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3answers
158 views

Can the Cosmological Constant explain an accelerated expansion?

From what I've learned so far, it appears that all models that attempt to explain the expansion of the universe are either based on Lambda-CDM or quintessence. The former support a big bang with ...
2
votes
1answer
139 views

What is the equation for the scale factor of the universe, a(t), for the best fit of data to the $\Lambda CDM$ Model of Cosmology?

Ideally I like a single formula or multiple formulas for different time ranges that would cover the time from the end of inflation through 100+ billion years after the big bang using the $\Lambda ...
1
vote
0answers
29 views

Is the Hubble parameter affected by 'peculiar velocity'?

Are there any direct observations showing the effect of peculiar velocity on the Hubble parameter. If the Hubble parameter is measured in the direction of our motion caused by our rotation in the ...
1
vote
1answer
175 views

Equation for Hubble Value as a function of time

I am trying to write the equation for the situation where the Hubble parameter $H$ would be changing over time. In other words, it would represent an accelerated expansion of the Universe. That is, ...
0
votes
0answers
23 views

Inflation of universe and Information stored therein

In an inflationary model of our universe, the space-time expands within a finite boundary. Some other models are also proposed where the universe is not explained to have been expanding rather the ...
2
votes
1answer
76 views

Will a space traveller slow down due to space expansion?

Photons of relic radiation loose their energy as they propagate through space. Will a space traveler loose their peculiar velocity as he travels through vast distances? Will he stop somewhere or still ...
-1
votes
1answer
102 views

If the universe can expand at a speed faster than that of light, why don't we feel the effect? [closed]

the universe, as I have read, is capable of inflating at a speed faster than that of light! How is that even possible if we don't feel the effect? or does it affect us?
1
vote
1answer
119 views

Metric expansion of space - past, present and future

Scientists say that out universe is expanding faster and faster. This was detected via the red-shift effect. Farther galaxies are moving from us faster than those that are more closely. But how can ...
5
votes
0answers
135 views

Does the radius of the Universe correspond to its total entropy?

I heard a claim that due to holographic principle, the surface area of the cosmic horizon corresponds to the universe's total entropy. As such the initial state had zero surface area and later ...
1
vote
2answers
146 views

Metric Expansion Of Space

I just do not understand this concept of metric expansion of space. Shouldn't the galaxies move away from each other. How can the space between them expand if the galaxies are not moving away from ...
11
votes
2answers
628 views

How is it possible the universe expanded faster than the speed of light during inflation?

In a documentary written in collaboration with Stephen Hawking, the narrator (supposedly Stephen Hawkings) says that by the time the cosmos was 10 minutes old, it had already expanded thousands of ...
2
votes
1answer
40 views

Cosmological and gravitational redshift in physics

I am interested in knowing what are the differences between gravitational and cosmological redshifts?
1
vote
2answers
46 views

Are high redshift masses corrected for relativistic mass dilation? They would appear more massive right?

A distant quasar would be less massive in its frame of reference than our observations would suggest. Are such highly red-shifted objects corrected for relativistic mass dilation?
0
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0answers
28 views

The influence of the expanding universe on the wave function

I was puzzled by a question on a physics fora about a possible connection between the expansion of the universe and the wave function. So, a photon's red shift tells us something about the expansion, ...
0
votes
2answers
166 views

Goodwins “proof” and space time

I read about Goodwin's "proof" that $\pi = 3.20$, it's BS and I know that. What I am wondering is whether his technique may have stumbled on something ( a warped space) years before Einstein. So I ...
2
votes
1answer
129 views

Cosmic event horizon

I had a question regarding cosmic event horizon. Let's say that a far away solar system has just crossed the cosmic event horizon due to the expansion of the universe. In that solar system let us ...
4
votes
5answers
595 views

Does the expansion of the universe soon after the Big Bang affect the amount of time that light takes to reach us?

If faster than light travel is impossible, how is it that light emitted from matter so close together in the time soon after the Big Bang is only now just reaching us? I would assume that there would ...
4
votes
2answers
1k views

Elasticity of Space; How does the expansion of Space affect gravity?

Does space have an elastic quality? What I was thinking about was if space is expanding, is it being 'stretched', like a balloon being blown up, and if so, is this causing gravity to weaken? Imagine ...
0
votes
3answers
226 views

Cosmological redshift interpretation

Can the cosmological redshift be interpreted as atomic frequencies increasing by the scale factor as the Universe expands? This explanation seems closer to the truth than the popular idea that a ...
2
votes
1answer
58 views

Will the Hubble constant reach zero asymptotically in the far future?

In the current accelerated expansion universe model will the Hubble constant reach zero asymptotically in the far future?
0
votes
0answers
64 views

What's the timescale until the Medium Crunch?

The future of the universe seems to be: clusters of galaxies drift apart due to space expansion until they all pass out of each other's cosmic event horizon. Gravitationally bound clusters overcome ...
1
vote
1answer
99 views

Quantum fluctuations and expanding universe

As far as I understand, Hawking radiation is formed at the edge of a black hole, when a particle/anti particle pair is formed and one of the particles falls into the black hole before the particles ...
4
votes
1answer
135 views

Does space expansion imply light will *never* reach objects currently distant enough?

Let's say two objects are at about twice the Hubble Distance from each other. One of them emits light towards the other. When light emitted from one reaches the Hubble Distance from its origin ...
2
votes
1answer
191 views

What limits range of gravitational attraction concerning space expansion?

Wikipedia says: Metric expansion is a key feature of Big Bang cosmology and is modeled mathematically with the FLRW metric. This model is valid in the present era only on large scales (roughly ...
1
vote
2answers
152 views

Variance in speed of light

While discussing this question (Does light have an unending journey?) I stumbled on the fact that light's speed is constant only in inertial frame. What I happened to do was add up the expansion of ...
2
votes
1answer
32 views

How distant is the origin of oldest space radiation reaching us?

A comment to my question straightens out a misconception. That places the furthest theoretically observable edge of universe at 13.798 bln light years away - this is how long light would take to ...
1
vote
0answers
37 views

Is the 74.2km/sec per megaparsec accidental? [duplicate]

The rate of expansion of the universe is 74.2km/sec per megaparsec The age of the universe is 13.798 bln years That places the furthest theoretically observable edge of universe at 13.798 bln light ...
0
votes
0answers
41 views

Calculate age of the Universe at 7 billion and 28 billion years old [duplicate]

If $1 / H_0 $ is about 14 billion years, then what happened when the universe was half its current age? Is the empirically determined $H_0$ supposed to have been twice its current value? And when ...
0
votes
2answers
150 views

Big Bang, What is wrong with such thinking? [closed]

Also if I think the Expanding of Universe like this: At the Start : The Amount of Matter and Anti-Matter is equal and they annihilate and all we had is Large Amount of energy. But some 'X' Thing, ...
2
votes
3answers
539 views

If everything in the universe doubled in size overnight, would it be noticeable?

By my understanding, if everything doubled in size, such as the Sun and the Earth, and because the space in between them (which is nothing) can't expand, would the gravities greatly change and the ...
0
votes
0answers
71 views

Trapping Light in a shell

I was curious about this. Is it theoretically (mathematically) possible to create a shell such that when a photon 'hits' the shell, the spacetime at the shell surface is such that the photon travels ...
4
votes
1answer
349 views

Is “A Brief History of Time” still up to date?

I have recently found my copy of Hawkings' A Brief History of Time which I have never finished. This time I'm determined to read it all the way through. However, the book is now almost 25 years old. ...
1
vote
1answer
234 views

Shear, viscosity and expansion of universe

What is the meaning of expansion, shear and viscosity in context of universe? How can we conclude a result after getting a numerical value of above terms?
0
votes
2answers
69 views

Red Shift and Light Speed

I read several questions/answers about red shift on this web site, but there is something I still don't understand. Why is red-shift considered to be the effect of expanding space-time, why it could ...
3
votes
1answer
82 views

How does pressure relate to cosmological expansion?

In my cosmology class, we've been talking about pressure in the Friedmann Equation for acceleration: $$ \frac{\ddot{a}}{a}=-\frac{4 \pi G}{3} \left(\rho+\frac{3p}{c^2} \right) $$ In particular, I've ...
4
votes
3answers
467 views

Why cosmic background radiation is not ether?

why cosmic background radiation is not ether? I mean it's everywhere and it' a radiation then we can measure Doppler effect by moving with a velocity.
1
vote
2answers
152 views

Does the black hole only increase?

I don't understand this: The more mass a Black Hole has, the more gravity it create! The more gravity it has, the more mass it can get! With this lines, someday, all the universe will be a black ...
1
vote
2answers
442 views

If the Big Bang theory suggests that the Universe is “expanding” then what is it expanding INTO? [duplicate]

I am a software engineer and not an astrophysicist but I want to know if anyone is working on sorting out what exists outside the universe? So what about outside spacetime? what is there? or shall I ...
5
votes
4answers
618 views

If the universe is expanding, what is it expanding into?

If the universe is expanding, what is it expanding into? When the big bang happened where did it occur? When the big bang happened how did it occur? Where did the energy come from? Energy can not ...
0
votes
2answers
165 views

What is the universe expanding into? [duplicate]

Due to curiosity, it made me wonder what is outside of the universe, is it a new chemical or just empty space? But empty space have protons appearing and disappearing in it, it basically still has ...
1
vote
3answers
100 views

What happened to high temperatures in the universe?

We know that after the big bang the temperature was about 10^32 K. But now the average temperature of the universe is about 4 K. What happened to the temperature at that time? Where did it go?
0
votes
2answers
85 views

The speed of light through space and its effects on black holes

I was curious about a couple of things that don't quite make sense to me: (and probably won't when I get the technical answer, but I'll ask it anywise.) When light travels through space, is its ...
1
vote
0answers
119 views

How fast is a true vacuum bubble going to expand?

If a true vacuum bubble will occur in our universe, how fast is it going to expand?
1
vote
1answer
107 views

Red shift and the expanding universe

Given that the universe is expanding because space itself is expanding, is that expansion occuring in all places and on all scales? Consider a photon emitted from a source billions of years ago. As it ...
4
votes
1answer
482 views

Additional merits to Wetterich's “Universe without expansion” compared to standard cosmological redshift interpretation?

A recent news item in Nature promotes Wetterich's preprint "A Universe without expansion". All sounds very exciting but hard to judge for non-experts. As I understand from the Nature's article, the ...
0
votes
1answer
99 views

Why does a doppler red shift prove expansion?

My question boils down to this. If the Universe was contracting the stars closer to the center would move faster to the middle than stars that were further away from the center. That would also ...
5
votes
3answers
305 views

What does string theory say about the metric expansion?

Specifically, what happens to those small intertwined hidden dimensions? Do those expand too?
0
votes
0answers
148 views

Maximum entropy Universe?

An attempt to understand the Friedmann equation describing a flat Universe using the principle of maximum entropy together with the laws of thermodynamics. This argument implies that the mass inside ...
3
votes
1answer
196 views

Fulvio Melia's linear Universe

I would be interested in what people think of Fulvio Melia's argument for a linearly expanding Universe. I realize that the experimental evidence seems to be pointing to an accelerating Universe ...
2
votes
2answers
149 views

Space expanding, or light slowing down? [duplicate]

This question seems a lot like one of those "Phylosoraptor" memes all over the Internet, and it might be very silly, but I've been thinking about this for a while. Is it possible that space is not ...