ASt201
If observers in all reference frames must agree about the speed of light, then they cannot always agree about ______ and/or _____?
Distance and/or time
In space, speed and movement of an object is always ______ to another object
Relative
Is the speed of light additive?
NO, the speed of light is ALWAYS the same
Moving clocks run ______
Slow
Postulate that states the law of physics are the same in all reference frames that are moving at constant speeds
The first postulate of special relativity
Space and time are bound together in a single entity called _______
Spacetime
Speed is always ____ to something else
Relative
The first postulate of special relativity...
Postulate that states the laws of physics are the same in all reference frames that are moving at constant speeds.
The postulate that states the speed of light (in a vacuum) is the same for all observers, regardless of relative motion or source of observer
The second postulate of special relativity
The second postulate of special relativity
The postulate that states the speed of light (in a vacuum) is the same for all observers, regardless of relative motion or source of observer
The speed of light is ______
Invariant
The speed of light is the _______ thing known, and only _______ can achieve this speed.
Fastest, light
Theory of relativity
Theory that states motion can only ever be measured in a relative sense
Theory that states motion can only be measured in a relative sense
Theory of relativity
What did Vera Rubin actually find?
She found that stars further away from the galaxy orbitted faster than those closer to the galaxy
What did Vera Rubin expect to see in her analysis of stars orbiting our galaxy
She expected to see that stars closer to the galaxy orbited faster than those further away
What is time dilation?
The idea that time runs slower when you are moving
What is true speed?
True speed is speed relative to the ground
What percent of the universe is dark energy?
68%
What percent of the universe is dark matter?
27%
What percent of the universe is ordinary matter?
5%
A galaxy composed of a random blob of stars, dust, and gas...
Irregular Galaxy
A type of galaxy composed of two galaxies that have merged to become one, causing a massive burst of stars
Antenna galaxy/Starburst merger
Cepheid variable stars
Stars that "pulse"
Cluster of very large galaxies, mostly elliptical, have very little star formation
Galaxy clusters
Elliptical galaxies
Type of galaxy with very little gas, dust, and star formation, very old and very large
Galaxy Clusters
Cluster of very large galaxies, mostly elliptical, have very little star formation
How are cepheid variable stars standard candles?
We can measure pulse time, which is correlated to luminosity
How are elliptical galaxies thought to be formed?
From a starburst/merging spiral galaxies. Use up all gas and dust to create lots of stars around a black hole
How do spirals in disk galaxies form?
They form by interactions/colliding with other galaxies
If we know the temperature and distance of a star, we can determine its...
luminosity
Irregular galaxy
A galaxy composed of a random blob of stars, dust, and gas
Lenticular galaxies
Disk galaxies with no spirals
Less luminous cepheid variable stars take _____ to pulse
Shorter
More luminous cepheid variables stars take _____ to pulse
Longer
Nodes of the cosmic web cause extreme _______ in spacetime
Dips
Objects whose luminosity is known...
Standard candles
Objects whose physical size is known...
Standard rulers
Starburst...
When galaxies collide and result in a massive burst of stars
Supernovae are all the same luminosity, therefore they can be used as...
Standard candles
Things close to us will have a ______ parallax angle
Large
Things far away from us will have a _______ parallax angle
Small
Three main components of a spiral galaxy
Disk, bulge and halo
We can use ______ to determine the size of the Earth's orbit
Radar
We can use ______ to determine the distance to objects in the Milky Way
Parallax
We can use ______ to determine distance to distant galaxies
Supernovae
We can use ______ to compare the distance from nearby star clusters to distant ones
Main sequence fitting
We can use ______ to determine from nearby star clusters to distant ones
Cepheid variables
What are nodes?
Galaxy clusters that show up on the cosmic web as being very dense
What does a disk galaxy with no spirals indicate?
That the galaxy has not been disturbed by any other galaxies in the universe
What is the "period" of a cepheid variable star?
The time between the pulses of a star
What three big galaxies are part of the local group?
Milky Way, Andromeda, and Triangulum
When galaxies collide and result in a massive bust of stars...
Starburst
Why are galaxies in the centre of a cluster elliptical and those on the edge are spiral?
There are more galaxies in the centre, so higher chance they will collide, starburst, and form elliptical galaxies. Less galaxies on the edge to collide with no spiral galaxies remain
Why might an elliptical galaxy show a blue stripe jetting from its center?
Energy and light produced when something falls into the black hole at its center
______ do not expand, only the space between them
Galaxies
At the end of the era of nucleosynthesis, how much of the mass is hydrogen and how much is helium?
1/4 helium and 3/4 hydrogen
Era of atoms
Era when universe gets very cold, converting all plasma to hydrogen and helium gas and dark matter
Era of nuclei
Era where the universe is filled with hydrogen and helium plasma
Era of nucleosynthesis
Universe era where protons collide to form and break atoms. Temperature of nuclear fusion
Era when the universe gets very cold, converting all plasma to hydrogen and helium gas and dark matter
Era of atoms
Era where the universe is filled with hydrogen and helium plasma
Era of nuclei
How do neutrons remain after nucleosynthesis?
They get stuck in atoms and make stable helium and deuterium nuclei
Hubble's Law equation...
v = Hd speed of object is proportional to distance
If a galaxy 1000 light years away explode, when will we see it?
We will see it 1000 years after its explosion, because the light takes 1000 years to travel to us
In what era is helium and dueterium formed?
Nucleosynthesis era
Name the three pieces of evidence for the Big Bang.
- Ratio of hydrogen to helium
- Uniform microwave glow in all direction
- Hubble's Law (Redshift, blueshift)
Oblers Paradox
If the Universe is infinite and unchanging, you should be able to see a star eventually, no matter where you are. The whole sky should be filled with stars
Particle Era
Universe era with equal numbers of protons, neutrons, electrons, and neutrinos all colliding at high rates
Peculiar Velocity
The movement and speed of an object NOT caused by the expansion of the Universe
The further away we look in space, the further back we look in _______
Time
The plasma of CMB should produce almost a perfect...
Blackbody
Universe era where protons collide to form and break atoms. Temperature of nuclear fusion
Era of nucleosynthesis
Universe era with equal number of protons, neutrons, electrons, and neutrinos all colliding at high rates
Particle Era
What causes small irregularities in the CMB?
Variations in temperature and density in the plasma
What does Hubble's Law prove?
The expansion of the Universe. It proves that everything is moving away. Objects further away are moving away faster and objects closer are moving away slower
What era does CMB light come from?
The transformation from the era of nuclei to the era of atoms
What is the cosmic microwave background?
Marks the moment in space and time when the plasma of the Universe cooled. It emits microwave that is invisible to the eye
What must occur for and object to come towards Earth?
The peculiar velocity must be greater than the rate of expansion of the Universe
When did the Universe start?
14 billion years ago
Where is the center of the Universe?
Nowhere! There isn't one
Why are there limited neutrons in nucleosynthesis?
Neutrons are unstable and decay into a proton and electron
Why is the cosmic microwave background different levels of red-shifted?
The Earth has a peculiar velocity of 170km/s. The CMB in the direction that we are moving in will be less redshifted. The CMB in the direction that we are moving away from is more redshifted
Why isn't the cosmic microwave visible?
Because it has been redshifted by a factor of 1100, so it is now microwave light to us
Any two spots on the CMB have the same...
Temperature
Data tells us that distant galaxies are moving slower, therefore, expansion is...
speeding up
Gravity should slow expansion down, so we expect distant galaxies to move ______
Faster
If the energy density is high, and the Universe is sphere, distant objects look ______
Bigger than expected
If the energy density is low, and the Universe is saddle, distant objects look _______
Smaller than expected
If the energy density is right, and the Universe is flat, distant objects look _______
The expected size
If the mass density of the Universe is _______, the expansion of the Universe will continue forever without slowing down
Zero
If the mass density of the Universe is ______ than the critical density, the expansion of the Universe will slow down, but never stop
Smaller
If the mass density of the Universe is "________", then the expansion will keep slowing down to a stop
Exactly right
If the Universe has high density, it will be shaped like a _____
Sphere
If the Universe has low energy density, it will be shaped like a _______
Saddle
If the Universe is a sphere, then straight lines...
Converge
If the Universe is flat, straight lines...
are flat
If the Universe is a saddle, then straight line...
Diverge
If you put ______ into an expanding Universe, you get an accelerating expanding Universe
Dark Energy
The geometry of space depends on ______ of the Universe
Energy Density