Everything is Time

In his book, Origin Story, David Christian points out the different techniques using which different fields of science find the age of something. And “age” is another way of saying “time”.

 

Let’s start with astronomy. How do they know the Big Bang happened 13.8 billion years ago? It started off when astronomers discovered that certain stars have the same brightness, i.e., their actual brightness is the same everywhere. When they see such a star, astronomers measure its perceived brightness as seen from earth (or a telescope in space). Using the two values (actual v/s perceived brightness), they can calculate the distance of the object in question. Next, take the current distances and speeds of galaxies, and work backwards to see when they must have all been together, and you get the age of the universe.

 

Geologists and paleontologists, on the other hand, used radioactivity to come up with the age of everything from ancient mummies to the earth to the solar system itself. If you know the half-life of a radioactive element, you know the ratio of the “before” and “after” elements to expect after different periods of time. Now reverse that thinking: if you find a certain ratio of “before” and “after” elements in a radioactive sample, you can calculate its age.

 

And biologists?

“Biologists have found that DNA evolves at a reasonably regular pace, so you can roughly date when two species diverged from a common ancestor by measuring differences in their genomes.”

 

All this talk of age/time reminded me of something from Simon Winchester’s book, Exactly. In science, we have seven “foundational units of measurement”. That’s just a fancy way of saying that all other units are some combo of these seven units. Here’s the kicker, as per Winchester:

“Frequency is now mentioned in no fewer than six of today’s seven units of measurement. Frequency is just about everywhere.”

Actually, Winchester uses the terms “time” and “frequency” interchangeably. But that’s OK since frequency is the inverse of time, i.e., f = 1/t.

 

Take, for example, the unit of length, meter: it is defined as the distance travelled by light in a certain amount of time. How about the other commonly used unit, the kilogram? Its definition too is based on frequency, and thus time. Even the definition of something seemingly unrelated to time as brightness (unit: candela) is now based on the second (time).

 

All of which is why Winchester says:

“The whole world now agrees…: time underpins everything… All are connected by time.”

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