Space has long intrigued humankind. It is the most extreme extension of our desire for exploration, knowledge and conquest.
In pushing the boundaries, in testing the unbelievable, the unimaginable and the seemingly impossible, individuals learn more about themselves, and the human race learns more about itself - and about the world.
Without visionaries and intrepid discoverers - the likes of stargazers, seafarers, explorers, mountaineers and divers - seeking to go deeper, higher, farther, then much progress would not have been made or knowledge gained.
Our world - and our minds - would be much smaller.
The price of such progress and adventure is often high.
Many paid with their lives in search of the ultimate dream. Many who did so laid the path for their successors.
Our fascination with space is also tied with fundamental questions about ourselves: from where did we come, who or what made us, and are we alone in the universe?
Through science, literature, film, art, music, religion and philosophy, many have posed questions and sought to find answers.
The race for space supremacy was in full flight by the middle of last century, largely spurred by nations' desire for military dominance.
After the ''giant leap'' for mankind made in 1969 with the moon landing, and post Cold War, there was finally a more co-operative approach to space exploration, cemented in 1998 with the International Space Station, a collaboration by 15 nations.
Pictures of Earth from space still have the power to dumbfound, let alone the array of those of our solar system and beyond which are now available.
The fact we can tick off a long list of achievements - men on the moon, numerous satellites in orbit and contributing to a range of facets of our everyday lives on Earth, an unmanned rover on Mars, samples collected from comets and asteroids, Voyager 1 sending back a raft of information on the solar system and now from interstellar space - all within living memory is extraordinary.
The term ''space tourism'' has now entered our lexicon and the realm of possibility, but the events of the past 10 days have been a sobering reminder of the dangers involved.
On Saturday, Sir Richard Branson's commercial space company Virgin Galactic's SpaceShipTwo exploded on a test flight above the Californian desert, killing a pilot and injuring another.
Sir Richard had been hoping to begin commercial passenger space flights - at a reported ticket price of about $US200,000 ($NZ258,000) - early next year.
Only a few days before, on Wednesday, an unmanned Antares rocket, built and launched by Orbital Sciences Corp, exploded seconds after liftoff from a commercial launch pad in Virginia.
(Nasa contracted private operators Orbital and Space Exploration Technologies, or SpaceX, to deliver cargo to the International Space Station after it retired its space shuttles in 2011. Previous missions by both companies have been successful.)
Authorities are now investigating both crashes.
There have been claims old parts may have been a factor in the Orbital crash, and new fuel a possible factor in the Virgin crash.
There are also reports Sir Richard was repeatedly warned about safety failings in its rocket engine system after three engineers died in a ground explosion during testing of a rocket engine in 2007, and that three senior Virgin Galactic executives had recently left the company.
The investigations must be allowed to run their full course until the facts are known.
But it is clear any commercial transport operator must ensure safety is paramount, and governments, civil aviation, national transport, space agencies and travel regulators in various countries will be watching warily.
And the desire to achieve must never be allowed to trump safety concerns.
Sir Richard's project may not get off the ground, although it seems unlikely that will diminish the dream forever.
We already have a presence in space and previous disasters have not deterred progress for long.
For, despite everything, it is in our nature to pursue the ultimate - infinity and beyond.
In reality, there are few barriers any more, except perhaps our imaginations.
