Space

Space (lecture notes)

the boundless three-dimensional extent in which objects and events have relative position and direction

• The original idea of a galaxy1 was way different than now as they previously believed that everything revolved around Earth
• Galileo first presented the idea that their previous depictions were inaccurate and was almost imprisoned for coming up with such an “obscure” theory
• He proved his theory by using a telescope
• Compared to the rest of the galaxy, we are very small
• The width of our galaxy 100,000 light years2 in diameter
• Most of the galaxies we see are called “spiral galaxies”, which essentially means they look like a spiral (but there are other kinds too, for example irregular, peculiar, lenticular and elliptical galaxies)
• All galaxies have one thing in common, and that they all contain stars, (potential) plantes, gasses and dust. They all have some sort of circular shape
• The center is a black hole or an extremely dense star (and even light can get sucked in)
• Galaxies are also not stationary and emit radiation (x-ray and gamma radiation)

*Note: We have never ventured out of our own galaxy, therefore online pictures we see may not be extremely accurate.

• When galaxies collide, due to the two black holes, they both will essentially destroy themselves
• There may also be a merging of black holes and will pull other gasses together and form even larger galaxies. Meaning that a larger galaxy can devour smaller galaxies to form even larger ones
• Movement of galaxies are caused by the expansion of the universe

Big bang theory:

There is a massive explosion and everything expands outwards, and scientists to this day still believe that this expansion is continuous. Thus causing the movement of things in space, the galaxy and therefore runs the risk of collision with another.

Scientists also believe that the circular shape is due to the explosion and the spinning around of that dense object (e.g. blackhole).

• Aside from galaxies, there are also things called nebulas3
• Nebulas are created after the death of a star
• Dwarf plants are left after the death
• The gasses left behind is the nebula

Keywords:

Astronomy — study of the universe and the objects within it

Astronomer  — person who studies astronomy

1Galaxy — huge cluster of various celestial bodies

Light pollution — brightening of the night sky caused by street lights and other man-made sources

2Light year — a unit of astronomical distance equivalent to the distance that light travels in one year

• 300,000 km/s

Eclipse — when the sun and moon perfectly align so we don't see the moon

3Nebula — Cluster of dense gasses where new stars are made

• Two types (dark and light)
• Different colors of nebulas identifies the different gasses it is made up of

Celestial objects — objects we can see in the sky