Dinosaurs were on Earth for about 175 million years. They've been extinct for about 65 million. Those are huge time frames to try and imagine, but think about this: Human beings have only been around for 100 thousand to 200 thousand years. That's tiny compared to the amount of time dinosaurs were around!
Not all dinosaurs went extinct at the same time though. Many different species or types of dinosaurs came and went over those 175 million years. Some well-known ones that were still alive at the time when dinosaurs went extinct were the tyrannosaurus rex and the triceratops! Some other dinosaurs alive at that time were the ankylosaurs and different types of raptors.
Many dinosaurs had already gone extinct by that time. Brachiosaurs and stegosaurs had already been gone for millions of years by the time the last dinosaurs went extinct.
Many scientists agree that not all dinosaurs went extinct. Some became modern birds!
Countdown to Extinction
Large time frames like millions of years and thousands of years can be hard to imagine. But maybe we can speed it up to get a sense of the scale. Imagine that a million years went by every five seconds. We're going to travel through time really quickly. And we'll start at about 240 million years ago. What time is it right now? Imagine that right now at this time, we are 240 million years ago. (We'll use 12:00 Noon as an example).
Right now (12:00:00), the first dinosaurs are evolving. Some of these early dinosaurs were called eoraptors.
In 7 minutes and 15 seconds (12:07:15), we'll see the first brachiosaurs, with their long necks that they use to reach leaves in tall trees.
In 3 minutes and 20 seconds, the last of the brachiosaurs will go extinct (12:10:35).
In 3 minutes and 45 seconds (12:14:20) we'll see the first tyrannosaur.
About 15 seconds later, the Tyrannosaurs and all the other dinosaurs will go extinct (12:14:35).
In 5 minutes and 24 seconds (12:19:59), we'll see the first modern human.
One second later (12:20:00), we'll be at the present.
About 20 minutes ago the first dinosaurs were here. They stayed for about 13 minutes. But only the very last second covered all the time that humans have been around!
Sources & links
"dinosaur." Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 30 Apr. 2010 "K”“T extinction." Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 30 Apr. 2010 Viegas, Jennifer. "Tyrannosaurus: One of the Biggest Flesh-Eating Predators of All Time." Discovery Dinosaur Central. 30 Apr. 2010. Viegas, Jennifer. "Brachiosaurus." Discovery Dinosaur Central. 30 Apr. 2010. Viegas, Jennifer. "Stegosaurus: The Solar Paneled Dinosaur." Discovery Dinosaur Central. 30 Apr. 2010.