Despite the vastness of the universe, collisions in space do happen, some on a tiny scale such as atoms or meteorite debris and some on the gigantic scale in terms of galaxies. Tiny cosmic collisions are nothing to worry about as they happen all the time. The Earth is constantly being hit by tiny meteors that burn up when they reach the atmosphere. Every month, the Earth travels through large areas of space that contains debris from comets (as in the case of the Leonids Meteor Shower) and/or asteroids (as in the case of the Geminids) that they shed as they orbited the Sun.
Imagine a time before the Earth, we're talking about 5 Billion Years ago when the solar system was being created. At the start was the ice and dust that made up the gaseous nebula which would later collapse upon itself to create the Sun and the planets that we know today. During that time, there were no planets, they were being created, they were formed from the collisions of different planetoids that's orbited the young sun. As the planetoids smashed into one another, they merged and created larger ones.
Phaeton is a hypothetical planet that once existed between Mars and Jupiter but one that didn't last long. It could've been ripped apart in a cosmic collision or a torn apart by the immense gravitational pull of Jupiter.
N.A.S.A. revealed in a news release that it had found a martian meteorite at Allan Hills in the Antarctic on July 20th, 2004. For the rock to have been discovered on Earth, Mars would've had to have been hit by an object that caused debris from the planet to fly off into space and land on this planet. In the future, we may find an Earth rock on Mars as the result of a impact collision.
At the beginning of the solar system, Earth was believed to have been involved in an almighty collision with a planetoid called Theia. The resulting debris from the collision is what is said to have made the Moon. Theia gets its name from the Greek Mythological Titaness who with her husband Hyperion gave birth to Selene, the Moon Goddess.
At the beginning of the Solar System, some 4.5 Billion years ago, the solar system was a little more crowded than it was today, there were more objects that orbited the Sun than there is today. Theia's orbit crossed that of the Earth and during one orbit, it came close, way too close and slammed into the Earth. The resulting collision caused debris to fly off into space and then coalesce into what we know as the Moon today. There is uncertainty as to whether Theia is still around or whether it was consumed into the Earth. It is believed that Theia was about the same size roughly as Mars. This collision is the most likely cause of why the Earth is tilted and why then we have seasons of the year.
Collisions are not just limited to the Earth, other planets in the solar system also had collisions. Venus had impact collisions but it doesn't have a moon. This has led to speculation that as to why, whether the impacts need to a type, size or angle to create the necessary debris.
Uranus is unique amongst all the planets in the solar system, in that it has a rotates on its side. This has led scientists to believe that the cause of the tilt was because of a giant impact with another celestial body.
Remember, the event of such a large object smashing into the Earth took place 4.5 Billion Years ago and nothing on this scale has happened since should hopefully calm any jittery nerves you may have.
If getting your head around this is hard to fathom when reading, have a look at the video below. Click on the image to open the link into another window.
Dinosaurs lived on this planet between 230 and 65 million years ago and before then, there were Prehistoric Animals. All of a sudden, the dinosaurs were wiped out in a mass extinction, the most likely theory and the one that has the highest support is that a meteorite smashed into the Earth in the Yucatan Peninsula off the coast of Mexico. The meteorite that smashed into the Earth was nowhere near as big as Theia, it didn't create a second moon. It did have the impact of throwing up dust and rock which blocked out the Sun and contaminating the atmosphere.
Dinosaurs reign therefore lasted 165 Million years which is a lot longer than humans have been. According to latest discoveries, humans have been on this planet for 2.8 million years after a human jaw bone was discovered in Ethiopia ref:B.B.C.
We've now got a technological stage where we could spot the next extinction level asteroid that is heading our way and react to it accordingly. Its not a hundred per cent guaranteed given what happened in Chelyabinsk on 15th Feb, 2013.
Ever since Russia sent up Sputnik 1 on 4th October 1957, we have sent an enormous amount of satellites into space and its getting pretty crowded up there. It wasn't helped when the Chinese blew up one of their own satellites (Fengyun 1 in 2007) thus exacerbating the situation. Six years later, a piece of the destroyed satellite damaged the Russian BLITS satellite ref:Space.
With more satellites going up all the time, there will be more of this sort of thing happening. Satellite operators monitor large objects and move their satellites and where necessary the international space station to avoid these collisions. It would only take an object the size of a petit pois pea to cause irreparable damage and loss of life. The hollywood film gravity covered this subject with Sandra Bullock playing the astronaut trapped in space trying to find a way back down to Earth.
In 2004, the world watched in awe as Comet Shoemaker-Levy 9 collided with Jupiter. It was the first time such an event had been witnessed and proof that its not just Earth that gets these collisions. Over time, Jupiter has provided Earth with a shielding mechanism as its pulled into its massive atmosphere possibly hundreds and thousands of objects that might have impacted the Earth. Other planets such as Mars and Venus have also suffered impacts from space.
Impacts zones on Earth are not that easy to spot due to the vegetation and how big they can be. The most famous impact site is Meteorite Crater in Arizona. You could be sitting in a crater that was caused by an collision but you wouldn't be able to see it unless you travel high above the planet/
You might think that the rights of Saturn are solid but they're not, they're individual clumps of rocks that orbit round the planet. These ice blocks travel round the planet can smash into one another and break into smaller pieces or merge to make bigger ones. Saturn is the most famous of the gas giant planets to have rings but all the gas giants have rings including Jupiter. Jupiter and Neptune's rings are quite faint to see but they are there. You can see an artists impression of the rings on the Jupiter page.
Although nor proven or disproved yet, there is a belief by some astronomers that Earth has a twin star and that that companion star is out there somewhere, probably out past the Oort Cloud and whenever it comes closer to the Earth, it causes a comet to start on its way towards the Earth. No one has seen this star. Its referred to as Nemesis. Nemesis is a brown dwarf star, something that because of its colour is not something that will show up when people are looking out for it. It won't necessarily collide with the Earth, it will affect other objects and fire them off towards us.
Our nearest neighbour is Proxima Centauri which is a small red dwarf that is about 4 light years away. A light year is actually distance not time and it represents the distance light travels in a year. We won't collide with that and due to the vast distances between us and other stars, we won't collide with any in our life time. That is not to say that there are solar collisions going in. Solar Collisions would are more likely to take place near the centre of a galaxy where the stars are closer together than way out in the suburbs that our Sun is in.
With star clusters such as M80 there are mysterious blue stars which it is theorized that they were formed by the collisions of stars. If they had been formed any other way, they would possibly have gone supernova long time ago. How stars collide depends on impact velocity, size etc. If they raced into one another, there's the possibility that one would be sent off flying into the recesses of the galaxy and beyond. If they didn't react so violently, they could cause a friendly merger. ref:Universe Today.
Scientists at LIGO have announced they have detected gravitational waves, caused by two Neutron Stars colliding. Neutron Stars are the remnants of a dead star and which are completely composed of Neutrons. The collision took place in a galaxy called NGC 4993 in the constellation of Hydra. The galaxy is around 130 Million Years ago. The Neutron Stars would have been collided at around the same time as the Dinosaurs who died out 65 Million Years ago. Nature
Just like stars can collide so can black holes, the remnants of dead stars. It was a black hole collision that took place 1.3 Billion Light Years away that enabled scientists to discover the existence of gravitational waves. Its not clear where the collision took place, just that it did. The resulting collision enabled scientists to detect Gravitational Waves, the last piece of Einsteins Theory of Relativity puzzle. The collision caused the flow of time to be speeded then slowed and then speeded again. ref:NY Times.
Black Holes as opposed to Supermassive Black Holes travel in the same way that stars do, that they rotate round the centres of galaxies and therefore have the chance of colliding with other black holes. Black Holes are more powerful due to their mass than stars and have the affect of feeding on other stars. Cygnus X-1, the most famous black hole is often illustrated as feeding off a star. It is unlikely therefore presumed that a star and a black hole will not actually collide, just black hole will collide.
Even though the universe is so vast and huge, galaxies do collide. Our own milky way has collided and cannibalised other galaxies over the time. Canis Major galaxy is currently being consumed by our Milky Way. It is theorized that Methuselah Star which is said by some is older than the universe is in our galaxy as a result of our galaxy colliding with an older galaxy. It isn't the last one we'll be consuming. Our galaxy will soon consume Large Magellanic Cloud and Small Magellanic Clouds before an eventual collision with the Andromeda Galaxy but that won't take place for another 5 billion years, phew.
Other collisions have taken place such as the one that caused the Tadpole Galaxy which has caused the galaxy to have a tail as opposed to being spherical or elliptical. When Andromeda which is twice the size of Milky Way way collides, our Sun might be slung off into deep space as we're in the suburbs of the galaxy. The Andromeda Galaxy is moving at an astonishing 75 miles a second towards us but given the vast distance it has to cover will take 5 billion years. In 5 billion years, our solar system will not be here, our star will most likely have gone supernova and all what remains is a supernova.
The screenshot below is from a You Tube video which you can see if you click on the picture, it'll open in a new window. The picture is what you might see if Earth was around when Andromeda and Milky Way are about to collide.
Had our solar system still been around when the collision occurred, our Solar System would escape undamaged. The distances between stars are so vast that complete solar systems would pass one another without affecting the other one. We'd have a lovely view of the oncoming impact but would not affect us much.
By far the biggest collision that could possibly happen is if that is there is a Multiverse and that two universes collide. There are some that think before the Big Bang, there were multiverse that collided and caused the creation of our universe. It might sound silly but there's no real way to prove or disprove this idea. If the multiverse does exist then its possible. According to Discover Magazine, our universe might have collided with another universe. "There are tantalizing hints that our universe has already survived such a collision-and bears the scars to prove it."
Futurism goes one step further and believes that our universe hints at colliding with another universe. It believes that 380,000 years after the birth of the universe, our universe did indeed collide with another universe. According to theory of inflation, the universe should've expanded in all directions evenly but it didn't.
Imagine how much power and energy a star has then how much a galaxy has and then the amount of energy our universe has is beyond our comprehension. Imagine if that universe is double, its mind blowing. The multiverse theory that is though of mainly when talking of collision is the bubble type rather than the many worlds where a decision in this realm creates a new one elsewhere.