Time: Looking Back and Forward
To look far out in the universe is to look far back in time.
Despite the blistering speed of light (rounded out to 300,000 kilometres per second), the vast distances in space mean that the time taken for electromagnetic signals to reach Earth from the sun is a little over eight minutes, more than three million years in the case of light from Andromeda our nearest neighbouring galaxy, and for light originating from the earliest stars, a little more than 13 billion years to reach Earth and the recently launched Webb telescope.
Grasping the significance of that perspective was made easier for me several years ago by Michael Shermer, who, working with his own telescope at home and looking at Andromeda, realized that the time taken for the light from Andromeda to reach his retina began its voyage 3.2 million years ago, or roughly the time that the iconic Lucy, left her footprints in east Africa.
The corollary to that mind-bending realization is the added realization that electromagnetic signals, whether originating from galaxies, giant black holes, collisions of black holes or neutron stars, are very old news by the time they reach Earth.
And going forward, we will never know what happened thereafter or what is going on now in those far distant corners of the universe. The events took place too far away for us to see them in "now" time.
And to add more stellar perspective it would take 200,000 years or roughly the time between the earliest origins of modern humans in Africa and the present, to travel across the Milky Way at light speed.
Or put another way, it would take 10,000 generations of humans to reach the far side of our galaxy travelling at light speed. Given that travel at anything approximating light speed is impossible because of Einstein’s general relativity, the reasonable conclusion is that we will never know what’s happening now on the other side of the Milky Way.
The saving grace is that what we’ve learned about events in the universe in the distant past is enough to construct plausible pictures of what happened in the past and going forward, suggest what may happen in the future.
Geology works much the same way. To look at successively older layers of rock is to look back in time from the present to as early as four billion years ago, soon after Earth formed. Indeed, by comparing similar rock formations around the world from the deep seas, cliff faces and mountains, the geological history of the Earth can be traced precisely.
Successive sedimentary layers also trace the origins of the earliest single cells, later more complex cells, still later, cell colonies, and later yet, complex multicellular organisms as well as multiple extinction events, the worst of which devastated well over 70 per cent of life in the seas and lands 250 million years ago.
Geology after all is a history text, writ large, which tells us about the formation of the Earth, early bombardments, the formation and movement of land masses and the creation and weathering of mountains – and reveals the major factors that govern climate change, including the carbon cycle over many millions of years.
One good read on the subject is Andrew Knoll’s well-written 2021 book, "A Brief History of Earth," which incidentally my 13-year-old grandson in Alaska is thoroughly enjoying now. And if he enjoys the material, you might too.
Then there’s the matter of genetics. Until recently, sequencing the genome was a challenging and expensive affair and in medicine used chiefly to identify genes that play roles in diseases and secondarily, how abnormal (mutant) genes are passed from one generation to another.
All of which became much more exciting recently because of the advent of relatively cheap and precise methods for editing the genome thanks to the work of Jennifer Doudna and Emmanuel Charpentier who shared the 2020 Nobel Prize in chemistry.
However, genetics has had another important impact: it reveals the migrations and matings of our human ancestors hundreds of thousands of years ago and with a broader brush, our deep, translate as ancient, genetic relationships to countless other species in which many solutions to body shape, brain development and metabolic challenges were solved long before modern or even archaic humans appeared.
So, like astronomy and geology, genetics provides historical perspective and reveals relationships of which only a few decades ago, we were unaware. That’s useful history to add to the history most of us learned, which usually began with written records and empires.
Well, it turns out that "written" applies to information in rocks and genes as well as text.
Dr. William Brown is a professor of neurology at McMaster University and co-founder of the InfoHealth series at the Niagara-on-the-Lake Public Library.