If the universe is only 13.8 billion years old, and nothing can travel faster than the speed of light (1 lightyear per year), how can the observable universe possibly be nearly 100 billion lightyears across? How do we reconcile the sheer size of the universe with the understanding that it all emerged from an infinitely dense point not so long ago?
In: Physics
Rate of expansion of universe is not bounded by the speed of light.
Another way to put it is nothing can travel faster than the speed of light inside the universe but the space inside the universe can stretch much faster; there doesn’t seem to be a limit on that.
Incase it’s still not clear, let me try another analogy albeit not completely accurate but its easier to understand. Imagine a slightly inflated balloon. Put two points A and B on that balloon and imagine an ant standing on point A. Now imagine the ant is the photon of light and balloon is its universe. Now lets say the ant can only travel at constant maximum speed of 9 meter per hour towards point B i.e nothing on that balloon surface can travel faster than 9m/hr. Now when the ant starts to move towards point B, you start inflating the balloon. In this case the ant has more distance to cover to get to point B. If you keep inflating the balloon faster and faster than eventually the ant will never reach point B as the balloon surface will be increasing faster than Ant’s speed of 9m/hr. Our universe expanded in a similar fashion. And as we chat, the distance between most galaxies are increasing due to mysterious dark energy and eventually we won’t be able to see other galaxies because light from those galaxies will never be able to reach us; also we will be long dead by then (sad face). Hope this makes it clear.
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