First of all, those are two completely different questions. What happens (presumably you mean after death?) doesn't necessarily have anything to do with why we are here.

It could be that nothing happens after death, but there is still some grand purpose to existence. Or it could be that there's an afterlife, but the universe itself is meaningless.

As to what do I really know? The answer is, of course, nothing. No-one can really know anything about what happens outside of our existence and anyone who tells you they do is either lying or delusional.

However we can make an educated guess (and not even a "so called" one, a real one based on centuries learning about the universe we inhabit) Every time we make a new discovery, it has turned out to have a natural explanation. As we learn more, the "god of the gaps" has grown smaller and smaller, to the point where we know that even if there is some mystical force underlying the universe, it has no measurable effect on it.

*related=http://videosift.com/video/Physicist-Sean-Carroll-refutes-supernatural-beliefs

If our consciousness really does continue after our physical bodies die, there has to be a mechanism for it, and there is zero evidence of any such mechanism.

It could be that we simply lack the tools or the understanding to detect this, but there isn't even anything leading us to ask the question (e.g. an unexplained phenomena that would prompt us to investigate a hypothesis that might lead to a theory).

As to why we are here? From a scientific point of view, there's no evidence to suggest there is a reason to anything. The universe just is. From a philosophical point of view, I've always liked Carl Sagan's idea that "we are a way for the cosmos to know itself".

TL;DR We really know nothing, but it's pretty unlikely that anything happens after death or that there is a reason we are here.

This video was much more succinct than Carl Sagan's Cosmos series segment on the same subject.

If there were a type 2 civilization, with such a device that could harness an entire star's energy - how would we on earth detect that? Maybe everything we think is a black hole is actually one of these?

Tags for this video have been changed from 'carl sagan, earth' to 'carl sagan, earth, pale blue dot' - edited by Grimm

You can demonstrate the effect of carbon dioxide on climate as easily as dropping a ball from your hand? People know that balls will drop because the see it for themselves, not because a former physicist and his dog say so.

In actual fact, the earth has not warmed in nearly 20 years, and the climate models do not help to explain this. They are useless for explaining or predicting changes on the scale of decades, and it's crazy to expect them to somehow predict changes much further in the future.

Warmism, from the start, has been based on obfuscation, concealment of data, dodgy statistics, and overcomplicated computer models that add very little to insight into the real physical phenomena.

Remember the hockey stick? That went the way of Carl Sagan's nuclear winter, which ought to provide a cautionary tale for Neil deGrasse Tyson.

Your child's future will have many problems, one of them being depletion of the fossil fuel supplies that we have come to rely upon for sustenance. Climate will change, as it always has, and some of that change will be caused by CO2.
Climate science could be helpful; it's a pity that it has been distorted into a completely political exercise, and a shame for science generally, which stands to lose a great deal of public trust.

Of all the currently alive people they could have chosen to fill Sagan's shoes, I'm impressed they got it right.

Your video, Carl Sagan's View On Science, Technology and the Government, has made it into the Top 15 New Videos listing. Congratulations on your achievement. For your contribution you have been awarded 1 Power Point.

Clarkium (after Arthur C. Clarke)
Saganium (after Carl Sagan)

Neil deGrasse Tyson has truly inherited Carl Sagan's legacy. I have never been more excited to see anything else in my life!

This video has been seconded as a duplicate; transferring votes to the original video and killing this dupe - dupeof seconded with isdupe by chicchorea.

*dupeof=http://videosift.com/video/Peter-Sagan-Roof-Parking

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The Carl Sagan guy was spot on with the voice.

The Sagan "hydrogen" line was awesome.

'Carl Sagan' looked far moore like Alan Partridge, but I applaud the concept

As the late and brilliant Carl Sagan would have said, extraordinary claims require extraordinary evidence "Bang 'em out!"