The age of our universe

Our universe is about 13.7 billion years old. It's a very very long time, and it's hard to imagine how long it actually is. But when I first learned about the age of the universe, I was disappointed, I thought 13.7 billion isn't long enough. I was expecting a number to "sound" bigger than billions, perhaps a number that we don't use anywhere else. I don't know what exactly I was expecting, but not something in billions for sure. We're talking about the universe after all, that's the thing that has all the other things in it. That's the thing where there's no outside, where time itself must have started. I guess I was expecting not to know the answer or it to be an infinity somehow.

But that didn't last long, I then realized it's actually a very long time, the number may not sound that big, which it really is, but for a time period, it's big, it's very very big. And I realized that because I thought this: the universe is 13.7 billion years old now, when will we say that it is 13.8 billion? That is 100 million years later. I understand that 100 million is way smaller than 13.7 billion to be impressed, but this time I was thinking about "waiting" 100 million years to pass, and it seemed to put things in perspective somehow. It's such a long time that it doesn't make much difference if we say 13.7 billion or 14 billion when we compare it to our "human time periods".

In such cases, when there's something really big or small, I try to compare it to something else to try to make sense of it.

There are a lot of comparisons and explanations about the age of the universe, and one of my favorites is an episode of Star Talk podcast where Neil deGrasse Tyson explains it by comparing it to a 100-yard-long football stadium's length. It's a great episode, and a great podcast overall, you should check it out.

The calendar in my head

Any time I think of a date or a period, I have this image of a calendar year in my head and I position those dates and periods on it. It's circular, divided into 4 parts, each part has its unique color and is divided into 3 months. Colors differ from time to time, but they are always different. It starts from the top at 01 Jan and moves forward clockwise. It's similar to a usual calendar, but it isn't divided into the 4 usual seasons, just 3-month parts starting from the beginning of the year as opposed to many circular calendars that seem to start "a little early" on the circle (15 degrees to the left). For some reason it helps pin dates visually and see them in an easier way for me.

circle-calendar

What I'd like to do is compare the age of the universe to a calendar year. For that let's imagine the circle calendar is not for a single year, but 13.7 billion years. It starts at the top, 13.7 billion years ago is 01 Jan, and it ends now - 31 Dec. We can now add some events to this calendar.

Our Earth is 4.5 billion years old, on our calendar, this would have been on around 03 Sep.

Dinosaurs first appeared about 233 million years ago and lived for about 165 million years. That would have started on 25 Dec and lasted until 30 Dec. They lived on Earth for less than 5 days. The Cretaceous-Paleogene mass extinction event happened 42 hours ago.

Wondering how long humans have been around? Early modern humans appeared about 300,000 years ago. On our calendar it's just about 11 minutes ago. Can you believe that? The universe existed for a whole year, and we appeared just 11 minutes ago. 5 days for dinosaurs doesn't seem that short now, does it?

Here are some more dates:

The big bang                                  - Jan 01 @ 00:00:00.000

Earth's formation, 4.5 billion years ago      - Sep 03 @ 00:39:24.963

First dinosaurs, 233 million years ago        - Dec 25 @ 18:54:50.453
Last dinosaurs, 66 million ago                - Dec 30 @ 05:46:10.686

Early modern humans, 300,000 years ago        - Dec 31 @ 23:48:28.958

Agricultural Revolution, ~10,000 BCE          - Dec 31 @ 23:59:32.358
Maya civilization, ~2,000 years BCE           - Dec 31 @ 23:59:39.269
Aristotle was born, 384 BCE                   - Dec 31 @ 23:59:54.458
Year 1, 1 CE                                  - Dec 31 @ 23:59:55.345
Industrial Revolution, 1760                   - Dec 31 @ 23:59:59.396
"Special Relativity" was published, 1905      - Dec 31 @ 23:59:59.730
I was born, 1984                              - Dec 31 @ 23:59:59.912
Someone else was born, 2000                   - Dec 31 @ 23:59:59.949
The year the world was supposed to end, 2012  - Dec 31 @ 23:59:59.977
A year ago                                    - Dec 31 @ 23:59:59.998

If you pay attention to the last 10 events, they all happen during the last second, 23:59:59, but they are spread over 12,000 years.

Humans have been around for a little more than 11 minutes or 690 seconds, while a year consists of more than 31 million seconds. If we subtract those 690 seconds from the 31 million, it doesn't really change. That's how short the duration of our existence is in comparison.

When we think about human history and evolution, it seems like quite a long time. Let's assume a human life is 100 years. 300,000 years is 3,000 times longer. Cats live 9 lives? Well, imagine living 100-year-long human lives for 3,000 times. That seems very long, doesn't it? Of course, it does, now take into consideration that it's still the same 11 minutes out of the whole year.

Something that seems really long time ago, is just 10 minutes ago compared to the age of the universe. This still doesn't let me imagine how long a 14-billion-year-long period is, nothing will ever do, but it puts things into some perspective.

References