Used to do that in Ubuntu since I was using it with VNC, as root:
mce will probably ruin your fun and light it back up when lighting conditions change where you are, you can ruin its day by typing stop mce and disabling it, temporarily at least.
Mind you, turning off mce will:
Cause the power button not to work
Cause the lock switch to stop working
Screen won't dim (but it's off in this case so... meh)
till you start it again (start mce).