According to currently accepted models, light travels at the same speed in all parts of the universe, and it has always traveled at this speed. Distance to galaxies is often measured in light-years, as in how many years it would take light traveling at over 300,000 km/s to cover that distance. So if some stars are billions of light-years away, it must have taken billions of years for that light to reach us, right?
Well, that could be a logical conclusion, if not for a couple of nuances. The farthest object in the universe is 47 billion light-years away. Does that mean, it took 47 billion years for light from that object to reach us?
That would depend on how long ago and at what rate do you assume the universe has been expanding. If you assume the universe to be 14 billion years old, you would come up with a rate of expansion that would allow that object enough time, to move from 14 billion light-years away to 47 billion light-years away. If you assume the rate of expansion to be something else, you would allow for a different rate of expansion. All of this, of course, only holds up if light indeed traveled linearly. If light got here by means of traveling in a straight line in 3 dimensions, than how far away that object is, would depend on how long ago we think light from that object left its source, not how far away from us it currently is.
The idea that light got here by means of linear travel at the accepted speed of light, has a problem in itself. The problem lies in the fact that temperatures throughout the universe are extremely uniform in all directions. The temperature deviates by only one part in 105. According to the Big Bang model, the universe developed different temperatures when it was very small. As it expanded, different parts of the universe would end up with different temperatures. The only way for temperature to be uniform throughout the universe would be if there was enough time for energy exchange between different parts. Let's assume, that when the universe was very small, one section of the universe (point A) developed at one temperature. Another section (point B) is at the same distance from us, but in the opposite direction from us than point A, and developed at a different temperature. So the distance from us to point A is the same as the distance from us to point B. And the distance from point A to point B would be twice as large.
Balloon illustrationIf it took 14 billion years for light from point A to reach us, it would take 28 billion years to reach point B. But wait, the light has to actually travel between point A and point B several times, for equilibrium in temperatures to be reached between two points.
So to answer the question, how far away an object is from us, you first need to assume how long ago light began to travel from that object, and that light got here in a linear fashion, and that it always traveled at the same speed. After you make all these assumptions, you still have to multiply that time period by several times to allow for temperature equilibrium to be reached between all parts of the universe.
So you could either try going in circles to try to assign an old age to the universe. Or you could go with the biblical statement that God “stretched out” the universe after creating it. How light from the stars got to us, would depend on how God created the universe and how He expanded it. If you go with the latter option, you don't need to assign huge ages to the universe. If you go with the former, the age of the universe would continue to fluctuate, depending on which assumptions you begin with.
There are several models which have recently been proposed by Christian astronomers, as to how exactly God went about creating the universe and expanding it. I will reference some of the models below, which would make for an interesting, but a more technical reading.
Lisle, Jason. Taking Back Astronomy. Green Forest, AR: Master, 2006. Print.