If the gravitational force is acting on each and every object in this universe then why is the space expanding?
If the gravitational force is acting on each and every object in this universe then why is the space expanding?
yes, gravity is indeed slowing things down! Or was, anyway. According to the best theory that we have, the so-called "concordance" model (also known as the "Lambda-CDM" model) of cosmology, for the first 8 billion years or so, gravity was winning, and the expansion of the universe.
However (again according to the best theory that we have) 70% of our universe is made of stuff that we just call "dark energy" (a phrase that simply hides our ignorance.) About the only thing we know about dark energy is that once it becomes dominant, it will cause the expansion to accelerate, because its gravity is effectively repulsive. OK, there is one other thing we know. As the universe expands, ordinary stuff becomes thinner, less dense, as the same amount of matter now occupies more space. But that's not how dark energy works; its density remains constant. So there was a point when the energy density of dark energy began to dominate over other forms of matter. This is what happened about 4-5 billion years ago, and since then, the expansion of the universe has been accelerating again.
yes, gravity is indeed slowing things down! Or was, anyway. According to the best theory that we have, the so-called "concordance" model (also known as the "Lambda-CDM" model) of cosmology, for the first 8 billion years or so, gravity was winning, and the expansion of the universe.
However (again according to the best theory that we have) 70% of our universe is made of stuff that we just call "dark energy" (a phrase that simply hides our ignorance.) About the only thing we know about dark energy is that once it becomes dominant, it will cause the expansion to accelerate, because its gravity is effectively repulsive. OK, there is one other thing we know. As the universe expands, ordinary stuff becomes thinner, less dense, as the same amount of matter now occupies more space. But that's not how dark energy works; its density remains constant. So there was a point when the energy density of dark energy began to dominate over other forms of matter. This is what happened about 4-5 billion years ago, and since then, the expansion of the universe has been accelerating again.
