So the other day my friend calls me up and says "hey, where are you?" and I say "at home." So he says "oh, I thought i just saw you driving your car by my house. Same poofy hair and silver pontiac and everything." and I say "sorry, not me :(" to which he replies "well maybe its like the family guy movie, where Stewie finds himself from the future... It's you from the future! But you drive the same car!"

A day or two later I am thinking of this situation... if future me has the same car, then surely he, or I, must have the same cell phone. So if someone were to somehow come back from the future, with a cell phone that they also had in the present, would both cell phones ring when someone called it?

And also, what if for whatever reason a cell company assigns the same number to two different phones? Do both ring, and the first to pick up gets the call, and the other one left out of the loop? Or would the 2nd person to answer also be able to join in the conversation?

...how can anyone answer this question?:psyduck:

I would hope your future self, wouldn't pick a date to arrive to your present in which your friend had just seen him, since he would remember that Scenario from maybe months before.

I suppose if someone called your cell phones, but of them would pick up the signal and depending on whoever picked up their phone first would be able to take the call. Though, I would also hope your future self wouldn't answer his cell phone if he has gone back in time, otherwise he might screw some things up.

Assuming GSM, phones are identified and assigned numbers based on the SIM card number. The phone contacts a base station, which then reports the cell phone's position back to the network. This is how roaming works - a cell phone can seamlessly drop a connection when it moves too far away and then reconnect to a closer base station.

In addition to that, GSM is designed with some pretty solid security (so people can't listen in on your phone calls). The cryptographic keys are exchanged in an encrypted handshake when the phone connects to a base station.

So, basically, whoever reconnected to the base station most recently would be able to use the network, while the other person would be shut out. I don't think the network sends a connection reset message, so you might not even know you were booted from the network for a couple of hours or so.

You would be able to test this quite easily if you worked for a phone company and could create two identical SIM cards.

There's a movie 'Primer' which asks this exact question too.

Also, it's quite impossible for the phone company to issue two SIM cards that are tied to the same phone number. Once the second one was activated, the original would be rejected by the network. This is what happens when you upgrade phones, and keep your number.

Time travel is impossible and you're all stupid burgerboys.

Edit: Except mb, he's just a fatty.

Pssh what do you know about time travel anyways. It is definitely possible, just not particularily practical. What with the needing infinite mass and such.

Unless you have Verizon or Sprint (minus nextel)