why is thread asleep?

In this example:

1.9.3p0 :001 > def threading
1.9.3p0 :002?> i = 0
1.9.3p0 :003?> while i <= 50
1.9.3p0 :004?> sleep(2)
1.9.3p0 :005?> i += 1
1.9.3p0 :006?> if i == 50
1.9.3p0 :007?> puts "the thread is finished at #{Time.now}"
1.9.3p0 :008?> end
1.9.3p0 :009?> end
1.9.3p0 :010?> end
=> nil
1.9.3p0 :011 > t = Thread.new { threading }
=> #<Thread:0x007f833d301660 sleep>
1.9.3p0 :012 > t.status
=> "sleep"
1.9.3p0 :013 > t.stop?
=> true
1.9.3p0 :014 > t.alive?
=> true
#few minutes later:
1.9.3p0 :015 > the thread is finished at 2012-10-25 21:52:43 -0400

As soon as threading is invoked in the new thread, I check its status.
And the status is "sleep". Why is it "sleep" and not "runnable"?

Oh I see, because of the call to Kernel.sleep forces the thread in a
sleeping state.