Questions tagged [universe]

Questions regarding all of time and space and its contents.

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7
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1answer
314 views

Age of the universe vs. its contents

A couple of decades ago I read an article (could have been either Astronomy, Space, or Science News) that suggested the contents of the universe may be older than the universe itself. Of course, that ...
3
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1answer
134 views

Universe becoming finite

If sometime in the distant future, the Universe stopped expanding, would this mean that the Universe was no longer infinite?
0
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3answers
2k views

How to leave the Universe

If the Universe is flat and expanding at the speed of light, that must mean that we could never leave it, because one would have to travel faster than the speed of light which is not possible. However,...
3
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1answer
292 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 ...
4
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1answer
577 views

How far are we from the edge of the Universe? [duplicate]

Following the Big Bang the Universe continues to expand, presumably and roughly equally in all directions. It is understood that the Big Bang occurred 13.798 ± 0.037 billion years ago. Is there any ...
32
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5answers
21k views

What's the fastest moving object in the universe?

We know that nothing can have proper velocities larger than the speed of light in vacuum. But are there any objects in space that get close to it? Any comets, or other objects thrown by gravity or ...
0
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1answer
196 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!
27
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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.
1
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1answer
494 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 ...
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 ...
5
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2answers
413 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 ...
1
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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
638 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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4answers
3k views

What is the volume of the universe?

Of course it is not exactly known how big the universe is, but I thougt that the universe is about 100 billion lightyears in diameter. But if that is true can you also make an estimation of the volume ...
1
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2answers
340 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 ...
3
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3answers
330 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
251 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
86 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 ...
0
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1answer
112 views

If a star orbited another star, how would that affect parallax measurements of the other star from the vantage point of the first?

Example: If hypothetically, the vantage point would move 2AU along an orbit around the star being measured, would that make it seem as if the other star moved twice the distance over the back-drop?
15
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3answers
569 views

Do parallel universes exist?

Do other universes like ours exist? If they exist, how do we know that they exist when we have even not seen the ends of our own universe?
19
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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 ...
2
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2answers
425 views

Can the theory of multiverse explain dark matter?

If there are many universes, they must have a gravity effect on each other. Since dark matter is measured through gravity, but we don't know the mass behind it, isn't it possible that it comes from ...
1
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2answers
124 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 ...
4
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4answers
486 views

What happens to photons that don't interact with something?

Say a photon left one of the first stars ever created in our universe. This photon has been traveling for 13+billion years through the vastness of space without ever hitting anything. Sure, it's ...
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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
-1
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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
539 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
398 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 ...
5
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3answers
2k views

Can there be an infinity of stars in the Universe? [duplicate]

I have a mind puzzle. Can there be an infinity of stars in the Universe ? I have 2 opposed reasonings, yet I don’t find any flaw in them. Can you help me here ? Answer A : No, the number of stars ...
3
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3answers
211 views

Why can't this be the simple (and obvious) explanation for the dimming of KIC 8462852?

Couldn't it be just a relatively large object, anywhere in the interstellar space between the star and Earth? I mean, look out the window at a far away car or a tree, then stretch out your hand and ...
2
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3answers
402 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
89 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
540 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(...
4
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1answer
481 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 ...
8
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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
304 views

What existed before the big bang [closed]

What existed before the big bang? What all thing are there inside big bang object ?.
6
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1answer
297 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
445 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?
8
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4answers
2k views

Does the mass of the observable universe ever change?

First do we have anyway to even estimate the mass of the entire observable universe? And then is there any data that shows mass being gained or lost? Would we ever know if someone was playing with ...
1
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2answers
296 views

How is a Galaxy formed?

How is a galaxy formed? I know that the center of our galaxy is considered to be Sagittarius A* and it's surrounded by a lot of stars (also a lot of neutron stars). But what makes this happen? I mean,...
0
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2answers
235 views

In a finite universe, what happens when light reaches the boundary?

If a universe is finite and is not expanding at a speed equal to or greater than c, what happens when light or another form of electromagnetic radiation traveling reaches the boundary?
1
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1answer
109 views

How can space expand in accelerating speed when dark energy is constant?

I came to know that dark energy is constant.As mentioned in the Friedmann equations How can a constant energy cause an ...
1
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1answer
154 views

Centerless expansion or a matter of perspective [duplicate]

I get this question a lot: Where is the center of the Universe? I see this question on the internet all of the time: Where is the center of the Universe? Now I have a question regarding all ...
4
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1answer
401 views

Solar System formation, considering its and the universe's age

It is known that the Sun is 4.6 billion years old, and the complete Solar System is of a similar age. The class of stars to which the Sun belongs seems to be quite common. Stars of its class can live ...
5
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1answer
197 views

Why are galaxies distributed as walls and voids, or spider webs?

I have wondered why the "walls and voids" of the cosmological galaxy distribution seem to resemble a "foam", like rising bread that's ready to fall, with "voids" corresponding to empty bubbles in the ...
21
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1answer
3k views

Does the recent news of “ten times more galaxies” imply that there is correspondingly less dark matter?

Nature: Universe has ten times more galaxies than researchers thought NASA feature: Hubble Reveals Observable Universe Contains 10 Times More Galaxies Than Previously Thought Headlines sometimes ...
18
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3answers
2k views

How can the 13.8 billion years old universe have a radius of 46 billion light years? [duplicate]

The universe is about 13.8 billion years old. Assume at the big-bang it starts from a small region and the maximum possible speed according Einstein is the speed of light how can the universe got a ...
2
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5answers
545 views

What is the speed of light relative to (in space)?

From what I understand the universe is expanding faster than the speed of light and accelerating so that it's possible that a given galaxy: $A$ will no longer be visible to another given galaxy: $B$. ...
4
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1answer
257 views

Are galaxies moving away from us faster than before?

Are all galaxies moving away from us at constant speed even those that may be moving in our direction as the space is being formed? How does nothingness appear to push matter? A black hole sucks as ...
3
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2answers
2k views

Does the age of the universe take into account General Relativity / Special Relativity?

It is generally accepted that the age of the universe is approximately 12-15 billion years old based on the speed of the expansion of the universe. Since everything is moving very fast away from us, ...