Archaeologists excavating Egypt's Avenue of Sphinxes announced this week that they have uncovered the remains of a nilometer, used to monitor the water level of the Nile.

The Avenue of Sphinxes, built by the 30th Dynasty king Nectanebo I (380-362 BC), was one of the most important processional routes in ancient Egypt. At 2700 metres long and 76 metres wide, it ran between the Luxor and Karnak temples, and was lined with statues in the shape of sphinxes.

Strange place for a depth gauge? Not really. The Egyptians were dependent on water and silt from the Nile's annual flood for their agriculture, and monitoring the river's level told them whether to expect famine, bountiful crops, or devastating floods in the months ahead. They used various devices to do this for more than 5000 years (until the Aswan Dam rendered the practice obsolete in the 20th century).

The first nilometers were simple marks on the riverbank, or on a column or post placed in the river. Later the Egyptians used steps leading down into the water, with depth markings alongside (see video). Then they got more sophisticated, with a channel leading away from the river into a dedicated well or cistern. Any knowledge about what the Nile was going to do was incredibly valuable, so these wells were often located inside temples, accessible only to priests or rulers.

The nilometer found at the Avenue of Sphinxes seems to be of this last type - it is a 7-metre-diameter cylindrical well dug into sandstone, encircled by a spiral staircase (see image). Clay vessels found at the bottom have helped the archaeologists to date it to the New Kingdom (1569-1081 BC).

The team has also found a 1600-year-old Christian church. It was built with limestone blocks recycled from ancient temples that stood along the route - the blocks are still decorated with scenes of Ptolemaic and Roman kings offering sacrifices to ancient Egyptian gods.

Ancient monuments from Stonehenge to Egypt's great pyramids are carefully aligned to astronomical events, telling us that from the very beginnings of civilisation, people have been fascinated by the heavens above us. Throughout history this has been a driving force for technology, such as the intricate cogwheels and pointers of the Antikythera mechanism, the astrolabe, equatorium, and telescope, not to mention mechanical clocks, which started off as huge astronomical displays.

And it is still going on today - some of the biggest, most sophisticated (and expensive) machines in the world are being built in order to make sense of the cosmos. Whereas the ancient Greeks, say, wanted to know things like how the solar system was arranged, when the next eclipse would be, or the distance from the Earth to the Sun, today we have different questions. Why is the universe expanding at an ever faster rate? What is the nature of the ‘dark' matter that makes up almost a quarter of the universe? Why does the universe appear fine-tuned for life? To probe such huge questions, physicists have had to build their machines literally at the ends of the Earth - from the coldest deserts and highest mountains to the deepest mines.

I'm reading a book at the moment called The Edge of Physics, published last month, in which science journalist Anil Ananthswamy (disclaimer: he's a friend of mine) visits today's cutting-edge physics experiments and tells their stories, I guess it's a cross between a science book and a travelogue. Scientists are so often portrayed as weedy white-coated geeks in labs, but the ones that Anil meets are more likely to be tough adventurers, willing to endure all kinds of physical hardship for their science. My favourite chapter so far is when Anil visits the vast frozen expanse that is Lake Baikal in Siberia. Hidden beneath more than a kilometre of ice is a neutrino telescope. The scientists who tend the telescope live for months in the blasting cold, sleeping in tiny wooden cabins perched on the creaking ice.

What I love about the book is that it portrays a real sense of wonder, a sense of our tiny place in an awesome universe. I think that would have been very much in tune with how ancient civilisations saw things too.

I find it amazing to look at artefacts that survive from the ancient world - just to think about all the centuries of history that they have existed through. But a lovely piece in the today's Observer goes one better, pointing out that plenty of organisms that were alive thousands of years ago are still going strong today. They range from the 2000-year-old welwitschia plant, a conifer that produces just two leaves in its entire lifetime, to actinobacteria that have been frozen in Siberian permafrost for a mind-boggling half a million years.

Photographer Rachel Sussman aims to photograph as many of these organisms as possible. To qualify, they have to be at least 2000 years old, meaning they would all have been around in the time of the ancient Greeks. She tells the Observer that the project has a two-fold message - "a humble, existential aspect in which the entirety of human history feels dwarfed by the longevity of life around us" - and an environmental caution. "We have these organisms that have quietly persevered for an unfathomable amount of time but which are now in jeopardy," she says. "The Siberian actinobacteria are half a million years old and live in the permafrost. If the permafrost isn't permanent, the oldest living things on the planet will die."

The picture above is of a brain coral, which can live for up to thousands of years. It isn't one of Sussman's, but you can see some of her photos on her blog.