# Age of universe

It's said that at the moment of the Big Bang, space expanded so that to an objective observer matter moved at thousands of times the speed of light. If so, how can we say the universe is 10-30 billion years old? Couldn't it be a billion years old with objects 10-30 billion light years away because of "riding the space wave"?

• It doesn't work like that. The age of the universe is approximated by analyzing the cosmic background radiation. And the universe cannot be a billion years old as Earth itself is around 5 billion years old. – Sam Feb 1 '20 at 4:27

The whole universe is likely infinite in size, and if so, it's always been infinite for all time $$t>0$$, where $$t=0$$ is the instant of the Big Bang; the size of the universe at $$t=0$$ is not mathematically well-defined. Please see Did the Big Bang happen at a point? for further details.