# Tagged Questions

The Sun is an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.

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### How is the sun's equatorial circumference measured?

How is the sun's equatorial circumference measured by scientists?
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### How does irradiance behave over time?

I am trying to clarify data on weather from the Royal Netherlands Meteorological Institute (KNMI); I have incorporated the Solar Position Algorithm (SPA), such that I can calculate sunset and sunrise ...
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### Calculating the length of day at any time of the year? [duplicate]

Is it possible to calculate the length of the day at various location (distances) from the sun? I hear agricultural scientists are able to do that. To make calculations easier assume there is no axis ...
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### Is there a simple yet accurate formula for where on Earth the Sun and Moon are directly overhead?

I'm trying to improve a site that shows the region of the Earth currently under daylight, and I need a formula that, given the current time, tells where (latitude/longitude) the sun and moon are ...
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### Does brown but transparent swimming pool water heat significantly faster than western style highly chlorinated pools?

Eastern European swimming pools are often brown tinted water. i was told it was the color of the chemical to keep the pools clean, but who knows. These pools did not smell unsanitary and may have even ...
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### When should angles be expressed in degrees vs. radians?

I am trying to calculate the albedo of a given latitude by following the methods of Brutsaert (1982), I have copied the formula below: 3.6 Shortwave and long-wave radiative fluxes Albedo ...
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### Must a vertical sundial face exactly South?

I am a sundial. I'm prepared to bet Your watch can't tell when the sun will set I once heard Frank King talk about sundials in particular this very cool one, which measures Babylonian hours ...
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### Attenuation mass-thickness for sunset light

We are able to look directly at the sun near sunset and sunrise, which clearly demonstrates the fact that our atmosphere attenuates visible light. Let's imagine it follows the typical attenuation ...
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### Do particles in the solar core travel at the same speed as they would in vacuum?

I just read the Wikipedia article on the Sun. The section on Solar Core states It has a density of up to 150 g/cm3[47][48] (about 150 times the density of water) Do the particles (atomic, and ...
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### How old is SUN ☉?

How do we know/calculate the exact age of sun ☉ ? ie. 4.57 billion years. What is the way to calculate it?
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### Have general relativistic effects of the sun's rotation been measured?

I was wondering if general relativistic effects of the sun's rotation have also been measured, like gravity probes A and B measured GR effects from the earth.
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Knowing ...
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### Why planets are rotating only in one plane? [duplicate]

Since gravity is three dimensional why planets are rotating only in one plane around sun.
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### Produciton of EM waves with differing wavelengths

Sun is the major source of electromagnetic radiation. Then if the source is the same, how are different EM waves with differing wavelengths produced?
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### How much energy is needed to curve the space so the Sun will come 1 meter closer to our planet? [closed]

How much energy/work will it take if our planet is: 5.9736×1024 kg or 3.0×10−6 Suns to move Sun and Earth 1 meter closer ...
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### Why can there be fire in space while there is no oxygen?

The sun is made of fire but fire needs oxygen right? So.. Why can there be flames in space, while there's no oxygen? Same idea as with the rocket engines of the spaceship, which also produce fire ...
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### The Sun Can Make Stuff Hotter Than Itself

We intuitively understand the direction that energy travels -- from the thing with energy to the thing with less energy. That's why the second law of thermodynamics is among the first things you learn ...
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### Distribution of each element and molecule as a function of distance from the Sun and as a function of time

Are there any graphs that show the distribution of each element and molecule as a function of distance from the Sun? And maybe even the time-evolution of each distribution over the solar system's ...
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### What is the mass distribution within the sun?

Jupiter is roughly 1/1000 the total mass of the sun. To get some idea of what effect Jupiter's gravity may have on the sun I'd like to know the approximate mass distribution of the sun. (i.e) the ...
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### Was Sun a part of a binary system?

I've read that many stars and other celestial bodies are found to constitute binary systems where the two bodies spin around each other. But our Sun is one of the exceptions. Could it be possible that ...
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### Finding radius of Earth through observation of Sun's motion

The question I'm about to pose is from a physics book I had recently bought. Since I am very interested in physics I am quite keen in understanding how this question can be solved. Before I present ...
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### What is the relation between surface area and radiation, if any?

Basically I wonder what happens to emitted radiation by douubling a light e.g. twice the surface area of the sun will emit how much more radiation? 4 times more? Is there a formula?
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### Refraction and scattered light for NLCs

For helping with judging NLC candidates (are they NLC or not) I have a set of formulas to calculate the minimum altitude (in km) of the candidate given an observed altitude (in degrees) of the ...
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### If there was no Earth, what would be the acceleration of gravity from here from the Sun?

Suppose there were no Earth to pull us back and we're hanging in the solar system. Assuming no other force of gravity from other bodies, what would be the $g$ from the Sun?
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### Are solar physics images of use to the night-time community?

I'm actually interested in cases of cross-discipline data re-use. I know that the SOHO/LASCO coronographs are used for comet finding, that solar telescopes were used to get information about Venus's ...
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### What is the apparent diameter of the sun as seen from earth?

I know this may not be physically accurate. For my purposes, basically 3D renders, I am assuming the sun rays are parallel rays from an infinitely far lamp. If the sky is clear, what size would that ...
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### How to determine day/night based on latitude, longitude and a date/time?

Is there a simple method of determining, given a UTC date/time, whether it is day or night at a given lat/long coordinate? I am currently using a formula based on a Sunrise/Sunset Algorithm from the ...
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### Do photons lose energy while travelling through space? Or why are planets closer to the sun warmer?

My train of thought was the following: The Earth orbiting the Sun is at times 5 million kilometers closer to it than others, but this is almost irrelevant to the seasons. Instead, the temperature ...
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### Surface UV exposure with cooler star

If the sun's surface was ~ 4000K (and earth closer to compensate), the UV component of the radiation would be less. However, UV makes ozone via photolysis of oxygen. Also, the stratosphere would ...
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### Are dangerous rays emitted during Solar Eclipse?

It is said one should avoid staring at Sun as it can damage the eyes, but it is also said that one should not come out in sun during eclipse as it emits dangerous rays. Is that true? If yes, why?
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### Does the spectrum of Sol's emission change as it ages?

A follow-up to my earlier question How would one navigate interstellar space? that just occurred to me; albeit on a different tack. Sol is probably in a state of continuous flux. The change of state ...
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### Get time from sun Azimuth

I want to know if I can determine the time where the sun's azimuth is at a given value. In other words, I want a function that takes the sun azimuth along with longitude or time zone and outputs the ...
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### Are planetary orbits measured from the Sun's surface or centre?

I would imagine planetary orbits are measured from the Sun's centre and not its surface. Is that true? I can't find anywhere that actually states this.
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### Is there an Algorithm to find the time when the sun is X degrees above the horizon for a given latitude B at date C

Is there an accurate algorithm / method to determine the precise time of day/night when the sun is X degrees above (or below) the horizon for a given latitude Y at date Z? Is this the same question ...
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### Is a water world possible, and for how long could it be stable?

I have several questions regarding this topic. First, could a water world be stable for thousands of years with most of its surface remaining covered in water. What would it take for this to be ...
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### Why don't we see solar and lunar eclipses often? [duplicate]

Since we see the new moon at least once in a month when the Moon gets in between of the Sun and the Moon at the night and as far as I know if this happens during the day, you'll get to see a solar ...
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### Transit of Mercury: how did he see it?

On November 7, 1631 Pierre Gassendi saw the transit of Mercury across the face of the Sun. How did he see it? I mean what instrument was used to reduce the apparent brightness of the Sun?
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### Reverse Sun position algorithm?

To find the sun's position (elevation, azimuth) we can use many algorithms including the PSA algorithm. These algorithm share the fact that the input is the local time, longitude and latitude and the ...
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### What proportion of a star's hydrogen is consumed in its life?

I've heard in a lecture that a star like the sun would burn 3% of its Hydrogen before expiring. I would have thought it would be much more.
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### Photons arriving from the Sun

Given that the Sun is a bit less than 10 light minutes away from Earth, is it correct to assume in principle (I understand actual processes in the core of the Sun make the situation at a photon's ...
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### Why does the moon look bigger at the horizon? [duplicate]

Possible Duplicate: Why does the moon sometimes appear giant and a orange red color near the horizon? Why does the moon look bigger at horizon or skyline than at other times e.g. at ...
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### What is the relationship between mass, speed and distance of a planet orbiting the sun?

After reading this fascinating story about a new exoplanet, I was wondering about how mass, speed and distance determine a circular orbit of a planet around a star. Given the mass of the sun and ...
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### Black out the sun?

How many observers would it take to cancel out the number of photons produced in a medium sized star like our Sun, thus making it dark? (I want to consume more photons than the star is generating)
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### What is the luminosity per square meter hitting the Earth's surface from the Sun?

So I know that the Sun's luminosity is $3.839 \cdot 10^{26}$. What I want is the luminosity per square meter at the Earth's surface. So this is what I have got so far: I know the distance to the ...
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### Is it safe to observe the sun through binoculars with welding glass in front? [closed]

I asked this on Reddit but didn't get much of a response. So here goes! I'm looking for low-cost ways to observe the Transit of Venus this summer. Since I'll only be able to see a few hours of it ...
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### The “official” mass of the sun as unit?

I'm searching for the "official" mass of the sun as a unit in astrophysics. The mass of the sun can be calculated by: $M_{\odot}=\frac{4\pi^2\times(1 \ \text{ua})^3}{G\times(1\ \text{year})^2}$ So ...
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### Is it proven that all “solar” neutrinos are coming from the Sun direction?

In "Observation of 8B solar neutrinos in the Kamiokande-II detector" (Phys.Rev.Lett., 63, 16(1989), http://prl.aps.org/pdf/PRL/v63/i1/p16_1) the Figure 2 shows that only small percentage of registered ...
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### Is dark matter really present around the sun?

Recently I read an article that there is dark matter around the sun but if it is so, than why can we see it clearly. If it is called matter than it shall show some hindrance in radiation we receive ...