AppearsIt appears the Earth's Magnetotailmagnetotail, which is a part it's of its Magnetospheremagnetosphere, is on the Earth's nightside,nightside; lengthwise exceeds 6,300,000 kilometers (3,900,000 miles) -; and is the furthest known observable feature of Earth.
UnableI am unable to explain why is it commonly not included in the "spheres" of Earth Science.
Note: The gravitational pull of Earth in theory spans the known Universe, though it's unlikely to have any observable affect, unlike the Earth's Magnetotailmagnetotail.