Sorry, we couldn't connect to our servers (UnkownHostException:authserver.mojang.com)

For the past few weeks I have been unable to launch Minecraft. Every time I open the application, my launcher loads the update info page for about 2 minutes, until it returns to the main username and password login page. I have made sure that my username and password are correct, that no firewalls or security measures are active on my mac. I have checked my router and my internet connection several times, it is perfect. When I enter my login information, the page has a loading bar until I am met with this. Please help me, I've been wanting to play Minecraft for some time now.