Tagged Questions
1
vote
2answers
43 views
Spread and direction of the cosmic background radiation
Something I can never understand is that where the cosmic background radiation spreads?
If I know well, the cosmic background radiation is actually the light of the Big Bang. If it happened exactly ...
0
votes
1answer
86 views
Is the underlying pattern of all dynamical physical processes in the universe actually chaotic? [closed]
After studying and pursuing research interests in chaos theory since the mid-1980s, I have to question whether standard physics (including all physical theories we currently use at all scales of size ...
5
votes
2answers
72 views
How do interstellar hydrogen atoms form stars?
I would like to learn the basics about how interstellar matter contracts into stars under the influence of gravity.
Some of my questions:
Let's assume an ideal and infinite large cloud of equally ...
0
votes
0answers
91 views
Theoretical early-universe cosmology [closed]
I wanted to know what are the cutting edge/recent papers to read w.r.t theoretical early universe cosmology.
I would like to know of recent review papers
I would like to know of areas which use ...
5
votes
2answers
424 views
How was the Oh-My-God particle observed?
How exactly was the Oh-My-God particle (ultra-high energy cosmic ray) observed and its energy measured?
5
votes
5answers
239 views
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 you ...
1
vote
1answer
63 views
Böotes Void and Dark Galxies
Wouldn't it be possible that Böotes Void, a space we generally consider to be "empty" be filled with a number of undetectable dark galaxies?
0
votes
2answers
69 views
A thought about Quasars
If Quasars are "beams" of energy exiting a super-massive black hole, in order for them to get through the black-hole's event horizon, they'd have to be traveling faster than the speed of light. My ...
3
votes
1answer
94 views
What would happen in the final days of the universe?
I would like to know the stages of how the universe would end and what would happen and what the possible scenarios are.
I understand that eventually all the stars would burn out and that would ...
3
votes
1answer
144 views
Why are black hole singularities stable?
The Friedmann equations says that huge matter densities lead to huge expansion rates. In Newtonian gravity, two massive point particles separated by an infinitesimal distance will experience an ...
0
votes
0answers
56 views
Space-time & solar mass
Does the space-time curvature described by Einstein have any affect on the accuracy of our determination in the age of a star or globular cluster? How does this affect our interpretion of how old we ...
1
vote
0answers
57 views
Thermal gravitational radiation and its detection
To my poor knowledge on the topic, the gravitational waves that are most likely to be detected by LIGO or other experiments do not have thermal spectrum. But I'm not certain.
I know that Hawking's ...
3
votes
2answers
1k views
Size of universe after inflation?
Wikipedia states the period of inflation was from $10^{-36}$sec to around $10^{-33}$sec or $10^{-32}$sec after Big Bang, but it doesn't say what the size of the universe was when inflation ended. ...
10
votes
2answers
352 views
Can $10^{23}$ stars be treated with methods of statistical mechanics?
Statistical mechanics is used to describe systems with large number of particles ~$10^{23}$.
The observable universe contains between $10^{22}$ to $10^{24}$ stars. Can we treat those many stars as a ...
3
votes
0answers
49 views
squeezed radiation astronomy
Squeezed electromagnetic vacuum does have a renormalized energy density smaller than the vacuum. So it makes it in my opinion a inconspicuous candidate for a dark energy carrier.
Are there ...
0
votes
1answer
70 views
Regarding binary systems
Are binary systems (in case of stars and other celestial bodies) more favorable than independent existence? I've been going through an article regarding pulsars, where it was stated that 'many pulsars ...
1
vote
2answers
44 views
Locating a Comet, how is it done?
How are the comet-hunters able to precisely locate/know about the required comets ? How can they distinguish between comets from such a far distance ? How are they able to estimate the exact time ...
2
votes
2answers
293 views
Parabolic or Hyperbolic?
How can astronomers find the difference between a parabolic and a hyperbolic comet ? What are the criteria that helps them distinguish these ? Can a parabolic comet switch over to become a hyperbolic ...
0
votes
0answers
22 views
Expansion of Universe [duplicate]
Possible Duplicate:
Why space expansion affects matter?
If the Expansion is prevalent, i.e. it is observable and true then shouldn't that result in the expansion of the Milky Way galaxy, ...
0
votes
1answer
131 views
Proportion of energy compared to mass in universe
In Wikipedia (http://en.wikipedia.org/wiki/Dark_matter), there is a picture that shows us the proportion of matter and energy in the current universe - CMB.
It seems to suggest there is nothing that ...
2
votes
2answers
238 views
Shouldn't stars disappear from our view due to expansion?
The currently accepted theory of the expansion of the universe would suggest that for any point in the universe, there is a 'boundary' (somewhat like the Schwarzschild radius) beyond which it cannot ...
1
vote
0answers
67 views
Cosmic radiation cutoff at LOW energies?
The energy spectrum of the cosmic radiation (not CMB) is limited to both sides.
I know about the GZK-cutoff at high energies. Basically the interaction probability for photons of energies above 10^20 ...
4
votes
0answers
37 views
Status of large-scale structure formation within cosmology today
Since the CMB results of the past decade, would it be fair to say that the consensus among cosmologists is that cosmic strings are no longer considered as a (major) source for density perturbations?
...
2
votes
2answers
167 views
Can the implications of dark energy be used to bridge the gap between Quantum Mechanics and General Relativity?
Can the findings of the Physics Nobel Laureates of 2011, namely the overpowering existence of dark energy (vacuum energy) have any implications in the quest the combine Quantum Mechanics and General ...
3
votes
3answers
215 views
How scientists estimated that our universe is 4% normal matter, 21% dark matter, and 75% dark energy?
Is there a simple way to understand how scientists estimated/calculated the following percentages?
12
votes
9answers
171 views
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 thought ...
1
vote
0answers
83 views
What is the meaning of colors in deep space pictures? [closed]
Are the telescopes really capturing these colors in deep space or are they just "artist's impression". What could make such vast space "red" or "green"?
2
votes
3answers
238 views
Why every galaxy is moving away from every other galaxy on astronomical scale? because of an explosion or because of creation of space?
Why galaxies move away from each other in general on the astronomical scale?
Which answer is correct of the following?
It is because of the big bang theory, everything is just moving away from ...
3
votes
1answer
24 views
What happens when astronomical bodies made up of Dark Matter collapse or collide?
Does dark matter not produce heat or radiation after a collision etc?
Or, we detect radiations having no generators?
4
votes
4answers
93 views
Is dark matter around the Milky Way spread in a spiral shape (or, in a different shape)?
Dark matter doesn't interact with electromagnetic radiation, but it, at least, participates in gravitational interactions as known from the discovery of dark matter. But does dark matter exist in a ...
1
vote
3answers
263 views
What was so surprising about accelerating cosmological expansion?
The 2011 Nobel Prize in Physics, as far as I understand, concerns the expanding universe -- galaxies moving away from each other at ever increasing speed (that's what I think I read in newspapers). ...
5
votes
1answer
127 views
How did enough material from other dying stars accumulate to start our sun and planets?
How far apart do scientists estimate was/were the dying star(s) that supplied the elements that comprise our sun, planet, and us? With stars so far apart and expansion of space (as I understand it) ...
3
votes
6answers
199 views
Are there free data available online from cosmology (or astrophysics) experiments that anyone can analyse?
One can understand a subject better in physics by trying to solve as many problems as one can from a textbook say. When it comes to experimental physics and data analysis, no book on experimental ...
8
votes
5answers
3k views
Stephen Hawking says universe can create itself from nothing, but how exactly?
Stephen Hawking says in his latest book The Grand Design that,
Because there is a law such as gravity, the universe can and will create itself from nothing.
Is it not circular logic? I mean, how ...
6
votes
1answer
14 views
Temperature of WIMPs
As a dark matter candidate, what should be the temperature and kinetic energy (or also the speed) of the WIMPs (weakly interacting massive particles) to agree with the observed distribution of dark ...
4
votes
1answer
29 views
Why do astronomers say that there is not enough matter in Universe?
I was reading today about the birth of the Universe and the conjectures about the matter that was supposed to exist at the moment of the Big Bang and what can be measured now.
There seems to be some ...
7
votes
3answers
74 views
What's dark matter and who discovered it?
I have heard about dark matter that's called the Master Of The Universe. What's this and is the dark matter the reason galaxies exist?
1
vote
1answer
440 views
Has Cosmological Natural Selection been disproved?
I've been reading Lee Smolin's Life of the Cosmos.
Great book and it makes a lot of sense that the conditions in black holes are the same as conditions at the big bang.
Question is, has his theory ...
24
votes
3answers
856 views
The Pioneer anomaly finally explained?
Pioneer 10 & 11 are robotic space probes launched by the NASA in the early 1970's. After leaving our solar system, an unusual deceleration of both spacecrafts has been measured to be approximately ...
2
votes
1answer
190 views
0
votes
2answers
135 views
Star trace in the sky
If the space of universe is expanding at fast rates..(even faster than light)
Why we do not see the trace of the stars?
A possible answer could be that the stars are only moving away but mantaining ...
3
votes
5answers
1k views
How do we know that earth moves around sun and that too in elliptical orbit
I know the basics of solar system like how earth moves around sun, and that we have so many planets, elliptical orbit of earth, and how far is sun from earth etc etc. I want to take a step back and ...
-2
votes
1answer
418 views
History of Man Acquired knowledge of solar system [closed]
I know the basics of solar system like how earth moves around sun, and that we have so many planets, elliptical orbit of earth, and how far is sun from earth etc etc. I want to take a step back and ...
1
vote
4answers
246 views
Cosmic background radiation
Where/what is emitting cosmic background radiation, and when did it come into existance, was immediately after the big bang?
I know that the universe isn't 3D in the traditional sense, and I don't ...
2
votes
1answer
184 views
If Fine Structure Constant in not uniform in space what would that imply for cosmic background?
Recently J.Webb submitted paper which has extraordinary claim - that Fine Structure Constant is different in different directions in space! He (with others) measured $\alpha$ using quasar spectrum ...
13
votes
6answers
845 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 ...
10
votes
1answer
309 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?
