The Space Age began with the launch of Sputnik 1 into orbit and an outbreak of terror in the US.
It was the height of the Cold War, October 1957, a time of Eugene McCarthy's communist witch-hunts, "duck and cover" nuclear drills and Hollywood's obsession with fantastical sci-fi flicks.
Then came the shock of the Soviet Union's satellite launch.
"Words do not easily convey the American reaction," the NASA historian Roger Launius wrote. "The only appropriate characterisation that begins to capture the mood on 5 October involves the use of the word hysteria. A collective mental turmoil and soul-searching."
Tens of millions of Americans rushed out of their homes to gaze skywards as the 83-kilogram sphere and its ungainly four antennae passed overhead. Children tuned into ham radios, listening in for its beeping signal.
"Soon they will be dropping bombs on us from space like kids dropping rocks onto cars from freeway overpasses!" decried Lyndon Johnson, then a Democratic senator and rival of the president, Dwight Eisenhower.
Eisenhower was under intense pressure. He had a panicked populace, a lynch-mob media and military chiefs urging him to rush into a space weapons program to counter the Soviet threat.
But Eisenhower, a former five-star general and Allied supreme commander during World War II, quickly saw the risks of a space arms race, as well as an opportunity.
Within days, his administration had congratulated the Soviet Union on its mighty scientific feat. He said Sputnik's orbit had affirmed an important principle: the freedom of international space for all nations.
This powerful idea of space as a "province of all mankind" had earlier been rejected by the Soviet Union. Now it had no choice but to accept it. Eisenhower stressed, and the Soviet premier, Nikita Khrushchev, concurred, that space should not be used for warlike activities.
So began a period of the development of space that has brought extraordinary economic benefits and a large measure of security to Earth. Globalisation would not have been possible without satellites. The financial system, the internet, modern air travel, weather and scientific research depend on space assets.
But as the space age enters its second half-century, there are growing concerns the world is on the verge of a hugely expensive and potentially catastrophic extraterrestrial arms race.
"It will bankrupt nations if they don't blow themselves up in the meantime," Brett Biddington, a former RAAF officer and author of a paper on space engagement, warns.
War in space is not an appealing prospect.
There are 800 operational satellites orbiting Earth, but strewn among them are 10,000 pieces of what is classed as space junk. The destruction of even 10 large satellites would cause enough debris orbiting the world at 36,000kmh to make space unusable for several decades, Theresa Hitchens, director of the US Centre for Defence Information, says.
"A space-based war may not wipe out humanity from the face of the Earth like all-out nuclear war, but it would be enough to send us back to the 1950s," she says
As it stands, there are no weapons in space. But in the past 18 months China and the US have successfully tested anti-satellite weapons that have hit targets hundreds of kilometres in space from the ground.
The US and, many suspect, China and Russia have active programs to build a suite of space weapons, from powerful lasers to nano-satellites that can bump a larger satellite off its orbit.
More than a dozen nations can reach space. About the same number have ballistic missile programs, the technology that underpins ground-based anti-satellite weapons.
There is no treaty banning conventional weapons in space. The US, in particular, has adopted an increasingly belligerent posture over its control of space.
"We are at a threshold," Hitchens says. "A lot of factors have come together and, frankly, it's frightening."
Among those factors is a fundamental change in the way military forces use space.
During the Cold War, Hitchens says, space assets were used for strategic military purposes. Reconnaissance satellites were used to spy on the other side, enforce treaty commitments and as early warning systems against missile attacks.
With only two major players involved, each side had a good idea of what the other was up to. The threats were well regulated and the development of space continued at a predictable and relatively harmonious pace.
But space is now used by military forces in an intrinsically different way: space assets are an essential part of everyday, tactical military operations.
It is called network-centric warfare, and there are no more enthusiastic proponents than the US and Australia. Simply put, all command and control communications, surveillance, targeting systems and military platforms are connected through what is called a satellite-based global information grid.
It gives everyone - from a commander in headquarters to a special forces soldier on remote patrol - access to a picture of the battle space.
Tank commanders who once pored over maps are now guided to their destination by the global positioning system. Bombing missions that would once take days to plan can be undertaken almost instantaneously as photographs and targeting information is emailed to an aircraft in flight.
The reliance on satellites is so pervasive in the wars in Afghanistan and Iraq that it has overwhelmed the bandwidth of US military satellites. According to Biddington, the US and its allies rely on commercial satellite operators for about 90 per cent of their bandwidth in the Middle East.
Satellites are crucial to modern military operations, making them extremely valuable targets. Moreover, they are vulnerable.
"Satellites are fragile," Ron Huisken, from the Australian National University, says. "They move fast, but you know exactly where they will be at any moment."
The US war machine would be thrown into chaos if several of its key satellites were blown up or permanently disabled.
Donald Rumsfeld, in a paper he wrote before he become US defence secretary, warned of a "space Pearl Harbour".
Those fears were stoked last year when China fired a ballistic missile 900 kilometres from the Earth's surface, downing one of its own weather satellites, creating a massive cloud of debris along the way.
At a space conference soon after, the chief of staff of the US Air Force, General Michael Moseley, said: "It's not lost on this audience what a strategically dislocating event that was, on par with the October 1957 Sputnik launch." Such a claim may have had a touch of hyberbole, but there is no doubt the US regards space, as Moseley put it, as "contested domain".
The US responded to China's test by shooting down one of its own satellites in February using its Aegis combat system. Unlike China it warned the rest of the world beforehand.
China's successful test of its anti-satellite missile - it is believed to have tried and failed three times before - came three months after the US released its national space policy, asserting its right to "space control" and to conduct "counter-space" operations to thwart any challenge from adversaries.
The policy, which effectively took the Bush doctrine of pre-emption beyond the stratosphere, also rejected "new legal regimes or other restrictions that seek to prohibit or limit US access to, or use of, space". According to Hitchens, the policy went even further than Ronald Reagan did when he was president. He gave impetus to the idea of weapons in space with his "Star Wars" missile defence shield.
"Reagan said he was still open to banning anti-satellite weapons. Bush has said he won't accept any treaty to ban weapons in space. It's very aggressive rhetoric, very unilateral rhetoric," Hitchens says.
Many arms control experts regard the rhetoric as destabilising, particularly when considered in tandem with the Bush Administration's controversial decision to drop out of the anti-ballistic missile treaty.
The treaty, among other things, prevented the US and Russia from putting missile defence systems in space.
Huisken says the withdrawal from the treaty was "as big a mistake as Iraq" and "absolutely certainly" has spurred Russia, and especially China, to expand military spending at a rapid pace.
"The message sent to Russia and China was that henceforth your confidence in your nuclear deterrent capability is based solely on a political promise from Washington."
Hitchens says it is vital to understand that satellites, with their predictable trajectories, cannot readily be defended by weapons, which means the role of ground-based and orbiting anti-satellite weapons is intrinsically offensive in nature.
This brings a new but inherently unstable dynamic of deterrence - you hit mine and I'll hit yours - to the table.
"These principles worked in the Cold War because there were only two countries, countries which, over the years, came to know a lot about each other," Hitchens says. "In space, there's a greater uncertainty and a greater chance for a misunderstanding or an accident escalating into a catastrophic outcome. Also, when you have multiple players, the deterrence theory becomes very difficult to maintain."
Much of the research and development undertaken into space weapons is shrouded in secrecy. It also involves dual-use technologies, giving those investing in it plausible deniability.
Hitchens estimates that the US is investing about $25 billion a year - when its military's "black budget" is included - on technologies that could be used in space, and that does not take into account its investments in reconnaissance and communications satellites.
China has flagged its intent with its anti-satellite tests, while Russia has the technology to quickly mobilise a space weapons program.
India and France, even Japan, have also shown a keen interest, Hitchens says.
"In many ways, India is the country that scares me the most. The Indian Air Force, for a decade, has been trying to kick-start a space weapons program," she says. The argument is gaining traction in New Delhi, not least because of China's activities and because India does not want to be left behind on space weapons as it was on nuclear weapons.
India did not have nuclear weapons when the Nuclear Non-Proliferation Treaty was signed in the late 1960s. It opted out so it could pursue them, but has been treated as something of a pariah since. Critically, its non-participation in the treaty has hampered India's ability to source uranium for civilian purposes.
"If there's to be a treaty [on space weapons], they want to be much further ahead," Hitchens says. "It's a potent political argument and it frightens me because if India moves forward and develops anti-satellite weapons, then the Pakistanis will want to do something and so will the Iranians.
"The dominoes will fall and, once you reach a critical mass, it will be very hard to stop, and very dangerous up there."
There is only one formal treaty governing space: 1967's Outer Space Treaty, which forbids putting nuclear weapons in orbit or on "celestial bodies" such as the moon.
China and Russia have loudly urged the US to begin talks on banning other weapons in space and even working on limiting anti-satellite weapons.
But the US and Israel have been the only two countries strongly resisting negotiations beginning in the United Nations. They say a pact would be unenforceable, noting that even a supposedly benign object in space could be used as an offensive weapon - for example a satellite that is manoeuvred to ram another.
Still, a new administration in the US next year could signal a change in attitude. Democratic members of Congress have been an important constraint on funding for space weapons programs.
Hitchens says many senior US military personnel and political leaders are acutely aware of the risks of a space arms race, notably the incredible expense and the problem of space debris.
But there remains a powerful clique of "space warriors" in the US and plenty of commercial interests - many tied up in the missile defence shield program - keen to earn billions of dollars from an expansion of weapons into space.
Perhaps, in the end, the US and the world needs a new political leader with the foresight of Eisenhower.
It was Eisenhower, after all, who famously warned in his farewell speech that "we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex".