2013.11.16 laser pointer 11

Although RocketNews24 does not condone misusing laser pointers, we still think they can be pretty cool to play around with like seeing how far across the Tokyo area a laser pointer can be seen. Engineer and astronomy enthusiast Takayuki Ohira recently tried out this experiment on a clear night. How far across the megapolis do you think the beam could be seen? Click below to find out!

Ohira, who designed the Sega Homestar home planetarium projector, told his Twitter followers last week that the “winter-like weather patterns” on November 11 made for an incredibly clear night to try out a laser pointer experiment. He wanted to see how far from his home in Kawasaki City his little store-bought laser pointer with a power output of 1mW could shine.

Ohira’s plan was to put the laser pointer on top of his telescope. The telescope would make the beam much more steady than holding it in his hand. He wrapped the laser pointer in paper to fit it into a tube on top of the telescope.

▼ A closeup of the wrapping process

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▼ Putting the laser pointer into the tube

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▼ Laser assembly complete!

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Ohira then put the telescope/laser device on the side of the Tama Hills in Kawasaki. He planned to aim the laser at the 52ndfloor observation tower at Roppongi Hills in the center of Tokyo. At 20 km (12.4 miles) away, the laser’s power would be tested to see if it could survive the “commute” across town.

▼ A basic overview of the experiment

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▼ The telescope/laser pointed in the direction of Roppongi Hills

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▼ A look through the telescope at the Roppongi Hills building 20 km away

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Take a look for yourself at the (approximate) location of Ohira’s laser and Roppongi Hills, which is 20 km to the northeast:


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Ohira then got a call from someone at the observation tower, they could see his laser!

▼ A picture taken at the observation tower of the laser 20 km away

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There you have it! On a clear night in Tokyo, a laser pointer can be seen at least 20 km away. So what did Japanese netizens have to say about the experiment? Although many thought that Ohira’s experiment was cool, some wondered about the safety of pointing a laser towards the middle of a large city. (Note: Hira later told his Twitter followers that he had taken every safety precaution in mind before doing the experiment.)

Of course everyone on the Internet is a critic and a few netizens were hoping to see a much farther distance, like from Ohira’s home to the moon. But a lot of netizens were more impressed with how clear the air of Tokyo was that night. Used to the clouds and smog, many were thrilled to see how clean the air looked!

I don’t think the point of this story was anything about laser pointers, but about how clear the air is in Tokyo during winter.

That’s cool and all about the laser, but I’m much more amazed he could take a picture of Roppongi Hills from 20 km away.

Even more amazing than the strength of this laser pointer is how clean the air in Tokyo was that night.

Try it in China! I’d be surprised if you could see it past 10 meters…

Have you ever tried to see how far you can shine a laser pointer? Of course, RocketNews24 encourages you to comply with all local laws and common sense before you try your own experiment!

Source: Hachima Kikou
Images: Wikipedia, Twitter – @ohiratec_mega