Rk Naresh

Hi ,

The force of gravity on a planet is determined by its mass and radius. The formula for calculating the gravitational force on the surface of a planet is:

F=G∗((m1∗m2))/r^2​

Where:

• F is the gravitational force
• G is the gravitational constant (a constant value)
• m1 and m2 are the masses of the two objects (in this case, the mass of the planet and the mass of an object on its surface)
• r is the distance between the centers of the two objects (in this case, the radius of the planet)

So, in this formula, both the mass and the radius of the planet play a role in determining the gravitational force. If you have a planet that is larger than Earth but less massive (i.e., lower density), it is possible for it to have less gravity than Earth. Similarly, if you have a planet that is smaller in size but more massive, it can have stronger gravity than Earth.

To directly answer your second question: No, a planet twice the size of Earth would not necessarily have twice the gravity. It would depend on the mass and density of that planet. If its mass is also roughly twice that of Earth, then the gravitational force on its surface would be greater than twice Earth's gravity. If its mass is less than twice that of Earth, the gravity would be less than twice Earth's gravity.

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Dr Aahed Alhamamy thank you for your contribution to the discussion

Yes, it can be possible, and I can give you a solid example that exists in real life and that too, in our solar system. Uranus is about 4 times wider than the Earth, and is 14x the mass. Yet, Uranus has the same gravity as Venus, a meagre 8.87 m/s2. Uranus has about 10% lower gravity than Earth's. Because the force of gravity depends on both mass and distance, planets that are puffy and less dense have less gravity at their cloud-tops or surfaces, which are far above the bulk of the mass in their interiors. This is why planets like Saturn appear to have less gravity than Neptune, despite Saturn's greater mass. That's because the planets weigh different amounts, and therefore the force of gravity is different from planet to planet. For example, if you weigh 100 pounds on Earth, you would weigh only 38 pounds on Mercury. That's because Mercury weighs less than Earth, and therefore its gravity would pull less on your body. The gravity of a planet, or other body, is proportional to its mass. The density of the Earth is about 5.51 g/ cm3. A planet with double the volume of the Earth would have to have half the density to have the same mass and hence the same gravity. However, as a gas giant, its density (1.27 g/cm3) is significantly lower than Earth's. Hence, why its surface gravity (measured from its cloud tops) is slightly weaker than Earth's – 8.69 m/s2, or 0.886 g. If Earth's diameter were doubled to about 16,000 miles, the planet's mass would increase eight times, and the force of gravity on the planet would be twice as strong. Thus, the gravitational acceleration of the planet will be twice of gravitational acceleration of the earth and option (d) will be correct option.If Earth's diameter were doubled to about 16,000 miles, the planet's mass would increase eight times, and the force of gravity on the planet would be twice as strong. Life would be: Built and proportioned differently. The increased gravity will cause the Earth itself to settle and compress adding even more heat. As the Earth shrinks, even a little bit, the surface will buckle causing great upheavals; new mountain ranges and volcanic eruptions will appear. All this mass shifting around will cause great earthquakes.

Gravity or gravitational attraction comes into existence only when there are more than one object. A single body cannot have gravitational attraction (towards what?). Within a large body, gravitational attractions are effective between individual 3D matter particles in it.

Gravitational attraction is between 3D matter particles of a body and 3D matter particles in another body and the distance between the bodies. Hence, increasing the size of one or the other body without changing their 3D matter content (without changing the distance between them) will not affect the gravitational attraction between the bodies.

The entire space, outside the most basic 3D matter-particles, is filled with an all-encompassing universal medium, structured by quanta of matter. Due to its structure, the universal medium is inherently under compression. A 3D matter-particle, in the universal medium, experiences compression from the universal medium. This property of the universal medium is gravitation. The magnitude of gravitation corresponds to the extent of the universal medium that exerts the pressure. The extent of the universal medium between two 3D matter-particles is always less than the extent of the universal medium on their outer sides. Hence higher gravitational actions on the outer sides tend to move the 3D matter-particles towards each other. This tendency is understood as gravitational attraction or gravity. Gravitational attraction (gravity) is the resultant (relatively a minor by-product) of separate gravitational actions on two 3D matter-particles by the universal medium. The constant of proportion of gravitational attraction between two 3D matter particles is enormous.

See: http://vixra.org/pdf/1206.0056v2.pdf

Nainan.

Dr Nainan Varghese thank you for your contribution to the discussion

Yes, a bigger planet can have less gravity than Earth, and a planet twice the size of Earth would not necessarily have twice the gravity.

The gravity of a planet depends on two things: its mass and its radius. The mass is the amount of matter in the planet, and the radius is the distance from the center of the planet to its surface.

The formula for calculating the gravity of a planet is:

g = G * M / r^2

where:

• g is the gravity of the planet
• G is the gravitational constant (6.674 * 10^-11 m^3/kg/s^2)
• M is the mass of the planet
• r is the radius of the planet

So, if a planet is twice the size of Earth, its radius will be twice as big, but its mass will not necessarily be twice as big. If the mass of the planet is not twice as big, then the gravity of the planet will be less than twice the gravity of Earth.

For example, Uranus is about 4 times wider than Earth, but it has only 14 times the mass of Earth. This means that the gravity of Uranus is about 10% lower than the gravity of Earth.

Therefore, it is possible for a bigger planet to have less gravity than Earth. The key factor is the mass of the planet, not its size.

Dr Murtadha Shukur thank you for your contribution to the discussion

The gravity of a planet, or other body, is proportional to its mass. The density of the Earth is about 5.51 g/ cm3. A planet with double the volume of the Earth would have to have half the density to have the same mass and hence the same gravity. Yes, it can be possible, and I can give you a solid example that exists in real life and that too, in our solar system. Uranus is about 4 times wider than the Earth, and is 14x the mass. Yet, Uranus has the same gravity as Venus, a meagre 8.87 m/s2. Uranus has about 10% lower gravity than Earth's.The bigger the mass, the stronger the gravity this is direct and unavoidable and bigger the size for a given mass, the smaller the gravity, since you are farther from the center of mass. A smaller planet can have stronger gravity if its density is higher. A planet only half the diameter of Earth could have a similar gravity of its density was twice that of Earth. If Earth's diameter were doubled to about 16,000 miles, the planet's mass would increase eight times, and the force of gravity on the planet would be twice as strong. Anything that has mass also has gravity. Objects with more mass have more gravity. Gravity also gets weaker with distance. So, the closer objects are to each other, the stronger their gravitational pull is.As the radius of the planet decreases, the force of gravity on the surface will increase because, for a sphere, the force of gravity on the surface is inversely proportional to the radius squared. The gravity of a planet, or other body, is proportional to its mass. The density of the Earth is about 5.51 g/ cm3 . A planet with double the volume of the Earth would have to have half the density to have the same mass and hence the same gravity.