About two weeks ago, George Clarke, a filmmaker from Belfast, posted a video to YouTube that has since received millions of hits. In it, he explains that he may have found the first evidence of time travel. In a short clip from the DVD extras included with Charlie Chaplin's 1928 silent film The Circus, a woman walks by in the background talking into what appears to be a cell phone. (As this movie has proven incredibly popular -- it's one of the highest-grossing silent films of all time -- it's unclear why this hasn't been spotted before, but the footage doesn't appear to be edited. I guess nobody watches the extras except for this guy.) The scene with the woman in question starts 2:42 in.

The Internet has been buzzing ever since the clip was posted. Time travel is a fun explanation, but what could the woman really be using? Assuming she's not just talking to herself and scratching her face at the same time, the most likely answer is that she's using a portable new hearing aid, technology that was just being developed at the time.

Four years earlier, in 1924, Siemens, the engineering conglomerate also responsible for building the first long-distance telegraph, filed a patent for "a compact, pocket-sized carbon microphone/amplifier device suitable for pocket instruments." This is how the device is described on Siemens' website:

For a while, the carbon amplifier patented by Siemens played a major role in hearing aid technology and significantly raised the volume of hearing aids. The electrical energy controlled by the carbon microphone was not fed to the received directly. It first drove the diaphragm of an electromagnetic system connected to a carbon-granite chamber. Current was transmitted across this chamber from the vibrating diaphragm electrode to the fixed electrode plate. The amplified current produced mechanical vibrations in the electromagnetic hearing diaphragm that were then transmitted to the ear as sound.

By 1929, Siemens, which continued to experiment with amplifying tubes, had produced several different products that aided in hearing.