space

• what was the big bang theory?


  about 13.8 billion years ago the whole Universe was a very small, extremely hot and dense region. From this tiny point, the whole Universe expanded outwards to what exists today.
• how does redshift prove the earth is expanding?


  Redshift is when the light from distant galaxies appears more red than expected. This happens because these galaxies are moving away from us, causing the light waves to stretch and shift towards the red part of the spectrum. Redshift provides evidence that the universe is expanding.

  
• life cycle of a star:

  
• what is a supernova?


  A supernova is a massive explosion that occurs when a star dies, and is one of the most energetic events in the universe:
• What is a nebula? 


   a giant cloud of gas and dust that floats between stars
• What causes dust and gas to pull together and form a protostar?

  Gravitational attraction
• What is nuclear fusion? 


  The process of combining two atomic nuclei to form a heavier nucleus, releasing a large amount of energy in the process.
• what is nuclear fission?


  Splitting of an atomic nucleus into two smaller nuclei.
• Which type of star has supernova explosions?


  Only massive stars, much larger than the Sun, end their life in a supernova explosion 
• what is evidence that suggests that the solar system is made from the debris of old supernova explosions?


  Elements like gold are created during supernova explosions of massive stars. The presence of such heavy elements on Earth suggests that our solar system formed from the debris of older supernova explosions.
• How can we describe an orbit?

  An orbit is the curved path of one celestial object around another celestial object.
• What is an example of an orbit?

  The Earth orbiting the Sun is an example of an orbit.
• According to Newton's first law, what happens to an object traveling at a certain velocity?

  An object will continue to travel at that velocity unless acted upon by a resultant force.
• If the Moon is traveling at $1023 \text{ m/s}$, what is this speed referred to as?


  This speed is referred to as instantaneous velocity.
• Why doesn't the Moon fly off into space despite its velocity?

  The Earth's gravitational pull exerts a strong attractive force on the Moon.
• What happens to the Moon's direction due to Earth's gravitational force?

  The gravitational force changes the Moon's direction slightly, allowing it to orbit the Earth.
• What does it mean for the Moon's velocity to be constantly changing?

  It means that even though the speed is constant, the direction is changing, affecting the velocity.
• What is the relationship between acceleration and change in velocity?

  Any change in velocity indicates that there is an acceleration.
• Why does the Moon accelerate even though its speed remains constant?

  The Moon accelerates because its direction is constantly changing as it orbits.
• What two factors result in a steady orbit?

  The instantaneous velocity of the orbiting object and the gravitational pull of the larger object.
• What happens if the Moon's orbit is pulled in closer to the Earth?

  The gravitational force will be much greater, potentially pulling the Moon in towards the Earth.
• What must the Moon do to maintain a stable orbit if it is closer to the Earth?

  The Moon must start traveling much faster to maintain a stable orbit.
• What is the takeaway regarding the relationship between the size of an object's orbit and its speed?

  The smaller an object's orbit, the faster it must travel to maintain a stable orbit.