Questions tagged [light]

Questions regarding electromagnetic radiation in the visible spectrum.

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21 views

New Years 2017 12:35am we saw three red and orange lights hover over our neighborhood [closed]

Three orange and red circular lights. Similar to a fluorescent light when it’s lights went off. Triangular and disappeared. All 3 travelled in the same pattern and disappeared in the same area.
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1answer
104 views

Faster than light?

From what popular science tells us, if I travel at close to the speed of light, I'd age slower. So if I travel at 99% of SOL and travel the distance of one light year, for other people one year has ...
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1answer
94 views

How do the sun's light rays come to the world?

How do they come to the world? One of my friends who is a flat earther told me about how the rays seem to gather at one point, which sort of proves that the sun is close to us and not very big, in his ...
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3answers
64 views

Absorption of light by matter

What determines whether or not photons can be absorbed by matter? Intuitively, the answer is that a charged particle can absorb photons (whether it's positively or negatively charged), and neutral ...
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2answers
862 views

Problem regarding the absorption lines of the sun

Some of the wavelengths of light that are emitted from the sun will be absorbed by atoms in the outer layer of the sun and also the atmosphere of the sun, and we see this as absorption lines in the ...
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2answers
61 views

How dark/bright are polar nights?

During the polar night directly at the pole the Sun sets once and—after a period of twilight—stays down for months at a time. The only sources of non-human-made light are the stars, the auroras, and ...
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1answer
87 views

how long a light year on earth will seem [closed]

First of all, sorry if this is not the right StackExchange to ask this question, but i don't know a better place (open to suggestion in case). So, the question: Suppose that for some reason, we can ...
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2answers
100 views

Events I cannot explain

In the last few days I experienced two events I cannot explain. I watch the sky since I was a child so I'm aware of most events like satellites, ISS, Iridium flares, etc... First event It was about 22:...
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1answer
90 views

At what distance wouldn't the Sun cast a visible shadow anymore? [closed]

How far from the Sun would a (dwarf) planet have to be so that the Sun is dim enough that it doesn't cast a shadow when you're standing on the planet? What magnitude is the border in brightness beyond ...
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0answers
50 views

Is cosmological redshift caused due to expansion of space or distance traveled by light?

If the universe wasn't expanding, would light still be redshifted after traveling some distance? Is there a way of being sure that it's the expansion that causes light to redshift and not just a ...
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1answer
68 views

First Confirmed Visual Observation of Gravitational Lensing

Is it possible to identify the first direct observation of the gravitational lensing? What object was lensed, and where did the energy detected fall on the electromagnetic spectrum?
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1answer
44 views

Light levels on other celestial bodies

What I'm trying to achieve For a series of realistic renders I am currently working on I am trying to calculate the light level on different celestial bodies, in terms of the luminous flux (in lumens)...
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What was up with the lights in the sky tonight? [duplicate]

I and my boyfriend where looking up in the sky tonight around 8:30 am. We noticed about 17 or more things, that looked like stars. They was perfectly spaced, and just vanished they was heading east. ...
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23 views

Light profile fitting related questions

I am computer scientist and now I'm working with some astrophysical projects. During this work I accumulated some questions and maybe here I would be able to find some answers or advice where to look ...
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1answer
82 views

If a black hole pulls every object in the universe, why there is a light around it?

I've seen some black hole images and I've seen some movies about it e.g(interstellar). I wonder why it has a light around it. Even if I know that light can't escape through it. Can someone enlighten ...
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30 views

What were the moving lights in the sky tonight? [duplicate]

Tonight we saw moving lights in the sky south east of Orion's belt. Anyone any ideas what they were? About 20 of them all going in the same direction east.
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46 views

If the distance between galaxies is increasing and the speed of light is constant will the most of the light from the universe ever reach us?

Will the light from other galaxies ever reach us if the universe is expanding?
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5answers
10k views

Are photons aged?

If a star is at a distance of one lightyear, how old are its photons when they reach earth (from the photons’ perspective)? If time dilation is near zero at light speed, can we assume that the light ...
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2answers
206 views

Is Olbers' Paradox Nonsense? [closed]

Ok, this is a bold question, I know. But, let me explain: After first hearing about Olbers' paradox, I found that something seemed 'off' about it, so I looked into the subject as much as my skills (...
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2answers
101 views

Why is blue light extincted more strongly than red?

We know that blue light suffers extinction more strongly than red (examples include ISM, atmosphere etc.), but why? Is it a property of the shorter wavelength itself? Can someone provide a conceptual ...
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0answers
70 views

Did a galaxy get discovered more than 30 billion light-years away? How does one observe light older than the estimated age of the universe? [duplicate]

I'm more into questioning mainstream science and pseudo-science to remain open-minded. Why is it that we are seeing light 30 billion light years away; when the estimated age of the universe is much ...
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0answers
33 views

line of at least 20 lights moving across the sky [duplicate]

We watched a line of at least 20 satellites moving in a line across the sky. They were visible to the naked eye. Could they be Starlink satellites? We are in Sandbach, Cheshire. It was about 18.00 ...
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60 views

can gravity be faster than light in some specific cases? [duplicate]

This is a follow up question from If an event occurs at a point in space time what will an observer experience first, it's gravity or the light from it? This https://en.wikipedia.org/wiki/...
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1answer
101 views

If an event occurs at a point in space time what will an observer experience first, it's gravity or the light from it?

Let's assume a person is close enough to an object in space time to be able to observe it's gravitational effects and the light coming from it. If that object suddenly pops out of existence (...
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28 views

If interstellar medium was dense plasma and light slowed down, would things appear to move slower far away?

Voyager 2 recently left the solar system and registered an increase in plasma density. If light moved slower in this dense plasma, would it appear like events in other solar systems played out slower ...
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1answer
96 views

How much photon is still in flight?

Since space is mostly empty, one might first think that the majority of the photons, e.g. emissions from the stars since the beginning of the universe, are still in flight and not absorbed by anything....
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332 views

Why the space is so dark even there are billions of stars and many quasars emitting light [duplicate]

In our galaxy itself, there are millions of stars, and there are many more other galaxies in our local group and billions in the observable universes. For sure they all emit a lot of light, still why ...
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1answer
117 views

How much starlight do black holes absorb?

Can it be calculated how much light from other stars a black hole of certain sizes would absorb? And how long will it take for the number of active stars to decrease to the point where Hawking ...
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1answer
26 views

Does The ISW Effect Predict Net Redshift Over Distance?

The Integrated Sachs–Wolfe (ISW) effect is concerned primarily with the study of the Cosmic Background Microwave Radiation (CMBR), but seems to demonstrate that photons passing through voids suffer a ...
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1answer
62 views

Beneficial astronomical uses of satellite constellations like Starlink?

Has any thought been given to software that would use predictable occultations by Earth-orbiting satellites to improve (rather than degrade) astronomical observations? Potential challenges I could ...
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3answers
2k views

Chromatic aberration in lens

Is there a way to prevent chromatic aberration without using an achromatic lens in refracting telescopes or in any other instruments...?
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1answer
408 views

Is the resulting light from a supernova a product of photons bouncing around in the Sun?

I was thinking about how photons formed in the centre of the Sun take quite a long time to exit the surface. And it occurred to me that at the end of a star's life (during a supernova, given that it's ...
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1answer
88 views

What is the intensity distribution of visible light over the solar disk?

What is the distribution of the visible spectrum over the solar disk? Images of the Sun using the visible spectrum suggest that the light emmitted from the edge is almost equal to the light emmited ...
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1answer
171 views

Does light from the sun reach the surface of Venus

I am aware we have images from the surface of Venus from the Venera missions but I am not sure if those images are taken using the visible spectrum the human eye can see. This is why I was wondering ...
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1answer
142 views

What is the final destiny of a photon?

What happens with a photon when it moves ouit of a galaxy into the 'infinity void', where there's nothing but 'darkness'? Does the photon decay in the end when there are no interactions?
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1answer
137 views

How to find the source of the light? [closed]

There are millions of galaxies out there in the entire universe. When a telescope is set to a direction to to identify the stellar objects, it can capture all lights from all the objects. How do we ...
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2answers
235 views

What's the actual speed of electromagnetic radiation in space?

The speed of EM radiation is very slightly less than $c$, because space is not quite a vacuum. Say EM travels at $(1-\varepsilon)c$. For example, this results in a slight delay between receiving a ...
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1answer
92 views

Do all stars of a given age and mass have relatively the same emission spectrum?

My understanding is that much of the visible light that we see during the day is given off from the Sun, and that means that most of the colors that we see are dictated by (with the exception of ...
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3answers
173 views

How do we measure distance in space?

I know that you can calculate the distance to another star for example, by using the phenomenon redshift to determine how much it has redshifted because of the expansion of the universe. But how do ...
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0answers
45 views

really fast moving star-like light [duplicate]

I don't know ANYTHING about astronomy but I know what I saw and 2 of my siblings saw it too. I initially thought it was a shooting star, but a Google search quickly made it clear that it wasn't. it ...
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3answers
335 views

Why doesn't it hurt to look at stars?

If I stare at the sun, it's bright and blinding. However, if I look at a star in the sky, it doesn't hurt. What causes this loss of energy that would otherwise damage one's eyes?
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1answer
79 views

how to define the universe itself is expanding greater than than the speed of light?

since we observe galaxies and other steller objects in very tiny tiny scale, and how we can understand that the speed of expansion on universe is higher than the speed of light ? even using the ...
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0answers
54 views

Could Hubble's Law simply be light's frequency decaying over time? [duplicate]

Is it proven that the frequency of EMR does not decay (at all, ever), and if not, could the observations that led to Hubble's Law simply be that the frequency of light decays over very large durations/...
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3answers
203 views

Do photons slow down as they approach the event horizon of a black hole?

So, if a black hole is so dense, that light cannot escape, what happens to the photons as the approach and go past the event horizon (or some other horizon, about which I am ignorant)? Do photons ...
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0answers
21 views

Polarization of an emission line

Say I have a flux density spectrum of a galaxy, as well as polarization spectra for the object in U, Q, and P. I want to find the polarization of some emission line in the spectrum. First, I can fit a ...
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1answer
107 views

Could an object, assuming possible, escape black hole by travelling above constant speed? [closed]

I am always hearing that after travelling inside a given BH's event horizon, the escape velocity is greater than c, which makes it impossible to escape. Suppose an ship is inside a BH. Assume it is ...
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2answers
226 views

Radiative Flux, Irradiance and Luminosity confusion

First of all I know there is a similar question here, but I feel is wasn't answered at all. My question is that I have seen many texts which says that Radiative Flux is equal to the Irradiance of a ...
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1answer
59 views

How do radio telescopes gather information about visible light?

Is the first image of a black hole that was captured by the Event Horizon Telescope what would be seen with a large enough optical telescope (or with the naked eye from a proper distance of the black ...
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1answer
158 views

If a black hole does not emit light, how can one take a picture of the black hole itself?

There's some discussion that the image composed by the Event Horizons Telescope is really just an accretion disk. To "take an image" of something, you need the light reflecting off of the surface of ...
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2answers
185 views

What is the actual visual characteristics of a black hole?

Is there a safe distance in which a black hole can be observed with the human eye? What is a safe distance? I have seen many computer simulated and artist renditions, and I am not sure if they ...

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