Flashcards in Lectures 1-6 Deck (70)
How many planets are there?
How many moons are there?
172 (disocvering one a year approx.)
Describe the Milky way. Type of galaxy no of stars etc.
-spiral galaxy, 100 billion stars orbitting a supermassive black hole, we are at the outer edge
What is a local group of galaxies?
-around 50 galaxies, held together by gravity, in ours= only 3 that are big -Milky Way
- Andromeda (M31)
most of the galaxies= dwarf- satellites of bigger galaxies
What is a supercluster?
Huge number of local groups then clusters held together by dark matter.
Which cluster do we belong to?
average distance from the Earth to the Sun
= 150 million km (150 000 000 km)
=1.5x10 to the eighth km
distance traveled by light in an Earth year.
9.46x 10 to the twelve km
3 x 10 to the 8 m/sec
age of universe
13.7 billion years
When look at star 12 billion light years away how old is it?
Then the universe was only around 2 billion years old.
How can you weight the Sun?
By measuring the velocity of an object orbitting around it and the distance.
What's the shortest time we consider and why?
10 to -43 seconds. Beacause that's when physics began to work as it does today.
When did the Planck era take place and what happened?
before 10 to -43 sec.
Don't have a theory to explain this period.
When did GUT era occur and what happened?
10 to -43 sec
temp 10 to 32 K
-Two forces operating, the GUT force and gravity (became separate from the rest here)
When did Electroweak era occur and what happened?
10 to -38
10 to 29 K
Elementary particles appear spontaneously from energy and back. GUT force splits into electroweak and strong forces.
Huge expansion of the universe= inflation
When did Particle era happen and what occured?
10 to -10
10 to 15 K - then the electroweak force splits into magnetic and the weak force= first time ever all four forces!
-elementary particles filling universe, then quarks combined to make protons and antiprotons.
When did Era of Nucleosynthesis happen and what took place?
10 to 12 K
-Fusion produces helium from protons (H nuclei)
When were nuclei formed?
10 to 9 K
fusion ceased, leaving normal matter 75% hydrogen 25% helium
When did atoms form?
380 000 years
Neutral atoms formed allowing photons to travel freely through space. Can't see further than that.
What is normal matter also called?
What does WMAP do?
Measures the temperature and density of the early universe. -density of matter= where hot spots= where lot of dark matter is
Why is the universe expanding?
Because of dark energy.
Where do stars form?
In the densest regions of matter in clouds of gas and dust.
How many motions does a person standing on the Earth experience?
-rotation of the Earth (1000km/h)
-orbiting the Sun (100 000 km/h)
-Sun moves with respect to the local stars (70 000 km/h)
-The milky way moving towards Andromeda (800 000 km/h)
What was the earliest recorded supernova?
RCW86 recorded in the Booh of Han in 185AD
When was Stonehenge built and possible purpose?
What is the Antikythera Mechanism?
First analog computer capable of calculating moon phases, eclipses. Dated 100BC.
How did Eratosthenes measure the Earth?
knew from the angle difference Syene to ALexandria of the shadow at noon= 7. 7/360= distance to Syene=5000
5000x360 circumference of the Earth= 42 000 km
modern value 40 100km.