The largest stars will die and give way to neutron stars and black holes. Stars like our own sun will become white dwarfs. Red dwarfs will lose their ability to continue fusion, turning into black dwarfs—a strange kind of non-radiating stellar object that does not yet exist in our comparatively young universe.
Eventually, the entire contents of the universe will be crushed together into an impossibly tiny space – a singularity, like a reverse Big Bang. Different scientists give different estimates of when this contraction phase might begin. It could be billions of years away yet.
Although the end of the universe as we know it is still very uncertain, there are four theories that aim to put us closer to understanding this aforementioned inconceivable concept: a heat death, The Big Crunch, The Big Rip, and vacuum decay.
The universe will get smaller and smaller, galaxies will collide with each other, and all the matter in the universe will be scrunched up together. When the universe will once again be squeezed into an infinitely small space, time will end.
Cyclic universes. A theory called "Big Bounce" proposes that the universe could collapse to the state where it began and then initiate another Big Bang, so in this way, the universe would last forever but would pass through phases of expansion (Big Bang) and contraction (Big Crunch).
Big Freeze, Big Rip, Big Crunch, Bounce or vacuum decay? Steven Strogatz speaks with theoretical cosmologist Katie Mack about the five ways that scientists think the universe could come to an end.
22 billion years in the future is the earliest possible end of the Universe in the Big Rip scenario, assuming a model of dark energy with w = −1.5.
The trite answer is that both space and time were created at the big bang about 14 billion years ago, so there is nothing beyond the universe. However, much of the universe exists beyond the observable universe, which is maybe about 90 billion light years across.
"There's really no sense of time." At the edge of the observable Universe, there's something else happening, according to Katie Mack, an astrophysicist at the Perimeter Institute for Theoretical Physics in Canada. The Universe is expanding from the Big Bang, and that expansion is stretching time too.
Authors' example. In their paper, the authors consider a hypothetical example with w = −1.5, H0 = 70 km/s/Mpc, and Ωm = 0.3, in which case the Big Rip would happen approximately 22 billion years from the present.
In the very final moments, objects held together by atomic and molecular forces will be ripped apart, electrons will be stripped from their atoms, atomic nuclei will be broken apart, and even quarks themselves will be separated from one another. If there are anything comprising quarks, they'll be ripped apart, too.
Because space isn't curved they will never meet or drift away from each other. A flat universe could be infinite: imagine a 2D piece of paper that stretches out forever. But it could also be finite: imagine taking a piece of paper, making a cylinder and joining the ends to make a torus (doughnut) shape.
Big Slurp. This theory posits that the universe currently exists in a false vacuum and that it could become a true vacuum at any moment. In order to best understand the false vacuum collapse theory, one must first understand the Higgs field which permeates the universe.
The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them.
We currently have no evidence that multiverses exists, and everything we can see suggests there is just one universe — our own.
According to NASA, time travel is possible, just not in the way you might expect. Albert Einstein's theory of relativity says time and motion are relative to each other, and nothing can go faster than the speed of light, which is 186,000 miles per second. Time travel happens through what's called “time dilation.”
In short, space-time would contain the entire history of reality, with each past, present or future event occupying a clearly determined place in it, from the very beginning and for ever. The past would therefore still exist, just as the future already exists, but somewhere other than where we are now present.
The world as we know it has three dimensions of space—length, width and depth—and one dimension of time. But there's the mind-bending possibility that many more dimensions exist out there. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 dimensions.
Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, traversable wormholes, and Alcubierre drives.
Our universe began with an explosion of space itself - the Big Bang. Starting from extremely high density and temperature, space expanded, the universe cooled, and the simplest elements formed. Gravity gradually drew matter together to form the first stars and the first galaxies.
Thanks to dark energy and the accelerated expansion of the Universe, it's physically impossible to even reach all the way to the edge of today's observable Universe; we can only get a third of the way there at maximum.
As it stands, the universe is the largest object that we are aware of. There is nothing larger, and everything we can smell, hear, taste, touch, or see is a part of it.
Typically, they shouldn't be able to merge easily. Once black holes get fairly close together in binary pairs, they can settle into fairly stable orbits with each other. The situation changes, however, if they're dancing together in a crowded environment.
By the year 1 trillion, the accelerating universe will have infinitely stretched the light from all external galaxies - assuming dark energy truly is Einstein's cosmological constant and not an unstable field that winds up destroying the universe.
For 13.8 billion years, the universe has been expanding, cooling and evolving. Textbooks often say that the start of this expansion — the Big Bang — was the start of time.