Tamil is the oldest language is it right?

Well, it is a matter of debate still. There is more research work to be done to ascertain if this may perhaps be true. However there are some strong indications to suggest this, as explained below.

Scientific basis:

Archaeological discoveries have so far found that Tamil was in use since 1000 BC - 500 BC, with the discoveries of ruins in Adichanallur among other places.

Tamil is usually regarded as the one that is least influenced by Sanskrit or all other languages in India. So this has led many scholars and researchers to hypothesize that Tamil and Sanskrit were contemporaries.

However an underwater city has been found off the coast of Tamilnadu (South Eastern India) which was called as Poompuhar in Tamil literature, these findings were popularized by researcher Graham Hancock with his research work in circa 2002 (watch his very recent & important interview by following the link provided below in the Sources and related links section).

Until then, Poompuhar was considered as myth & mocked at, similar to how Troy's existence was considered as myth until it was discovered & found to be true. Hancock estimates that the ruined underwater city might be at least 9,500 years old or closer to the last ice age (10,000 BC), when ice melted to raise the sea level, which would account for the disappearance of many other ancient port cities & civilizations around the world (like Dwaraka off Gujarat coast, Yonaguni ruins near Japan, new underwater ruins near Alexandra, Egypt, etc).

But there has apparently not been much interest from Indian/Tamil nadu governments to research it more to discover the hidden past.

There are references in Ramayana & Mahabharata to some of the Tamil kings and kingdoms/empires. Also trade contacts between ancient Tamil kingdoms & Greece, Egypt, Indonesia, Cambodia, Thailand have been found. Some researchers consider the Indonesian empire Sri Vijaya as part of Chola empire.

We'll have to wait for some more time to let science tell us the truth.