expansion of the universe lecture 6 Flashcards
what does special relativity imply?
that the laws of physics are invariant in all inertial frames
what is minkowski spacetime?
spacetime of special relativity - adds time as the 4th dimension to 3D space
general relativity?
prefers no particular state of motion - einstein said it could be extended to gravitational fields
what is curved spacetime?
Minkowski spacetime is distorted and curved - einsteins geometric description of gravity
What does Einstein’s field equations describe?
How matter influences the geometry of spacetime
why did Einstein introduce the cosmological constant?
At the time, it was assumed that the universe was static and had uniformly distributed matter, therefore would form a finite and 3D hypersphere - he couldn’t get consistent results from his field equations as gravity would cause an initially static universe to contract on itself
what is the FLRW model?
an exact solution to Einstein’s field equation of general relativity - describes an isotonic, homogenous, expanding universe. Assumes the spatial distance is time dependent which is denoted by the scale factor and has zero curvature
What does homogenous mean?
that the average amount of material between 2 points is the same
what does isotropic mean?
see the same in all directions
what is Slipher discover?
The redshift of galaxies - made spectographic studies and noted that the galaxies had high dopler shifts
How did Hubble know that the universe was expanding?
He used cepheid variables to measure distances of galaxies and found a linear relationship between the distances of galaxies and their redshifts
After Hubble discovered that the universe is expanding what did it mean for the scale factor?
The scale factor increases with time - neither space nor objects in space move, only the scale factor changes
What did Lemaitre suggest?
that the universe is expanding and that the further away a galaxy is the more space has expanded since light has left that galaxy
