9 Answered Questions for the topic Cosmology


How is distance measured to far away stars and galaxies?

What I need is an accurate description of the methods used to determine the distance to Andromeda. The Parallax method is for nearby objects as I presume. The red shift method applies, but how do... more
Cosmology Astronomy


How is Doppler redshift of distant galaxies established?

Doppler redshift of distant galaxies gave first hint that the universe is expanding. I am curious to know how this redshift is actually measured and interpreted from observation. Suppose I observe... more


How would we see a near-lightspeed object emitting light?

Consider an object travelling near the speed of light relative to us (let it be a spaceship or a star), which is emitting light (consider it monochromatic resulting from a two level electronic... more


In astronomy what phenomena have theory predicted before observations?

As far as I know, astronomy is generally an observational science. We see something and then try to explain why it is happening. The one exception that I know of is black holes: first it was... more

What is the purpose of the universe?

There are two extremes known as **creationism** vs **evolutionism**. Let's consider creationism for a moment, and imagine that God exists, and he/she has created us. The question that obsesses my... more

What is the most compelling evidence of General Relativity in the presence of matter and energy?

The most oft-cited [triumphs](http://en.wikipedia.org/wiki/Tests_of_general_relativity) of GR are things such as the shifting perihelion of Mercury, gravitational redshift experiments, and... more

What are the different ways to measure the spatial curvature of the universe?

Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
Cosmology Math Physics Maths


Deuterium synthesis baryon to photon ratio

The synthesis of heavier elements started with the formation of deuterium (n+p -> D+γ). Deuterium has a binding energy BD = 2.22MeV, so we might expect that deuterium forms when kT ~ BD, since a... more

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