These are two strange claims.
We often think of the expanding universe like an exploding firework whose fragments all radiate out from the rocket, but that's evidently not the best way to think of what's going on in our universe.
Imagine instead a child blowing soapy film in a plastic ring.
As the bubble floats in the air it continues to expand, but - and this is the point - there's no central point from which the expansion grows. The whole bubble expands as if every point were the center.
This is something like what scientists have in mind when they say that the universe has no center. The universe is, strangely enough, like the surface of the bubble, and it's unimaginably vast.
Watch this five minute video to get an idea of how immense it is: When scientists say the universe had no cause they mean that it had no physical cause in space and time. It arose out of nothing and there's no scientific explanation for how it happened.
It's not that we don't know the scientific explanation, but rather that there can't be one. This is because until there was a universe there was no space, time nor matter, nor were there any physical laws that could have mediated its creation.
Science can't operate in a scenario in which there are no parameters, no laws and no forces. Apart from these, science has nothing to work with and nothing to investigate.
Thus, either the universe was uncaused or, if it did have a cause, its cause was beyond space, time and matter. In either case, science can't say anything about it, although theology can since a cause beyond space, time and matter powerful enough and intelligent enough to create a vast, finely-tuned universe sounds very much like God.
Of course, one who believes the universe is uncaused can side-step the conclusion that God created it, but rejecting the principle of causality merely to avoid the God conclusion is intellectually regrettable.
If, on the other hand, you accept the principle that whatever comes into existence must have a cause of its coming into being then you're acknowledging that the cause of the universe's coming into being must either be God or something very much like God.
It's hard to imagine any other plausible option.
To put it simply, God is a little bit like the girl in the picture producing the bubbles.
