This question is too vague to be answered - please give us something to start with!
Long period comets originate in the Oort Cloud.
it has been increasing the last 200 years
Long-period comets have periods of over 200 years.The longest would probably be somewhere around a million years (comparable to the orbital periods of objects in the Oort cloud); much longer than that, and it will go away far enough to be captured by the gravitational field of other stars.
Long period comets originate in the Oort Cloud.
Short period comets have a period of less than 200 years Long period comets have a period of more than 200 years.
A comet with a period of 200 years or more.
A comet with a period of 200 years or more.
Not more than 200 years - less than 200 years. As to the "why", that's because this is how "short-period" vs. "long-period" is defined. Any comet that takes less than 200 years for one revolution is defined as short-period.
200 years
they where living over 200 millions years they where living over 200 millions years
The Great Wall was built over many years. It is believed the original Great Wall was built over a period of approximately 20 years. The Great Wall which is mainly in evidence today was actually built during the Ming dynasty, over a period of around 200 years.
The Jurassic period - about 200 million to 145 million years ago.