Dinosaurs weren't around in 20AD. Crichton hadn't written Jurassic Park yet. You would gave to wait almost 2000 years to be eaten by a dinosaur.
I agree with Wolfy (and Mark Twain). With basic knowledge of engineering, and considering the decent metallurgy of the time, it would be possible to revolutionize farming, everyday life, and warfare/defense. Add making innovations in sanitation, medicine, food storage, etc. You could also use ethics and philosophy to found a rational religion. A Golden Age in 20AD to progress to an amazing 2020!
While that sounds good, its unlikely to happen... ---
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