This Wednesday, October 4, your phone will play a sound and vibrate, and there is nothing you can do about it if you live in the US. But it's not aliens or your cell phone rising up against you. It's just another nationwide test from the United States government.

Federal Emergency Management Agency (FEMA) has confirmed that the test will take place on October 4 at 11:20 AM PT / 2:20 PM ET. Every cell phone that's on and within range of a tower will receive a message that states, "THIS IS A TEST of the National Wireless Emergency Alert System. No action is needed." Phones set to Spanish will receive the message in Spanish, and there will be a "unique tone" and vibration effect, too.

FEMA said the purpose of this test is to "ensure that the systems continue to be effective means of warning the public about emergencies, particularly those on the national level." If there is bad weather or another "significant" event, the test will be delayed to October 11.