If there is one word associated with scientific curiosity, it’s “why”. Why is the universe expanding? Why are cases of cancer rising in young people? Why is the sky blue?
In contrast, it is rare for us to give so much attention to questions that begin with “when”. Indeed, it is often written almost in passing that the universe began 13.8 billion years ago, that our planet is 4.5 billion years old or that Homo sapiens evolved 300,000 years ago. Yet these confident statements conceal plenty of scientific intrigue, mystery and uncertainty. All of which might make one wonder, well, why? Why don’t we focus on “when” a little more?
Asking when forces us to sharpen our thinking, to carefully define our terms and think through what beginnings really look like. It is in this spirit that we tackle seven of the most crucial “when” questions in a special package beginning here “When did time begin? Hint: It wasn’t at the big bang “. Each piece shows that “when?” can be one of the most interesting questions it is possible to ask.
Asking when has already taught us so much about the grand sweep of cosmic history
To take one example, we have recently begun to find that the first galaxies appeared far earlier than we thought possible. The “when” here dramatically changes our understanding not only of the early universe, but also of how the chemical elements that went on to create life as we know it could have come about. Without “when”, there is no “how”, and certainly no “why”.
Science is increasingly well-equipped to investigate when things happened. We can deduce dates in the distant past using evidence from radioactive isotopes or by extrapolating from known points in history. Our special feature serves as a reminder of how much asking when has already taught us about the grand sweep of cosmic and terrestrial history, from the switching on of the first stars to the first life on this planet.
Asking why is also an important part of scientific curiosity, of course, and something we do often, but let’s not give it all the glory. It’s time “when” got some of the limelight too, because if not now…
This article is part of a special series exploring seven of the biggest chronological conundrums of all time. To read the other stories in this series, come back later today:
When did time begin? Hint: It wasn’t at the big bang
Why it’s so hard to tell when Homo sapiens became a distinct species
When did the first galaxies form? Far earlier than we thought possible
Tomorrow:
When did life begin on Earth? New evidence reveals a shocking story
When did plate tectonics begin? The question is crucial to early life
We’re uncovering a radically different view of civilisation’s origins
Why geologists can’t agree on when the Anthropocene Epoch began
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