Blurs

Imagine that humanity disappeared tomorrow. Not gradually. Not even after centuries of decline. Just gone. The cities would remain. For a while. Buildings would eventually collapse. Roads would crack. Vehicles would rust away. Power stations would ultimately fail. Forests would reclaim abandoned suburbs. A few thousand years would pass. Then tens of thousands. Eventually, most obvious evidence of our civilisation would disappear. Some traces would remain; fragments of concrete, unusual concentrations of metals, plastic residues, deep mines, artificial radioactive signatures. Now imagine something much more difficult. What if an industrial civilisation had existed on Earth millions of years before humans? What if it had risen, flourished and disappeared long before our ancestors were capable of building cities? Would we know? Or could an entire technological species vanish so completely that modern science would mistake its planet for one that had never hosted anything more advanced tha...

Look up at the night sky and there is one object that seems so permanent that it is easy to forget how unusual it is. The Moon.  It controls the tides. It brightens the night. It moves across the sky with remarkable regularity. It has influenced calendars, navigation, mythology and human culture for thousands of years. But the Moon is more than something we see. Its gravity interacts with Earth on a planetary scale. It raises ocean tides. It gradually slows Earth's rotation. And, importantly, it helps stabilise the orientation of Earth's rotational axis. So what would happen if the Moon had never existed? Would Earth still have developed oceans? Would the climate have remained suitable for complex life? Would evolution have taken a completely different path? And, perhaps most intriguingly: Would humans ever have evolved at all? There is no way to know for certain. But the physics and geology allow us to explore the possibilities. First, how did the Moon get here? The leading ex...

For more than half a century, black holes have occupied a strange position in our understanding of the Universe.  They are predicted by Einstein's general theory of relativity, supported by increasingly strong observational evidence, and now routinely detected through their effects on surrounding matter and spacetime. But there is a fascinating alternative idea. What if some objects we call black holes aren't actually black holes at all? What if, instead, they are dark stars — incredibly compact objects whose gravity is so extreme that they look almost indistinguishable from black holes, but whose internal structure is fundamentally different? The concept sounds like science fiction. Yet physicists have explored versions of it for decades. And some modern theories suggest that the distinction between a black hole and an exotic compact object could be much more subtle than we once imagined. What Is a Black Hole? A black hole forms when enough mass becomes concentrated within a s...