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Perhaps you are one of those who, when they hear news, ask themselves, "How will they know that?"
We were told that the moon is moving away from the Earth. And it's not that we doubt it, but how do you know it?
Scientists Adam Rutherford and Hannah Fry, who are investigating the BBC's public doubts, found the answer to our question in a somewhat complicated way. do not worry, we will find out, but on the way we will discover amazing things.
It all started with a question from listener Eddie Griffith:
"The other day I was watching the James Bond Goldfinger movie.He boasts that his laser is powerful enough to project its light on the Moon, is it really possible and how powerful should this laser be? "
" The Most Devilish Opponent For Those Who Do not Remember From the plot of this film, Auric Goldfinger is a devilish megalomaniac obsessed with gold and he plans to blow up a bomb inside Fort Knox – hence James' name Bond, an evil genius.It is stocked since 1937. Large part of the US gold reserves, so that their own gold reserves are more valuable.
James Bond learns the plan, but they remove it and take it to the secret lair of Goldfinger, where they extend and attract it
After the Having heard about the power of his laser, Goldfinger ignites the burning ray and moves it between Bond's legs toward his … crown jewels.
But let's go back to the question, that it was not precisely if a laser could burn the intimate parts of the famous spy, but if we could see the light of its ray on the surface of the Moon if it was projected in his direction.
Could it be powerful to reach the moon?
Megawatts? Terawatt? Petawatts? Prepare for numbers of sizes like 1,000,000,000,000,000.
"I had very little time to prepare the answer since I was asked the question, so that's only an estimate," warns the physicist Andrew Pontzen. 19659003] "I calculate that if you want to create a point of light on the surface of the moon, you would need a laser with a power of 200 megawatts."
"A watt is the measurement used in light bulbs, as well as for perspective, today a good light bulb is 10 watts, so this laser has to be 20 million times stronger. "
And will we have such powerful lasers? Of course, and more!
One of the most powerful in the world is found in Didcot, UK, and it's called Super Intense Gemini Laser. What would happen if he pointed his laser on the moon?
"Probably too powerful," says physicist Ceri Brenner
"His power is about half a petawatt."
Emergency explanation: One petawatt (PW) is 10 watts to 15 watts or, what is the same, 1,000 terawatts or 1,000 trillion (1,000,000,000,000,000). ) watts. A petawatt laser generates this power for an interval of a few femtoseconds
Explanation of urgency II: A femtosecond is the unit of time equivalent to one billionth of a second, that is to say, in one second there is a billion billion. femtoseconds. They correspond as much in one second as the seconds correspond in 100 million years (ie 3,153.6 million),
But should not it be very powerful for that it reach the moon? 19659003] "When laser light is so powerful, it is difficult to cross the Earth's atmosphere," says Brenner. "The laser would burn the air when it crossed it."
Excuse me? How does the atmosphere burn?
"When traveling, the intensity of light is such that it simply converts air into plasma."
Would it burn the sky? "19659003" Without a doubt, it would produce a powerful beam. These are the rays: the plasma channels, "Brenner answers, with the same simplicity with which others explain how to cook an egg.
Be careful when shooting.
Anyway,
Better to get back to this 200 megawatt laser … but once you add the extra effects to compensate for things like diffraction in the # 39 Earth's atmosphere that spreads light, you might need a gigawatt.
This is basically equivalent to the power of a nuclear generator. And probably, the laser should be about 15 meters in diameter.
But after they left our mouths open, talking about petawatts and femtoseconds, it does not seem so bad anymore.
The man who shoots Rays to the Moon
Trying to finally fulfill the mission of solving the doubt of the listener, Rutherford and Fry discover a physicist who actually fires laser pulses on the moon.
He's called Tom Murphy, from the University of California San Diego, USA, and is dedicated to what they call "laser measurement experiments."
Tom Murphy casts rays of light toward the moon
Murphy uses a gigawatt laser at the top of a mountain in New Mexico and triggers impulses in the mirrors left on the moon by astronauts from three missions of the Apollo program and two Soviet lunar rovers.
Consider that for when the light arrives For our natural satellite, it is so tenuous that telescopes are needed to see it … and that – unlike Goldfinger – it does not use its laser for any purpose criminals, but for scientific purposes.
"Indeed, we use it for scientific purposes such as to test whether the general theory of relativity correctly describes the lunar orbit," Murphy confirms.
For this, they must measure how far the moon is.
"It's a simple idea: we send short pulses of light even the reflectors on the moon.These impulses return to Earth and we simply measure how long the round trip took, and we use the speed of light to convert it into distance. "
And that's how it gets away from the moon. 19659003] "The moon migrates slowly, due to the tidal acceleration, and moves, on average, about 3.8 centimeters a year farther from Earth."
But there is there a reason to worry because we do not want it to go away …
"No, the effect diminishes as & & l, 39; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; It is not a mechanism that will let it escape, "says the physicist.
What a relief!
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