What is dark matter, and how is it affecting the universe?
In astrophysics, dark matter is matter that does not emit or reflect enough electromagnetic radiation (such as light, X-rays and so on) to be detected directly, but whose presence may be inferred from its gravitational effects on visible matter. Among the observed phenomena consistent with the existence of dark matter are the rotational speeds of galaxies and orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter also plays a central role in structure formation and Big Bang nucleosynthesis, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than is directly observable, indicating that the remainder is dark.
Does the Spectrum of the Sun have a red shift or a blue shift?
As seen from Earth, *on average throughout the year*, the solar spectrum is blueshifted. Even if the Earth was not rotating and was in a circular orbit, (so there is no doppler shift due to radial motion towards or away from the sun) there is a time dilation effect due to the motion of the Earth in its orbit tangentially to the sun. As a result, time passes slightly more slowly on Earth than at the solar photosphere so light coming from the sun will appear to have a somewhat higher frequency in the Earth's frame of reference. Consequently it will be bluer as seen from Earth. The gamma factor due to the Earth's mean orbital velocity (look up special relativity on wiki or something to see what a gamma factor is) works out to be about (1-5x10^(-9)), so on average throughout the year visible light from the sun is blueshifted about 500 MHz (peanuts compared to the 10^15 Hz frequencies of visible light!) As noted above, at any single point in time this effect is dwarfed by radial motions due to the Earth and the solar rotation, but averaged throughout the year a VERY small blueshift is what would be observed with precise instrumentation.
Which bacterium is used to turn milk to curd?
Lactobacillus is the bacteria which is used to convert milk into curd. Conversion of milk into curd is done by the process called fermentation. The bacteria eats the sugar in the milk and produces lactic acid which then turns the milk proteins to curdle and gives the milk a tangy taste.
What are three ways that we are able to detect interstellar matter?
1. Reflection of starlight 2. Absorption of starlight 3. Emission of it's own light Reflection: Interstellar matter is often found in the vicinity of young stars. The light passing through the gas and dust around these young stars is bluish. These clouds are called reflection nebulae and are detected visually. Absorbtion:The presence of matter blocks light reaching us from distant stars. This would appear visually as a dark cloud in a region of the sky. Sometimes referred to as extinction of starlight. Emission: Interstellar gas may be heated by the ultraviolet light of hot stars. This causes the gas of the clouds to visibly glow. In such a case, the ionized hydrogen molecules emit a red light. Called emission nebulae. When not heated, cold interstellar matter (composed mainly of neutral hydrogen gas) emits light at a wavelength of 21cm. Giant molecular hydrogen clouds are accompanied by carbon monoxide molecules which emit radiation at 2.6mm. These would be measurable in the electromagnetic spectrum.
Earth and sun.?
Neither. They both move around the center of gravity of the Sun-Earth System.( The Earth exerts a gravitational attraction on the Sun, just as the Sun does on Earth.)