If Alert log file is lost

One of my friend asked me whether if in any case the
alert log file is lost what happens?

It is automatically created whenever there needs to
be a new entry into the alert log.

Lets see a practical explanation

[oracle@oracle11gr1 ~]$ sqlplus /nolog

SQL*Plus: Release 11.1.0.6.0 - Production on Sat Apr 19 15:35:05 2008

Copyright (c) 1982, 2007, Oracle. All rights reserved.

SQL> conn /as sysdba
Connected.
SQL>
SQL>!

[oracle@oracle11gr1]$ cd /u01/app/oracle/diag/rdbms/orcl/orcl/trace
[oracle@oracle11gr1 trace]$
[oracle@oracle11gr1 trace]$ ll alert_orcl.log
-rw-r----- 1 oracle oinstall 144278 Apr 19 15:26 alert_orcl.log

[oracle@oracle11gr1 trace]$ pwd
/u01/app/oracle/diag/rdbms/orcl/orcl/trace

[oracle@oracle11gr1 trace]$
[oracle@oracle11gr1 trace]$ mv alert_orcl.log alert_orcl_bak.log

[oracle@oracle11gr1 trace]$ll alert_orcl.log
ls: alert_orcl.log: No such file or directory

[oracle@oracle11gr1 trace]$exit

SQL>
SQL> CREATE TABLESPACE EDR_VECTOR_SPIND DATAFILE
'/u01/app/oracle/oradata/orcl/user.dbf' SIZE 4M AUTOEXTEND ON
MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL SEGMENT SPACE MANAGEMENT AUTO; 2 3

Tablespace created.

SQL>
SQL>
SQL> !
[oracle@oracle11gr1 ~]$
[oracle@oracle11gr1 ~]$
[oracle@oracle11gr1 ~]$ cd /u01/app/oracle/diag/rdbms/orcl/orcl/trace
[oracle@oracle11gr1 trace]$
[oracle@oracle11gr1 trace]$
[oracle@oracle11gr1 trace]$ ll alert_orcl.log
-rw-r----- 1 oracle oinstall 392 Apr 19 15:33 alert_orcl.log

[oracle@oracle11gr1 trace]$
[oracle@oracle11gr1 trace]$ more alert_orcl.log
Sat Apr 19 15:33:15 2008
CREATE TABLESPACE EDR_VECTOR_SPIND DATAFILE
'/u01/app/oracle/oradata/orcl/user.dbf' SIZE 4M AUTOEXTEND ON
MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL SEGMENT SPACE MANAGEMENT AUTO
Completed: CREATE TABLESPACE EDR_VECTOR_SPIND DATAFILE
'/u01/app/oracle/oradata/orcl/user.dbf' SIZE 4M AUTOEXTEND ON
MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL SEGMENT SPACE MANAGEMENT AUTO

[oracle@oracle11gr1 trace]$