Universe Flashcards
What is Hubble’s law?
“The increase in red shift is proportional to the distance away from Earth.”
Why does red shifting occur?
As the light from other galaxies travel through the expanding universe, its wavelength is stretched and thus shifted the longer red wavelengths .
What is CMBR?
Cosmic Microwave Background Radiation is the gamma rays released in the moment of the big bang that have been stretched due to the expansion of the universe into microwaves.
Who discovered the existence of CMBR?
Arno Penzias and Robert Wilson (by accident)
How do we measure the composition of a star?
Different atoms absorb different wavelengths of light and as the light from a star passes through it’s atmosphere, some wavelengths will be absorbed and will show up as black ‘absorption lines’ on a spectrum of light. By comparing where these black lines are positioned with experiments of different elements on Earth we can determines what elements are in the star.
This process is called spectroscopy.
How do we measure red shift?
By looking at the absorption lines on a spectrum from a distant star and comparing them to the absorption lines created by elements on Earth. The absorption lines from a distant galaxy will be redshifted to longer wavelengths when compared to the experiment on Earth.
Why do galaxies further away from us have longer wavelengths?
Further away galaxies are moving faster away from us due to the expanding universe so light from these galaxies have also been stretched into having longer wavelengths that are red shifted.
What is the theory of the big bang?
It states that universe started from an infinitely small point (singularity) that suddenly expanded creating the universe. It’s known that the universe is still expanding and it’s rate of expansion is accelerating.
What evidence is there to prove the big bang?
Cosmic red shift
- The atomic absorption lines from far off galaxies appeared to shift to the red end of the spectrum when compared atomic absorption lines of the same elements on Earth and the further away the galaxy, the greater the red shift. This indicates that wavelengths of these far off galaxies have been stretched over time due to the expansion of the universe. Subsequently. if the universe is expanding and moving away from us, it must have come from a single point (singularity).
CMBR
- CMBR was initially the gamma radiation emitted just after the big bang with a small wavelength however, due to the expanding universe, the wavelength of this gamma radiation, like the light from distant galaxies, have also been stretched out until it became the microwaves we detect today.
- CMBR can be detected everywhere we look which must mean it must be the light released everywhere in the universe after the big bang (when atoms first formed).
What is the speed of light?
3x10⁸ (Roughly)
What evidence is there to prove the big bang?
Cosmic Red Shift
- When comparing the absorption lines on a spectrum created by one element in a laboratory to the absorption lines created by one element from a distant galaxy we see they have been shifted to the red end of the spectrum with a longer wavelength.
- The fact the light from these far away galaxies have been redshifted suggests their wavelength has been stretched as it travelled through the expanding universe.
Cosmic Background Radiation
- This light was released just after the Big Bang as grammar radiation and has travelled through the universe to the detected as longer wavelength microwave radiation. This suggests it has been stretch in an expanding universe as it travelled
- CMBR is detected everywhere which means it must have been released from everywhere which can only be explained by the big bang.
OVERALL
- If the universe is expanding, logically, it must have originated from a singularity which would have been the big bang.
