How would your present weight change if earth had twice the mass that it does now?

The weight would be doubled

Explanation:

The weight of an object on Earth is equal to the gravitational attraction exerted by the Earth on the object:

where

G is the gravitational constant

m is the mass of the object

M is the mass of the Earth

r is the distance between the object and the Earth's center

We see that the weight (F) is directly proportional to the Earth's mass (M): so, if the Earth had twice the mass that it does now (M'=2M), then the weight F would be also doubled, in fact:

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the arctic is a region of the planet, north of the arctic circle, and includes the arctic ocean, greenland, baffin island, other smaller northern islands, and the far northern parts of europe, russia (siberia), alaska and canada.