa ditemui pada kecepatan 266/333/400 Mhz sedangkan DDR2 pada kecepatan 400/533/667/800 Mhz.
# DDR2 mengkonsumsi daya lebiah rendah (1,8 volt) daripada DDR (2,5 volt).
# Modul DDR memiliki jumlah kaki 184 pin sedangkan DDR2 berjumlah 240 pin.
# CAS Latency (CL –waktu tunggu dalam mengirimkan data) pada DDR biasanya berkisar pada angka 2,2,5 atau 3. pada DDR2 biasanya berupa angka 3,4 atau 5 clock. Namun pada DDR2 bisa terdapat pula Additional latency (AL) mulai 0,1,2,3,4 atau 5 clock. Jadi pada DDR 2 dengan CL4 dan CL1 akan memilki angka latency sebesar 5.
# Controller internal pada DDR mengerjakan 2-bit data dari storage sedangkan DDR2 daat mengerjakan 4-bit sekaligus.
Memori DDR2 telah didukung oleh motherboard High-end. Kita mengcompile di bawah suatu daftar yang pendek dengan perbedaan-perbedaan utama antara memori-memori DDR2 dan DDR.
DDR memori-memori secara resmi ditemukan dalam 266 MHz, 333 MHz dan 400 versi MHz, sedangkan memori-memori DDR2 ditemukan dalam Versi 400 MHz, 533 MHz, 667 MHz dan 800 MHz. Kedua jenis memori ini memindahkan dua data per siklus jam. Oleh karenannya clock yang terdaftarkan bersifat clock nominal, bukanlah riil. Untuk mendapat clock yang riil bagilah clock yang nominal dengan dua. Sebagai contoh, DDR2-667 memori sebenarnya bekerja pada 333 MHz.
DDR2 memori mengkonsumsi power yang lebih rendah yang dibandingkan dengan memori DDR.
DDR memori disupply dengan power 25 V sedangkan memori DDR2 disupply dengan power 18 V.
Pada memori DDR, penghentian yang memberi hambatan penting bagi membuat pekerjaan memori ditempatkan di motherboard, selagi di memori DDR2, sirkit ini ditempatkan di dalam chip memori. Ini adalah salah satu pertimbangan kenapa tidak mungkin untuk memasang DDR2 memori pada socket DDR dan sebaliknya.
DDR modul-modul mempunyai 184 kontak, sedangkan modul DDR2 mempunyai 240 kontak.
Pada memori DDR, “CAS Latency” (CL) parameter – adalah waktu keterlambatan memori yang mengirimkan suatu data yang diminta –,dapat dari 2, 25 atau 3 siklus jam. Di memori-memori DDR2 CL dapat dari 3, 4 atau 5 siklus jam.
Pada memori DDR2, tergantung pada chip, ada satu latency tambahan (AL) dari 0, 1, 2, 3, 4 atau 5 siklus jam. Jadi di dalam suatu memori DDR2 dengan CL4 dan AL1, latency itu adalah 5.
Pada memori DDR2, menulis latency sepadan dengan baca latency ( CL +AL) kurang 1.
Secara internal pengontrol di dalam memori DDR bekerja prapembebanan dua data Bits dari area penyimpanan (task yang dikenal sebagai “prefetch”) sedangkan pengontrol di dalam memori DDR2 memori berkerja dengan men loading empat bits pada awal.
Ini adalah perbedaan-perbedaan utama antara DDR dan DDR2. Kita akan menjelajah mereka sedikit lebih pada halaman-halaman yang berikut. Untuk lebih terperinci penjelasan, kita merekomendasikan anda untuk membaca dokumen yang berikut: http://download.micron.com/pdf/pubs/designline/dl3Q03.pdf
Aspek Secara Fisik
DDR dan DDR2 modul mempunyai ukuran secara fisik sama, tetapi DDR modul mempunyai 184 kontak, sedang modul DDR2 mempunyai 240. Di Gambar 1 anda dapat membandingkan perbedaan antara tepi penghubung DDR2 dan DDR .
Dengan demikian sama sekali tidak mungkin untuk menginstal suatu modul DDR2 di suatu socket DDR dan sebaliknya.

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Formation and evolution of Galaxy

Main article: Galaxy formation and evolution
The study of galactic formation and evolution attempts to answer questions regarding how galaxies formed and their evolutionary path over the history of the universe. Some theories in this field have now become widely accepted, but it is still an active area in astrophysics.
Formation
Current cosmological models of the early Universe are based on the Big Bang theory. About 300,000 years after this event, atoms of hydrogen and helium began to form, in an event called recombination.



Nearly all the hydrogen was neutral (non-ionized) and readily absorbed light, and no stars had yet formed. As a result this period has been called the "Dark Ages". It was from density fluctuations (or anisotropic irregularities) in this primordial matter that larger structures began to appear. As a result, masses of baryonic matter started to condense within cold dark matter halos. These primordial structures would eventually become the galaxies we see today.
Evidence for the early appearance of galaxies was found in 2006, when it was discovered that the galaxy IOK-1 has an unusually high redshift of 6.96, corresponding to just 750 million years after the Big Bang and making it the most distant and primordial galaxy yet seen. While some scientists have claimed other objects (such as Abell 1835 IR1916) have higher redshifts (and therefore are seen in an earlier stage of the Universe's evolution), IOK-1's age and composition have been more reliably established. The existence of such early protogalaxies suggests that they must have grown in the so-called "Dark Ages".
The detailed process by which such early galaxy formation occurred is a major open question in astronomy. Theories could be divided into two categories: top-down and bottom-up. In top-down theories (such as the Eggen–Lynden-Bell–Sandage [ELS] model), protogalaxies form in a large-scale simultaneous collapse lasting about one hundred million years. In bottom-up theories (such as the Searle-Zinn [SZ] model), small structures such as globular clusters form first, and then a number of such bodies accrete to form a larger galaxy. Modern theories must be modified to account for the probable presence of large dark matter halos.
Once protogalaxies began to form and contract, the first halo stars (called Population III stars) appeared within them. These were composed almost entirely of hydrogen and helium, and may have been massive. If so, these huge stars would have quickly consumed their supply of fuel and became supernovae, releasing heavy elements into the interstellar medium. This first generation of stars re-ionized the surrounding neutral hydrogen, creating expanding bubbles of space through which light could readily travel.


Evolution

I Zwicky 18 (lower left) resembles a newly-formed galaxy.
Within a billion years of a galaxy's formation, key structures begin to appear. Globular clusters, the central supermassive black hole, and a galactic bulge of metal-poor Population II stars form. The creation of a supermassive black hole appears to play a key role in actively regulating the growth of galaxies by limiting the total amount of additional matter added. During this early epoch, galaxies undergo a major burst of star formation.
During the following two billion years, the accumulated matter settles into a galactic disc. A galaxy will continue to absorb infalling material from high velocity clouds and dwarf galaxies throughout its life. This matter is mostly hydrogen and helium. The cycle of stellar birth and death slowly increases the abundance of heavy elements, eventually allowing the formation of planets.
The evolution of galaxies can be significantly affected by interactions and collisions. Mergers of galaxies were common during the early epoch, and the majority of galaxies were peculiar in morphology. Given the distances between the stars, the great majority of stellar systems in colliding galaxies will be unaffected. However, gravitational stripping of the interstellar gas and dust that makes up the spiral arms produces a long train of stars known as tidal tails. Examples of these formations can be seen in NGC 4676 or the Antennae Galaxies.
As an example of such an interaction, the Milky Way galaxy and the nearby Andromeda Galaxy are moving toward each other at about 130 km/s, and—depending upon the lateral movements—the two may collide in about five to six billion years. Although the Milky Way has never collided with a galaxy as large as Andromeda before, evidence of past collisions of the Milky Way with smaller dwarf galaxies is increasing.
Such large-scale interactions are rare. As time passes, mergers of two systems of equal size become less common. Most bright galaxies have remained fundamentally unchanged for the last few billion years, and the net rate of star formation probably also peaked approximately ten billion years ago.
Future trends
At present, most star formation occurs in smaller galaxies where cool gas is not so depleted. Spiral galaxies, like the Milky Way, only produce new generations of stars as long as they have dense molecular clouds of interstellar hydrogen in their spiral arms. Elliptical galaxies are already largely devoid of this gas, and so form no new stars. The supply of star-forming material is finite; once stars have converted the available supply of hydrogen into heavier elements, new star formation will come to an end.
The current era of star formation is expected to continue for up to one hundred billion years, and then the "stellar age" will wind down after about ten trillion to one hundred trillion years (1013–1014 years), as the smallest, longest-lived stars in our astrosphere, tiny red dwarfs, begin to fade. At the end of the stellar age, galaxies will be composed of compact objects: brown dwarfs, white dwarfs that are cooling or cold ("black dwarfs"), neutron stars, and black holes. Eventually, as a result of gravitational relaxation, all stars will either fall into central supermassive black holes or be flung into intergalactic space as a result of collisions.

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