# All Questions

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### Eclipse Cycle Calculations Needed

I am writing a work of fiction about a world where: The length of a year is 335 days. The world has two Moons. Moon A is Larger and further away with a 78 day lunar orbit. Moon B is smaller and ...
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### Local Standard Time Meridian - LSTM (Units)

I was just wondering what units I could scale down to (or or shouldn't) for working out values like Local Solar Times, or Local Time etc... From the papers I'm looking at, I can't see any mention of ...
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### Dish antenna as parabolic mirror for OPTICAL telescope?

Can i use a chrome painted dish tv antenna as a parabolic reflector for my Optical telescope ? Given that glass mirrors are quite expensive, i am thinking of using a Dish TV antenna and coating its ...
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### Is it practical to hand grind a convex parabolic or hyperbolic mirror?

I know it's practical to hand grind a convex spherical mirror and that it's practical to make a concave parabolic mirror from a spherical one. But as I understand it, the procedure for doing so depend ...
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### How can a supernova cause a gravitational wave?

With the recent results of LIGO, I read a lot how limited the detection capabilities where and how one could only expect to measure the most extreme events like black hole mergers and supernovae. I ...
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### Is it safe to watch solar eclipse's reflection in water?

There will be a solar eclipse soon at my area... naturally I want to watch this with my son. Is it safe for us to watch the solar eclipse's reflection in the water? There is a swimming pool near my ...
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### Can there be life in black hole? [closed]

Can there be life inside a black hole is it possible that we are living inside a massive black hole right now? This is because i see no reason why we cant be inside a super massive black hole the only ...
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### Oxygen in a methane atmosphere akin to methane in oxygen atmosphere?

If we assume a planet the size of Earth with an equally dense atmosphere of nitrogen and methane, rather than oxygen, and it's in the goldilocks zone. Would a hypothetical alien species be able to use ...
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### Does planets revolves around all the 88 constellations? [closed]

I am a beginner / novice and I have got very little knowledge about astronomy Please tell me whether 'Planets' revolves around all the 80+ constellations or not
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### What are gravitational waves actually? [duplicate]

I read about the LIGo experiment recently, but i didn't understand their significance. Although, it's clear to me that the gravitational waves do exist and are caused by large accelerating bodies in ...
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### Can visible wavelength spectroscopy study an exoplanet's chemical composition directly?

I know spectroscopy of light in visible wavelengths is very effective for studying and determining the chemical composition of bodies within the solar system and bright objects outside of it. However, ...
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### Would humans hear gravity waves from a binary BH fusion nearby?

The frequency of the gravity waves detected by aLIGO recently were in the audible sound spectra. Actually spanning over half of the keys of a piano, I've been told, during 2/10 or so seconds. Would a ...
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### Physical laws in other universes

In the theory of multi-verses, we can imagine countless other universes where the constants of nature, including the amount of dark energy in a volume of space and possibly even shapes of hidden ...
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This Question and Answer got me thinking. If atmospheric seeing at visible wavelengths is the result of refractive index inhomogeneity, would it also be a similar problem for mm to cm wavelengths? ...
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### Does the accelerating expansion of spacetime mean that the pace of time is changing?

Space expands everywhere, also here. And time is inseparable from space. Does this mean that time also "expands" as in changing its pace? Is the changing rate of time also astronomically observable? ...
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### What is the schedule for science runs of aLIGO (and VIRGO)?

Advanced LIGO seems to operate only intermittently. Is there a schedule for at what times it will be able to register new gravity waves? Even if no formal schedule is available, what main factors ...
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### How useful are filters for spotting nebulae?

Recently I've been trying to spot a couple of nebulae, IC59 and IC1318. The skies at the site are modestly dark (4.5 on the Bortle scale), I'm using an 8" scope, and I've slowly scanned around the ...
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### Do massive bolide entries coincide with meteor showers?

Are exceptionally large, bright, meteors (such as Tunguska or Chelyabinsk) more common during common meteor showers like the Perseids, or the Leonids? If not, why is that? Do the meteor showers ...
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### Distinction between metric expansion and objects just moving apart from each other?

I see explanations likes this: Galaxies and other sources, then, are not strictly expanding away from each other but rather are attached to the fixed grid on the expanding fabric of spacetime. ...
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### Why is this video showing radio waves transmitted from a radio telescope?

I saw this video at Space.com and I noticed that at 00:05 the animation illustrates waves propagating from space into The Dish at Parks Observatory, but at 00:50 the direction of propagation is ...
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### What would harnessing of gravitational waves look like?

We have harnessed and learned to generate and control sound waves, light waves, water waves, and electromagnetic waves in general. What would be needed for science to be able to generate and use ...
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### How much of a difference do good lenses make?

I recently purchased a Celestron PowerSeeker 114EQ and with it I got three lenses (which I assume are low quality), a 4mm, a 20mm and a 3 x Barlow. I can get pretty decent views of the moon but a ...
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### Rate of Mass Loss from the Solar Wind

This is problem 1-4 from Principles of Stellar Evolution and Nucleosynthesis by Clayton: Assuming at the Earth a characteristic velocity of 400km/s and density of 10amu/cm$^{3}$ for the solar wind, ...
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### How are the element abundances calculated for a meteorite in the Hydrogen log10 scale?

In astronomy, solar abundances are often calculated or tabulated per $10^{12}$ H atoms. I understand that in case of the Sun this can be done because H atoms are in majority or are present for a scale ...
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### How often do meteorites hit earth

I heard of one that occurred in 2008 in the Nubian Desert in sudan, how often does it happen? Is there a catalogue of all hits or is it very rare? Related link (This is what inspired my interest not ...
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### What exactly is meant by “expanding universe”? [duplicate]

What exactly is meant when we say the universe is expanding? I understand stars and galaxies are getting farther and farther away from us, but are individual particles (atoms, molecules, anything ...
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### SDSS. Google Sky and DeCaLs

(1) Please go through following image Possible Super Red Giant? However sdss shows it as galaxy! Am I missing something. (2) Google Sky shows object in latitude and logitude format like this. Is ...
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### What happens to the information on the event horizons of two merging black holes?

What happens to the hairiness/information on the horizons of two black holes if they collide? After Hawkin the information of the matter which has fallen into the blackhole is encoded on the surface ...
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### Description of Henyey tracks on wikipedia incorrect?

So, if you search for Henyey tracks on wikipedia (I know, the shame of it!) you will come across this statement: The Henyey track is characterized by a slow collapse in near hydrostatic ...
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### What are the advantages and disadvantages of a 2-inch eyepiece versus a 1.25-inch eyepiece?

I'm considering picking up some new eyepieces for my telescope and am interested in comparing 2-inch and 1.25-inch eyepieces. Are there any disadvantages to 2-inch eyepieces? Are 2-inch eyepieces only ...
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### Stellar data for data mining [closed]

Where could I find detailed data from stars? Like spectrum, x ray and so on ? Because I would like to do some data analysis on it.
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### In what manner is the spectrum of a black body really a continuum?

Usually they say the spectrum of a black body is a continuum and emits radiation at every frequency. Is it really a continuum like a line or are there (small) intervals? For example, can a body emit ...
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### How to configure Celestia to work with a spherical mirror projection on a dome

I find hints around the web, e.g. http://www.cosmodome.net/mirrordome.php that Celestia can be projected on a dome using a spherical mirror projection configuration. The problem is that I can't find ...
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### When you travel fast around a black hole, do you experience high speed yourself?

When an object in the space comes close to a massive body (like a black hole or a neutron star), we see from Earth that its speed significantly increases while it is close to the body. As we know, ...
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### Will gravitational waves too far away ever reach us?

Gravity is the curvature of spacetime, and its effects travel at lightspeed. However, space is expanding; eventually, light from distant galaxies will become more and more redshifted, and we will no ...
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### Size of the Universe [duplicate]

The number of atoms in the whole Universe seems to be finite, yet the Universe is infinite in dimensions? How it is possible in the Universe?
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### Procession of the Equinox

I just learned about procession of the equinox, i.e. the Earth's axis tilts one degree every 72 years. And it takes 72 years/degree x 360 degrees = 25,920 There are many theories to this, i.e. ...
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### When was visible light for the first time created?

"A few minutes into the expansion, when the temperature was about a billion (one thousand million) kelvin and the density was about that of air, neutrons combined with protons to form the universe's ...
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### Could science be lost if a phenomena is observed before predicted? [closed]

An observation could validate the predictions made by a previous theory. If something unpredicted is observed, then a new theory which is compatible with the observation should make predictions which ...
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### Origin of the Universe [closed]

I heard on a you tube video that a new theory came out in 2015 . The theory is that there was no "Big Bang" and that the Universe has no beginning .
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### How to figure out a moon phase for July 1937

I would like to know how to figure out the moon's phase for July 4, 1937 at 9:34 pm. Thank you.
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### Is there a variation of ISO 8601 for julian calendar dates?

If I want to write a date in the Gregorian calendar, I can write it in the ISO 8601 format; today would be 2016-02-20. The advantage is that there are many parsers available to let computers read in ...
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### What is the current state of gravity in the vacuum of space? [closed]

Is Gravity in the vaccum of space decelerating or exspanding? please explain why,when and how in detail, Along with a credible reference. If Science has not concluded either please give a reference as ...
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### Where is the flaw in this hypothetical concept of escaping event horizon using another's blackhole flyby?

imagine two black holes approaching each other in a way that they will perform just very close flyby. You have a spaceship just below the event horizon of one black hole in line between centers of ...
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Question: Approximately once in 5 years people on Earth can observe bright comets whose nuclei have radius about 1km. The orbits of such comets are close to parabolic. Assuming that these nuclei are ...
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### Are black holes really singularities?

Can't black holes just be super dense objects? They could still be black (having the color of black never really required special physics, after all) and have a really strong gravitational field. If ...
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### Earth's Versus Catastrophic Meteor

How evasive is the Earth to Catastrophic Meteors? Google says the Earth is approximately 92.96 million miles from the Sun. It also says the suns radius is 432,474 miles. Therefore, it is 93,392,474 ...
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### What is the formulat to compute King tracking rate for a given set of topocentric coordinates?

Canbury Tech has a good background on King tracking rate, which approximates the average sidereal motion of a refracted star across the sky. Most amateur telescope mounts have some sort of notion of ...