Exam 1 Flashcards
Cosmic Address
Earth, solar system, Milky Way, local group, supercluster, universe
Scientific Method
Is a way to falsify, not prove, ideas; thus all scientific knowledge is provisional. Observation idea - hypothesis - prediction - further observation/ test the prediction - tested theory
Theory
All theories have enough supporting evidence behind them that we can move forward under the assumption that they are correct unless a test proves otherwise.
law
A set of observations that can make predictions without explaining why. Give predicted value. What is going to happen but can’t tell why
hypothesis
Testable (predictive) explanation of the observation on its way to becoming a theory.
Occam’s Razor
Simple is better fewer assumptions
- Newton’s gravity vs Einstein’s gravity
- Scientific “aesthetic” values simplicity
Linear vs. Logarithmic scales
Linear- constant slop, Slope = change in y / change in x
Logarithmic (logs)- helps plot numbers with a large discrepancy between them or exponential growth (highlights detail)
Celestial Sphere
Objects that we see in the night sky and different distances. Projecting these objects onto an imaginary sphere yields the celestial sphere.
Zenith
Directly overhead
Horizon
the boundary of what we can see in the sky 90 degrees from the zenith
Celestial Poles
NCP/SCP north and south directly above Earth’s poles say fixed doesn’t change
Celestial equator
Align with longitude and latitude. Projection of Earth’s equator into space
Rotation direction of the Earth
Earth rotates counterclockwise
Axial Tilt, Equinox/Solstice why and how does this affect the seasons?
Earth’s axial tilt is 23.5 degrees
If the earth had an axial tilt of 0 degrees we would have no seasons at all 90 degrees makes seasons extreme.
Moon Phases
It is caused by the arrangement of the sun and moon relative to the Earth.
New - waxing - full - waning - new
Eclipses
When one body gets in front of the other and light is affected.
-Solar Eclipse
3 types:
total- whole disc of the sun is blocked
partial- only part of the sun is blocked
annular- only the interior of the sun is blocked, leaving a ring, the annulus.
Lunar Eclipse
the moon is in Earth’s shadow orbit and is not parallel why we don’t have as many solar eclipses.
-Line of Nodes
Intersections between the moon’s orbit and the Earth’s orbit
Eclipses only happen when a full/new moon is near the line of nodes
Geocentric vs. Heliocentric Model
Geocentric is the model that the earth is at the center. Problem with geocentric model spots on the moon, Jupiter’s moons, and phases of Venus.
Heliocentric is the sun at the center.
Newton’s Law of Gravity
-Mass vs. Weight
-Center of Mass
weight- A force between a planet’s gravity and a given mass (Fweight = MGplanet)
Orbits
-Escape Velocity, circular velocity, bound/unbound orbits
Escape velocity- velocity at which you leave the planet. Depends on both the radius and mass of the planet.
Circular Velocity- only leads to a circular orbit, distance from Earth isn’t changing.
Bound orbit- More circular velocity but less than escape velocity
Unbound orbit- escape velocity or more
Tides
The force of gravity changes over distance. The tidal force is from this difference.
Tides are caused by differences in strength in the moon’s, and the sun’s gravity over the Earth.
Tidal Bulge
Distortions where high tides are happening
Tidal Locking
Matching the rotation of an object with the rotation of its orbit- Synchronous rotation
EM Spectrum
-Wave characteristics: Period, Frequency, wavelengths
-Photons
Atomic Structure
-Spectral lines of distinct energy
-Spectra: emission,absorption
Spectra- The measure of a source’s brightness as a function of wavelength/ frequency visible solar spectrum
Brightness at yellow/green wavelengths
Presence of dark lines/features
Doppler Shift
The frequency of a wave can be altered by the emitting object’s motion
-shift in frequency/wavelength due to emitting object’s motion
-Shift depends only on radical velocity- velocity towards/away from the observer
Blackbodies and their Spectra
Temp- measurement of how fast particles are moving. Measures how much thermal energy an object has.
Thermal Equilibrium - temp balance - energy absorbed in thermal equilibrium = a blackbody spectrum
-Wien’s Law
-Stefan Boltzmann Law
Wein’s Law- wavelength shifts to be bluer. Temp gets larger and gets bluer but wavelengths get smaller.
^peak = 2.9X10^6nm k / T
Stefan Boltzmann Law- Total amount of luminosity goes up
L=T^4
Brightness Changing as a Function of Distance
Brightness is the amount of light arriving at a location.
-Depends on how far away the source is and how luminous/bright the source is
Inverse square law B=L/r^2
Telescopes
Device for collecting and focusing light and used across the EM spectrum.
-Focal length
-Focal Plane
Focal Lenth- The distance light travels within a telescope before coming to a focus. Make the picture appear bigger but may see less of the sky.
Focal Plane- Where light from a telescope forms an image retina focal plane of the eye.
-Angular Resolution
-Aperture
Angular Resolution- The ability of a telescope to separate two different objects visually
Aperture- The size of a telescope’s light collecting area. Determines how much light collecting power a telescope has the ability to see fainter objects
-Diffraction Limit
-Atmospheric Seeing
Diffraction Limit- best angular resolution achievable if the telescope were built perfectly.
Atmospheric Seeing- Temp/density variations in the atmosphere distort light. Limit on resolution due to atmosphere.
Reflecting vs. Refracting
- Most modern telescopes are reflecting
Reflecting-
- Ones that use mirrors.
- Historically difficult to figure/make well.
- Heavy primary mirror at bottom.
- No Chromatic aberration.
- Most wavelengths can be reflected efficiently.
- More compact at long focal lengths.
Refracting-
- One that uses lens
- Historically easier to figure/make well
- Heavy primary lens at the top
- Suffers from Chromatic aberration
- Not all wavelengths have a lens material
- Really long focal lengths/ long tubes
-Integration time
-QE
Integration Time- Time interval that a detector (your eye, camera) is collecting light.
QE- Quantum Efficiency- How much response for how much light recieved.
Gravitational Waves
are ripples in spacetime. When objects move, the curvature of spacetime changes and these changes move outwards (like ripples on a pond)
Computers
Needed to simulate complex models, compare to observations
Chandra: X-ray
James Webb Space Telescope (JWST): IR
Laser Interferometer Gravitational-Wave Observatory: Gravitational Waves
Perturbations of space-time curvature is detectable by way of sensitivity detectors - long baseline optical interferometers.
