We can look back about 15 billion light years which gets us near the big bang but since the bang was surely omnidirectional there is a second half of the universe we will never see right?

Answer 1

sorry. Try this, we (the parts (atoms ... particles) that make us up) were all a part of the bang. in a sense we're still inside it ... or its residue. Everything we can see is big bang.

and the latest guess is 13.7 billion years.

First of two assumptions, is that there is a they on the other side of the universe. The second assumption. Imagine one drop of rain falling in the middle of the Pacific Ocean. Just one drop of rain. No waves or wind. Will there be a crashing wave on the west coast of the US. Will the people in Siberia even notice it. The big bang, when in relation to infinity, would be almost as imperceptable. Thanks to the work of scientists Penzias and Wilson (1965) using the Bell Laboratories Holmdell and Horn Radio Telescope in New Jersey, the result of the explosion commonly called the Big Bang is detectable, and is detectable at the same temperature no matter what direction we look for it. Penzias and Wison were working on communications development. They first thought that their finding was an anomaly, and they even cleaned out their equipment, thinking it might have been caused by bird droppings and dirt that had accumulated inside it! It became clear what was happening when they communicated with others who were working on the Big Bang. We can search "to the edge" in any direction we choose, and so we can explore every part of the universe without having to leave a half of it as unobservable.