Questions regarding the space in which all matter is thought to exist.

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21
votes
4answers
10k 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 ...
14
votes
2answers
978 views

Age of the universe and time dilation

Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old. How much sense does it make to talk about the age of the ...
12
votes
1answer
184 views

On what scale does the universe expand?

According to the theory (or my understanding of it), the universe is not only expanding, but speeding up. If the galaxies are moving apart, are the solar systems within them also moving apart from ...
11
votes
2answers
449 views

How exactly is our universe mapped?

Watching this youtube video shows that our planet is nothing more than dust in the wind. At the 2:50 mark in the video, you will see a view of the whole Milky Way. At the bottom you will see this ...
11
votes
2answers
408 views

Why does a planet rotate and revolve?

Why do planets rotate and revolve in the universe?
11
votes
1answer
523 views

Explaining Dark Matter and Dark Energy to layman

With my little knowledge, I know this: Dark Matter The center of a galaxy controls/attracts its objects (stars, planets, comets etc.) towards itself because of gravity. But the mass of the center of ...
10
votes
1answer
601 views

Layout of the universe

I've been working on a space game in my spare time, and lately I've been thinking on how to lay out the universe. Though I've searched around and found it hard to get a good view of what the universe ...
10
votes
3answers
797 views

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

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 ...
10
votes
1answer
8k views

How many sun-like stars are there in the universe?

After yesterday's announcement of the Kepler telescope finding a huge amount of newly observed exoplanets, i saw a headline claiming that as much as 22% of sun like stars in the universe have planets ...
10
votes
2answers
373 views

How are Galaxy Super Clusters Generated

I have seen pictures of clusters of galaxies, usually used in regards to theories of dark matter and galaxy formations. One of the most famous ones has the perceived shape of a stick-figure. If I am ...
9
votes
8answers
2k views

What's the largest non-spherical astronomical object in the universe?

Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of ...
9
votes
2answers
536 views

Why is the observable Universe larger than its age would suggest?

The age of the Universe is estimated at 13.8 billion years, and current theory states nothing can exceed the speed of light, which can lead to the incorrect conclusion that the universe can't have a ...
9
votes
2answers
227 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 ...
9
votes
1answer
197 views

Where is all the antimatter?

The universe supposedly started off with equal parts matter and antimatter and they are said to annihilate each other. Also, nature is famous for it's balance between everything. So all we see is ...
8
votes
3answers
272 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?
8
votes
2answers
160 views

Is the diameter of the observable universe a relative quantity?

The diameter of my observable universe is 90 billion ly measured in proper distance. But isn't lenght a relative quantity in the theory of Relativity? Could an observer moving at a different velocity ...
7
votes
2answers
220 views

Is the Hubble Ultra-Deep Field image representative of the entire sky?

The Hubble ultra-deep field image is a photograph of an area of sky equivalent to a 1mm x 1mm piece of paper held a metre away from the eye (one thirteen millionth of the entire sky). It contains an ...
7
votes
1answer
135 views

Are there any alternative explanations for the gravitational force we attribute to dark matter?

It always seemed counter-intuitive to me that we observed an measured a gravitational force and since the universe has not enough mass to account for it, the conclusion was to say there's a different ...
7
votes
4answers
191 views

Why does it make sense to say the universe has no centre?

If we suppose we and everything in the universe is perfectly flat. That is, we have width and depth, but no height. And we are situated on the surface of a balloon blowing up with air and expanding ...
7
votes
2answers
234 views

Is there any difference between parallel universes and multiverse?

Nowadays we come across with these two terms - parallel universes and multiverse. I wonder if this is the same thing or its two entirely different principles because the names are a bit confusing to ...
6
votes
7answers
309 views

Is there any practical use for astronomy?

Although astronomy is very cool and the things we are learning are awesome, is there really any practical use to knowing the things we know about the universe? Do other fields of science draw from ...
6
votes
4answers
211 views

Can there be a 2nd possibility deduced from the fact that galaxies are moving away from us?

I just read that according to the BBT the universe is expanding. This is evident from the fact that distant stars (and galaxies) are moving away from us. But it could also happen that the universe is ...
6
votes
3answers
170 views

Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?

we know that stars fuse hydrogen into helium starting at 3 MK; 13 MK in the Sun's core; carbon fusion starts at above 500 million K, and silicon fusion starts at over 2700 million K for comparison; ...
6
votes
3answers
301 views

How does light affect the universe?

When light is emitted by for example a star, that star loses energy - which causes it to reduce its gravity. Then that energy begins a journey for potentially billions of years, until it reaches some ...
6
votes
1answer
373 views

is there any theory or observational evidence that our universe is electrically neutral or not?

It seems our universe is neutral in large scale. There is CP violationwiki problem about matter and dark matter. Similarly is there any theory about whether our universe is electrically neutral? ...
6
votes
2answers
153 views

Is ours the first universe?

I see here that after a very long time into the future, "Estimated time for random quantum fluctuations to generate a new Big Bang". This begs the question, do we speculate that our big bang was the ...
5
votes
3answers
140 views

Are black holes expanding?

We know that it is a commonly heard claim that in every black hole there is a universe. It is also believed that the universe is expanding. If we use both of these, can we conclude that every black ...
5
votes
1answer
797 views

How many earths fit in the observable universe?

I was pondering our insignificance, when I wondered - how how much smaller is our planet then the (observable) universe? And being as I dont know how to do the math, I'm asking it here. So how many ...
5
votes
2answers
1k views

Our universe the surface of a 4-dimensional sphere?

The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
5
votes
1answer
225 views

Does our universe have to be embedded in a higher dimensional space?

I've heard that our universe may be open or closed. If it's closed it might have a toroid shape. If this is the case, would that imply that our 3 spatial dimensions have to be embedded in a higher ...
4
votes
2answers
252 views

Is the universe expanding faster than speed of light?

The celestial bodies like stars and galaxies are moving away from each other. How fast are they moving apart? Is that speed more than the speed of light?
4
votes
3answers
1k views

Does the universe have an edge?

I've heard the universe is just an empty cavity. Does the universe have any edge or stop or is it just an infinite empty cavity?
4
votes
2answers
102 views

Is dark energy evenly spaced throughout Universe?

Are there certain parts of the Universe that are expanding faster than others? Is there anyway to definitively measure this?
4
votes
1answer
118 views

Universe as 2d sphere surface - a round trip?

If Universe's analogy is 2D surface of the sphere, could we come around in circle? Say on Earth you decided to travel straight in one direction, after completing one full circle you'd find yourself at ...
4
votes
2answers
172 views

How can we predict a Big Crunch when all galaxies are moving further apart?

I've read that the further away a Galaxy is from us the faster it moves away. By this logic how can scientists predict that there will eventually be a big crunch when every piece of matter is ...
4
votes
1answer
115 views

What it would look like to observe people with a different time flows?

As I learned, that the bigger gravity source you are influenced by the more slow time ticks for you, the farther away you are from a gravity source the faster times ticks. So Imagine two different ...
4
votes
1answer
117 views

Where are we in an approximate timeline of the possibly habitable universe?

Our universe is supposedly 13+ billion years old and our Sun is a third generation star. It seems to me that we are now in a relatively young stage of the universe. How many generations of stars will ...
3
votes
4answers
1k views

What would we find if we could travel 786 trillion light years in any direction

I've sometimes heard of galaxies that are millions or billions of light years away but if we could instantly travel 786 trillion light years in any direction, what are we likely to find? And what if ...
3
votes
2answers
137 views

How and when did we learn about the universe?

I'm 13 - I'd like to know how we found/discovered important details about the Universe. I know we have found many different things about the Universe, but when did we find how amazingly large the ...
3
votes
2answers
352 views

Why are distant galaxies not visible in the observable Universe?

Assuming that the Universe is and has been expanding ever since its creation (Big Bang theory), the galaxies that are now at the 'edge' (not visible theoretically) must have been (at some point in ...
3
votes
2answers
732 views

What is the physical, geometric shape of the universe?

I'm not asking about theoretical ball, vs saddle, vs flat surface which is just a metaphor with 2D space. It's hard to say as we see very little of it, and we see them in the past because light ...
3
votes
3answers
249 views

How is the universe bordered?

This answer says that some models describes the universe as finite. How do those models describe the universe's border? Does the border (theoretically) exist? Is it a solid border? Do they predict ...
3
votes
1answer
52 views

visualisation of the universe's expansion

in physics we were learning about the universe and the big bang. we were being told that everything came from one point and 'exploded' outwards, and is continuing to expand. I felt that this ...
3
votes
2answers
181 views

Has life been discovered outside of Earth?

I've just watched a movie that made me curious as to whether life has really been discovered on another world such as Europa??
3
votes
1answer
132 views

Solar System formation, considering its and universe's age

It's been said 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 ...
3
votes
2answers
198 views

Can the theory of multiuniverse explain dark matter?

If there are many universes they must have an gravity effect on each other. Since dark matter is measured through gravity but we dont know the mass behind it, isnt it possible that it comes from ...
3
votes
2answers
134 views

Is the universe simply a mass of atoms in 'void'; what does it look like?

I've always been stumped with the question of what lies beyond the universe, and I've come to the firm conclusion - void (i.e. completely empty). Does it make sense then to think of the universe as a ...
3
votes
3answers
141 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 ...
3
votes
1answer
30 views

What is driving the expansion of the Universe?

Is it just the momentum from the Big Bang? If yes, how can it account for the acceleration of the expansion? Why isn't the collective gravitational force slowing it down? What part does dark energy ...
3
votes
1answer
67 views

How do we know the current state of the universe by observing it from Earth?

Since light travels at the constant speed and takes more than a billion years to travel from the distant parts of the Universe, how do we know the state of the distant regions? Do those still exist or ...