All Questions
Tagged with cosmology space-expansion
1,604
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What happens if we let time expand in the FLRW metric?
If we multiplied the time differential (dt) by a scale factor that depends on time in the FLRW metric, what would this imply on cosmology? In particular, what are its implications on the cosmological ...
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What is the change in vision and measurement between curved space and flat space, especially for measuring cosmic background radiation?
In a curved space, the light bends as it travels and acts like it is going through a lens. In a (positively) curved universe, a small object appears larger. If we know the actual size of an object, ...
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What important milestones happened in the first attosecond after the Big Bang?
I googled "the first attosecond after the Big Bang", but didn't get any relevant results. So, I am asking the question here, in hopes of being more successful. What happened during the first ...
- 1,252
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Big Bang as stretching space time?
I am still new to researching the big bang so please be patient. I am having trouble envisioning the expansion. As I understand under current theory it is not to be thought of as a singularity ...
- 101
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Expansion of the universe and superluminal speeds - an analogy
To illustrate, let's imagine the whole universe having a coordinate grid. Essentially a great big mesh grid of interlocking meter sticks.
Now... Einstein's theory of relativity tells us that nothing ...
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Cosmological constant, dynamical friction and structure formation?
I would like to ask a question about an interesting article that I found (https://repositorio.unesp.br/server/api/core/bitstreams/b8a5a5b8-4b3b-4198-9f5d-bf69431db1ae/content)
In the context of ...
- 2,462
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Value of $H$ at the emission of the CMB
According to the lambda CDM model, $H_0$ is around 67.7. If this value was calculated from a value for $H$ at the emission of the CMB, what was it, or do we have constraints on its value at that time?
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Ejected bodies, dynamical friction and dark energy?
I have a question after reading a couple of papers (https://arxiv.org/abs/1707.06220 and https://www.arxiv-vanity.com/papers/1102.0007/).
Here, the authors seem to indicate that when bodies like stars ...
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Difference between new inflation and chaotic inflation
I'm trying to understand the difference between new inflation and Linde's chaotic inflation. From what I understand, according to the old inflation, during inflation empty space remains empty, so its ...
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How big was the surface of the cosmic background radiation?
The cosmic microwave background radiation is the furthest and oldest visible light in the universe. But the universe has expanded considerably since that light was emitted. At the time that that light ...
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Are the mass, diameter and age of the Universe frame dependent?
Mass of the observable Universe is known to be $1.50×10^{53}$ kg. Age is approximately known to be 13.7 billion years.The observable Universe is a sphere with diameter of roughly $8.8\times10^{26}$ m.
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Does inflation theory assume a finite universe?
Inflation theory has it that the early universe was causally connected, and could “mix”, hence explaining relative homogeneity of the CMB. The universe then rapidly expanded and became causally ...
- 139
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Can a receding body due to the accelerated spacetime expansion be "rescued"?
Once a body "crosses" the limit where dark energy wins over gravitational forces (Is there a distance from a gravitational source where the influence of gravity and dark energy are balanced ...
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Is Dark Energy Taking Over?
First question, trying to keep it simple 😃
Because it's constant it grows in magnitude as the universe expands, whereas normal matter does not? Is this accurate as far as we know?
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How to derive deceleration parameter in terms of redshift?
How do I get q in terms of $z$ specifically of this form:
I want to derive the second equation from the first but I'm getting an additional $ \frac{a^2}{H^2}\ $ in the second term
$$ q= -\frac{\ddot{a}...
