Topic 13-Measuring The Universe And The Big Bang Flashcards
Why are there black lines in the spectrum?
The spectra of all the stars contain black lines, where wavelengths have been removed from the continuous spectrum by elements that make up the star -this is called an absorption spectrum. By comparing these absorption spectra to the spectra of different elements here on earth, astronomers can tell which elements are present in the star.
What is Hubble’s law?
The speed of recession is proportional to the distance of the galaxy away from the earth
What was Hubble also the first person to do?
Hubble was the forts person to use stellar spectroscopy to measure the speed of galaxies away for the earth using redshift. The absorption spectra of many stars appeared to be displaced of shifted to slightly longer wavelengths due to the stars in the galaxies moving away from the earth.
What is the Big Bang theory?
The theory states that about 13.7 billion years ago all the matter in the Universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion, and it is still expanding today.
What is CMBR (cosmic microwave background radiation)?
As the Universe expanded, stretching the fabric of space, so the wavelength of the gamma rays was stretched as well - the cosmological redshift. Over 13.75 billion years of expansion the wavelength has been stretched so much that the background remnant of these gamma rays are now have the wavelength of microwaves - the Cosmic Microwave Background Radiation (CMBR), discovered by accident direction they pointed their microwave telescope they always picked up the same background signal. They quickly realised that these signals were the remnant of the gamma rays produced at the moment of the Big Bang, cosmologically redshifted to microwave wavelength.
What does cosmological redshift tell us ?
Cosmological redshift shows us that the rate of expansion is increasing; that is the expansion of the Universe is ‘accelerating’.
