The Universe everything we can touch feel sense

The Universe • everything we can touch, feel, sense, measure or detect. • includes living things, planets, stars, galaxies, dust clouds, light, and even time. • Before the birth of the Universe, time, space and matter did not exist. . Cited from: https: //www. esa. int/esa. KIDSen/SEMX 4 EBE 8 JG_Our. Universe_0. html

• contains billions of galaxies, which contain millions/billions of stars. • The space between the stars and galaxies is largely empty. • Space is also filled with radiation (e. g. light and heat), magnetic fields & high energy particles (e. g. cosmic rays). Cited from: https: //www. esa. int/esa. KIDSen/SEMX 4 EBE 8 JG_Our. Universe_0. html

• the visible Universe is at least 93 billion light years across. • A light year is the distance light travels in one year (about 9 trillion km). • Travelling at the speed of light (300, 000 km per second), it would take 100, 000 years to cross our Milky Way galaxy alone. Cited from: https: //www. esa. int/esa. KIDSen/SEMX 4 EBE 8 JG_Our. Universe_0. html

The Big Bang Theory

Time begins • The universe begins ~13. 7 Billion years ago (= age of oldest stars)

• In 1927, the Belgian priest Georges Lemaître was the first to propose that the universe began as a single point, a singularity, that stretched, expanded, & continues to expand = Big Bang Theory • It is the leading scientific explanation as to how the Universe began.

• The universe begins smaller than the size of a single atom • It was hotter and denser than anything we can imagine. • The universe began as a violent expansion – All matter and space were created from a single point of pure energy in an instant – there was NO explosion