I ran the following command on linux

>> dig .

I got the following response

;; AUTHORITY SECTION:
.           281 IN  SOA A.ROOT-SERVERS.NET. NSTLD.VERISIGN-GRS.COM.     2010032400 1800 900 604800 86400

1. why does the response not contain the IP address of the root server?
2. what do the numbers at the end of the reply mean. one of them is probably (definitely) the date.
3. why does it report 2 root servers a.root and nstld.verisign?

4. when i send the following queries

   dig com.

   ;; AUTHORITY SECTION:com. 51 IN SOA a.gtld-servers.net. nstld.verisign-grs.com. 1269425283 1800 900 604800 86400

again i do not get the ip addresses. when i query for the gtld server specified i can get the ip address. why is the response of dig net. same as that of dig com. except that instead of 51 we have 19 in the response.