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Every one knows that here on Earth we can detect the presence of a magnetic field large enough to be capable of moving the needle of a compass , by applying on it a moment when it is not aligned with the lines of force acting on that point . Of course the bigger question is why on earth we would want to do it this way . Since human beings are part of this fragile and mysterious web , whenever we pollute or neglect the earth we pollute and neglect our own wellsprings . In your case - - it 's to keep you healthy so that when I come back to Earth we can have a grand time together . On Earth we have been experiencing Environmental issues that lead to many important Environmental Science study project .