# Tag Info

Accepted

### Is the Universe really expanding at an increasing rate?

I don't take this at face value because we should expect more distant objects to have higher observed speeds and therefore higher observed red-shifts. That's true. That was the original Hubble ...
• 22.9k
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### Are there ways to estimate size of the "whole universe"?

tl; dr The universe is probably infinite, but if that's the case it's impossible to verify. If the universe is finite, and small enough, and the global curvature is equal to the curvature of our ...
• 10.4k
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### BIg Bang Happened everywhere

Okay, I think I know what Max Tegmark is talking about in the video. He is referring to the fact that, when you observe the cosmic microwave background radiation (CMB) — i.e. the radiation that was "...
• 33.8k

### Did cosmological inflation occur at speeds greater than $c$?

The simple answer to your question is "yes" - the universe expanded at much greater speeds than $c$ during the inflationary epoch. This period of time was very quick but very dramatic, lasting from ...
• 34.1k
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### What explains the existence of energy/matter if it cannot be created or destroyed?

That's a very complicated question! First, let's remember that Moses didn't bring the Law of Conservation of Energy down from Sinai on stone tablets -- it's something that we've observed to be true ...
• 7,390
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### Why can't we point the centre of the universe from inflation graph we see?

That diagram does not depict the entire universe. At most, it depicts the history of what is now our observable universe (specifically, a 2D slice through it), with us at the center only because we're ...

### How could universe inflate itself out of the very dense and curved early spacetime? Could it happen in a black hole too?

Great question! Sorry for this huge response, and it might not be a satisfying answer, but it'll address your questions. Sadly, as with most of astronomy, the Big Bang is surrounded in mystery. It is ...
• 7,750
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### Does the universe expand at the same rate everywhere in the universe?

What's outside the observable Universe, we can't say anything about, but averaged over large enough scales ($\gtrsim$ a billion lightyears), it does indeed seem to be expanding uniformly. However, ...
• 33.8k

### Does time slow down because the universe is expanding at an accelerating rate?

Yes, time does run slower for far-away objects, as observed from our point of view; this is a prediction of general relativity. And yes, because expansion accelerates, this time dilation slowly, very ...
• 33.8k
Accepted

### Dark Energy Expansion

Is Cosmos seriously using that exact number? Egads... if they are, don't take it too seriously, but otherwise they're probably conceptually correct. How do we know it was dark energy? In cosmology,...
• 7,684
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### How can cosmic inflation make an infinite universe homogeneous?

Inflation is used to explain why the observable universe is extremely homogeneous. Without inflation, we can do the following crude calculation. The cosmic microwave background was formed about 300,...
• 118k
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### Could the accelerating expansion of universe inidicate we are surrounded by "denser" space?

It's a pretty clever idea and a solid question that unseen mass might cause gravity outside the observable that tugs on the universe and might be the cause of dark energy as opposed to some unknown ...
• 22.9k
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### What will the universe be like in a googolplex years time?

That is nearly long enough to reach heat-death, which is estimated as about $10^{10^{120}}$. What that means is rather speculative, since it depends on various events that we have never observed, such ...
• 91.4k
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### Could Dark Energy be a "Cosmic Gravity Background"

There is in fact a cosmic gravitational wave background. These waves are expected to be stochastic, having originated in the early universe (much earlier than the cosmic microwave background). Random ...
• 34.1k
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### Does wavelength affect redshift caused by the metric expansion of space?

Standard cosmological models predicts that the cosmological redshift and the speed of light are wavelength-independent. This result is confirmed observationally e.g. by Ferreras & Trujillo (2016), ...
• 33.8k

### Is the expansion of the universe greater than the speed of light?

After inflation, the expansion of the universe did indeed slow down. During the inflationary epoch (lasting roughly $1 \times 10^{-33}$ seconds), the universe expanded by a factor of $10^{26}$. That's ...
• 34.1k

### What is the explanation for rapid inflation just after the big bang?

With normal matter, the strength of gravity depends on the stress-energy tensor, which, in an isotropic homogeneous universe, has trace of $\rho + 3p$. The positive pressure from relativistic ...
• 2,857
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### How long was the hyper inflation phase?

Googling "hyperinflation" mostly returns articles about Zimbabwe and the Weimar Republic, so I'm going to assume that you are referring to what is usually just called (cosmological) inflation. We are ...
• 33.8k
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### Looking back in time by looking further away

Before the advent of telescopes, we could only look back in time from a few years (for nearby stars) to a few thousand years (for the most distant stars visible to the unaided eye). In addition to ...
• 33.8k
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### The universe is dying vs the universe is ever expanding

Both are true. The universe is "dying" in the sense that stars eventually run out of hydrogen, and there aren't infinite amounts of hydrogen in galaxies to replace old stars. This will take a very ...
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• 33.8k
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### How does inflation justify the nonexistence of magnetic monopoles?

Let me start off by stating that scientists have not conclusively proven that magnetic monopoles do or do not exist. There has never had a confirmed detection of one so the jury is still out on if a ...
• 14.5k