The study of the large-scale structure, history, and future of the universe. Cosmology is about asking and answering questions about the "big picture" - the extent, origin, and fate of everything we know.

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18
votes
6answers
1k views

Why isn't dark matter just matter?

There's more gravitational force in our galaxy (and others) than can be explained by counting stars. So why not lots of dark planetery systems (ie without stars) ? Why must we assume some undiscovered ...
-5
votes
1answer
329 views

Why is there something rather than nothing? [closed]

Why is there something rather than nothing? And before you answer "God did it," consider Carl Sagan's reply "then how did God come about?"
2
votes
1answer
352 views

Possibly naive question about quantized space-time

I beg your pardon in advance if this question is naive. In Quantum Mechanics, discrete values of measurements occur only in relation to bound states. This is because of the general solution for the ...
9
votes
10answers
2k views

What is the most efficient way to destroy the universe? [closed]

Don't worry... I won't actually do it, just would like to know how.
10
votes
1answer
346 views

How many atoms per light year does light encounter when traversing interstellar space?

Interstellar space is pretty empty but there a small number of of atoms (mostly hydrogen?) floating around. How many atoms per light year would a photon encounter while traversing interstellar space?
7
votes
4answers
688 views

Nature of decoupling of matter and radiation

I have a question about cosmology. At popular level people explain the time of decoupling of matter and radiation as the moment when temperature falls enough for nuclei and electrons to recombine into ...
6
votes
3answers
398 views

What current alternatives are there to the standard concordance model of cosmology?

The current "standard model" or concordance model of cosmology is Lambda CDM which includes late time acceleration due to a cosmological constant, cold dark matter as the missing matter component and ...