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At around 7:15 AM, Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a huge fireball moving across the sky, nearly as bright as the Sun. A few minutes later, there was a flash that lit up half of the sky, followed by a shock wave that knocked people off their feet and broke windows up to 650 km (400 mi) away. The explosion registered on seismic stations across EurasiaEarth Eurasia is the combined land mass of Europe and Asia. Eurasia is alternatively considered to be a continent, or a supercontinent composed of the continents of Europe and Asia. Due to the perceived cultural differences between Asia and Europe by Euro, and produced fluctuations in atmospheric pressureAtmospheric pressure is the pressure caused by the weight of air above any area in the Earth's atmosphere. Standard atmospheric pressure atm is discussed in the next section. Air masses are affected by the general atmospheric pressure within the mass, cre strong enough to be detected by the recently invented barographA barograph is a recording aneroid barometer. The aneroid cell, through a gear or lever train, drives a recording arm that has at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper. The recording materias in BritainThe United Kingdom of Great Britain and Northern Ireland is a state in Western Europe, usually known simply as the United Kingdom the UK Britain or less accurately as Great Britain . The UK was formed by a series of Acts of Union which united the formerly. Over the next few weeks, night skies over Europe and western Russia glowed brightly enough for people to read by. In the United StatesThe United States of America also referred to as the United States U. America ¹ or the States is a federal republic in central North America, stretching from the Atlantic in the east to the Pacific Ocean in the west. It shares land borders with Canada in, the Smithsonian Astrophysical Observatory and the Mount Wilson ObservatoryThe Mount Wilson Observatory is an astronomical observatory. It is located on Mount Wilson, a 5715' peak in the San Gabriel mountains near Pasadena, California, to the east of Los Angeles. It was first directed by George Ellery Hale, who brought the 40-in observed a decrease in atmospheric transparency that lasted for several months.
Had the object responsible for the explosion hit the EarthEarth also known as the Earth or Terra is the planet on which we live, the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harbouring life. The pla a few hours later, it would have exploded over EuropeFor the band of the same name, see Europe (band . Europe is a continent forming the westermost part of the Eurasian supercontinent. Europe is bounded to the north by the Arctic Ocean, to the west by the Atlantic Ocean, to the south by the Mediterranean Se instead of the sparsely-populated Tunguska region, producing massive loss of human life.
Surprisingly, there was little scientific curiosity about the impact at the time, possibly due to the isolation of the Tunguska region. If there were any early expeditions to the site, their records were lost during the subsequent chaotic years — World War I, the Russian Revolution, and the Russian Civil War.
The first expedition for which records have survived arrived at the scene almost two decades after the event. In 1921, The Russian mineralogist Leonid Kulik, visiting the Podkamennaya Tunguska River basin as part of a survey for the Soviet Academy of Sciences, deduced from local accounts that the explosion had been caused by a giant meteorite impact. He persuaded the Soviet government to fund an expedition to the Tunguska region, based on the prospect of meteoric iron that could be salvaged to aid Soviet industry.
Kulik's expedition reached the site in 1927. To their surprise, no crater was to be found. There was instead a region of scorched trees about 50 kilometres across. A few near ground zero were still strangely standing upright, their branches and bark stripped off. Those further away had been knocked down in a direction away from the center.
During the next ten years, there were three more expeditions to the area. Kulik found a little "pothole" bog that he thought might be the crater, but after a laborious exercise in draining the bog, he found there were old stumps on the bottom, ruling out the possibility that it was a crater. In 1938, Kulik managed to arrange for an aerial photographic survey of the area, which revealed that the event had knocked over trees in a huge butterfly-shaped pattern. Despite the large amount of devastation, there was no crater to be seen.
Expeditions sent to the area in the 1950s and 1960s found microscopic glass spheres in siftings of the soil. Chemical analysis showed that the spheres contained high proportions of nickel and iridium, which are found in high concentrations in meteorites, and indicated that they were of extraterrestrial origin. Expeditions led by Gennady Plekhanov found no elevated levels of radiation, which might have been expected if the detonation were nuclear in nature.
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