Question: how did the Dinosaurs come to exist on our planet millions of years ago? was it a comet? if so how did that create the dinosaurs? was it a combine of molecules creating a cell? what caused the dinosaurs to exist and how?

Damian Bailey answered on 17 Jun 2013:

Wow, cool question and something that I taled a little bit about during the Times Cheltenham Science Festival (http://www.cheltenhamfestivals.com/science/whats-on/2013/will-humans-evolve-in-the-future/). There are lots of theories about how life started on what we affectionately call “Early Earth” but since we scientists weren’t around at the time to prove or disprove them means that no fully accepted theory currently exists! You’re right in that some scientists think that life was “kick-started” by cosmic dust carrying simple molecules like water, ammonia, methanol and carbon dioxide that can form the “building blocks of life”, DNA and RNA that help make proteins. Some scientists have even calculated how much organic life was transmitted to Earth during the time that it was getting slammed by comets; in fact, one calculation suggests that over 10 trillion (10,000,000,000,000) kg were delivered each year (wow, that’s more than Tesco delivers!). Some scientists also think that conditions on Earth helped jump-start life, two competing theories if you like! (bring out the boxing gloves!).
Eventually cells started to replicate and got together (such social beasts!), clumped together to form more complicated bacteria and thanks much to the work of a super-famous scientist Charles Darwin, they evolved over billions of years to form the Jurassic Park dinosaurs! Dinosaurs existed between 230 million years ago and 65 million years ago evolving through a series of changes from more primitive reptiles. A mass extinction event at the end of the Cretaceous period (some think it was that Comet again, but not the same one!), 65 million years ago, ended the reign of dinosaurs on Earth. Recently, many scientists have come to the conclusion that, while dinosaurs may have disappeared, some of them evolved into birds long before the extinction event that wiped out the other dinosaurs – and so, in a sense, dinosaurs are still around today!