[qmi@localhost: ~]$ dig +short . SOA
a.root-servers.net. nstld.verisign-grs.com. 2013061701 1800 900 604800 86400
[qmi@localhost: ~]$ host a.root-servers.net
a.root-servers.net has address 18.104.22.168
a.root-servers.net has IPv6 address 2001:503:ba3e::2:30
The answer to the above lookup means that the SOA a.k.a. "start of authority" record starts at the a.root-servers.net computer which provides the domain zone for the "." domain. The "." (dot) is called the "root domain", which in the DNS hierarchy means the most top-level domain. The other result simply just an IP address entry to that highly important server (in fact, most probably it is a shared unicast load-balancer front-end that serves several back-end servers). Let's look at the top-level name servers as well by asking the NS records. This will show us the name servers responsible for the "." domain.
[qmi@localhost: ~]$ dig +short . NS | sort
That's where it all starts :)