End of the Universe

How the Universe

Possibly Ends 

 We know about our universe’s past : the Big Bang theory predicts that all matter, time, and space began in an incredibly tiny, compact state about 14 billion years ago. And we know about the present: scientists observations of the movement of galaxies tell us that the universe is expanding at an accelerated rate. But what about the future? Do we know how our universe is going to end? Cosmologists have three possible answers for this question, called the Big Freeze, the Big Rip and the Big Crunch.

 To understand these three scenarios, imagine two objects representing galaxies. A short, tight rubber band is holding them together— that’s the attractive force of gravity. Meanwhile, two hooks are pulling them apart— that’s the repulsive force expanding the universe. Copy this system over and over again, and you have something approximating the real universe. The outcome of the battle between these two opposing forces determines how the end of the universe will play out. 

The Big Freeze scenario is what happens if the force pulling the objects apart is just strong enough to stretch the rubber band until it loses its elasticity. The expansion wouldn’t be able to accelerate anymore, but the universe would keep getting bigger. Clusters of galaxies would separate. The objects within the galaxies– suns, planets, and solar systems would move away from each other, until galaxies dissolved into lonely objects floating separately in the vast space. The light they emit would be redshifted to long wavelengths with very low, faint energies, and the gas emanating from them would be too thin to create new stars. The universe would become darker and colder, approaching a frozen state also known as the Big Chill, or the Heat Death of the Universe. 

But what if the repulsive force is so strong that it stretches the rubber band past its elastic limit, and actually tears it? If the expansion of the universe continues to accelerate, it will eventually overcome not only the gravitational force – tearing apart galaxies and solar systems– but also the electromagnetic, weak, and strong nuclear forces which hold atoms and nuclei together. As a result, the matter that makes up stars breaks into tiny pieces. Even atoms and subatomic particles will be destroyed. That’s the Big Rip. 

What about the third scenario, where the rubber band wins out? That corresponds to a possible future in which the force of gravity brings the universe’s expansion to a halt— and then reverses it. Galaxies would start rushing towards each other, and as they clumped together their gravitational pull would get even stronger. Stars too would hurtle together and collide. Temperatures would rise as space would get tighter and tighter. The size of the universe would plummet until everything compressed into such a small space that even atoms and subatomic particles would have to crunch together. The result would be an incredibly dense,hot, compact universe — a lot like the state that preceded the Big Bang. This is the Big Crunch. Could this tiny point of matter explode in another Big Bang? Could the universe expand and contractover and over again, repeating its entire history? The theory describing such a universe is known as the Big Bounce. In fact, there’s no way to tell how many bounces could’ve already happened— or how many might happen in the future. Each bounce would wipe away any recordof the universe’s previous history. 

Which one of those scenarios will be the real one? The answer depends on the exact shape of the universe, the amount of dark energy it holds, and changes in its expansion rate. As of now, our observations suggest that we’re heading for a Big Freeze. But the good news is that we’ve probably got about 10 to the 100th power years before the chill sets in — so don’t panic it's gonna take a long time. 

Gravitation Wave

The Gravitational

 Waves

Gravitational waves are ripples in the fabric of spacetime, predicted by Einstein’s laws of general relativity, but they are incredibly difficult to detect. To see them you need a detector that can accurately measure distances 10,000 times smaller than a proton. Thats crazy! That’s like trying to measure the distance from our Sun to the nearest star to accuracy of the width human hair. But we have a technology on Earth that can do that:  ALIGO the Advanced Laser Interferometer Gravitational-wave Observatory, and back in November 2015, on a Monday morning, LIGO detected the first gravitational wave that humans have ever directly observed. Where they came from and what this means for space science is nothing short of mind blowing!

A long long time ago, in a galaxy far faraway. 1.3 billion years ago and1.3 billion light years away, two black holes were stuck in a perilous orbit around one another getting closer and closer. Black holes are incredible objects, they pull of their gravity - the amount they bend spacetime - is so strong that no light can escape them. No one knows what exists in the centre ofa black hole as normal physics completely breaks down. What we do know is that they are infinitely dense. One of these orbiting black holes was 29 times the mass of the Sun and the other was 36 times the mass of the Sun, but they were only about 200km wide. Which is tiny in comparison to the Sun which is over a million kilometres wide! And these black holes were orbiting each other really really fast, about the same frequency as the blade on a blender.

Imagine that, such massive objects rotating so quickly. These orbiting masses created ripples in the fabric of spacetime called gravitational waves, and the closer they orbited the bigger these waves got, until the black holes collided at half of the speed of light. And when they merged they formed a new blackhole that rang kind of like a bell, throwing out colossal amounts of energy as gravitational waves until it settled into a perfect sphere. And all of this happened in 0.2 seconds. And in the collision, they turned a huge amountof mass into gravitational wave energy. They lost a mass equal to three times the mass of the Sun which got turned in to gravitational wave energy by Einsteins equation E=mc^2. This created a huge wake of gravitational waves that ripped out in all directions at the speed of light. And, and this is the thing that gets us, over that last fifth of a second this collision released more than ten times more energy than total output of all of the stars in the entire rest of the Universe! It just completely boggles the mind! Meanwhile on Earth… At this exact time our planet was looking very different to what we see now. It was a barren wasteland, there was no grass or trees, in fact no plants or animals at all. Life at this stage had only come as far as microscopic multicellular creatures that lived in the sea.

And while the gravitational waves tore through space towards us all of the complex life on Earth evolved and grew: plants and animals developed, amphibians crawled on land, there was extinctions, reptiles and dinosaurs and mammals, more extinctions. Primates evolved into all of human civilization right up until Saturday 12th November 2015 when the scientists at LIGO turned it on to begin their initial tests. A mere two days later and just in time the gravitational waves flew past us and the first direct detection on Earth was made. And that sound bumping is actually what these waves sounded like. Even though gravitational-waves are ripples in spacetime and not ripples in the air, they vibrate at similar frequencies, so we canactually turn them into sound waves and listen to them … boop … It might not sound very impressive, but detection of gravitational waves means a huge amount for science. The results of this detection have already been profound. This is the very first time that black holes have been directly detected, in fact gravitational waves are the only way you can directly detect them!

It will hopefully be able to look at what makes stars go supernova, and might be able to probe the very nature of spacetime and see if it is made of things called cosmic strings. But the most exciting thing is that we don’tknow what it will find. This is one of the best parts of science,when you’ve got a new tool to peer into a realm of reality that you’ve never been able to access before. Who knows what you’ll find? May be you’ll discover things that help explain some of the great mysteries of the Universe, maybe we’ll find things that we can’t explain at all, and then we have to come up with new physics. In any case I find it super exciting and no one can’t wait to see more results. So there you go, those are the basics of gravitational wave astronomy.

Galaectic Collision

Milkyway 

Vs 

Andromeda

 Astronomers have used the Hubble Space Telescopeto forecast a future cosmic pile up: the titanic collision of the Milky Way and the Andromeda galaxy in about four billion years time. The Andromeda Galaxy, some 2.2 million light-years away, is the closest spiral galaxy to our home, the Milky Way. 

For around a century,astronomers have known it is moving towards us, but whether or not the two galaxies wouldactually collide, or simply fly past each other, remained unclear. Now, a team of astronomershas used the Hubble Space Telescope to shed light on this question, by looking at the motion stars in the Andromeda Galaxy. We wanted to figure out how Andromeda was moving through space. So in order to do that we measured the location of the Andromeda stars relative to the background galaxies.

 In 2002 they were in one place, and in 2010 they were in a slightly different place. And that allowed us to measure the motion over a period of eight years. The motion is actually incredibly subtle,and not obvious to the human eye, even when looking at Hubble's sharp images. However,sophisticated image analysis revealed tiny movements that the scientists were able to project into the future. Based on these findings, it is finally possibleto show what will happen to the Milky Way over the next eight billion years, as theg galaexies drift closer, then collide and gradually merge into a single, larger, elliptical galaxy with reedish stars. 

And might the Solar System should in fact survive this huge crash. The reason we think that our Solar System will not be much affected by this collision between the Milky Way and Andromeda is that galexies are mostly empty space. Even though our galaxy, as well as the Andromeda Galaxy, has a hundred billion stars in it, they are very far apart. So if two galaxies actually collide with each other, the stars basically pass right between each other and thecthe of two stars directly hitting each other is really, really small. So the likelihood that our Solar System will be directly impacted by another star, for example, in Andromeda as we collide with it is really, really small. Well, if life is still present on Earth when this happens, the changes in the sky will be quite spectacular. 

This collision will be very very slow because the time scales on the scales of galaxies in the Universe are very very long. So you have to think, millions of years but even then over these timescales over millionsof years, we will see big changes. If we wait a few billion years, Andromeda will be huge on the sky. It will be as big as our Milky Way because we'll be very close to it. And then later, when the galaxies merge, the merged remnant of the Milky Way Galaxy and Andromeda will look more like an elliptical galaxy and we'll be sitting right in it. So the view of the Milky Way on the nightsky will be completely gone and this band of light will be replaced by a more spheroidal distribution of light. And so, the Sun, born in the Milky Way almost 5 billion years ago will end its life in a new orbit, as part of a new galaxy. 

Where it All Started

THE BIG BANG THEORY

The Bang theory is a cosmological model of the the universe from the earliest known period through its subsequent full-scale evolution. The model describes how the universe expanded from its initial state of very high density and high temperature and offers a comprehensive explanation for a broad range of analysed phenomena, including the abundance of light elements, the Cosmic Microwave Background (CMB) radiation, large-scale structure, and Hubble's law – the farther away galaxies , the faster they are moving away from Earth. If the observed conditions are generalised backwards in time using the known laws of physics, the prediction is that just before a period of very high density there was a singularity. Current knowledge is insufficient to determine if anything existed prior to the singularity.

Georges Lemaître first observed in 1927 that the expanding universe could be traced back in time to an originating single point, calling his theory that of the "Primeval atom". For much of the 20th century scientific community was divided between supporters of the Big Bang and the rival steady-state model, but a wide range of evidence has strongly favored the Big Bang, which is these days universally accepted. Edwin Hubble concluded from analysis of galactic redshifts in 1929 that galaxies are drifting apart; this is an important observable evidence for an expanding universe. In 1964, the CMB was discovered, which was critical evidence in favor of the hot Big Bang model, since than the theory predicted the existence of a background radiation throughout the universe.

The known laws of physics can allow us to calculate the characteristics of the universe in detail back in time to its initial state of extreme density and temperature.  Detailed measurements about the expansion rate of the universe the Big Bang is placed at around 13.8 billion years ago, which is also considered the age of the universe.After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. Giant clouds of these primordial elements – mostly hydrogen, with some helium and lithium – later came together through gravity, forming early stars and galaxies, whih are the ancestors of stars and universes which are visible today. 

Besides these primordial materials, astronomers also observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang theory and various observations indicate that it is not the conventional baryonic matter that forms atoms. Measurements of the redshifts of Supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy's existence.