Proof Of Work
History of Humankind
The Great Pyramid of Giza (also known as the Pyramid of Khufu or the Pyramid of Cheops) is the oldest and largest of the pyramids in the Giza pyramid complex bordering present-day Giza in Greater Cairo, Egypt.
It is the oldest of the Seven Wonders of the Ancient World, and the only one to remain largely intact.
Egyptologists conclude that the pyramid was built as a tomb for the Fourth Dynasty Egyptian pharaoh Khufu and estimate that it was built in the 26th century BC during a period of around 27 years.
Initially standing at 146.5 metres (481 feet), the Great Pyramid was the tallest man-made structure in the world for more than 3,800 years.
Over time, most of the smooth white limestone casing was removed, which lowered the pyramid’s height to the present 138.5 metres (454.4 ft).
What is seen today is the underlying core structure. The base was measured to be about 230.3 metres (755.6 ft) square, giving a volume of roughly 2.6 million cubic metres (92 million cubic feet), which includes an internal hillock.
The dimensions of the pyramid were 280 royal cubits (146.7 m; 481.4 ft) high, a base length of 440 cubits (230.6 m; 756.4 ft), with a seked of 5+1/2 palms (a slope of 51°50’40”).
The Great Pyramid was built by quarrying an estimated 2.3 million large blocks weighing 6 million tonnes total.
The majority of stones are not uniform in size or shape and are only roughly dressed.The outside layers were bound together by mortar.
Primarily local limestone from the Giza Plateau was used. Other blocks were imported by boat down the Nile: White limestone from Tura for the casing, and granite blocks from Aswan, weighing up to 80 tonnes, for the King’s Chamber structure.
There are three known chambers inside the Great Pyramid. The lowest was cut into the bedrock, upon which the pyramid was built, but remained unfinished. The so-called Queen’s Chamber and King’s Chamber, that contains a granite sarcophagus, are higher up, within the pyramid structure. Khufu’s vizier, Hemiunu (also called Hemon), is believed by some to be the architect of the Great Pyramid.
Many varying scientific and alternative hypotheses attempt to explain the exact construction techniques.
The funerary complex around the pyramid consisted of two mortuary temples connected by a causeway (one close to the pyramid and one near the Nile), tombs for the immediate family and court of Khufu, including three smaller pyramids for Khufu’s wives, an even smaller “satellite pyramid” and five buried solar barges.
The Colosseum (Colosseo[kolosˈsɛːo]) is an oval amphitheatre in the centre of the city of Rome, Italy, just east of the Roman Forum.
It is the largest ancient amphitheatre ever built, and is still the largest standing amphitheatre in the world today, despite its age.
Construction began under the emperor Vespasian (r. 69–79 AD) in 72 and was completed in 80 AD under his successor and heir, Titus (r. 79–81).
Further modifications were made during the reign of Domitian (r. 81–96).
The three emperors that were patrons of the work are known as the Flavian dynasty, and the amphitheatre was named the Flavian Amphitheatre (Latin: Amphitheatrum Flavium; Italian: Anfiteatro Flavio[aɱfiteˈaːtro ˈflaːvjo]) by later classicists and archaeologists for its association with their family name (Flavius).
The Colosseum is built of travertine limestone, tuff (volcanic rock), and brick-faced concrete.
The Colosseum could hold an estimated 50,000 to 80,000 spectators at various points in its history having an average audience of some 65,000; it was used for gladiatorial contests and public spectacles including animal hunts, executions, re-enactments of famous battles, and dramas based on Roman mythology, and briefly mock sea battles.
The building ceased to be used for entertainment in the early medieval era.
It was later reused for such purposes as housing, workshops, quarters for a religious order, a fortress, a quarry, and a Christian shrine.
Although substantially ruined because of earthquakes and stone-robbers (for spolia), the Colosseum is still an iconic symbol of Imperial Rome and was listed as one of the New 7 Wonders of the World.
It is one of Rome’s most popular tourist attractions and also has links to the Roman Catholic Church, as each Good Friday the Pope leads a torchlit “Way of the Cross” procession that starts in the area around the Colosseum.
The Colosseum is also depicted on the Italian version of the five-cent euro coin.
The Great Wall of China (traditional Chinese: 萬里長城; simplified Chinese: 万里长城; pinyin: Wànlǐ Chángchéng) is a series of fortifications that were built across the historical northern borders of ancient Chinese states and Imperial China as protection against various nomadic groups from the Eurasian Steppe.
Several walls were built from as early as the 7th century BC,with selective stretches later joined together by Qin Shi Huang (220–206 BC), the first emperor of China.
Little of the Qin wall remains. Later on, many successive dynasties built and maintained multiple stretches of border walls. The best-known sections of the wall were built by the Ming dynasty (1368–1644).
Apart from defense, other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration.
Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watchtowers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.
The frontier walls built by different dynasties have multiple courses. Collectively, they stretch from Liaodong in the east to Lop Lake in the west, from the present-day Sino–Russian border in the north to Tao River (Taohe) in the south; along an arc that roughly delineates the edge of the Mongolian steppe; spanning 21,196.18 km (13,170.70 mi) in total.
Today, the defensive system of the Great Wall is generally recognized as one of the most impressive architectural feats in history.
As history has left behind, monumental architectural constructions that we can admire and reamain in awe as we look at them, after thousands of years since the first stone was put, in today’s world our digital PoW can be seen and admired the same as the Great Wall of China or the Piramid of Giza !!!
Wich brings us to the question, what is Free talking about ?!?
Bitcoin-type Proof Of Work
In 2009, the Bitcoin network went online. Bitcoin is a proof-of-work digital currency that, like Finney’s RPoW, is also based on the Hashcash PoW.
But in Bitcoin, double-spend protection is provided by a decentralized P2P protocol for tracking transfers of coins, rather than the hardware trusted computing function used by RPoW.
Bitcoin has better trustworthiness because it is protected by computation. Bitcoins are “mined” using the Hashcash proof-of-work function by individual miners and verified by the decentralized nodes in the P2P bitcoin network.
The difficulty is periodically adjusted to keep the block time around a target time.
Since the creation of Bitcoin, proof-of-work has been the predominant design of peer-to-peer cryptocurrency. Studies have estimated the total energy consumption of cryptocurrency mining.
The PoW mechanism requires a vast amount of computing resources, which consume a significant amount of electricity. Recent estimates from the University of Cambridge put Bitcoin’s energy consumption as equal to that of Switzerland.
Each block that is added to the blockchain, starting with the block containing a given transaction, is called a confirmation of that transaction.
Ideally, merchants and services that receive payment in the cryptocurrency should wait for at least one confirmation to be distributed over the network, before assuming that the payment was done.
The more confirmations that the merchant waits for, the more difficult it is for an attacker to successfully reverse the transaction in a blockchain—unless the attacker controls more than half the total network power, in which case it is called a 51% attack.
2ASICs and mining pools
Within the Bitcoin community there are groups working together in mining pools.
Some miners use application-specific integrated circuits (ASICs) for PoW. This trend toward mining pools and specialized ASICs has made mining some cryptocurrencies economically infeasible for most players without access to the latest ASICs, nearby sources of inexpensive energy, or other special advantages.
Some PoWs claim to be ASIC-resistant, i.e. to limit the efficiency gain that an ASIC can have over commodity hardware, like a GPU, to be well under an order of magnitude.
ASIC resistance has the advantage of keeping mining economically feasible on commodity hardware, but also contributes to the corresponding risk that an attacker can briefly rent access to a large amount of unspecialized commodity processing power to launch a 51% attack against a cryptocurrency.
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