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Lasers Could Hide Us From Evil Aliens (washingtonpost.com)
An anonymous reader quotes a report from Washington Post: Most of the time when we talk about silly scientific papers related to alien life, we're talking about crazy ideas for how to find aliens. But a new study in the Monthly Notices of the Royal Astronomical Society proposes a way of hiding from aliens. Humans are so fickle. A lot of our search for Earth-like planets (and, by extension, for life as we know it) hinges on transiting planets. These are planets that pass in front of their host star in such a way that the transit is visible from our perspective. The movement of the planet in front of the host star makes the light from that star dim or flicker, and we can use that to determine all sorts of things about distant worlds -- including how suitable they may be for life. Professor David Kipping and graduate student Alex Teachey, both of Columbia University, determined how much laser light it would take to mask the dimming caused by our planet transiting the sun, or cloak the atmospheric signatures associated with biological activity, [such as oxygen, which is achievable with a peak laser power of just 160 kW per transit].
From the report: "According to their math, it would take 10 continuous hours of shining a 30 MW laser once a year to eliminate the transit signal in visible light. Actually replicating every wavelength of light emitted by the sun would take about 250 MW of power."
Yes, this might work, as long as you know exactly where the aliens are observing your transit from. If you didn't know their location then they could be anywhere in the sky and the transit would be at different times, so you wouldn't know just when to hide the transit or where to point the highly directional laser beam. I take this as another admission that we know about the aliens and this time we know where they are watching from. However, they likely have already visited us (or we wouldn't know about them) and so they know we are here and are not going to be fooled by our laser trick.
I'm an American. I love this country and the freedoms that we used to have.
At the worst, Nova Express would simply have to explain that he meant "in all directions away from the sun at all times". Maybe he assumed readers would pick up on that limitation on their own.
I think the more important limitation not mentioned here is the time scale.
If we want to hide the fact there is oxygen production on our planet, the lasers would have had to be turned on over 3 billion years ago.
To hide the planets existence in general, the lasers needed turned on over 4 billion years ago.
Sorry to say but this paper was published just a tad too late to be useful for anything related to its stated purpose.