The Beautiful Cosmos

During the day, some of us are lucky enough to be able to look up and see a clear blue beautiful sky and ‘our’ radiant Sun. During the night, most of us can gaze into the night sky and see lots of little bright points, stars. When we look up and see what we call ‘our Sun’, it can be hard to imagine that what we see also looks like this:

Image above: False-colour image of our Sun. Photographed by: Atmospheric Imaging Assembly of NASA’s Solar Dynamics Observatory.

Most of you may look at this and instantly know that it’s a Star. However, there are a fair amount of people who don’t realize that our night sky is full of millions of Stars like this, smaller, bigger and some the same size. Some people don’t know that the Sun is actually a star. I’ve got to admit that the image above looks nothing like what I see with the naked eye when looking up into the Sky:

You’ve probably been told that staring directly at the Sun is bad for your eyes. However, we don’t have to have uncomfortable staring contests with the Stars to try and get them to give up their secrets! After years and years of research, scientists have managed to find out quite a bit about the oh-so-secretive Stars without losing a staring contest.

Firstly, stars go through the same process that we do in the sense that they are born, live and then die. The difference is that they do it far more dramatically and take a much longer time doing it. Depending on the mass of the Star, the lifetime can range from a few million years to trillions of years!

The birth:

Naturally, this is where the comparisons between humans and Stars have to stop. The birth place of a Star is a huge, cold cloud of gas and dust, nebulae/nebulas.

Image above: Chandra, Hubble, and Spitzer image NGC 1952

These clouds begin to shrink, a result of their own gravity. As a cloud begins to shrink it gets smaller and the cloud breaks up into clumps. Eventually, these clumps reach high enough temperatures and get so dense that nuclear reactions begin. When the temperature reaches about 10 million degrees Celsius, the clump becomes a new star, a protostar. A protostar is not very stable. In order to live on, the protostar will need to achieve and maintain equilibrium, a balance between gravity pulling atoms towards the center of the protostar and gas pressure pushing heat and light away from the center. When a star can no longer maintain this balance, it dies.

How do we “know” any of this?

Infrared observatories such as ESA’s Herschel space observatory (launched in May 2009) are able to detect the heat that comes from such stars that we are not able to see, and therefore give us the information we need to research further.

Image above: Artist’s impression of the Herschel Space Observatory

If the critical temperature in the core of a protostar is never reached, it ends up as a brown dwarf, never achieving “star status”. However, if the critical temperature in the core of a protostar is reached then nuclear fusion begins. It is no longer classified as a protostar. It’s defined as a Star in the moment that it begins fusing the hydrogen in the core into helium. Simply put, nuclear fusion is a nuclear reaction where two or more atomic nuclei collide at high speeds and form a new type of atomic nucleus, in this case hydrogen forms helium.

“When a star can no longer maintain this balance, it dies.”

At “Star Status”, Stars spend the majority of their lives fusing hydrogen. So what happens when the hydrogen fuel is gone? Well, the Stars fuse helium into carbon and after a while, into even heavier elements. Maintaining the balance between gravity and gas pressure becomes very hard. The Stars eventually start to collapse on themselves. Before the Star’s inevitable collapse, nuclear reactions outside of the core cause the dying Star to expand outwards and this is what we call the “Red Giant” phase. It really is as dramatic as it sounds.

How dramatic the death is, depends on the mass of the Star. Our Sun is expected to turn into a white dwarf Star. If a Star has a slightly larger mass than our Sun, it may undergo a supernova explosion and leave behind a neutron Star. If even larger, at least three times the mass of the Sun, the Star could even implode to form an infinite gravitational warp in space, a black hole!

Image above: Computer generated image of a Black Hole

Stars live the majority of their lives in a phase that we call the Main Sequence. Our Sun is currently in the main sequence. However, not all the Stars in the Universe are in the main sequence. When we peer into the night sky, we see history. Perhaps you have spotted a few red Stars in the night sky? There’s a chance that the Stars you saw were already dead when you saw them.  Why? Well, these stars are so many light years away that it takes a very long time before the visible light reaches our eyes. When we look up, we are looking at what a Star used to look like X light years ago (X depending on how far away the Star is).

Some stars are only just beginning to form, others are in the Main Sequence and some have begun to die. Luckily for us, there is an amazing diagram, The Hertzsprung – Russell diagram that shows the relationships and differences between Stars:

  If you look at the HR-Diagram, you can see many dots. Each dot represents a Star. The Universe has many Stars in it; hence there are many dots on the diagram.

The diagram shows the temperature of the Stars and the Star’s luminosity. The vertical axis represents the Stars luminosity. Luminosity is the amount of energy a Star radiates in one second, where every Star is compared to each other based upon our Sun. Our sun is in the yellow part of the main sequence, and therefore has luminosity 1, all other Stars are compared to ours in this sense.

The horizontal axis represents the Star’s surface temperature, in Kelvin. Here we have higher temperatures on the left and lower temperatures on the right. Usually we go from lower to higher; however, it’s more adequate to see that a star in the upper left corner of the diagram is both hot and bright. A star in the upper right corner of the diagram is both cold and bright, what kind of star would this be? Take a look at the diagram.  Happy Star hunting!

Sources:

http://www.esa.int/esaKIDSen/SEMY06WJD1E_OurUniverse_0.html

http://www.nasa.gov/audience/forstudents/9-12/features/stellar_evol_feat_912.html

http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html

http://essayweb.net/astronomy/blackhole.shtml

http://www.spitzer.caltech.edu/images/2857-sig09-009-NASA-s-Great-Observatories-View-of-the-Crab-Nebula

http://apod.nasa.gov/apod/ap101207.html

http://www.esa.int/Our_Activities/Space_Science/Herschel

In the late 1960′s, gamma-ray bursts were discovered. However, this was not an intentional discovery.  They were discovered by the U.S. Vela satellites that were actually built to detect gamma radiation pulses emitted by nuclear weapons tested in Space! Why? Well, the USA suspected that the USSR might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. However, that wasn’t the case.

On the second of July in 1967, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons’ signature. The team at the Los Alamos Scientific Laboratory (led by Ray Klebesadel) were rather uncertain of what had happened. However, they didn’t consider the matter urgent and filed the data away for investigation.  As more Vela satellites were launched with better instruments, they continued to find these gamma-ray bursts in their data. They analyzed the different arrival times of the bursts as detected by different satellites and the team was able to determine rough estimates for the sky positions of sixteen bursts.

So what were these mysterious outbursts? Was America about to get bombed?

Well, America wasn’t about to get bombed, so that’s one less thing we have to read about in our history books! Instead, it was suggested that the gamma-ray bursts happened inside of the Milky Way Galaxy. This theory was found incorrect when in 1991, the Compton Gamma Ray Observatory, and its’ Burst and Transient Source Explorer instrument was launched. This instrument provided data that showed an absence of gamma-ray bursts in our galaxy and therefore, they had to be beyond our galaxy.

Alright, well, get to the point. Where are gamma-ray bursts?!

Gamma-ray bursts are flashes of gamma rays (electromagnetic radiation of high frequency)  that are associated with very energetic explosions that have been observed in distant galaxies. They are known to be the most radiating electromagnetic events in the Universe. The bursts can last from ten milliseconds to several minutes (a typical burst lasts 20-40 seconds). This is usually followed by an “afterglow” emitted at longer wavelengths such as X-ray, ultraviolet, optical, infrared, microwave and radio.

Picture above: An Artist’s illusion that shows the life of a massive star as nuclear fusion converts lighter elements into heavier ones. Sooner or later, the process comes to and end and the star will collapse and form a black hole. It is theoretically possible that a gamma-ray burst can be formed during the collapse.

There are two different types of Gamma-ray bursts, long and short:

Long gamma-ray bursts: Most of the gamma-ray bursts we have observed, have lasted for longer than two seconds and are then classified as long gamma-ray bursts. Long gamma-ray bursts tend to have the brightest afterglows and are studied in much greater detail than short gamma-ray bursts. From what we have observed, most long gamma-ray bursts are a result of a galaxy with rapid star formation, a core-collapse supernova and generally the deaths of massive stars.

In March 28 2011, there was a very unique gamma-ray burst (GRB 110328A), one that lasted more than two and half months! The event is interpreted as a supermassive black hole devouring a star (probably a white dwarf) and emitting its beam of radiation towards Earth.

Short gamma-ray bursts:

Gamma-ray bursts that have a duration of less than two seconds are classified as short gamma-ray bursts. There are not as many as these as long gamma-ray bursts, only 30 % of those we have observed. Many short gamma-ray burst afterglows have been detected and most of them have been found in regions of little (or non) star formation (such as large elliptical galaxies and the center regions of large galaxy clusters). There have been none that are associated with supernovae. It is believed that they originate from the mergers of binary neutron stars or a neutron star with a black hole.

Picture above: An Artist’s illusion of a gamma-ray burst. The energy from the explosion is shown as two oppositly-directed jets.

So there we have it, no nuclear tests, no blowing up the USA, just a wonderful and fascinating gamma-ray burst!

Sources:

http://astro.berkeley.edu/research/grbs/grbinfo.html

http://www.nasa.gov/mission_pages/swift/bursts/

After being (very unexpectedly, may I add) on Tumblr's radar and receiving many new followers, I feel as popular as Isaac Newton, if only I had his brain! We've all heard of him but do we all know what is he actually known for? Laws!

Yes you heard me, laws. More specifically, Newton's laws of motion. 

Picture above: Isaac Newton (1643-1727), the man that changed our understanding of the Universe with his three laws of motion. 

Before learning these laws, we might want to know what a force actually is and what it does!

A force can change the speed of an object and it can also change the form of the object. The unit for force is (big suprise) N, for Newton. We can say a force is any influence that causes an object to change, for example it's movement, direction or even geometric construction could change. 

Picture above: Forces can also be described as a push or a pull on an object. For example gravity or magnetism. 

Another thing that can be handy to know, is what a vector quantity is. As written in one of my past posts about time: Scalars are quantities that are fully described by a magnitude alone (Time and Mass), whilst Vectors are quantities that are fully described by both a magnitude and a direction (Velocity and Force).

The first law: 

If the net force, which means the overall force acting on an object, is zero, then the velocity of the object is constant. 

If an object is stood still, then the net force will equal zero. Why? Imagine a table placed on the ground, there will be the gravity force keeping the table on the ground and a force coming from the ground up against the table (called the Normal Force: http://en.wikipedia.org/wiki/Normal_force). These two forces will be of the same size, in opposite directions. 

Picture above: Fn = Normal Force

As the object is stood still, Newton's first law says the net force is equal to zero. 

A video explaining Newton's first law: http://www.youtube.com/watch?v=5-ZFOhHQS68

Newton's second law: 

This law states that the net force of an object is equal to the mass of the object and the acceleration. When an object is influenced by forces, then the object has an acceleration in the same direction as the sum of the forces (the net force). 

A video explaining Newton's second law: http://www.youtube.com/watch?v=P5OSVfL_BtA&feature=relmfu

Newton's third law: 

When two bodies exert forces on each other, the forces will be equally big and in opposite directions. So if a first body exerts a force F1 on a second body, then the second body will at the same time exert a force on the first body. F1 and F2 are then equal in magnitude and opposite in direction.

So next time you give someone a hug or... even punch them if you feel that angry, just remember Newton's third law! 

A video explaining Newton's third law: http://www.youtube.com/watch?v=NfuKfbpkIrQ

Sources:

Physics book: H.Aschehough @ Co. [W. Nygaard] 2007

http://www.physicsclassroom.com/class/newtlaws/u2l3a.cfm

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

Pictures:

Have you ever heard of the amazing and inspirational Carl Sagan?

Carl Sagan was an American astronomer, astrophysicist, cosmologist, author and science communicator. Why inspirational? Well, there are many intelligent beings in the world but not all of them are capable of communicating and appealing to the people like Carl Sagan did. Carl Sagan did this through his books and various media (The Cosmos being especially popular). 

Why bring him up now?

Well, today, along with many other humans, Carl Sagan was born 78 years ago on November 9th 1934. So happy Carl Sagan Day! 

"For small creatures such as we the vastness is bearable only through love." - Carl Sagan.

"If you wish to make an apple pie from scratch, you must first invent the Universe". - Carl Sagan.

I recommend all of you to listen to this video by Symphony of Science "A glorious dawn ft. Stephen Hawking": http://www.youtube.com/watch?v=zSgiXGELjbc

Picture source: 

Aren't all of them the same? No, they're quite different actually. The confusion lies mostly around the fact that both Speed and Velocity are measured by m/s (meters per second) and Acceleration measured by m/s^2. This does not mean they're the same though.

Speed is the rate of motion/rate of change of position. It doesn't have a specific direction. Therefor, speed is a scalar quantity expressed as distance moved per unit of time. Speed is the magnitude component of velocity. Velocity contains both the magnitude and direction components and is a vector quantity.

When we talk about how fast something moves, we mean how far it can move in a given time, whilst when we talk about acceleration, we mean how the velocity changes in a given time.

How do we measure speed?

Galileo Galilei is said to be the first to measure speed by considering the distance covered and the time it takes. He defined speed as the distance covered per unit of time. As an equation: 

Here, v is velocity, d is distance and t is time.

This equation is simple but very useful. You can find the velocity, distance and time by using this equation (providing you know 2 of the components). However, as this equation is simple, the velocity has to be constant (the speed is always the same). This might seem unrealistic, but it's very precise. 

Picture above: A graph showing the distance, time and constant speed. The time is on the X-axis, whilst the distance is on the Y-axis. We usually use m/s for velocity (meters per second). 

Velocity as you most likely know, cannot always be constant. This is when instantaneous speed comes in. Instantaneous speed is the velocity of an object at a certain time. The graph below is an example of measuring instantaneous speed.

In the picture above there are tangents drawn across the points in time, in order to find the speed. You then calculate (for example, here they divide Delta Xp with Delta Tp on both tangents) the slope for the new tangent(s) you have drawn and get the instantaneous speed. There are faster ways to calculate the instantaneous speed but those require more advanced equations and mathematics. 

When the speed varies with time, the movement is accelerated. You can have both positive and negative acceleration. For example, when a car stops, the velocity sinks and therefor the acceleration becomes negative. When a car increases it's velocity, the acceleration becomes positive.

In Physics, we also use constant acceleration. This equation can be used to find the acceleration, start velocity, end velocity and time: 

Usually there is a line above the "a" to point out that it's the constant acceleration.

Picture above: Here we see the different types of graphs for Position, Velocity and Acceleration. 

Sources:

http://www.intmath.com/kinematics/1-velocity-graphs.php

http://en.wikipedia.org/wiki/Speed

http://www.edinformatics.com/math_science/acceleration.htm

http://homepages.wmich.edu/~kaldon/classes/ph113-4-lectures.htm

"NASA's Mars rover Curiosity has discovered what appears to be an ancient streambed, suggesting that water once flowed in large volumes — perhaps hip-deep in places — across the Martian surface."

- www.space.com

What's the first thing you think about when you think of the Second World War or the Cold War?

Hitler? Evil? Stupidity? Death? Well, obviously I'm not here to talk about War, I'm here to talk about rockets! Yes, rockets! 

During the Second World War, the development of rockets was greatly improved. Rockets have been used since the 13th century, both for fireworks and for the military. However, it was the German's military rockets, V1 and V2, that were made in the 1930-1940s, that helped us take a big step towards the technology that today, could get us off of the face of the Earth. In the 1950-1960s the main usage of rockets was to transport atom bombs, which is not so much the case today. Rockets led us into the Space Age and the race for the Moon.

Picture above: A damaged V1 found by the Allies. 

Today, rockets are used for much more than that one task of destroying. They are now used for fireworks, weaponry, ejection seats, satellites, human spaceflight and space exploration! However, it's certainly not as simple as just imagining up a rocket and flying to the Moon. It's extremely complicated, dangerous and expensive. Very few rockets are made to send humans to Space, mostly because of the huge risk of putting astronauts near the highly explosive fuel and not to mention the price! 

So what happens when a rocket launches? Newton's third law is very useful here. Basically, the fuel gets thrown out one way, whilst the rocket moves in the opposite direction. Different fuels are used, either in solid or fluid form. "When two bodies interact by exerting force on each other, these forces (action and the reaction) are equal in magnitude, but opposite in direction."

Picture above: Proton Rocket heading for Space.

Besides the risks and money, what's stopping us? Well, it's not as simple as applying Newton's third law and launching off into Space. We've got gravity to think of! It's easier to escape the Earth's gravitational pull and settle into the Earth's orbit then it is to go further into Space, especially if we're wanting to land on the surface of another celestial object. 

There are five phases of space exploration with rockets as we know it:

Phase 1: Launching the rocket up into Space, escaping the Earth's gravitational pull. For even a satellite to get into the Earth's orbit, it must have a speed of over 28 000 km/h. 

Phase 2: The easiest way to get as far away as possible from the Earth and into Space, is to fly past a planet, asteroid or comet (using the gravitational pull of the object to bend around and fly on). This need a speed of 40 320 km/h. 

Phase 3: It's quite complicated to send a spacecraft or satellite into the orbit of a celestial object. You would need exact calculations, to see at what exact speed you would need to enter the orbit and not fly straight past it, or get sucked in by the gravitation pull. You would also need other types of rockets (attached to the main rocket) to help slow you down, or even boost your speed.

Phase 4: Landing on the surface of a celestial object is MUCH harder than flying around it. In order to land successively, you'd need very exact controlling, safety and to be slowed down.

Phase 5: Returning home is quite complicated too, especially if you're to land on a planet and pick up samples, you'd need extra fuel for the way back home and the extra weight makes the rocket heavy and expensive. 

Whatever the expense, it's always useful, FOR SCIENCE! 

Sources:

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

http://en.wikipedia.org/wiki/Rocket

http://www.historylearningsite.co.uk/v_weapons.htm

http://en.wikipedia.org/wiki/Rocket_launch

50 years or more ago, we hardly knew anything about the Moon, simply that it is there. We can compare it to as we 'know' gravity today, we don't know much about it, just that it's there and is quite important for us. However, I doubt another War will help us understand gravity.

The Cold War helped us understand the Moon quicker, when two superior countries fought to be the first on the Moon. Both the USA and Soviet Union received many brilliant Scientists and research from Germany when WW2 ended. They both fought hard but of course, only one of them could be the first and that was the USA.

From the day that we first landed on the Moon, we have been going back and forth  but never actually staying there for very long. Some may call this a waste of time and money, some even suggesting that we could instead buy a new football stadium, as this is clearly more important. However, we have been collecting more and more important data from the Moon and have been planning how we can colonize the Moon.

NASA has plans for a Moon base for 2020, however they are criticized for investing so much in Mars, that we won't be able to get to the Moon before Mars. However, USA isn't the only hope we have for getting to the Moon as we are already developing the right technology that we need for the colonization of the Moon. 

There are both advantages and disadvantages when it comes to the colonization of the Moon.

Advantages:

- Valuable resources, such as iron, aluminium, water (if we're able to utilize it), oxygen and hydrogen and helium-3.  However this can also be a disadvantage, who is to claim these resources? Does America think they claim the Moon because they landed on it first? That won't go down well.

- As it's so close to the Moon it should be easy to contact the Earth and travel back and forth.

- We could launch rockets from the Moon to Mars with locally-manufactured fuel. It may be easier to launch from the Moon, as the Moon's gravity is lower, requiring a lower escape velocity. 

- If the Moon were colonized, it could prove that humans can survive in low gravity and that would be valuable to know for Mars.

- At the Lunar North Pole, there could be eight hours on sunlight per day during the local summer and therefore there could be a farm, with the crops rotating in and out of the sunlight for the entire summer, providing food.

Disadvantages: 

- We couldn't rely on Solar Power because of the long lunar night and the huge temperature swings (123c to -153c)!

- The water may exist in an ice form in a colder landscape than people have ever mined. Carbon and nitrogen could also be in the same cold traps as the ice. If we couldn't get to these, then they would have to be imported and this could be very expensive and would limit the colony's rate of growth and keep it dependent on Earth. 

- We don't know if humans could cope with the low-gravity on the Moon, it could result in permanent effects like loss of bone and muscle mass and a depressed immune system. 

- With a lack of atmosphere, there's more of a chance for the colony to be damaged by a meteorite.

- Moon dust is formed by micrometeorites. It sticks to everything and can damage equipment, possibly toxic.

Of course there's thousands of advantages and disadvantages to think of, these being the ones I think most important. However, we cannot stay on the Earth forever, we must expand and even if it takes thousands of years before we can properly live on any other planet, we will get there and we will develop the technology. This is the first step.

Sources:

http://cosmosscience.tumblr.com/post/8040155856/its-not-all-about-usa-you-know

http://en.wikipedia.org/wiki/Colonization_of_the_Moon

Have we found it yet? Yes, yes-- Wait, nope, it's gone again, wait, there it is again! Yes, I'm talking about the Higgs boson, also known as "the god particle". 

Lately there has been a lot of discussion about having found this particle but we have not actually been able to prove it's existence. What is the Higgs boson? What is all the fuss about? How do we know if we have found it or not?

The Higgs boson is a theoretical elementary particle that fits into the Standard Model of particle physics, or according to some.. misunderstanding beings, a particle that proves the existence of their god(s). To understand what the Higgs boson "is", we have to go right back to the very beginning, the Big Bang. 

Particles began to form just after the theoretical implosion made time, space and energy out of nothing. The Universe supposedly consists of two different groups of elementary particles, these two groups being (according to the Standard Model of Particle Physics) the fundamental fermions and the fundamental bosons. 

Fermions: Quarks, leptons and their antiparticles.

Bosons: Gauge bosons and the Higgs boson.

The popular theory on how the Universe came to be tells us that quarks, anti-quarks and photons came first, then bosons, which were followed by the Higgs boson and etc.

So why is the Higgs boson so important, if we do not think it came first?

Well, finding the Higgs boson probably won't tell us that much about how the Universe came to be, as so much came before it and after it. However, it could fill a huge gap in the Standard Model that's been there for quite a while.

What gap?

The Standard Model of particle physics doesn't explain how some particles gain their mass and therefor, in 1964 the Higgs mechanism was suggested by Peter Higgs and six other physicists. 

The Higgs mechanism is theorized process that gives mass to elementary particles, the particles supposedly gain mass by interacting with the Higgs field, which is believed to permeate the Universe. So what we're hoping to get out of the Higgs Boson, is how these certain particles gain mass and this sort of information would help us understand our Universe better, or at least, before something else that is completely baffling comes along! 

How could we ever find such a thing? 

You have most likely heard about the Large Hadron Collider (LHC) at CERN (in Geneva, Switzerland), one of the main goals of the LHC is to test the existence of the Higgs boson and examine it. 

The LHC works by smashing together two beams of protons at close to light-speed, which results in a vast shower of particles that are only created at high energies. Physicists look for the Higgs in the vast shower of particles. 

Haven't they found it? 

On July the 4th, typically enough, physicists decided to announce that they had possible evidence of the Higgs boson and if not the Higgs boson then they are "more than 99%" sure that they've found a new elementary particle. It was supposedly weighing roughly 125 times the mass of the proton.

"This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found," Joe Incandela, spokesperson for LHC's CMS experiment, said in a statement. "The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."

You can read more about this here: http://www.space.com/16428-higgs-boson-particle-lhc-findings.html 

So let's just hope it's not another false alarm because their budget is cutting tight!

Sources:

http://cosmosscience.tumblr.com/post/6696460454/the-big-bang-theory

http://en.wikipedia.org/wiki/Higgs_boson

http://en.wikipedia.org/wiki/

https://espace.cern.ch/CRSS/default.aspx

This article implies that the oh-so-mysterious higgs boson may have been found, then again we've heard this all before. Let's hope so!

There is often confusion to as what the difference between antimatter and dark matter is. Simply put, antimatter is composed of antiparticles (just like how "normal" matter is composed of particles) and dark matter is that which we cannot see with our telescopes and it is hard to prove its existence. There's more to it than just that though!

So what is an antiparticle? Well, the elementary particles in the Universe appear to have partner particles, antiparticles. They share many of the same characteristics but many of them are the opposite of those for the particle. For example, the electron has its antiparticle the antielectron, these two have the exact same masses but they have the complete opposite electrical charges (+ and -). 

Picture above: Electric field induced by a positive electric charge.

Picture above: Electric field induced by a negative electric charge.

So what happens when a matter particle meets its' antimatter particle? Annihilation! Which means that they completely destroy each other and Einstein's E=MC^2 tells us that they then release the equivalent of their rest masses in the form of pure energy. For example, when an electron meets its antielectron, these two will annihilate and produce a burst of light with the energy corresponding to the masses of the two particles. 

Life based on matter has evolved here and so, it's possible that life based of antimatter has evolved elsewhere, perhaps we have antimatter twins! However, since antimatter particles and matter particles annihilate each other, it probably wouldn't be a very good idea to meet!

What else is there in the Universe? (Or perhaps /our/ Universe, as there could even be more than one Universe!) Well, there is that which we call Dark Matter. The big difference between Antimatter and Dark Matter is what I previously mentioned, you cannot see Dark Matter with telescopes but we think it's there.

Dark Matter is a type of matter that in theory, is a large part of the total mass of the Universe. It does not emit or absorb light or other electromagnetic radiation at any significant level. How do we know about it then? 

We think something is there because we can see the gravitational influence it has on the Universe. There have been various experiments and estimations (one of them being that Dark Matter is estimated to constitute 84% of the matter in the universe and 23% of the mass energy) , where we see the gravitational influence, which suggests that there is ten more times matter in the Universe than that we can see with our bare eyes and telescopes! Dark Matter is what the Universe is thought to made out of, we just have yet to find out what it REALLY is.

How can we try to prove the existence of Dark Matter? An example that some use is the fact that the velocity of rotation for spiral galaxies depends on the amount of mass contained in them. Our own spiral galaxy is an example, we have detected amounts of matter from the outer parts of our galaxy and we have found that there must be about 10 times as much matter for it to be going at the speed that it currently is, meaning something that we can't see is making the outer parts of our spiral galaxy rotate faster. We've found this to be the same for many spiral galaxies, where the velocities can be measured.

Do they have anything to do with each other? 

Dark matter or at least some of it could be antimatter but it's either highly unlikely or we've got it all wrong. In theory, if dark matter was antimatter then we would expect it to annihilate with matter whenever they meet and this would supposedly release burst of energy primarily in the form of light. However, we've seen no such thing and this leads us to another question: If dark matter isn't antimatter, then what is it? 

Sources:

http://en.wikipedia.org/wiki/Antimatter

http://csep10.phys.utk.edu/astr162/lect/cosmology/antimatter.html