The notion of the size of the observable universe and its relationship to the distance of light travel is an intriguing topic. While it might seem intuitive that the size of the observable universe should be at least twice the distance light has traveled, the actual situation is more complex due to the expansion of space.
The observable universe refers to the portion of the universe from which light has had enough time to reach us since the Big Bang. It represents the region we can observe given the finite speed of light and the age of the universe. The age of the universe is estimated to be about 13.8 billion years.
However, the expansion of the universe must be taken into account when considering the size of the observable universe. Space itself has been expanding since the Big Bang, which means that the distance between objects has been increasing over time.
Due to this expansion, the light from a distant galaxy that has been traveling toward us for billions of years has had to traverse an increasing amount of space, which expands as the light propagates. As a result, the distance between us and the source of that light has increased during the travel time.
Taking all these factors into consideration, the current estimation of the radius of the observable universe is about 46.5 billion light-years. This means that the farthest objects we can observe are about 46.5 billion light-years away from us.
It's important to note that the term "light-year" is a unit of distance rather than time. It represents the distance that light can travel in one year, which is about 9.46 trillion kilometers. So when we say the observable universe has a radius of 46.5 billion light-years, it means the light from those objects has traveled that distance to reach us.
In summary, the size of the observable universe is much larger than twice the distance light has traveled since the objects in the universe are receding from us due to the expansion of space. The estimation of the observable universe's radius is currently around 46.5 billion light-years.