universe

• before the big bang there was no universe. rather there was a singularity - an infinitely small point, and before whose existence all the known laws of nature break down
• from this singularity, a rapid expansion occurred called the 'big bang,' marking the beginning of our universe.
• the expansion started by the big bang and is still going today (meaning the universe is continually getting bigger)
• there was a belief that the expansion of the universe would eventually slow down, stop, and then reverse, leading to a contraction known as the "big crunch" and the eventual end of the universe
• evidence suggests that the universe will keep expanding forever
• in the first second after the big bang, the temperatures were extremely hot and particles of matter and antimatter collided
• what is matter?


  a physical substance that occupies space and has mass
• what is antimatter?


  opposite of matter, having similar properties but with opposite electrical charge. it has no mass and takes up no space but is still there
• in the first second after the big bang, the collisions of matter and antimatter destroyed each other and released bursts of light
• after the collisions a relatively small amount of matter was left and became the building blocks of everything we know today
• after about a second after the big bang, the universe began to cool
• as the universe began to cool, particles called quarks and electrons began to form
• what is a quark?

  a subatomic particle that makes up hadrons
• a few minutes after the big bang, the quarks started to clump together to form slightly larger particles called protons and neutrons
• these protons and neutrons then began to come together to form the nuclei (central part) of atoms
• atoms are what make up everything
• as the universe cooled further, the atomic nuclei began to capture electrons to make fully formed atoms
• these atoms then began to interact to form more complex molecules and particles
• the first galaxies formed about a billion years after the big bang
• galaxies are thought to have been formed by dark matter (an invisible material left over from the big bang) bringing clouds of gas together until they compacted to form galaxies
• smaller clouds of gas condensed further to form stars. rings of gas and dust orbiting these stars then condensed further attracting more matter forming planets
• the milky way is estimated to contain between 200 and 400 billion stars and be about 100,000 light years across
• the canis major dwarf galaxy is the closest galaxy to us and 25,000 light years away from the milky way
• galaxies can take various shapes including spiral, barred spiral and elliptical
• the steady state or infinite universe theory suggests that the universe is infinite in extent and has always existed in roughly the same form as today
• a star referred to as a cepheid has variable brightness and over a certain period of time, it changes from bright to dark repeatedly
• the period of variation a cepheid has is used to measure the absolute magnitude of the star
• hubble used cepheid variables to measure the distance to a number of galaxies
• what is red-shift?

  redshift is the displacement of an astronomical object's spectrum toward longer (red) wavelengths
• when atoms are heated, they emit light at specific wavelengths
• atoms emit light at specific wavelengths, depending on the element. this gives each element a signature colour
• what is redshift?

  the stretching of light waves emitted by objects moving away from us
• slipher's observations changed the accepted understanding of the universe because he discovered that galaxies are moving rather than static
• until slipher's discovery it was generally believed that galaxies were static and that the universe was not changing
• slipher's observation of the light emitted by galaxies indicated that most galaxies are getting further away from us
• the redshift of light from distant galaxies indicates that they are moving further away from us
• some of the galaxies closest to us are moving towards us because of gravity
• redshift occurs when the atoms that produced light are getting further away from the observer
• if atoms were getting closer to the observer, the wavelengths would be shortened, or blueshifted
• elements emit the same patterns of light wherever they are in the universe