E4.2Olber's Paradox: If Newton's model was true then this would imply that the night sky ins infinitely bright as there are an infinite number of stars in the sky.
Suppose stars are distributed in an infinite number of thin shells. If each has a Luminosity of L, related to the apparent brightness (b) and distance d, this would imply that the apparent brightness is inversely proportional to the square of the distance.
d
Heinneman HL Physics, Chris Hamper
E4.3 On observing galaxies through the Hubble telescope we have observed a red shift in a majority of their spectra which suggests that they are moving away from us, supporting the notion that the universe is not static but is expanding.
E4.4: If galaxies are moving away from each other, logically, this must mean that at some point in the past they were closer together. Extending this idea, we know that once, the entire universe must have been concentrated in a single spot called the singularity. We believe that about 13 billion years ago, the universe must have begun with an explosion called the Big Bang. Space and Time began following the Big Bang.
E4.5 4.6 4.7: Cosmic Microwave Background radiation (CMB radiation) was observed by Penzias and Wilson when they received excess noise from their radio. This is an echo of the Big Bang still echoing in the universe. Penzias and Wilson found that the intensity of the radiation that they received corresponded to that of waves in the microwave region. Substituting this in Wien's displacement law equation they found the average temperature of the universe to be 2.7 K.
The Big Bang model resolves Olber's paradox as if the galaxies are moving away from each other and are red shifted then this means that we won't be able to see them. This is why the night sky appears dark.
E4.8
Heinemann HL Physics - Chris Hamper
Open Universe: This will continue to expand. Gravity will slow it down but not stop the expansion
Closed Universe: This will eventually collapse back on itself; this is called the big crunch and the reverse of the big bang will occer.
Flat universe:This will
E4.9 Critical density is the mass per unit volume that would create a flat universe.
E4.10 If the actual density of the universe is lower than critical density then this would create an open universe, but is the actual density of the universe is higher than the critical density then this would create a closed universe
E4.11
Dark matter is matter that is not visible as it emits little or no radiation.
WIMPs are Weakly Interacting Massive Particles. These are hypothetical particles serving as one possible solution to the dark matter problem. They are held together by weak forces and gravity. As they do not interact through electromagnetic radiation it is not possible to detect them and as they do not interact with strong nuclear force, they do not create atomic nuclei. (http://en.wikipedia.org/wiki/WIMPs)
MACHOs are massive astrophysical compact halo objects. This is another hypothesis as to what dark matter is which claims that dark matter is made of the same substance as 'ordinary matter' but just happens to emit little or no radiation making them invisible. (http://news.bbc.co.uk/2/hi/8508662.stm)
It is difficult to determine the density of the universe because we cannot detect dark matter as it does not emit electromagnetic radiation; therefore we know neither its exact volume nor its mass. Knowing the density of the universe in important because this will allow us to determine the fate of the universe; whether it is open, closed or flat.
E12. Current scientific evidence suggests that we have an open universe.
E13. International projects include the study of Drake's equation which consists of a series of variables that, when multiplied together, give the probability of us finding extra terrestrial life.
Other links:
http://insciences.org/article.php?article_id=8795- Finding dark energy
http://insciences.org/article.php?article_id=6839- Black holes
E14.
Arguments for astrophysics:
- Understanding the nature of the universe and attempting to answer questions like why we are here and whether or not there is intelligent life other than us
- Develops technology which may improve the quality of life in the future
- To colonise new planets if, in the future, the earth becomes inhabitable
- To understand the fate of the universe and what our future might be
- Money could be used for economic development instead
- Money could be used to conduct more pragmatic research like medical or energy sources
- Is the information really worth the cost?
No comments:
Post a Comment