2 added 354 characters in body
source | link

Well, assuming classical mechanics(which is of course not applicable for our universe), of course our universe does have a fixed centre of mass.

I don't know which level you are in, but if you have the knowledge of general relativity(in which the idea of centre of mass seems pretty stupid) go through the other answers. But if you are somehow interested in the point of view of the classical physics too, you are welcome to read this answer.

See, centre of mass is primarily arises just from a statistical idea which later turns out to be of a greater significance, as the centre of mass of all bodies interacting with each other remain unaccelerated.

Wait, did i say ALL BODIES INTERACTING WITH EACH OTHER? Yes, indeed.

The idea is, any action we take involves more than one bodies. And of course you know that centre of mass remains unaccelerated.

Now, since all the possible centre of masses are unaccelerated, centre of mass of these masses will also remain fixed, giving the universe a fixed CM.

Now one may ask, SUPPOSE I'M PICKING UP A BOX FROM THE GROUND ONTO MY HEAD. WHO'S MOVING OTHER THAN THE BOX? HOW IS THE CENTRE OF MASS BALANCED HERE?

The answer is(sequentially), when you picked up that box you had to apply some amount of force on the box in order to provide an upward acceleration. The reaction from the box caused your weigh more. Earth felt force from your feet more than before. This caused the earth move just a bit away from a box. The Earth is really massive. So the shift on centre of mass is not so negligible. This balances the movement of he centre of mass of you, earth and the box. So that C. M. remains fixed and your question is answered😊.

Thank you😊

Well, assuming classical mechanics, of course our universe does have a fixed centre of mass.

See, centre of mass is primarily arises just from a statistical idea which later turns out to be of a greater significance, as the centre of mass of all bodies interacting with each other remain unaccelerated.

Wait, did i say ALL BODIES INTERACTING WITH EACH OTHER? Yes, indeed.

The idea is, any action we take involves more than one bodies. And of course you know that centre of mass remains unaccelerated.

Now, since all the possible centre of masses are unaccelerated, centre of mass of these masses will also remain fixed, giving the universe a fixed CM.

Now one may ask, SUPPOSE I'M PICKING UP A BOX FROM THE GROUND ONTO MY HEAD. WHO'S MOVING OTHER THAN THE BOX? HOW IS THE CENTRE OF MASS BALANCED HERE?

The answer is(sequentially), when you picked up that box you had to apply some amount of force on the box in order to provide an upward acceleration. The reaction from the box caused your weigh more. Earth felt force from your feet more than before. This caused the earth move just a bit away from a box. The Earth is really massive. So the shift on centre of mass is not so negligible. This balances the movement of he centre of mass of you, earth and the box. So that C. M. remains fixed and your question is answered😊.

Thank you😊

Well, assuming classical mechanics(which is of course not applicable for our universe), of course our universe does have a fixed centre of mass.

I don't know which level you are in, but if you have the knowledge of general relativity(in which the idea of centre of mass seems pretty stupid) go through the other answers. But if you are somehow interested in the point of view of the classical physics too, you are welcome to read this answer.

See, centre of mass is primarily arises just from a statistical idea which later turns out to be of a greater significance, as the centre of mass of all bodies interacting with each other remain unaccelerated.

Wait, did i say ALL BODIES INTERACTING WITH EACH OTHER? Yes, indeed.

The idea is, any action we take involves more than one bodies. And of course you know that centre of mass remains unaccelerated.

Now, since all the possible centre of masses are unaccelerated, centre of mass of these masses will also remain fixed, giving the universe a fixed CM.

Now one may ask, SUPPOSE I'M PICKING UP A BOX FROM THE GROUND ONTO MY HEAD. WHO'S MOVING OTHER THAN THE BOX? HOW IS THE CENTRE OF MASS BALANCED HERE?

The answer is(sequentially), when you picked up that box you had to apply some amount of force on the box in order to provide an upward acceleration. The reaction from the box caused your weigh more. Earth felt force from your feet more than before. This caused the earth move just a bit away from a box. The Earth is really massive. So the shift on centre of mass is not so negligible. This balances the movement of he centre of mass of you, earth and the box. So that C. M. remains fixed and your question is answered😊.

Thank you😊

1
source | link

Well, assuming classical mechanics, of course our universe does have a fixed centre of mass.

See, centre of mass is primarily arises just from a statistical idea which later turns out to be of a greater significance, as the centre of mass of all bodies interacting with each other remain unaccelerated.

Wait, did i say ALL BODIES INTERACTING WITH EACH OTHER? Yes, indeed.

The idea is, any action we take involves more than one bodies. And of course you know that centre of mass remains unaccelerated.

Now, since all the possible centre of masses are unaccelerated, centre of mass of these masses will also remain fixed, giving the universe a fixed CM.

Now one may ask, SUPPOSE I'M PICKING UP A BOX FROM THE GROUND ONTO MY HEAD. WHO'S MOVING OTHER THAN THE BOX? HOW IS THE CENTRE OF MASS BALANCED HERE?

The answer is(sequentially), when you picked up that box you had to apply some amount of force on the box in order to provide an upward acceleration. The reaction from the box caused your weigh more. Earth felt force from your feet more than before. This caused the earth move just a bit away from a box. The Earth is really massive. So the shift on centre of mass is not so negligible. This balances the movement of he centre of mass of you, earth and the box. So that C. M. remains fixed and your question is answered😊.

Thank you😊