Questions tagged [universe]

Questions regarding all of time and space and its contents.

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4
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1answer
165 views

How can heavy elements exist when the universe is young compared to the lifetime of a star? [duplicate]

Our sun is said to be incapable of producing heavier elements, and these are thought to originate from older stars dying and going supernova. If our sun is 4-5 billion years old, and has a lifetime of ...
2
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2answers
2k views

Will a black hole swallow the universe?

If black holes swallow stuff, will a big black hole eventually swallow the universe? The universe will eventually go dark, because there will not be enough matter to make stars, and all that will be ...
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0answers
71 views

How to derive the equation for the age of a flat universe with a positive cosmological term?

Can anyone show the steps involved in deriving this equation from the friedmann equation with the cosmological constant involved
8
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1answer
161 views

Does the CMB pattern evolve in a human lifetime?

I was thinking, as CMB is a snapshot of a slice of the Universe during recombination, how much the cmb is changing with time ? I mean as we progress in time we look a CMB a bit more faraway each time, ...
1
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1answer
112 views

Question on Friedman equation involving cosmological constant

This is the question: By considering both the Friedmann and acceleration equations, and assuming a pressureless Universe, demonstrate that in order to have a static Universe we must have a closed ...
2
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1answer
50 views

Where can I find source data for the graph of metric expansion over time, as shown in this ESA web page?

This web page from ESA/Hubble, shows the size of the universe over time. (I know that "size of the universe" is a gross simplification and open to multiple definitions and ambiguity, but this kind of ...
3
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3answers
115 views

Account for radiation energy in the statement “total energy of universe is zero”

I've read in Hawking's book The Theory of Everything that total energy of the Universe is zero. He explained this by saying that if there are two bodies separated by a distance and having some mass, ...
9
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4answers
1k views

Why black holes are extremely cold?

"The most massive black holes in the Universe, the supermassive black holes with millions of times the math [sic] of the Sun will have a temperature of 1.4 x $10^{-14}$ Kelvin. That's low. Almost ...
0
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1answer
78 views

SETI search for extraterrestrial life [closed]

In all these years of listening, why hasn't SETI detected anything ? Is there no intelligent life out there or is it too far away to detect ?
0
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1answer
62 views

Is the Cosmos a super set of the Universe and any hypothetical multiverse(s)? [closed]

I'm quite lost on the definitions of words like omniverse, megaverse, multiverse, meta-universe, universe, and cosmos. I used to think the Universe and the Cosmos were essentially the same things, but ...
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3answers
7k views

What would happen to a polished marble statue left in space for a million years?

Consider it doesn't collide with any other objects. Would it be preserved perfectly in the vacuum or would its surface be damaged by anything like UV rays, radiation, gas, space dust, etc?
0
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1answer
101 views

what happens when we keep going radially away from earth?

Is the generally accepted belief in the science community, that if one sits in a spaceship and move away from Earth where r (distance between earth and my ship) is continuously increasing, can one ...
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1answer
262 views

Use of type-I a supernovae as standard candle

Why only type -Ia supernovae are used as standard candle to calculate age of universe and why not type II, type Ib, type 1c ?
2
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2answers
87 views

What happens if one day aliens want to talk to us. How can we talk to them? [closed]

Always I wonder about that if some day alien wants to talk to us, then how can we talk to them? They didn't know any of the language on the Earth. What will be the basic building blocks for it?
2
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1answer
202 views

If the Universe is Flat, why does it look 3D from our View?

So I know that the universe is flat in a 4D point of view, but what about a 3D point of view? The universe does not SEEM flat from our view, so how can it really be so? Please answer more simple, im ...
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2answers
147 views

Is there any way to tell which way is the next universe? [closed]

Is there a observable void outside our universe that can give a clue on how far the next on is? How many universes can surround ours? What does a universes gravity well look like?
3
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2answers
65 views

How to fix a Direction in the context of universe? [duplicate]

My question is regarding the direction/orientation of earth. Is it a constant with reference to universal parameters?
-1
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1answer
84 views

Can the shedding of radiation of stars contribute to the red-shift of the universe?

The sun is losing mass(1.5cm per year) by emitting radiation and the orbits of the planets are widening because of the weakening gravity of the sun. Are most of the stars shedding mass via ...
3
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1answer
126 views

Universe becoming finite

If sometime in the distant future, the Universe stopped expanding, would this mean that the Universe was no longer infinite?
3
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1answer
291 views

Would a future hole in the Cosmic Microwave Background show us the edge of the universe?

If my understanding is correct, the Cosmic Microwave Background always come from our event horizon. By event horizon I mean the edge of the observable universe. If the universe is finite does it mean ...
0
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1answer
195 views

How can we ge to the exoplanet Proxima b? [closed]

I would like to know please how can we get to the exoplanet Proxima b. I heard it is the potentially habitable exoplanet closet to Earth at only 4.2 light years away. So exciting!
26
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1answer
7k views

Are there more stars in the universe than grains of sand in the Earth?

My ten year old daughter asked me this question at breakfast and I initially said yes, but on second thought I was also puzzled.
5
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2answers
407 views

What is a probability of a particle launched from earth hitting any object in the universe?

Imagine I pointed a laser into the night sky. How likely is it that a particular photon will ever hit anything? This question bothered me for a while. I know very little about astronomy. When I asked ...
3
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1answer
652 views

What will the universe be like in a googolplex years time?

It will be cold and dark in 10^(10^100) years. What else can be said of the state of things in the far distant future? Will everything have fallen into supermassive black holes and then radiated ...
1
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1answer
491 views

What is beyond the observable universe? [closed]

What is beyond the edge of the observable universe? Scientists say that the Big Bang is the cause of all creation in the known universe, but it would seem the bang must have happened in the center of ...
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0answers
99 views

Which physical quantity is the real/definitive tracer of galaxy evolution? [closed]

Which physical quantity is the real / definitive tracer of galaxy evolution? Let me explain better: if you aimed at understanding as much as possible about the evolution of galaxies and you had to ...
3
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3answers
622 views

How can the universe be expanding faster than speed of light? [duplicate]

So the story goes like this: A long time ago, 13.799±0.021 billion years to be exact, something happened. It was a big bang, loud explosion and universe came to existence. It grew and grew, and now ...
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2answers
333 views

Is an expanding universe equivalent to a universe in which everything is shrinking?

Why do we always think of the universe as expanding? Surely, from our perspective an expanding universe would look exactly the same as a universe in which everything is shrinking away from ...
4
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1answer
184 views

Will universe's lakes get boiled by the CMBR?

From what I can understand, Cosmic Microwave Background Radiation (CMBR) is microwave now, but was initially visible light emitted long time ago. The microwave is producing a wave that’s about 12 ...
8
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2answers
1k views

Is the age of the universe relative to an observer's location in that universe?

According to Wiki the age of the universe is 13 billion years old, and I was taught that background radiation made the universe uniform in all directions. Doesn't this define a sphere of space in the ...
57
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4answers
16k views

Does the Milky Way move through space?

Does our galaxy moves through space? Or does it stay in a single location? If it does move, what causes it to move?
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3answers
325 views

What's the name of outside the cosmic horizon?

The word we use to refer to what's inside the cosmic horizon is the 'universe', so what would you call the empty space outside of the horizon?
0
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1answer
248 views

Why do we we even exist? [closed]

It came to my mind one day that why does this universe even exist and why do we even exist and like we are enclosed in the so called atmosphere and a floating rock in space called the Earth, so is ...
3
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1answer
84 views

Based on the smallest number of photons that can deliver information about a star, what is the largest size of the universe?

I was watching a summary video about the Banach-Tarski paradox and it led me to a question. If I (a) assume the universe is infinite and (b) assume it is possible to receive a single photon of light ...
18
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3answers
4k views

What exactly is the “paradox” in Olber's Paradox?

To the extent of my understanding, Olber’s paradox states that if the universe was static and homogeneous, we should see a star at every point in the night sky and therefore the night sky should be ...
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2answers
122 views

Why aren't other kinds of energies considered in the mass-energy of the universe?

Mass-Energy of the Universe: 5% ordinary matter, 27% dark matter, 68% dark energy What about other energies such as thermal energy, potential energy, kinetic energy, chemical energy, and radiant ...
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1answer
142 views

How can we say that the universe is expanding [closed]

How can we say that universe is expanding as we r sure about that energy is neither created nor destroyed then from where does this more energy come from
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1answer
83 views

What questions will we be able to answer if we find life on other celestial bodies? [closed]

Will that be able to answer questions such as our origins or why we exist? Will it unlock some sort of new perception towards anything?
3
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1answer
532 views

Total mass of light? [duplicate]

I know that light is considered as energy, and as such has a mass. So it is certainly taken into account in universes models and calculations. So I'm wondering: How much of the total mass of the ...
3
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3answers
384 views

How does dark energy remain constant?

According to cosmological constant, dark energy should have a constant density but since the universe is expanding so is the volume of the universe and so should the mass of dark energy. But how does ...
2
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3answers
395 views

Is our universe flat?

I heard our universe is flat. Then one question is puzzling in my mind. If our universe is really flat, why we measure distance from any point across in a spherical way. In other words, why we say, ...
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2answers
86 views

The # of Estimated Galaxies increased 10 fold. Where does that leave our # of stars estimate?

I have found oddly different answers through my multiple google searches. I found one article that mentioned this did not alter the estimated number of stars in the universe. Link: http://www....
1
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1answer
535 views

Finding equation for energy density of matter

I'm trying to get an equation for the energy density of matter of the universe $\rho(t)$, assuming the number of particles is conserved and rest mass energy is much greater than kinetic energy. $\rho(...
7
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1answer
2k views

Will we start seeing galaxies disappear due to Universe expansion? [duplicate]

Does the fact that universe is currently expanding at an accelerating rate means that far far away objects (FAO) might start disappearing with time, set aside the "red shift"? I'm saying this ...
4
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1answer
474 views

How can the observable universe shrink in a Big Rip?

As far as I know, the Big Rip occurs when the scale factor reaches infinity in a finite time. This will only happen in a universe dominated by phantom energy (i.e. a universe with an equation of state ...
4
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1answer
299 views

What existed before the big bang [closed]

What existed before the big bang? What all thing are there inside big bang object ?.
5
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1answer
295 views

Who first hypothesized that the universe is accelerating?

I couldn't find this answer anywhere. Before 1998, was there a notable physicist who conjectured that the universe is accelerating and perhaps even submitted some equations to support it (and the ...
2
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1answer
438 views

What is high redshift?

I'm curious about the difference between low redshift and high redshift universe. Is there any defined limit of redshift beyond which we call things high redshifted?
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2answers
11k views

How can 'HD 140283' be older than the universe?

Scientists have known about the star HD 140283, informally nicknamed the Methuselah star, for more than 100 years, since it cruises across the sky at a relatively rapid clip. The star moves at about ...
3
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1answer
633 views

Latest cosmological parameters

I'm looking for the latest values (with uncertainties) of the four main cosmological density parameters $\Omega_i$ : \begin{align}\tag{1} \Omega_{\text{mat}} &={} ?, &\Omega_{\text{rad}} &=...