Have you seen The Dark Knight yet? No? What’s wrong with you, go add to its box-office gross now. It deserves it. No, I’m not kidding. Also, stop reading since there’s about to be some minor spoilers.
This post was inspired by my mom, who wants to know how plausible the various two major cell phone schemes are. Let’s see.
1. Lucius Fox develops a very snazzy phone which can emit sound pulses. The reflections of those pulses are received by the phone and reconstructed into a sonar image of whatever room the phone happens to be in. The idea is not inherently absurd. Submarines use it to find other subs and ultrasound machines use it to examine unborn children, to take just two of the most familiar examples. Could this work to characterize a room? Sure, to an extent. But as with any wave, there’s tradeoffs. Low frequencies can’t see detail, but high frequencies can’t see around corners. If you approach a high school band from a distance, you’ll hear the drums from the greatest distance not because they are louder but because they are lower frequency and can more easily bend around obstacles. Thus without a direct and unobstructed path to whatever surface it’s supposed to measure (as in fetal ultrasound), the phone is going to be hard pressed to see anything at all.
To make matters worse, air is not a continuous fluid. For a lot of purposes it can be treated as one, but as frequency becomes very high the wavelength begins to become comparable to the intermolecular spacing. This tends to cause severe attenuation at high frequencies, limiting the range badly.
Don’t even get me started on the signal processing problems. Real-time inverse Fourier transforms of gigabits per second per phone? Not happening. And how in the world is the phone supposed to pick up direction and phase information in the incoming wave with adequate resolution in the first place?
It’s just not happening. The concept is not absurd, but it is impossible in practice.
2. Batman arranges for his own program code to be installed in nearly every cell phone in Gotham City. On activation, it turns every phone into both a continuous bug, listening in on its surroundings even with the phone turned off. He hooks the millions of signals into a computer and scans for the Joker’s voice in order to find his location.
Now this one is not merely plausible, it’s a reality. Law enforcement has already used cell phones as bugs and tracking devices. I’m not sure if the processing power of the installed phone company hardware is enough to simultaneously monitor every phone to look for a specific voice, but it’s certainly not beyond the realm of possibility. Anybody with Bruce Wayne’s wealth could certainly afford it. Lucius Fox believed this is much too great of a power for Batman to have since it invades the privacy of the good people of Gotham; Batman agreed and told Fox to destroy the hardware once the Joker was found. I think it’s unlikely the FBI would feel the same way.
So if you’re doing something (criminal or not) that requires privacy, don’t bring your cell phone. Or at the very least remove its battery.
10 responses so far ↓
1 CCPhysicist // Jul 29, 2008 at 11:35 am
The phone company doesn’t need the computer, or didn’t you follow any of the stories about tapping into a main hub and sending a really big stream of bits off to the computers at No Such Agency? All you need is a switch set to “on”.
2 Uncle Al // Jul 29, 2008 at 12:41 pm
Carnivore/DCS1000, RIP, Altivore, ECHELON, WinWhatWhere. Government has come for a piece of all mankind. “It’s a cookbook!”
3 st // Aug 2, 2008 at 3:48 am
I don’t understand why you have to pull the battery. Is this for a stock phone or for a possibly sabotaged phone?
I saw this information elsewhere, but I didn’t understand it then either.
If you have a stock phone that is turned off, then it isn’t doing anything. Otherwise the battery would run out. That’s my reasoning.
4 Maynard Handley // Aug 31, 2008 at 9:00 pm
“[sonar phone] The concept is not absurd, but it is impossible in practice.”
Hmm. Bats manage to do it adequately in the volume of a cell phone, which gives us a proof that it is, in fact, NOT impossible in practice.
It may not be possible to do it using the most obvious DSP techniques, but that’s a different issue, and simply means that one needs to use different techniques.
5 Women Football Jerseys // Jul 11, 2011 at 12:33 pm
I desired to thank you for this amazing post. I definitely favorite every little bit of it. I have you bookmarked your web site to look at the latest stuff you place. ny Giants Jerseys
6 klikopolo // Sep 10, 2011 at 11:13 am
Thank you so much for providing individuals with such a breathtaking chance to check tips from this site. It is often so lovely and stuffed with a good time for me and my office mates to visit your site on the least three times weekly to learn the newest things you will have. Not to mention, I am also at all times contented with all the unique opinions served by you. Some 2 ideas in this posting are honestly the most impressive we have all had.
7 Marilee Pearlstein // Sep 13, 2011 at 7:13 pm
I just wanted to construct a brief note so as to appreciate you for all of the amazing solutions you are writing on this website. My time intensive internet investigation has at the end been honored with useful suggestions to share with my guests. I would state that that many of us website visitors are very much endowed to exist in a wonderful website with so many special individuals with very beneficial principles. I feel truly privileged to have come across your entire web site and look forward to plenty of more fabulous times reading here. Thank you once again for all the details.
8 activity holidays // Jan 3, 2012 at 11:30 pm
Thank you for another informative web site. Where else may I get that type of information written in such an ideal method? I’ve a challenge that I am simply now running on, and I’ve been at the glance out for such information.
9 Fire Rated Doors // Jul 11, 2012 at 10:28 am
Wonderful work! That is the kind of information that are meant to be shared across the internet. Disgrace on Google for not positioning this publish upper! Come on over and talk over with my website . Thank you =)
10 magic TV box // Aug 20, 2012 at 10:34 pm
Wow! This can be one particular of the most beneficial blogs We have ever arrive across on this subject. Actually Excellent. I am also an expert in this topic so I can understand your effort.
Leave a Comment