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Questions regarding all of time and space and its contents.

2
votes
2answers
64 views

Light beam (1 photon) in the limited universe?

If our universe is not infinite, what happens with the light beam (or photon) when it will travel through the whole universe? For example, observable universe according to wikipedia has diameter 93 ...
0
votes
2answers
117 views

Why do we presume that the universe has always expanded?

When I read about the universe having always expanded from a 'singularity', I can't help but wonder if that is perhaps not the case. If a singularity is a point at which everything is infinite and is, ...
0
votes
2answers
106 views

Does the edge of the Universe travel faster than the speed of light?

The Universe is expanding faster than the speed of light then does that mean matter at the edge of the universe is also traveling at the speed of light or are ether opposite sides of the universe are ...
2
votes
1answer
93 views

Yet another Question about the expansion of universe

A galaxy 13 billion light-years distant is 94% of the way to the big bang. The universe was 800 million years old when the light was emitted. That galaxy today is traveling away from us at 94% of the ...
3
votes
1answer
95 views

Methodology for size of Universe

I understand that the Universe could be either finite or infinite and that it is, at the least, "very large". :) My question is, why doesn't the math involved in making the CMB and other predictions, ...
2
votes
1answer
88 views

What explains the existence of energy/matter if it cannot be created or destroyed?

If the energy/matter that was contained in the singularity before the Big Bang had always existed, and if it’s true that energy/matter cannot be created or destroyed, then what explains its existence?
5
votes
4answers
144 views

Influences from outside the observable universe explaining dark energy and expansion?

Could some influence from outside the observable universe be causing the expansion?
4
votes
1answer
118 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
votes
2answers
144 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 ...
2
votes
0answers
26 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
7
votes
1answer
114 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
vote
1answer
29 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
votes
1answer
39 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
votes
3answers
78 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, ...
8
votes
3answers
214 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
votes
1answer
66 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
votes
1answer
48 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 ...
23
votes
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
votes
1answer
89 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 ...
4
votes
1answer
88 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
votes
2answers
72 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
votes
1answer
118 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 ...
-3
votes
2answers
128 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
votes
2answers
62 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
votes
1answer
75 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 ...
4
votes
1answer
115 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
votes
1answer
211 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 ...
2
votes
2answers
177 views

How can we ge to the exoplanet Proxima b?

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
votes
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
votes
2answers
276 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 ...
2
votes
1answer
304 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
vote
1answer
302 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 ...
1
vote
0answers
93 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
votes
3answers
349 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 ...
1
vote
2answers
245 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
votes
1answer
178 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
votes
2answers
540 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 ...
54
votes
4answers
13k 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?
3
votes
3answers
180 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
votes
1answer
161 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
votes
1answer
65 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 ...
15
votes
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 ...
1
vote
2answers
88 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
votes
1answer
115 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
0
votes
1answer
79 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
votes
1answer
259 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 ...
4
votes
3answers
215 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 ...
1
vote
3answers
299 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, ...
1
vote
2answers
70 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
vote
1answer
268 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(...