# All Questions

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### 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 ...
48 views

### Will we ever end up in the black hole? [duplicate]

Since we are spiraling around the black whole will we spiral into the black hole?
289 views

### First night on a telescope questions

So I recently got into astronomy and I am using my fathers old Meade EQ1-B reflector telescope. This is my first night using it and I have come across a few questions. To begin, the telescope was left ...
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### How are East and West defined on other bodies of our solar system?

I noticed that East and West appear swapped on maps of the Sun, even though the Sun rotates around its polar axis in the same sense as Earth. See for example below Sun disk with a Venus transit ...
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### What was the age of the universe when the average density was one atmosphere?

How long did it take after the Big Bang for the average density of the universe to reach one Earth atmosphere at sea level? How about the density of water? Is there a chart of densities that relate to ...
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### Assumption of our universe being the surface of a 4-D sphere in order to describe relative uniformity in the cosmic microwave background?

It seems as if this is necessary to assume in order for the CMB to make an sense. Otherwise, an instantaneous infinite Euclidean space model would work. The issue is, with any visualization of the Big ...
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### How did Copernicus get the idea of heliocentric model?

The heliocentric model marked the beginning of modern astronomy. But what were the reasons which led Copernicus to think that the earth orbited the sun. I've read that his model was based on ...
174 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 ...
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### Inability of Hubble to clearly resolve nearby celestial objects

The Hubble space telescope performs incredibly detailed and stunning imaging of celestial bodies that are many, many light years away, and yet when it attempts to image objects within our own Solar ...
303 views

### Why don't we feel the speed of earth moving

When we move our vehicle, we "feel" the speed of it. However, when stationary, we still are moving,but moving by quiet a speed. We know that earth moves with X ...
17 views

### First meteor(s) of Lyrid meteor shower?

So I am a newcomer to Astronomy - only aged 15 - and am currently looking upon the sky in hopes of witnessing several meteors. This is my first time ever - maybe - seeing them. I just went inside for ...
1k views

### What is the formula to predict lunar and solar eclipses accurately?

A number of ancient civilizations had devised methods to predict exact dates and times of such eclipses, marking them as important events. Hence I assume the predictions were based on calculations, ...
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### Movement of the satellites of the planets . . .

Is the movement of the satellites (moons) of a planet coplanar, like the planets being coplanar around the local Sun?
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### Finding a Kerr Black Holes

I understand that Kerr Black Holes are purely theoretical and have not been found anywhere in the Universe. However, they are theorized for possible means of time travel. I am attempting to prove in ...
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If the big bang is true, after the emission of light from the hydrogen plasma, the universe was still expanding. Why would we expect to see uniform radiation if earth very well could have formed ...
131 views

### Collision of 2 black holes

There is a large number of visible Supernovas. Each week - about a 20 Supernovas Type 1a around the Universe. Is there collisions of Black Holes? What is this collision called? E.g. 2 black holes ...
95 views

### Position and velocity vectors of nearby stars?

One of my favorite tools for modeling the solar system is the Horizons Ephemeris generator where I can get position and velocity vectors of various bodies. Is there something similar for neighboring ...
165 views

### Why don't planets and asteroids have (cometary) tails?

Comets have tails. We all know that, and a lucky few have seen the better known. So why don't the planets (e.g. Earth, Mars) have tails? Why don't asteroids don't have tails?
290 views

### What is the name of that which exists beyond the Universe?

"The Universe is commonly defined as the totality of existence" but that is more of a philosophical position. Empirically we know (or believe) that it is of finite size some believe it is expanding ...
370 views

### What was the length of year 1 million years back?

We know that the universe is gradually expanding and this indirectly means that the gravitational force between sun, earth, planets and other stars (roughly anything in the universe) is gradually ...
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### Do solar systems have to evolve in a galaxy?

Is it possible for a solar system like ours to exist and evolve apart from all other star systems and galaxies. Sort of like a stand alone solar system or rogue solar system for lack of a better name. ...
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When reading an article on using Jovian moons to calculate longitude, I came across this passage: Periodically, Jupiter eclipses each of the four large moons as they pass into the planet's mammoth ...
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### Might the universe be really small yet seem infinite from spherical reflections? [closed]

if a single source of light quite small, was placed somewhere inside a completely reflective sphere, quite large, what would the reflections look like from the light source's point of view within that ...
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### Einstein General relativity and bending of space [closed]

As Einstein's General relativity suggests that the space time curves in the presence of matter, which is experimentally proven too, this phenomenon also explains orbits. My question is if the ...
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### “How the Universe Works”: is it scientifically accurate? [closed]

The documentary/mini-series How the Universe Works is based on scientific evidence and according to what is known nowadays, or sheer bunk? Throughout the series, are there any particular topics which ...
30 views

### Telescope in Sun's gravity lens focus - pointing, gain, distortions

A telescope located in the gravitational focus of the Sun can use the Sun as a magnifying lens. The focus begins 550 AU away, but maybe a 700 or 1000 AU distance is needed to get rid of disturbances ...
55 views

### Density of hydrogen between galaxies

From watching a video on youtube, it states that Dark Matter is 6 times more abundant than known matter. I was wondering if it was possible to have hydrogen clouds between the universes galaxies. The ...
86 views

### Adjust axis labels in ds9

How can I adjust the axis labels in ds9? I'd like to have something like: So far I only managed to get floating points (tl h%f3): or the leading hours are missing (tl h%f1 m): Edit: I tried ...
184 views

### What can we expect from the first accurate image of a black hole? (wich will be taken soon)

From recent news from the Max Planck Institute for Radio Astronomy: The European Research Council (ERC) has awarded 14 Million Euros to a team of European astrophysicists to construct the first ...
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### What is meant by Electronic Beam Steering and how is it achieved?

I recently came across an article about the Murchison Wide Field Array which said directivity is achieved by Electronic Beam Steering and not by Mechanical methods. It would be helpful if someone can ...
295 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 layout the universe. Though I searched around and found it hard to get a good view of what the universe ...
115 views

### How would water waves behave in partial gravity?

Would an "indoor" pool of water on the Moon or on Mars behave differently than on Earth? Would the waves caused by a splash be higher or lower? Would they propagate faster or slower? Would boyance be ...
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### How powerful a telescope would allow me to view the astronauts aboard ISS do a space-walk?

This arose from a comment posted against a question elsewhere on the stackexchange How powerful a telescope/binoculars would allow me to view the astronauts aboard the ISS do a space-walk? Aperture? ...
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### How to calculate the movement of the object passing near other object in space?

Assume object A is moving through the space and is passing near the other object (B). Assume the gravitational influence of other objects can be ignored. How to find the equation describing the ...
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### Present distances between planet. How can I find them?

It's "commonly known" how distant are our solar system planets from Sun. But we can't easily say that about planets, which distances can differ greatly, without some observations (or simulations, ...
168 views

### What is the minimum mass required so that objects become spherical due to its own gravity?

Is this minimum mass known? or maybe, is it given in terms of density? If so, how much density is the minimum to have an spherical object due to its own gravity?
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### Can a black hole reach a limit where it can no longer attract more matter?

Can a black hole reach a limit where it can no longer attract more matter? If so, what happens with that black hole? Does the black hole die? Does the black hole decrease its size?
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### What's the furthest object observable by the naked eye from earth?

From XKCD: Caption: 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers. So, ...
527 views

### Doesn't gravity attract objects in space until they collide?

If the formula to calculate the force of gravity of two objects is: $$F1 = F2 = G * (M1 * M2/r^2)$$ Why do planets stay in orbit? Or is there another formula at work?
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### 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 ...
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### 3D Positions of Nearby Stars

I have come across a number of star catalogs that list stars by right ascension and declination, along with other data such as magnitude. Is there a star catalog that lists the 3-D position of stars ...
108 views

### Why is every year the same number of days despite the gravity in the solar system?

I was just watching a Geoff Marcy talk on YouTube showing how they infer the presence of planets transiting distant stars. The supposed periodicity wasn't always quite regular from what I could see, ...
118 views

### What’s the object between the earth and the sun currently showing in Google maps?

If I select satellite imagery in Google maps and zoom out, the earth is shown in space. It shows light/dark regions correctly updated, but there’s an object between the earth and the sun. It looks too ...
55 views

### What is the connection between moons, rings, and gaps?

I was watching this video and they said that the rock probably has a moon. Is the reason they assume it has a moon is because there is a gap between the rings created by the moon's orbit around the ...
1k views

### Why is only one side of the Moon visible from Earth?

Why do we only ever see the same side of the moon? If this is to do with gravity are there any variables which mean we might one day see more than we have before?
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### Is it possible that all dark matter is made of rogue planets (free-floating planet)?

Is it possible that all dark matter is made of rogue planets (free-floating planet)? (and other stuff like asteroids or meteoroids)
104 views

### Build a high quality telescope from scratch [closed]

I am interested in building a high quality portable telescope from scratch in an attempt to better understand how telescopes work. What kind of materials do I need? How would I go about putting the ...
202 views

### What is the most extreme weather found on another planet?

On Venus, there is really inhospitable weather, as well as within the gas giants in our solar system. Are there examples of even more extreme weather on planets found in other solar systems than ours? ...