Cosmoslogy Flashcards
How does galaxies being red shifted support the big bang?
Big Bang predicts all galaxies will be receding etc
Red shift is caused due to Doppler effect by relative motion due to galaxy and earth. As the wavlength has increased it means it’s moving away from us
- this supports idea that galaxy is receding away from earth, and that the universe is expanding, which is what the big bang states
Explain CMBR as evidence but properly
Wait what is acc dark energy for
Studies showed that not only is the expansion of the universe accelerating, but the RATE OF EXPANSION is accelrwtion too
This can only be explained if propelled by some energy. Dark energy is something used to explain the accelerating rate of expansion of the universe
If the rate of expansion is accelerating , then why does HUBBLES law break down for large distances
The rate of expansion is not constant, explained by dark energy, and so the further down the galaxies have expanded so much such thst for their distance their velocity is too much for HUBBLES law to be true
Remember if the questions says explain why something decreases?
Must say because of relationship etc , can’t just stats why , else it would be state question
Remember how to find min wavelength of x ray
Assume all the energy from an accelerated electron is transfered to an x ray (in reality about 1%)
And go from there
Don’t lack, why can’t Hubble law be used for stars in own galaxy?
Only appplies to galaxies not stars and planets within own galaxy
Remember that it’s not because star coming towards us, only applies to GALAXIES DONT LACK
Also when comparing powers always, and when you see total power especially, what to do
Don’t lack, use LUMNIOSITY Z EQUATUIN
Don’t use I = p/A , because using the surface area it doesn’t make any sense dont be bot
How to draw the gradient for HUBBLES qiestison
Must take it through gradient
How to find the distance if don’t know HUBBLES constsnt
Have to pick any set of values and find the Hubble first, then use that to find distance lager
Readdd the question, if it says distance from EARTH, and talking about angles, what to do
Draw a trig diagram
The distance away DOESNT NECESSARILY mean the centre or whatever, it just means close to it.
So for this question, we place the absolute bottom of the galaxy away from the earth.
- it says angle at the earth, meaning has to be theta at the earth
In general if it was stars close to the earth, we can use parallax
- as it’d galaxies and really FAR away we have to do normal trig
Don’t lack, remember subtended at earth = angle there, distance from earth means distance AWAY from earth (not sun) , and that the placement of the galaxy can be anywhere such that it’s still that far away
Remember to that galaxy has t9be vertical in order for there to be an angle in the first place
How to use table of data to explain Big Bang etc
Show that they back an expanding universe, as galaxies are receding and FASTER AWAY GALAXIES are receding faster, meaning it’s accelerating in expansion
Show how HUBBLES law proves Big Bang as it shows universe expanding
- and then calculate HUBBLES law a few times
- can also then find age of universe if want
How ti make emissions liens more spaced out in diffraction growing
2 ways IMPORTSNT
Means increasing theta
Either do this using arc tan o / A, to increase this answer need to make o/A big as possible, thus reduce A, as we can’t change o, therefore increase distance between slitd and screen
Or it’s agsin / ( N lambda / d ). To increase this we need to lower d, thus to lower d say use a grating with more slits per mm !
Don’t lack, if it says how is an emission lime ( it spectrum ) made what to say
De excitation of an electron from high to low energy level emits a photom
