Is time real, or is it just an illusion? In our latest video, we meet Jim Al-Khalili, physicist and author of On Time, at the Royal Observatory Greenwich, the home of the Prime Meridian, to explore one of the deepest mysteries in science.

From space-time at the heart of Albert Einstein’s theory of relativity to the arrow of time, entropy and the origins of the universe, Al-Khalili explains why physicists remain divided over the true nature of time.

Could the past, present and future all exist at once? And is time travel really possible? Join us for a mind-bending journey through one of physics’ greatest puzzles.

Picture the world 100 or 200 years from now. What are you imagining? Hotter temperatures, melting glaciers or alpine places without snow? With heatwaves happening across Europe this summer, it’s not that hard to visualise.

Now picture Europe in a deep freeze where temperatures hit -20°C in London. Both of these scenarios might be the future we’re heading for, thanks to climate change. And there’s an even more worrying indicator: while almost the entire planet has been warming, there’s one patch in the North Atlantic Ocean just south of Greenland where temperatures have been falling.

Scientists call it the “cold blob”, and some think it could be a warning that one of Earth’s most important climate systems is beginning to change and may soon hit a tipping point where climate change no longer happens gradually. If this system flips, it could have devastating consequences that change all of our lives as we know them.

At Grotte Mandrin in France, a Neanderthal discovery has challenged everything we know about our human relatives. We travelled to the cave to meet palaeoanthropologist Ludovic Slimak, who discovered Thorin, one of the last known Neanderthals, reshaping our understanding of human history.

From the remarkable preservation of remains to the groundbreaking DNA evidence there, Slimak explores how an isolated Neanderthal population survived for tens of thousands of years, even interacting with early Homo sapiens, before disappearing. Thorin’s story challenges assumptions about intelligence, identity and survival, offering a new perspective on what it means to be human.

Scientists once believed they could pinpoint the moment when humans first appeared. But as new fossils have filled in our evolutionary history, that defining moment has begun to disappear – replaced by a far stranger picture of what it means to be human.

Lucy is one of the most famous fossils ever discovered, but in recent years her spotlight has dimmed. She was part of the species Australopithecus afarensis and for decades was considered one of our earliest known human ancestors. To understand Lucy is to understand the story of discovery, human evolution and, ultimately, the changing story of us.

Could a “demon” break one of the most fundamental laws of physics? Maxwell’s demon has puzzled physicists for more than 150 years. What began as a thought experiment about heat and entropy is now part of our understanding of information, computation and the laws of thermodynamics. Physicist John Goold explains the paradox and what the demon reveals about the relationship between entropy, measurement and the quantum world.

Could our universe have more dimensions than the three of space and one of time that we experience?

Recent results from the Dark Energy Spectroscopic Instrument (DESI) have renewed interest in whether our current picture of the universe is complete. Some theories suggest that extra dimensions could help explain three of the greatest mysteries in physics: the nature of dark energy; the invisible influence of dark matter; and why gravity is so much weaker than the other fundamental forces.

From string theory to braneworlds, the search for extra dimensions pushes the boundaries of science and could reveal that the reality we experience isn’t all there is.

In the centre of our galaxy sits a monster 4.3 million times the mass of the sun. But Sagittarius A* is tiny compared with other black holes in the universe, with some reaching up to 40 billion times the mass of the sun. They are the point where our laws of physics break, and how these giants get so big has puzzled scientists for decades.

Becky Smethurst is an astrophysicst at the University of Oxford and her work looks at how these behemoths affect the galaxy around them. Â鶹´«Ã½‘s digital features editor, Jacklin Kwan, sat down with her to discuss what black holes are, how the supermassive ones get so big and Smethurst’s amazing career.

Dinosaurs are the biggest creatures to have ever walked on land, dominating Earth for over 130 million years. But how could such extraordinary creatures have simply vanished in the blink of a geological eye? For decades, we’ve assumed these prehistoric megafauna – a staple of our childhoods and Hollywood movies – went extinct for one simple reason: the asteroid that hit Earth was so unimaginably large that it changed everything in one single blow. But now, thanks to new research, an even more intriguing idea has emerged: size alone doesn’t explain what happened.

The real reason the impact was so devastating may have been its angle. Had the asteroid arrived a little steeper, the outcome might have been different. A little shallower, different again. And for life on Earth at the time, predominantly dinosaurs on land, marine creatures in the sea and pterosaurs in the air, it appears to have struck at almost the worst possible angle imaginable, launching vast quantities of rock, dust and climate-altering gases high into the atmosphere and triggering one of the greatest mass extinctions in Earth’s history.

Quantum mechanics and general relativity don’t fit together, and a big part of the issue comes down to gravity. For decades, the accepted route to an ultimate theory of everything has involved taking our best theory of gravity and squeezing it into the frame of quantum mechanics. Yet, almost a century later, scientists still haven’t managed to make gravity fit. Ivette Fuentes is a professor of quantum mechanics who conducts experiments at the scales where quantum theory and general relativity interplay. Fuentes sat down with Â鶹´«Ã½ features editor Thomas Lewton to discuss the issues and fascinating theories that pop out when we try to fit classical and quantum mechanics together.

Read more: The experiments that could finally explain gravity

Homo sapiens have been around for about 300,000 years. Often, our big brains and intelligence are credited with making us the most successful species to have ever walked on Earth, but that isn’t entirely true. There was another species of human that survived on this very same planet for nearly 2 million years, which was the grandparent of so many other human species, including us. They explored new continents. They mastered tools. They may have controlled fire. And they did it all with a brain barely half the size of ours. Enter Homo erectus, a species that may force us to confront an uncomfortable possibility… that intelligence alone isn’t what makes a species successful.

Read more: How Homo naledi is changing what we know about death