Questions tagged [hubble-constant]

Questions about the Hubble constant, the constant factor of the rate of expansion in the universe

8 questions with no upvoted or accepted answers
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How did pressure evolve in the (early) universe?

I am trying to derive how the cosmological pressure $p(t)$ evolved over time in the universe, especially in the radiation and matter dominated epochs. There are some very nice explanations how $H(t)$ ...
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232 views

Why the Hubble constant is so inconsistent?

Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant: 67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey 73.00±1.75 Hubble Space ...
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26 views

Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant

The Sunyaev–Zeldovich effect (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) ...
2
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46 views

How many galaxies are predicted in the observable universe? Does it contain dwarfs? Is there any size-ratio diagram?

According to quite recent research the observable universe contains about 2 trillion galaxies ($2 \cdot 10^{12}$). But what is counted there? Does this number also contain dwarf galaxies? According to ...
2
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114 views

Clarifications about distances in cosmology

I would like to get clarifications about some usual notions of distances in cosmology. First, is the comoving distance the current distance of objects whose light has been reached by us now, i.e. ...
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64 views

Catching up with Hubble domain galaxy at constant acceleration: is it possible? If yes, what time will it be when I arrive?

An elf gave me a magic spaceship for Christmas: it can maintain a thrust of $\alpha = 10\ \mathrm{N/kg}$ indefinitely. Otherwise, I'm still constrained by physics. I plan to set out on a journey into ...
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69 views

What is the age of the universe if you were standing in a galaxy far far away such as GN-Z11?

If we agree with the universe starting from a Big Bang, 13.8 billion years ago, expanding at different rates governed by the Hubble constant of 67.4 km/s/Mpec, somewhere about 13.4 billion light years ...
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36 views

Must all galaxies in a galaxy cluster have the same expansion rate?

If we observe a distant galaxies cluster where all galaxies travel with the same speed away from us, except for one galaxy whose speed is significantly lower than of the neighboring galaxies. Does ...