# All Questions

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### What was “space” like before big bang?

I have a simple question which I think about often but have no answer. If The Big Bang is true, than if the whole space was just a point 14 billion years ago, then what was around that point, some ...
121 views

### What is spacetime 'made' of?

General relativity is often explained as saying spacetime is curved by gravity, what does this mean? How could we perceive a curve in spacetime when there is no external "straight" reference frame for ...
182 views

### Does the Sun impose back it's tidal forces onto the Earth (such as the Earth's to the Moon)?

It is known that each year the Moon is moving away from the Earth due to tidal forces. What about the Earth relative to the Sun?
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### How to calculate when the moon is highest in the sky to the earthbound observer?

Like when is the new moon highest in the sky? Or third quarter? How do I know this for any general moon phase? Thanks.
793 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 ...
300 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 ...
84 views

### Is there a photo that shows a iron meteor or asteroid in space in raw form having no layers of fusion crust?

A raw iron meteor or asteroid in outer space should be in its raw form having no signs of fusion crust from the friction of atmospheric entry and should therefore show distinctive signs like the ...
18 views

### plane of moons orbit, self spin with respect to earth's self spin and orbit around the sun? [on hold]

is there an image of plane of moons orbit, self spin with respect to earth's self spin and orbit around the sun? is that Geodesy related or Astronomy related?
61 views

### Is there sufficient evidence to confirm additional Planet in solar system

I have watched this scishow episode where Hank says that astronomers believe there is another planet in our solar system. Link He says that it's because how asteroids and comments are being pushed ...
34 views

### Calculating longitude from star culmination

Here is the problem: I need to calculate longitude of observing place. And I know time (in UTC+1) of star culmination (Sirius) and star altitude. I also know RA (right ascension) and Dec (declination) ...
101 views

### Why do planets tend to rotate in the same direction although they have formed from tumbling asteroids?

The axial tilts of asteroids seem to vary randomly (let me know if this premise is wrong), while the planets have a strong tendency to rotate in the same way. If planets were formed by colliding ...
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### Why are stars more metallic closer as you move closer to the galactic bulge?

As I see it, most of the stars in the galactic bulge are Population I stars. However, as one moves farther from the galactic bulge, star metallicity decreases. In fact, halo stars are almost entirely ...
33 views

### Red dwarf variation in Luminosity

I recently saw this video. The creator of the video says that one of the reasons for non-existence of life on planets around red dwarfs might be that these stars can increase luminosity roughly by a ...
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### Is there really no difference between up and down in ISS? [migrated]

ISS is actionally falling towards the earth and therefor they don't feel gravity. But ISS is falling in a direction towards the earth. So the astronauts living in ISS probably live in ISS in a manner ...
59 views

### How can a naked singularity be possible?

How can we have a singularity, without a black hole around it? How would one form? What does it do?
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### Astronomy Jokes [migrated]

Disclaimer: I battled with myself for a few days over whether it would be a good idea to post this question on Astronomy SE. Inspired by Jon Skeet Facts question on Meta SO, I decided to go for it. ...
58 views

### Good textbooks for a descriptive astronomy course

Brief tale of woe My department at a small public university in the US has decided to begin offering a descriptive astronomy general education course for the first time in a couple of decades and we ...
113 views

### Could an impact have resurfaced Venus 300 million years ago?

Venus surface isn't older than about 300 million years. The only explanation I've come across is that some kind of global volcanism resurfaced the planet. But couldn't it have been an impact event? A ...
29 views

### Angular Separation

Two stars A and B are located on the celestial equator. The RA of star A is 02h 0m 00s and that of star B is RA 07h 00m 00s. What is the angualar seperation between star A and B?
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### Could Venus or Mercury have a moon that we haven't detected?

Let's consider Mars' two moons for a moment. They're small, not even spherical, and most likely are captured asteroids. They weren't discovered until the late 1800's. Telescopes are much more powerful ...
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### Why argon instead of another noble gas?

I noticed that the atmospheres of Earth and Mars have a little bit of argon in them (1% to 2%). I checked Venus, too, which has 0.007% argon, but that's still more than any other noble gas in the ...
9k views

### Did atoms in human body indeed come from stars?

I think I am not alone who saw videos about that we (humans) are made of same atoms which someday were in stars. In other words, some atoms in our bodies are from stars which exploded billions of ...
3k views

### Is the Earth going to evolve towards Mars' fate or Venus' fate?

Upon reading on this site (and many others), one can think that Mars might have supported life in a distant past (discovery of liquid water, valleys, mountains...). On the other hand, Venus is the ...
385 views

### Where can I find a set of data of the initial conditions of our solar system?

As title suggests I'm in need of a set of data of our solar system. Similar to this http://bima.astro.umd.edu/nemo/archive/#iau25, specifically dubinsky milky way-andromeda data. I'm creating a ...
23 views

### Where can I find/visualize planets/stars/moons/etc positions?

What resources are available to find the positions of planets, stars, moons, artifical satellites, asteroids, and other heavenly bodies?
217 views

### Orbits in a binary star system

I know of three sets of stable orbits in a binary star system: orbiting closely around star A, orbiting closely around star B, or orbiting distantly around both stars (and their mutual center of ...
119 views

### Lack of objects between heliopause and Oort cloud?

If we take a look at a logarithmic scale of the Solar System, there appears to be a large gap between the heliopause and the Oort cloud: Why is that? There are some objects in the gap, but why are ...
109 views

### Why wasn't there any oxygen in the beginning of the earth?

In the total beginning of the earth there was CO2, N2 and H2O. So there was O2 but always in bond with Carbon and hydrogen, but what is the reason for that? Is O2 always reacting with free ...
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### What accounts into calculating the Hubble constant?

From my understanding, the Hubble constant $H_0$ calculates from observed redshifts $z$ of distant galaxys against their proper distance $D$. The current value appears to be 67.80(77) ...
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### Where is the materials of comet after it crashed into the sun?

If a comet crashes into the sun, where will the substance (eg: water,silicon) be? Will they be inside the sun? Or they will be ejected from sun again?
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### What Would it Look Like Inside Jupiter's Great Red Spot?

From what I've read, Jupiter's 'Great Red Spot' is an unbelievably powerful storm. Do astronomers and scientists have any idea of what that might look like if it were possible to be inside/below it? ...
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### Best planets profile for a tattoo of the solar system [closed]

I want to get a tattoo of the solar system. The gap between the planets should not be preserved and the differences in sizes will only be symbolic. I found the following My question is if all stars ...
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### Is there an objective difference between space expansion and reduction in speed of light

I just read an article about the cosmological model of an inflationary universe. As you probably know it basically states that space itself is subject to an expansion over time. Since there is no ...
63 views

### are modern flat earthers still believe the earth is flat not round? [closed]

I saw a video in youtube and read few articles about how flat earthers believed that earth is actually flat but not round. They even presented facts about how everything which is true right now is ...
53 views

### What is the distance of earth from 7 planets, moon and sun at a point of time?

I wanted to know the distance of the 7 planets(mercury, mars, venus, jupiter,saturn, uranus, neptune) each (or at least 5 planets) from the earth and the angle that it will make with a line connecting ...
104 views

### How/where to check where the Sun is (constellation)?

I would like to check in which constellation the Sun was in at some time in the past, any recommendations how to do that?
35 views

### How to read Babylonians' tablet that were used to track Jupiter's movements?

There is a science news article on how Babylonians used geometry to track Jupiter’s movements. Here is an image of cuneiform tablet which shows Jupiter's movements. From a layman's point of view, ...
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### When is it a good aproximation to consider a star to be an ideal gas?

I am currently taking a first course on stellar astrophysics, and I noticed that in some cases we use the ideal gas equation of state for stars, so we also use $\gamma =5/3$. Of course it can only be ...
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### Is Ceres in the inner solar system or outer solar system?

Do we consider the dwarf planet Ceres to be in the inner solar system or outer solar system (or possibly neither / in between). It is located within the asteroid belt, but is the asteroid belt part ...
52 views

### How would FTL travel appear through window of ship? [migrated]

How would faster-than-light travel appear through window of a space vessel? All the movies and TV shows like Star Trek and Star Wars seem unrealistic: Star Trek credits: passing stars get bigger ...
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### Does any satellite communicate only through laser? [migrated]

I have read (here) + heared (on astronomy podcast) that radio waves decay or are undistinguishable the more distance they travel. Do any of man made satellites communicate with Earth solely by ...
43 views

### What is “emission measure”?

Many papers mention emission measure, and some of them give the expression of EM, BUT there is no clear definition of EM. My question is what EM is on earth? Its unit is supposed to be cm-3. How to ...
109 views

### Why don't storms on gas giants move to the poles, like hurricanes on Earth do?

On Earth, hurricanes usually move from the equator to the poles. But if you look at a picture of Jupiter, you'd see that the Great Red Spot isn't anywhere near the poles. So the question is: why don't ...
63 views

### At what size to objects burn up in the atmosphere when falling from orbit?

As the title suggests, I am wondering the maximum size an object can be so that it will completely burn up when entering and falling through earths atmosphere. I'm focusing on man made objects, not ...
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### What are the prerequisites for a meteorite to reach the ground?

I'm sure it's a function of atmospheric entry angle, meteorite mass (and possibly composition/density), and its velocity, but what function is it? Above all, how does it depend on velocity? Will the ...
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### What effect does a natural satellite have on a planet's rotation and revolution?

how is the rotation and revolution of a planet that does not have a natural satellite different from a planet that has say 1 natural satellite (ex. earth and moon system).
190 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 ...
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### How old was “student-Earth” when life first formed? [closed]

this section is meant to explore the relative timings of various important events in Earth's history by re-imagining Earth as a 20-year student. You will need to scale geologic time from the age of ...