Answer:
Acceleration is the change in velocity, not the velocity itself; therefore, an object can have zero velocity but not zero acceleration because the velocity will be changing.
Remember Dark Energy is repulsive, the more the faster the universe expands (indeed accelerates), so the faster it would cool down and increase its size, not the other way. Now, no one knows what it is. For instance, if Dark Energy would rather be some other geometric effect, it could have a different ending than just if it is a cosmological constant term. So far, though, all experimental data do not favor anything else that is not compatible with just a cosmological constant ... We'll need to wait few years (~10 years) to get to know much better this with missions and ground experiments that are undergoing or planned to be launched.
Explanation:
Light Light from a moving source travels at 300,000 km/sec (186,000 miles/sec).
Note:
The Speed of Light Is Constant.