The Universe Flashcards
Hadrons are….
Everything that has quarks
Every particle has a….
Corresponding anti-particle with the same mass, and opposite charge
An anti-electron is
The anti-particle of an electron
A conservation law is….
Something that stays the same before, and after an event
The standard model of matter
The standard model of matter
Leptons Hadrons Neutrinos Electrons Mesons Baryons
An event in particle physics
Anything such as a reaction of collision
Events can occur if….
Charge, Baryons, and number of Leptons are conserved
Hubble’s discovery was….
All galaxies are moving away from us, and more distant galaxies are moving away faster
Why can we conclude the universe is expanding?
Because the data we see from our galaxies, ties in with our understanding of expansion
Why is antimatter rare?
Because it quickly combines with matter and disappears to make energy
Where does evidence of the standard model come from?
Analysing tracks in particle detectors
What is explained by the exchange of bosons?
Forces of attraction and repulsion
An attractive force can come from….
Exchanging particles
H0 will be large, and the universe will be young….
If the universe has been expanding quickly (Hubble’s constant)
H0 will be small, and the universe will be old
If the universe has been expanding more slowly (Hubble’s constant)
About 13.7 billion years ago….
The universe was small and hot but space itself began to stretch and cool
Empty space has….
More energy than anything in the universe combined
Dark energy could be….
Empty space, or just a property of space
Dark energy can not be….
Detected or measured but we do see its effects
Dark energy is there….
To expand the universe, but it may cause a big rip
If dark energy exists….
We don’t know where it is or how to detect it
It’s possible that Dark energy could be….
A cosmological constant, however, when tested the results came out negatively
Empty space could be….
Virtual particles forming that are made of nothing, and then disappear. The energy from those particles could be dark energy
A Big Crunch will occur if….
Gravity takes over and the universe begins to contract rather than expand.
If energy and matter balances….
Neither a big rip or Big Crunch will occur, it will be something in between
Dark matter….
Interacts with gravity and is a gravitational force in the universe, impossible to detect
Why is dark matter not anti-matter?
Because anti-matter produces gamma rays when interacting with normal matter
Normal matter isn’t….
Strong enough to form galaxies, this is why we believe in dark matter
Why can’t dark matter be normal matter with no stars?
Because there are no particles to detect
Dark matter makes….
It possible for galaxies to exist
Why can’t dark matter be a black hole?
Dark matter can’t be a black hole because it is scattered
3 things we know about dark matter
It interacts with gravity, it exists, there’s a lot of it
Gravity is….
The force of attraction between all mass
What does gravity do?
Pulls the universe together and slows its expansion
Why must dark energy exist?
Because the universe is not slowing its rate of expansion, it’s speeding up, meaning there is an extra source of energy we don’t understand
Energy causes….
Expansion
The energy at the time of the Big Bang….
Causes the expansion of the universe
To figure out the effect of gravity….
We need to figure out the amount of matter in the universe
Dark matter will….
Slow the expansion of the universe because it contributes to the gravitational force attracting matter to itself
Bluer light is emitted by….
Higher frequency light waves
Redder light is emitted by….
Lower frequency light waves
Light from stars is not….
Just visible light but can include all parts of the electromagnetic spectrum
Why do we use the spectra of stars?
To find out what elements they are made of
The elements in the cooler, outer part of the star….
Absorb certain wavelengths of light, leaving a dark line spectrum
Depending on the temperature….
the radiation of a hot object peaks at a different wavelength - and so looks a different color.
The spectral lines are redshifted….
If the star is moving away from us
The spectral lines are blue shifted….
if the star is moving towards us
Henrietta Levitt theory….
If we know for sure how bright a star really is and we see how bright it seems to us, we can figure out far away it must be.
Cepheid variables are….
Stars whose brightness varies over time. The period of their brightness changes depends on how bright they are.
We measure the period of….
A Cepheid variable star to find out its actual brightness. We compare this with how bright it seems from Earth. From this we figure out the distance to the galaxy it is in.
Why are stellar spectra so dark?
The elements in the cooler, outer part of the star absorb certain wavelengths of light leaving a dark line spectrum
The Doppler effect….
The apparent change in the frequency of a wave, caused by relative motion between the source of the wave and the observer
What are stereographs?
Instruments built by scientists to separate light with gratings
Each element….
Absorbs light of a particular frequency and colour
Redshift
Anything you can see changes colour depending on their relative emotion to you. You can’t see the minute difference with your eyes but astronomers can use this effect to tell if stars are moving away or towards earth
Heated elements….
Give off particular colours of light due to their atomic structure
If the element is cool in the atmosphere of the star….
Those atoms will absorb the light at that colour and produce the line
Stars behave like….
Black bodies, this is why there are different colours of stars
Why don’t we see green stars?
Because stars with peak wavelengths in green, also emit a lot of radiation in the red blue part of the spectrum
Depending on temperature….
The radiation of a hot object peaks at a different wavelength, looking like a different colour
All objects emit electromagnetic radiation….
According to their temperature
Cooler objects emit waves with….
Lower frequencies (radio/microwaves)
Hot objects emit waves at….
A higher frequency (visible/ultraviolet)
Cooler objects like humans and plants….
Emit most radiation in the infrared part of the spectrum
A blackbody is….
An idealised object that absorbs all electromagnetic radiation it comes in contact with
Black bodies emit thermal radiation….
In a continuous spectrum according to their temperature
Blackbody radiation describes….
The relationship between the temperature of an object and the wavelengths of the electromagnetic radiation it emits
