# All Questions

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### Age of the universe

A Galactic year is estimated to be around 250 million "terrestrial" years. That means there will be about 4 rotations per billion years. And age of the universe is estimated to be near 13.8 billion ...
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### If we lived in a multiverse, what would our universe most likely then be named? [closed]

For instance, we live in the Milky Way Galaxy. We don't just call it "The Galaxy", because we know there are multiple different galaxies. So if we lived in a multiverse, it wouldn't make much sense to ...
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### Is light bending around my finger? [closed]

I was hoping that astronomy enthusiasts/scientists would help me out with a simple question about light. Hold your outstretched hand up to any bright light source (the sun, or even a light bulb) so ...
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### Heavy bombardment - Why has things cooled?

I was always taught and lead to believe that at the beginning of our solar system, there was a period of heavy bombardment, which is conceivable. Why has it just stopped and we are at peace from ...
629 views

### If Venus and Mars changed places, would we then have 3 habitable planets?

This is the supposition: Venus is too hot, Mars is too cold. If they switched places then Solar energy would change to make both more Earth like. We might as well have had three instead of just one ...
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### How can I calculate the orbital periods in a binary star system?

I have two stars, with known masses and known orbital radius. How do I calculate the orbital periods of both stars?
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### What would the sky have looked like when galaxies first started to form?

If I stood on a theoretical earth at the time that galaxies were just starting to form, what would the sky have looked like? Due to the smaller size of the universe would it have been densely packed ...
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### What is that void that the universe is growing into? [duplicate]

We understand that this is the universe and it is essentially full of space and time, but what is on the outside of the universe, and isn't that nothing, something, and how far does that reach. I.e. ...
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### Why does the darkening of the Moon go from left-to-right during an eclipse?

In anticipation of the upcoming April 2014 lunar eclipse, I decided to use the 3D virtual planetarium software Stellarium to simulate what it is supposed look like where I live, since I've never ...
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### How close would quasars have been to each other?

My understanding is that quasars are the early phase of formation of galaxies. At the time quasars were forming, the universe would have been smaller and therefore things closer to each other. About ...
127 views

### Absolute magnitudes of stars

Where to find comprehensive list of absolute magnitudes for stars of different spectral types? I need published paper or web page with data and reference to the source.
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### Are many exoplanets synchronously tidally locked like Mercury?

The only tidally locked planet in the Solar system i Mercury. But it is synchronously tidally locked 3:2, because of the relatively high eccentricity of its orbit, so doesn't turn the same side ...
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### Why doesn't the earth's surface collapse onto itself? [closed]

From what I know the sun (or any other star) nuclear fission keeps it from collapsing under its own gravity until the fuel runs out, if that's so why doesn't the earth surface like the tectonic plates ...
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### Location on (or in) the celestial sphere

First off, I apologize if I am breaking any site-etiquitte. Secondly, this is probably extremely elementary. For a lab, I was given the question: When we are sitting in a planetarium, where are ...
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### regarding curvature of earth [closed]

i am having one doubt in earth's curvature.....this question may be dumb... How much we need to travel on earth to feel the curvature of earth. hypothetical case: for ex we are building a vehicle ...
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### What method is used to calculate the 'quality' of a solar/planetary image?

What sort of algorithm is used to calculate the relative quality of an image, such as is performed by PIPP, Registax, or Avistack? Such applications take planetary or solar images and prior to ...
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### if the big bang only expanded the universe when and how did it originate? [duplicate]

If the big bang expanded the universe from a singularity point, that means that there was matter before, so where and how did matter form for the first time if it's even possible to know such a thing? ...
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### Why do objects burn when they enter earth's atmosphere?

Why do all objects burn when they enter our atmosphere? is this because of our atmosphere composition? and does this happen on other planets as well?
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### How can we infer the mass of SMBH in galaxies that are not active anymore?

I know it is possible to infer the mass of a supermassive black hole (SMBH) by many methods, i.e., stellar orbits for out Galaxy, Iron line profile from the accretion disk, and probably other methods ...
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### 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 ...
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### If NASA is going to capture an asteroid with a spacecraft, wouldn't a UFO be able to manuever a celestial body? [closed]

This article got me thinking If NASA is going to use our primitive space exploration technology to capture an asteroid wouldn't an Extra Terrestrial species have used UFO's to maneuver celestial ...
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### Can someone explain a Geostationary Orbit in a simpler way?

According to Wikipedia (link), a geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit (GEO), is a circular orbit 35,786 kilometres (22,236 mi) above the Earth's equator ...
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### strange moonset around 10 pm (3.2 2014, NZ) - explanation?

during a visit to New Zealand we observed (on 3.2 2014) a strange moonset in Te Anau. Around 10 pm, shortly after sunset, the moon appeared, but then quickly began to go down, and about 1 hour or ...
172 views

### Do black holes die?

I know of stars actually dying (exploding as a supernova) but I have never heard of what happen to black holes. Do they continue to live forever, waiting there for more matter to absorb? Do they ...
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### Could I create a staircase to the moon and walk to it? [closed]

Assuming one could create a staircase and walk to the moon, would escape velocity still be a factor in leaving the Earth's gravitational pull? I'm not a physicist but am just curious to know.
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### Can we only see the past of the universe? [duplicate]

So I was reading some interesting stuff about universe and Big Bang and wanted to make sure one thing. As far as I understand everything we can see about universe is the past, right? I mean all the ...
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### What would happen if we put a small part of White Dwarf or Neutron Star on Earth?

I would know what would happen if we put a small part (let me assume 1 cm$^3$) of White Dwarf or Neutron Star on ...
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### Why haven't Earth and Venus got any tiny moons? Or have they?

Why haven't some meteoroids gotten caught in Earth's or Venus' orbit? AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities ...
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### What are the concrete technical arguments supporting the idea that the wave function of the universe can be written as partition function?

In this talk, the not yet settled down idea that the wave function of the universe could potentially be written as the partition function of a scale invariant statistical field theory is mentioned: ...
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### Is everything quantum entangled?

So, I am learning about quantum entanglement in my quantum course and had a thought. If the Big Bang is the creation of everything - time included, and this came from a single "source". Would it not ...
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### What are the masses of the two stars (given the information provided)?

If anyone would at least be willing to point me in the direction of finding the answer, or help me solve it I'd appreciate it. I don't know how to go about this, and need to know how to solve this on ...
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### What does black hole evaporation correspond to in the accelerating universe / black hole analogy?

In the same way, as a black hole emits Hawking radiation corresponding to its temperature $$T = \frac{\hbar}{r_{BH}}$$ the accelerating universe can be described as all of the stuff falling ...
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### Can looking at the sun through solar viewing eclipse shades everyday harm your eyes?

I have a pair of Solar Viewing Eclipse Shades that say "Safe for Direct Solar Viewing" and would like to know if my eyes would be harmed if I looked at the sun everyday for about a minute wearing ...
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### Would it be possible to calculate the expected frequency of impact craters of all sizes on Earth

Can the expected frequency of all sizes of impact craters on Earth be calculated based on the preservation of impact craters seen on the Moon? Taking into account the difference in gravity and ...
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### Class presentation on the Sun, ideas? [closed]

Tomorrow I have to give a [high school] class presentation on a topic of the solar system. I have thought of the Sun, as I have always believed it to be the central part of the Solar System. So I am ...
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### How are rogue planets discovered?

Planets are usually found by observing a star and waiting for the light level to drop when a planet passes in front of it, but what about rogue planets that don't have host stars?
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### Why is the speed of light 299,792,458 meters/sec?

Ok, I am majoring in physics (4th year) and I never understood this fundamental (kinda) question. Maybe I haven't explored it enough. For example, why does it take 8min20sec for the light from the ...
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### Formulas to determine the illuminated phase and orientation of the Moon

The phase of the Moon (the bright limb) looks different depending on where on Earth the observer is located and the time of the observation. I've located this video and the accompanying spreadsheet ...
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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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### Matter/mass exist into the space. Where does space exist? [duplicate]

It is said that before big bang there was nothing. Not even space/time. So, now where does space exists?
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### Is it possible to calculate the time of day given latitude, longitude and solar elevation angles (zenith, azimuth, elevation)?

I am trying to determine the time of day of some images I have. I know the lat/lon, the day and year of image. I also know the 3 solar angles (zenith, azimuth, and elevation). Is there MATLAB or ...
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### How many earth-like planets do we know at this moment?

Well, the title says everything... How many earth-like planets have we discovered out there? Discard too big (made of gas), too cold, too hot, etc. Consider earth-like sun distance, size, temperature, ...
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### Could black holes be creators of dark matter?

At the tremendous forces of gravity inside a black hole, can "matter" be transformed into a more degenerate form; "dark matter" (if that truly what dark matter is)? I know the inside of a black hole ...
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### A clock travelling “faster than the speed of light” [closed]

When a clock travels close to the speed of light as observed by us, it should tick slower. Does this mean that, when using this clock to measure a second - it could travel much more than 300 000 km ...
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### 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 ...
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### Integral calculus for the Olympiad? [closed]

This year I am going to participate at the Astronomy Olympiad, in the beta group (seniors) - 15 years old or above. I have already participated at this Olympiad in the alpha group (juniors)... now, a ...
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### Do stars have exactly sphere shape?

Planets (at least, some of them like Earth) aren't exactly spherical - but what about stars? Is Sun perfectly spherical, for example? What may be the reasons if it isn't? What about other stars?
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### If the earth stopped rotating, would we really fly inertially at 1000mph? [closed]

I heard this on Prof. Neil Tyson's StarTalk podcast (this episode) and had a question about it. In a Q&A session, a listener had asked what would happen if Superman really did stop the earth from ...