Blurs

For more than a century, scientists have tried to answer one deceptively simple question: Where did the Moon come from? The Moon is our closest natural companion, but its origin remains one of the great stories of planetary science. The leading explanation is the giant-impact hypothesis. According to this model, the young Earth was struck by a large planetary body roughly 4.5 billion years ago. Material thrown into orbit eventually gathered together and formed the Moon. It is a powerful explanation. But it is not the only conceivable way to imagine the Moon's origin. What if the Moon wasn't created primarily from Earth at all? What if it was something that already existed? What if, before Earth and the Moon reached their present configuration, another planetary body existed in the inner Solar System — and a catastrophic event destroyed most of it? Perhaps the Moon could be the surviving remnant. This is not the established explanation for the Moon. There is currently no compell...

Look at Saturn and it is difficult not to wonder what Earth would look like with rings. A vast band of ice and rock stretching across the sky. A permanent feature visible from the surface. Shadows moving across the planet as the ring system changed with the seasons. It sounds like science fiction. But Earth may actually have had something resembling a ring system in its distant past. Not necessarily a beautiful, permanent structure like Saturn's — but a temporary ring of debris could have formed around our planet after a massive collision. And the most intriguing possibility is that such an event may have played a role in creating the Moon. Earth wasn't always the quiet planet we know today The young Solar System was a chaotic place. Planets were still forming. Asteroids and planetary embryos were moving through unstable orbits, occasionally crossing paths. Collisions were not unusual. Some were relatively small. Others were catastrophic. The leading explanation for the Moon...

We tend to picture the universe as something that simply keeps going. Stars stretch into galaxies. Galaxies form enormous clusters. Beyond those clusters are more galaxies, more empty space, more darkness. And beyond that? We instinctively imagine… more. But there is a problem with that picture. When cosmologists talk about the universe being infinite, they are not necessarily saying they have established that it literally extends forever. They are describing one possible geometry of the universe — one that fits remarkably well with what we currently observe. So here's a strange question: What if the universe isn't infinite? And if it isn't, does that mean there must be an edge? And if there were an edge, what could possibly be beyond it? The universe doesn't necessarily need an edge Our everyday experience makes the idea of a finite universe difficult to comprehend. A football has a surface with a finite area. Walk far enough across it and, eventually, you come back to...

The first crewed mission to Mars is often imagined as the beginning of humanity's journey to another world.  But getting astronauts there is only half the problem. Can we actually bring them home? Mars has fascinated humanity for centuries. From the canals imagined by nineteenth-century astronomers to today's robotic explorers, the Red Planet has gradually changed from a distant point of light into a destination. But there is a question that receives surprisingly less attention than the journey there: If humans eventually land on Mars, will they actually be able to come back? A mission to Mars is not simply a longer version of a trip to the Moon. The distances are enormous, launch windows are limited, communication is delayed and returning a crew safely requires spacecraft, fuel, power and life-support systems to work hundreds of millions of kilometres from Earth. And unlike the Apollo missions, astronauts travelling to Mars could be away from Earth for years. Mars Is a Long Wa...