<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>johnw</author><text>There&amp;#x27;s noway that this is going to be practical within the current laws of physics. You can&amp;#x27;t use a wide beam to cover an area because the amount of energy available drops by orders of magnitude the further you get from the transmitter. If you used a focussed beam (which is what they are suggesting) then you need a separate beam that tracks and follows the location of each device. So to cover a very small area you&amp;#x27;d need multiple transmitters tracking and beaming sound to the exact location of each device. And the transmitters are going to have to be very close by, and then there are all the obstacles between your pocket and the transmitter that will block the beam. You might as well just use an inductive charger. But still, just like solar freaking roadways and perpetual motion machines we want to believe and since most people don&amp;#x27;t understand the science these ridiculous and impossible ideas draw people in again and again.&lt;p&gt;There&amp;#x27;s a more in depth analysis of why this won&amp;#x27;t work here: &lt;a href=&quot;http://www.eevblog.com/2014/08/07/ubeam-ultrasonic-wireless-charging-a-familiar-fish-smell/&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.eevblog.com&amp;#x2F;2014&amp;#x2F;08&amp;#x2F;07&amp;#x2F;ubeam-ultrasonic-wireless-...&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>Audacious Plan to Make Electricity as Easy as WiFi</title><url>http://www.bothsidesofthetable.com/2014/10/30/the-audacious-plan-to-make-electricity-as-easy-as-wifi/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>pocketstar</author><text>I am skeptical of the claimed safety of uBeam. The FDA does not advocate the safety of ultrasound.&lt;p&gt;From the article: &amp;quot;Was it safe? Well … for starters it is just an inaudible soundwave being transferred – as in the kind also used for women during pregnancy.&amp;quot;&lt;p&gt;From the FDA: &amp;quot;Even though there are no known risks of ultrasound imaging, it can produce effects on the body. When ultrasound enters the body, it heats the tissues slightly. In some cases, it can also produce small pockets of gas in body fluids or tissues (cavitation). The long-term effects of tissue heating and cavitation are not known. Because of the particular concern for fetal exposures, national and international organizations have advocated prudent use of ultrasound imaging. Furthermore, the use of diagnostic ultrasound for non-medical purposes such as fetal keepsake videos has been discouraged.&amp;quot;[0]&lt;p&gt;[0]&lt;a href=&quot;http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/ucm115357.htm&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.fda.gov&amp;#x2F;Radiation-EmittingProducts&amp;#x2F;RadiationEmitt...&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>Audacious Plan to Make Electricity as Easy as WiFi</title><url>http://www.bothsidesofthetable.com/2014/10/30/the-audacious-plan-to-make-electricity-as-easy-as-wifi/</url></story>