Week 4 - the rate of rotation of galaxies. Another major piece of evidence is the fact the inner and outer parts of galaxies appear to rotate at the same rate. This does not make sense, on the basis of calculations of the gravitational force from the stars and dust clouds that are visible in galaxies. Use your understanding of circular motion to show how angular velocity of a star, around the centre of a galaxy, should depend on the distance from the centre of the galaxy. (Assume that the mass of the galaxy acts as if concentrated at the centre). Post your conclusions, together with comments on what distribution of matter would explain observations.
from BBC - GCSE bitesize I found that due to the stars that we see changing colour the frequency of the light radiation the stars are moving further away due to the indication of change in light. meanwhile I think the reliability of the source is very strong as it was written by a source which is used to educate students. meanwhile it was published in 2011 and therefore is quite a recent and new source of energy. however this could also mean It can be a weak source as there may be little knowledge as we haven't had much time to look further into this evidence.
ReplyDeleteOverall I think the source is very reliable in telling evidence about the expansion of the universe because of why and when it was written.
There is data available that appears to support the idea of an accelerating universe, such as information on the cosmic microwave background - the aftermath of the Big Bang - from the Planck satellite. However, Professor Subir Sarkar said: 'All of these tests are indirect, carried out in the framework of an assumed model, and the cosmic microwave background is not directly affected by dark energy.
ReplyDeleteHe added,
'So it is quite possible that we are being misled and that the apparent manifestation of dark energy is a consequence of analysing the data in an oversimplified theoretical model - one that was in fact constructed in the 1930s, long before there was any real data.
I think this source is reliable as it includes information from a highly educated individual, whom has studied extensively in this topic area.
There are theories that show an increase in the rate of expansion of the universe and these include ideas such as Red-Shift and the Doppler effect. These can be viewed normally on earth and have solid evidence to back and support them and so they are quite strong theories that that show an increase in the rate of expansion of the universe.
ReplyDeleteIn the 1990s, scientists thought that the universe's expansion was slowing down, but after studying supernovae and Hubble's noticing the red shift, they realised the universe's expansion is actually accelerating. Hubble noticed this whilst observing other galaxies, and saw that light coming from them shifted to the red end of the spectrum (Doppler effect), so they must be moving away from us. This evidence is reliable because is something that scientists can clearly observe from Earth and is something that after many observations, scientists could see it is true.
ReplyDeleteSome evidence for the increase in rate of expansion of the universe is Hubble's discovery that the increasing distance of galaxies correlate with increasing red shifts of the galaxies (meaning the galaxies are moving away from us).One interpretation is that the photons are believed to be being stretched by the expansion of space itself. This theory is strong as this can be observed and lots of galaxies and the interpretation of the observation is the only one that fully explains what is being observed.
ReplyDelete