Questions tagged [cosmology]

Questions about the origin, history, evolution and fate of the Universe.

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5
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3answers
477 views

How did the Milky Way and Andromeda Galaxy separate before they began their collision course?

How did the Milky Way and Andromeda Galaxy separate before they began their collision course? I understand that gravity is pulling together the two galaxies, but what separated them in the first ...
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1answer
467 views

Is there anything like a supermassive white hole? How are they formed? And where are they present?

The idea of a 'super massive white hole' is sometimes discussed regarding GR,SR and the destination of material 'lost' in a black hole. Is there any good theoretical or observational evidence for ...
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0answers
54 views

How many times has the sun orbited the galaxy? [duplicate]

Even if our solar system is not in a stable orbit around the center of the galaxy (is it?), since the birth of our sun, how far has it traveled relative to the center of the galaxy?
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1answer
170 views

How can we use hypervelocity stars to determine the origins of the Universe?

I was reading this article finding evidence of Universe's origin, which describes that in 1 trillion years we may lose the ability to determine how the universe was created. The answer seems to be ...
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7answers
5k views

The laws of physics through out the universe

How do we know laws of physics are the same throughout the universe? Intuitively I would say they would vary in two natural ways: the constants in the equations may vary or the math in the equations ...
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1answer
71 views

Can we observe the Milky Way on the edge of the universe? [closed]

If you traveled outward and outward in a straight line, indefinitely and pugnaciously, you would never arrive at an outer boundary. Instead, you would come back to where you began. Hence, in the same ...
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2answers
2k views

Which are the most energetic events in the Universe?

That's the question. I know about gamma ray bursts, is there anything more energetic?
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2answers
4k views

Which came first: Galaxies <=> Stars <=> Planets?

If a galaxy is defined as a collection of planetary systems (and all matter in between), and a planetary system is defined as a collection of planets circling a star (and all matter in between), and a ...
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1answer
48 views

Does Big Bang red shift affect the frequency of both light waves and individual photons?

With regard to the wave/particle duality of light, does Big Bang red shift affect both the frequency of light waves, and, the frequency of individual photons? I assume that the e=hf formula relates to ...
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2answers
3k views

Why is there a supermassive black hole at the center of every galaxy?

According to https://en.wikipedia.org/wiki/Sphere_of_influence_(black_hole) the gravitational sphere of influence of a supermassive black hole is really limited compared to the size of its hosting ...
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1answer
416 views

Future redshifting and effect on the 'pitch' of CMB radiation

After discovering this question exploring the sound of a blackbody, I started wondering about the sound of the Cosmic Microwave Background radiation from the Big Bang, specifically what the current ...
2
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1answer
189 views

What may be the period and speed of revolution of the star that is closes to galactic centre?

The Sun moves at the speed of 220km/s around the galactic center in a circular orbit. The sun is located at about 30,000 light years from the galactic center. The Sun orbits around the center of the ...
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2answers
684 views

Boötes Void numbers, 2016

As a general science (hence Wikipedia!) reader, the latest information I have is that 60 galaxies "have been found and counted" inside the Boötes void, this of 1997. (1) What is the latest count of ...
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1answer
74 views

A good place to start? [duplicate]

I am a high school student (going into 11th grade next year), who will be taking an introduction to astronomy and astrophysics as part of my core curriculum. As such, I would like to get a head start ...
0
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1answer
162 views

Seeing a galaxy (quasar) greater than 46.6 billion light years away

Assuming the Big Bang was 13.8 Billion Years ago: Is it possible to observe a Galaxy's redshift showing distances slightly greater than that, like 48 Billion Light Years away? I understand that in a ...
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1answer
1k views

Three-torus model of the universe

I want to ask a question about the Three-torus model of the universe, as described in wikipedia: https://en.wikipedia.org/wiki/Three-torus_model_of_the_universe "is a proposed model describing the ...
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2answers
198 views

How is it possible that the CMB approaches the earth from all directions?

I presume that the photons from the CMB approach the earth from all directions, otherwise we couldn't detect them with a picture where it is present everywhere in the universe with a tiny anisotropy. ...
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1answer
146 views

How do we know that there is no border at the end of “infinite” space? [duplicate]

It has been suggested that space and beyond is infinite, but admittedly the same hypothesis was made by virtue of the fact that it is physically impossible to prove otherwise. How do we know that ...
4
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1answer
234 views

How can cosmic inflation make an infinite universe homogeneous?

As it is explained in this video, one of cosmic inflation's observable effects is the homogeneity of our universe. Inflation allows two points on the different sides of the observable universe to be ...
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1answer
263 views

Is the Drake equation based on a logical fallacy? [closed]

I often wonder why the Drake equation gets taken so seriously and why popular scientists in general say "it's probable' life exists elsewhere in the cosmos. My problem is that the mechanism for ...
1
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1answer
66 views

Light that travels eternally because of inflation?

What happens with electromagentic waves that are emitted into intergalactic space, but reach not any object because of inflation? Lets assume that photon A and photon B are emitted. Photon B hits ...
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1answer
2k views

What are the 10 most abundant elements in the universe by number of atomic nuclei?

I've seen websites that show the ratios of the 10 most common elements but they compare them by relative mass. I think it's more interesting to know the relative abundances of atomic nuclei because ...
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1answer
237 views

How could we tell if the Universe is infinite? [duplicate]

I've heard from a number of people that the Universe is infinite, and from my perspective, I can't see how this can actually be known, especially given that the Universe started out a finite size and ...
2
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1answer
486 views

Physical laws in other universes

In the theory of multi-verses, we can imagine countless other universes where the constants of nature, including the amount of dark energy in a volume of space and possibly even shapes of hidden ...
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3answers
442 views

Distinction between metric expansion and objects just moving apart from each other?

I see explanations likes this: Galaxies and other sources, then, are not strictly expanding away from each other but rather are attached to the fixed grid on the expanding fabric of spacetime. Thus, ...
4
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1answer
144 views

How are the element abundances calculated for a meteorite in the Hydrogen log10 scale?

In astronomy, solar abundances are often calculated or tabulated per $10^{12}$ H atoms. I understand that in case of the Sun this can be done because H atoms are in majority or are present for a scale ...
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2answers
184 views

Is parallel universe possible [duplicate]

Does parallel universe really exists or just science fiction which ain't possible? Can we ever know?
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3answers
2k views

Existence of gravitons?

For a lot of my uninformed life, I have doubted the existence of gravitons or even that gravity is an actual "force" (like electromagnetism). This is because my vision of general relativity was that ...
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2answers
104 views

Large hadron collider [closed]

Whether the collision of particle will lead to a massive WORMHOLE or if BLACKHOLE is also possible? How much I know is that it's created for einstien's E=mc^2 ,conservation of energy from mass and ...
2
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1answer
533 views

How can a naked singularity be possible?

How can we have a singularity, without a black hole around it? How would one form? What does it do?
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1answer
109 views

What accounts into calculating the Hubble constant?

From my understanding, the Hubble constant $H_0$ calculates from observed redshifts $z$ of distant galaxys against their proper distance $D$. The current value appears to be 67.80(77) $\frac{km}{s}Mpc^...
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3answers
1k views

On the cosmological principle

Just more of a conceptual question on the mutual inclusivity of the cosmological principle. That is to say, I was wondering if it were possible to have a Universe that were isotropic but NOT ...
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2answers
257 views

At what rate are stars accelerating?

How fast stars accelerating away from a central point? Are they increasing in acceleration or decreasing? If possible could you please provide a plot of the acceleration of stars away from the central ...
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2answers
940 views

Are objects in the universe moving away from each other at the same acceleration?

This is a follow up question to Does the universe expand at the same rate everywhere in the universe?. If the universe is expanding, then it would seem necessary for each object (ie galaxy) to be ...
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1answer
450 views

could dark energy be a force coming from the hyperspace outside the universe?

It seems to me that the expansion of the universe is only being looked at one way. a repelling force, basically being the opposite of gravity. After pondering this for many nights, I began to wonder ...
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2answers
196 views

How to disentangle a very distant star's relative velocity vs. redshift distance

We measure a star's relative velocity towards or away from us via its Doppler-shifted spectrum. This is also how we measure the distance of very distant stars: measuring the shifts in the spectrum ...
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1answer
173 views

Is there any other theory, apart from the Big Bang paradigm, which describes the birth of universe? [closed]

The Big Bang theory is the approved theory of the "birth" of Universe. Are there any other theories which can explain how our Universe came into existence?
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1answer
109 views

The largest discrepancy in the history of science

I watched a cosmology lecture given by Leonard Susskind that convinced me to put my money on dark energy being a pressure caused by energy that is evenly distributed throughout the "vacuum" of space. ...
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2answers
99 views

Is the Astronomy community still concerned about the lumpyness of matter distribution in the universe?

A decade or so ago, when I was still a science undergrad, one of the open questions in astrophysics was to explain the uneven distribution of galaxies in the observable universe. That is, why did the ...
2
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1answer
161 views

Are galaxies moving away with constant acceleration?

Suppose that we could measure the current acceleration with respect to us of a distant galaxy chosen at random in our observable universe (Ignore the peculiar motion of the galaxy). Is the ...
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0answers
54 views

Why is the E-mode polarization spectrum out of phase with the Temperature spectrum?

The E-mode polarization power spectrum of the Cosmic Microwave Background displays the same acoustic peaks that can be seen in the (more famed) temperature power spectrum. However, they are out of ...
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1answer
578 views

Hubble law, cosmological redshift and distance

I have got confused with some cosmology formulas which calculate distance. The most famous formula is indeed the Hubble law which says (nowadays) velocity is proportional to Hubble's parameter at ...
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3answers
2k views

What does Stephen Hawking mean by 'an infinite universe'?

In the recent $100m search for extra terrestrial life project project, Stephen Hawking is quoted in the following way: "We believe that life arose spontaneously on Earth," Hawking said at Monday's ...
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1answer
165 views

How to find the distance between two quasars

I want to calculate the distance between two quasars of which I know the angular position and the red shift. Let $Q_1=(\alpha_1,\delta_1, z_1)$ and $Q_2=(\alpha 2,\delta 2, z_2)$ and suppose $z_2 > ...
4
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0answers
45 views

Why didn't we have inflation when the theory of everything and GUTS broke symmetry? [closed]

Inflation seems to have occurred when the symmetry breaking of the electroweak occurred. But do we know of any reason why we did not have inflation when gravity separated from the other forces or ...
8
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2answers
381 views

Is the diameter of the observable universe a relative quantity?

The diameter of my observable universe is 90 billion ly measured in proper distance. But isn't lenght a relative quantity in the theory of Relativity? Could an observer moving at a different velocity ...
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1answer
67 views

Does the universe prefer a velocity?

As I understand it, the distribution of matter is roughly homogeneous across space -- anywhere I stand in the universe, there will about the same amount of matter in every direction around me. Is the ...
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0answers
62 views

Available data on the Milky way around 1920

In a book by Alexander Moszkowski, there is an Einstein quote about a hypothetical size of the universe (100 million Light years). Moszkowski claims that Einstein had deduced that from the ...
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4answers
632 views

Is the Universe really expanding at an increasing rate?

Here's what I just read from Wikipedia's page on the Hubble Space Telescope: While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. ...
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1answer
523 views

Will Hubble's law always be accurate?

We have Hubble's law: $$v=Hd$$ where H is the Hubble parameter, which is decreasing in value, but it will be constant in the distant future. So, assuming the Standard Model of Cosmology holds true, ...

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