# How far is universe?

To convert this density to mass we must multiply by volume, a value based on the radius of the "observable universe". Since the universe has been expanding for 13.8 billion years, the comoving distance (radius) is now about 46.6 billion light-years.
A.

### What will happen when the universe stops expanding?

In a closed universe, gravity eventually stops the expansion of the universe, after which it starts to contract until all matter in the universe collapses to a point, a final singularity termed the "Big Crunch", the opposite of the Big Bang.
• #### What is the big bounce theory?

The Big Bounce is a hypothetical cosmological model for the origin of the known universe. It was originally suggested as a phase of the cyclic model or oscillatory universe interpretation of the Big Bang, where the first cosmological event was the result of the collapse of a previous universe.
• #### What is the theory of the Big Crunch?

The Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately causing the cosmic scale factor to reach zero or causing a reformation of the universe starting with another Big Bang.
• #### What is a rip in the space time continuum?

Edit. The space-time continuum, also known as the space-time fabric, was a way to transfer between dimensions, provided the continuum was "ripped" which created a hole between each place. Waru was transported to the galaxy's universe through such a rip in the fabric of space-time, and back to his own again in 14 ABY.
B.

### What is meant by the heat death of the universe?

The heat death of the universe is a plausible ultimate fate of the universe in which the universe has diminished to a state of no thermodynamic free energy and therefore can no longer sustain processes that increase entropy.
• #### What is the maximum entropy?

The principle of maximum entropy states that the probability distribution which best represents the current state of knowledge is the one with largest entropy, in the context of precisely stated prior data (such as a proposition that expresses testable information).
• #### What is the entropy at equilibrium?

An isolated system therefore approaches a state in which the entropy has the highest possible value. This is a state of equilibrium. In equilibrium, the entropy of the system cannot increase (because it is already at a maximum) and it cannot decrease (because that would violate the second law of thermodynamics).
• #### Can you have a negative entropy?

A negative entropy means that "wasted" energy is transformed on work. On some local processes you can obtain a negative entropy, but the global process has always a positive entropy. For example, if you burn fuel, you get water, CO2 and some other wastes.

Updated: 26th November 2019