At first sight the answer to this question should be obvious. It's equivilent to asking "if a tree falls in a forest and nobody is there to hear it does it make a sound?"
Of course you'd say, the tree falling disturbs the ground and vibrations make a noise regardless of whether anybody is there to pick up these vibrations.
However when you look at the microscopic scale, at atoms, photons and electrons etc. things start to behave very differently.
At this level things change depending on whether or not they've been observed. If you have two photons from the same source that are in a state of "entanglement" measuring one changes the other, instantly, even if they're millions of miles apart.
This raises a number of interesting questions about whether large scale events can be dependant on such observation based realities - the classic example is "Schroedinger's Cat".
In this thought experiment a cat is placed in a box and depending on whether or not a radioactive decay breaks a tube of poison, the cat lives or dies. However according to quantum mechanics until the lid is opened and the experiment observer the cat is both alive and dead at the same time.
As strange as it seems it appears that in certain circumstances reality actually depends on observation