Since we have received no apparent signals of intelligent life in the past 70 years or so can we conclude none exsist in 70 light years from us?

No.

This is a very intelligent question, thank you.

As a comparison, let us turn the table and look at humans on Earth and someone in space listening to see if we exist.

Humans have been on Earth for only a tiny portion of the age of the planet, and of the time we have been here, only within the last hundred years have been transmitting in earnest.

Anything beyond a hundred and fifty light years away wouldn’t know we existed yet.

How far is that? Well, it’s mostly everywhere in space. No intelligent life “out there” likely knows we’re here.

Similarly, we are listening. There could be an advanced civilization with cell phones and GPS and geostationary planets and all that within 75 lights years from here (very, very close) and we wouldn’t know about it here yet.

The chances of that happening? Very low.

Life is out there. Chances they are withing listening range before our species becomes extinct? Very low.

All this takes places within our own neighborhood here in our section of the Milky Way galaxy. Beyond that is the rest of our galaxy, Andromeda, and …. there are long distances involved — hundreds of millions of billions of years. There could be life very close to us but we wouldn’t hear them yet because they might be 300 or 10,000 years away from developing transmission technology! Or they might be a million light years away in a galaxy far, far away.