Future of our Universe (Part II)

Today we continue to talk about the future of our dark-energy dominated universe. Our, you, we know we learned that our universe is dominated by dark energy and this dark energy is accelerating expansion of the universe. So what’s happened in this dark-energy dominated universe in the future? Last time, we saw up to here, so our neighbor Andromeda galaxy and our Milky Way galaxy will merge in about six billion years. What happens farther into the future? Let’s have a look. In about 100 billion years from now, local group galaxies will merge into one gala-, one large galaxy, so after, merging into Andromeda galaxy, we have another galaxy, so this is Andromeda, but we have smaller several other galaxies in our local universe.

And then those galaxies, all of them, will eventually merges into our Milky Way galaxy. That happens in 100 billion years.

And in about 150 billion years, all galaxies outside the local super clusters will pass behind a cosmological horizon. Therefore their galaxy will be, no longer be detectable. So, in our local super cluster we have a group of galaxies, in local super cluster these are the, uh, galaxies in our local super cluster. So these galaxies are bound to each other by gravity. So they don’t go too far away. But the galaxies outside of this local super cluster they are not bound by the gravity, so they will go far away and far away and far away with the expansion of the universe.

In the 150 billion years from now, the expansion of the universe will push them out of the cosmological horizon, so the light from these galaxies can no longer, uh, reach the earth. So that means they’ll become invisible, we cannot observe galaxies outside of the local super cluster anymore. That’s a little sad feature of the universe. And in 100 trillion years, 10 or 10 to the 14th years, star formation will end. So there will be no stars forming at this time. Then all the steller object, all the stars currently we have is going to end up in a degenerated remnants.

In a short sense, white dwarfs or neutron stars or black holes, these are remnants of the stars at the end of its life. So, there will be no new star, and all the current stars gonna die, so there will be no nuclear fusion, and then all luminous objects will cool and become faint, and so the universe will become extremely dark, so there are no stars, right? And then, all the current stars gonna die, so universe will become darker and darker and darker. And in about one quadrillion, ten to the 15th years, even planets are full of run from orbit by a close encounter with another star.

So planets right now orbiting around the star, for example solar system, there’s a Mars and Uranus and Venus, these planets will fall into a star, or when the star in this long amount of time encounter with another star, because of gravitational interaction did start the front away from the out of the orbits. So, planets will start to disappear. And in 10 the 19th years stellar remnants escape galaxies or fall into black holes, so the similar thing happens in 10 to the 19th years for stars in a galaxy, so stars in a galaxy, they’re with the galaxy encounter with another galaxy, ejected from the galaxy.

Um, so 90 percent of them are ejected from a galaxy and then leaving a small fraction, only 10 percent is going to fall into the center of super-massive black holes at the center of the galaxy. And in 10 to the 34 years, nucleons start to decay. Neutrons bound into nuclei are also expected to decay with a half-life comparable to that of the proton, so the proton decay time is about 10 to the 34 years, that’s believed to be, so nucleons start to decay. And the planets are also made of nucleons and protons, right? So they would decay into a simple cascade process from heavier elements to pure hydrogen while radiating energy.

So, eventually all baryonic matter will have been changed into photons and leptons, so new grounds disappear, decay and disappear. In 10 to the 40th years, it’s going to be black hole era. Black holes it will dominate the universe at this time, everything has become a black hole. They will slowly evaporate via Hawking radiation. So at this time everything’s going to be black hole, the only thing remaining is black hole. But even black hole is going to slowly evaporate with the Hawking radiation. The more massive black hole takes more time, but, for example, with a black hole with the solar mass, one solar mass, will vanish via Hawking radiation in 10 to the 16, 66 years.

If it’s a super-massive black hole it needs more time, but in 10 to the, about 10 to the 100 years, it will evaporate, even black hole disappear. Then 10 to the 100 years, one googol years from now, it’s gonna be “dark era.” After all black hole have evaporated the universe will be nearly empty. Photons, neutrinos, electrons, positrons, there are some of them will fly from place to place, but universe is so big, density is so low, so, how to ever encounter each other? Gravitationally, universe is still dominated by dark matter, electrons and a positron. So this is a very, very sad universe, there’s no energy, even black hole, disappears, it’s dark, and then universe is empty.

So, are we lucky to live now, because at least we can observe other galaxies in the universe now. If we look at the night sky with telescope we can see other galaxies. But, in the future, some get, most of the galaxies outsi- outside of the super cluster will fly away, and then eventually it will become black hole era and empty universe. So, if we are born in this kind of far future in the universe, we don’t even know there are other galaxies outside the Milky Way. We don’t know there are stars if the star formation is ended.

So, in this sense, maybe we are lucky to live in a current era— at least we can observe thousand galaxies to learn and study about our universe.