By Ph. RECLUS
Astronomers often refer to large telescopes as « time machines » because they allow us to travel back in time. Telescopes collect light from distant stars and galaxies that has taken millions, if not billions of years, to reach us. Looking up into the night sky, we can see what these stars and galaxies looked like in the past. It gives us unique insight into how our universe has evolved over time. With large telescopes, we can literally travel back in time and observe events that happened long before humans existed on Earth.
What is the evidence that the universe began in a hot, dense state 13.8 billion years ago?
Evidence that the universe began in a hot, dense state 13.8 billion years ago can be found in cosmic microwave background radiation (CMBR). It is a faint glow of light emitted in all directions in space, which has been measured and studied by scientists since its discovery in 1965. The CMBR provides evidence for the Big Bang theory, as it is believe it to be leftover radiation from when the universe was first created. Further research on CMBR revealed that it is remarkably uniform throughout space, supporting the idea that it is a remnant of an initial hot and dense state.
The atoms in our bodies and all the stars in the 100 galaxies make up a small percentage of the contents of the universe. What are the two dominant ingredients of the universe and why are astronomers so uncertain of their physical nature?
Astronomers have long been uncertain about the two dominant ingredients of the universe: dark matter and dark energy. Although they are known to make up a large part of the universe, their physical nature remains a mystery. Scientists have been trying to understand these mysterious substances for decades, but until now their efforts have yielded few concrete answers. In fact, only two properties of dark matter and dark energy are known with certainty: their masses and their presence.
The first major discovery in the search for dark matter came in 1933 when Fritz Zwicky, a Swiss-American astronomer, discovered that the centers of galaxies must contain more mass than the rest of the galaxies combined.