In cosmic terms, half a century is a mere blink of an eyelid. But for mankind, much has happened in the 50 years since Sputnik 1, the first artificial satellite, was launched by the Soviet Union on 4 October 1957.
Despite being little more than a sphere of metal that let out radio-frequency beeps, Sputnik 1 triggered a thrilling space race that led to astronauts soon orbiting the Earth and walking on the Moon before the 1960s were out, as Richard Corfield describes. Since then, spacecraft have visited planets, flown past comets and even landed on an asteroid.
To mark the 50th anniversary of Sputnik 1, Physics World looks back at the story of that particular mission and examines some of the benefits of modern satellite technology. Satellites, of course, underpin communication networks and are essential for observing the Earth to monitor the effects of, say, deforestation or climate change.
Indeed, as Roger L Eason, the physicist who invented the US Global Positioning System (GPS), explains, GPS is proving so vital for navigation and surveying that Europe, Russia and China are all planning rival satellite systems.
However, all is not rosy up above. Bruce Dorminey describes how the International Space Station (ISS) has been a successful collaboration between the US, Europe and the Soviet Union and is giving us insights into how the human body reacts to long periods in orbit.
But the ISS has swallowed such vast sums of money (NASA alone has contributed $100 billion) that many have questioned if the scientific pay-back from the 200 or so experiments carried out on the station in low-gravity conditions have been worthwhile.
Another concern, as Laura Grego from the Union of Concerned Scientists points out, is the potential weaponization of space. Satellites are sitting ducks for enemy nations, who might find it tempting to use a missile to knock out, say, a crucial military spy satellite.
Moreover, when China destroyed an ageing weather satellite earlier this year in a test of its nascent anti-satellite weapon system, the explosion created some 2500 new trackable pieces of "space junk", ranging from spent rocket stages and disused satellites to smaller items like astronauts' rubbish bags, and immediately increased the chances of a low-Earth-orbiting satellite colliding with another object by up to 30%. As Edwin Cartlidge reports, many observers think that more needs to be done to persuade nations to prevent further space junk being created in the first place.
Finally, Dan Clery looks at why the US is cutting back on Earth observation using satellites while Europe is increasing its investment in this important area.
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