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

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0
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1answer
110 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. ...
5
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1answer
736 views

How likely and severe is the threat of a gamma ray burst to earth?

In the National Geographic article: http://news.nationalgeographic.com/news/2009/04/090403-gamma-ray-extinction_2.html it is suggested that a gamma ray burst likely caused a mass extinction in earth's ...
2
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1answer
85 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 ...
14
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1answer
209 views

Dark Matter Particle Candidates

Dark matter appears to dominate the matter component of the universe as compared to luminous, or baryonic, matter. Though it does not interact electromagnetically (it doesn't absorb, scatter, or emit ...
12
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3answers
1k 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 ...
10
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3answers
623 views

How do we know dark matter/dark energy exists?

I've never quite understood the theory behind why dark matter and dark energy exist. I know it has something to do with gravitational pull being stronger than what we calculate it SHOULD be, could ...
7
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3answers
156 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 ...
4
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1answer
2k views

When will the Milky Way “arrive” at the Great Attractor, and what all happen then?

The Great Attractor is described as a location to towards which the Milky Way, along with all other galaxies in the Laniakea Supercluster are moving. How long will it take for the Milky Way to "arrive"...
2
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2answers
100 views

Is mass+energy conserved when a new universe forms inside a black hole?

My understanding is that there are credible theories out there in which the formation of a singularity in a black hole also represents the beginning of a new universe via a big bang. We can't see the ...
4
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3answers
174 views

Strong force and metric expansion

If the expansion of the universe (the metric) continues (and perhaps is accelerating), in a very large but finite time the expansion of the metric will clash with the effects of the strong nuclear ...
3
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1answer
129 views

What does black hole evaporation correspond to in the accelerating universe / black hole analogy?

In the same way, as a black hole emits Hawking radiation corresponding to its temperature $$ T = \frac{\hbar}{r_{BH}} $$ the accelerating universe can be described as all of the stuff falling ...
3
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1answer
155 views

Evolution of the Hubble parameter

In the lambda-CDM model describing an accelerating Universe, the Hubble parameter is currently decreasing with time. Will it continue to decrease forever?
2
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1answer
113 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 ...
1
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1answer
368 views

what is a Friedmann model?

Can you explain what is a Friedmann model to a layman? And also give some examples of Friedmann models, specially I would like to know if the lambda-CDM model is considered a Friedmann model.
1
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1answer
86 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 ...
1
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2answers
203 views

Why doesn't this paradox disprove (some) multiverse quantum gravitational theories?

As I understand it, one theory of the multiverse is that there are an infinite number of universes separated by small distances in other (than our observable 3/4) dimensions and that gravity is weak ...