The history of life on Earth is interesting. Consider the following, we compress the entire lifespan of our home planet into 24 hours. The age of the Earth is about 4.6 billion years i.e. 4600 million years, which by the way we have not known about for that long. The current age was calculated approximately during the 1950’s. Most earlier calculations and predictions gave shorter estimates. Using todays estimates of the age of the universe, the Earth has existed for almost exactly 1/3 of the age of the universe.
But back to the life part, life appeared on our planet as early as 04:00 in the morning on the compressed timescale as small microbes, but then it took a really long time before anything new happened. At 20:30 the life on earth still consisted just of microbes. But now the first plants appeared in the oceans, twenty minutes later the jellyfishes and at 21:04 the well known trilobites appears. At 22:00 plants start to grow on land, and at 22:24 there are forests and insects. At approximately 23:00 we can see the dinosaurs which exists for about 45 minutes before the extinction event wiped them out. Humans arrive at 23:58:47 (one minute and 17 seconds before midnight). On this scale the life of a human is about 1 thousand of a second which by comparison is about the the same length as it takes for the flash on your camera to finish.
Our planet is a dangerous place to live on, there have been numerous occations of extinctions when many of the species have died out. Most of theese occations we do not know exactly what happened, but there are some different things that might have happened:
- Global warming
- Global cooling
- Changes in waterlevel
- Depletion of oxygen in the ocean (Anoxia)
- Huge leaks of methane from the bottom of the ocean
- Comets and meteors
- Hypercanes (extreme form of hurricanes)
- Big Solar flares
And of course there exists other possible theories also.
Five of the extinctions are commony called ”The big five” which includes the events ”End Ordovician”, ”Late devonian”, ”End permian”, ”End Triassic” and ”End cretaceous”.
The biggest one of them all were the ”End Permian” one that happend 251 million years ago, this was before the dinosaurs. A whopping 95 % of all species died out (96% of marine species and 70% of the land species). It took about 6 million years for the life to recover again. In june 2006 there was found a huge meteor crater under the Antarctic ice sheet that might be the cause of this extinction event. The crater diameter is about 480 km (thus twice the size of the crater that have been suggested as the one that killed the dinosaurs). This is not proved of course but it’s one theory.
Big objects from space impacts with the Earth quite frequently, and in the 24 hour day above you would be able to see about three impacts per minute from objects larger than 2km in diameter. And those are big ones. The history of humankind has yet been spared the really big ones, but U.S. Geological Survey in fact estimates that impacts that release as much energy as the atomic bomb dropped over Hiroshima in Japan during the war happens about once every year. In modern history the biggest recorded impact wats the one in Tunguska in Russia 1908, 80 million trees were destroyed, but there was no crater left as the object exploded before it hit the ground.
The other four of the big five extinction events wiped out around 70% of all species.
Another interesting thing to note is that among the 7 biggest extinction events are ”Present day” listed, this is disputed but a survey showed that 70% of asked biologist think this is the fact, and some research points to that 50% of all species might be gone in as little as 100 years or possibly a few hundred years, and this is of course extremely fast.
Some species die and new ones come forth, this seem to be normal throughout the history of life on Earth and we should be happy we are still alive. It has been discovered that the more advanced a species is the faster it seems to die out, we are now pushing the limit of this average lifespan, but perhaps we are intelligent enough to prolong this. But if a big catastrophic event occurs there might be little we can do of course and we might also be stupid enough to destroy ourselves.
Anyway 99.99 % of all species that have ever existed on our planet is no longer with us.
RIP all billions of species!! Hmm I have a feeling that I don’t miss some of them though 🙂