Questions tagged [light]
Questions regarding electromagnetic radiation in the visible spectrum.
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When stars explode why can we still see them?
This might be a silly question but if light travels at the speed of light and time is frozen in that speed then why the stars we see could be dead already and not just instantly disappearing from the ...
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If it only takes 8 minutes for that light to reach the Earth, what took up most of the time? [closed]
If it only takes 8 minutes for that light to reach the Earth, what took up most of all that time to get to the Earth?
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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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The light of which star is next to reach the earth?
I heard that the sky wouldn't be dark at night if the light of every star had already reached the earth.
Of which (currently invisible) star will the light reach the earth next and when will that be?
...
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Why is the H-alpha line slightly shorter in wavelength (656.28 nm) in air than in vacuum (656.46 nm)? Shouldn't it be longer?
Perhaps this is a question better suited for Physics SE, but since the H-alpha line is so important in astronomy, I'm posting this here....
I would, naively, assume that wavelengths would be longer, ...
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Existence of a "reflecting" star [closed]
Wasn't even sure about what the title should be, but I had a thought and I wonder whether it may be possible or not.
Is it possible that there is a star which acts as a mirror and reflects back the ...
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Using a telescope to look at the Earth History in Some Detail [closed]
The following paragraph is a scientific fact.
When we look distantly into the universe (with telescopes) we see galaxies
(or whatever else you see) as they were millions years
ago- in other words ...
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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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is this really true that speed of light is same as we look from different parts of universe?
According to the theory of relativity. The speed of light is same for every observer. But how can we know that this applies to more than a local region? What if light travelled to us from a distant ...
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Why does light from objects take time to reach us? [duplicate]
Why does the light of objects such as the Sun, stars etc. take time to reach us?
E.g. Why does sunlight take 8 minutes to reach us, instead of reaching our eyes as soon as it rises.
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In a finite universe, what happens when light reaches the boundary?
If a universe is finite and is not expanding at a speed equal to or greater than c, what happens when light or another form of electromagnetic radiation traveling reaches the boundary?
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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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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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why there is a circle of light surrounding Sun and Moon?
One day when I was playing basketball I saw a circle around the bright Sun. It is a perfect circle with a radius of about 20-30 km.
Why does this circle of light form? I have seen the same also ...
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I saw an orange light in the sky which changed into flashing lights, what is this? [duplicate]
It's Saturday 15th July 2017 and currently 00:44. I saw this strange object at around 00:35. I was looking out my window and spotted a bright orange light moving at a steady speed across the sky, it ...
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How long would a near-light-speed trip to proxima centauri take from the traveler's and the earth-observer's perspectives?
Lets say the spaceship is traveling at .9c to Proxima Centauri. How long does this trip take from the observational standpoint of the passenger vs. the observer from Earth?
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An hypothetical timepiece on board of a spaceship. Please Help [closed]
On board of a hypothetical spaceship, I have a hypothetical clock consisting of 2 mirrors and a light beam is being reflected between the mirrors to measure the time. Now if we hypothetically exceed ...
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The relation between the light of full moon and the distance between the sun and the earth
If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth?
Thanks for your help.
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TIME TRAVEL-Can it be really done? [closed]
Is it posssible for us to time travel?
Is light essential factor or the dark matter and dark energy?
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Seeming conflict between most distant objects and age of universe (both estimated)
There was a recent article on bbc.com for laypeople like me titled "The mystery of how big our Universe really is", which prompted me to post the following question in their comments section ...
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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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LLR & Orbital Motion
As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
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What is the galactocentric aberration?
At the Wikipedia about an aberration, there is the phrase:
a recommended galactocentric aberration constant of 5.8 µas/yr
What is the galactocentric aberration? How is it calculated correctly? An ...
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How come we see something xx light years away? [duplicate]
If we are at point A in the universe and something is say 13 billion light years away, wouldn’t we have to travel wayyyy faster than the speed of light from the Big Bang in order to turn around from ...
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How can a black hole stop light from being emitted when all observers see light traveling at the same speed? [duplicate]
Quite literally every science show talks about black holes with a similar phrase: so dense that nothing, not even light, can escape.
Let's say I am in space a safe distance from an object. I drop an ...
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Volume of the observable universe [duplicate]
What about the volume of the observable universe?
Can we find it?
And what is the result in cubic light years?
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Astronomical data bases express spectra in flux density, e.g. ergs/s/cm2/Angstrom( or Hz) how can I calculate the flux, i.e. ergs/s/cm2?
I have light spectral data from astronomy data bases in flux density (flux/Angstrom or flux/Hz) and would like to calculate the flux. How can I calculate the flux from the flux density?
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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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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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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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Light/Dark energy/Dark matter
So I have been working on my comic book project that takes place on another planet. But in my story, there will be warp gates and there will be other civs that can travel between stars. I am ...
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With all the stars in the universe, why isn't the sky saturated with light? [duplicate]
Space is dark. But if we direct telescopes to seemingly dark portions of sky, we see that it is filled with galaxies. If the universe is theoretically infinite, wouldn't an infinite number of photons ...
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If FTL travel is possible, can I look back in time to a younger earth? [closed]
For this question assume that.
We found a way to go faster than light.
I build a ship that could go faster than light and go to another planet with this ship in the span of mere hours. The ship was ...
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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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Speed of light in cosmic voids [closed]
If temperature affects the speed of light (a contentious issue, I gather) then is it possible that the speed of light outside our solar system or galaxy, which might be minimally warmer than the ...
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Can light be curved due to heavy gravitational force?
Lets suppose there is a huge planet having large amount of gravitational pull, then will the light passing through the planet get attracted towards it.
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Star like lights at night [closed]
me and my friends likes to stargaze at night and every time we see this star like light that glides in one direction. they sometimes even cross in the middle then disappear sometime. i observed that ...
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What would happen if a spaceship goes faster than the speed of light? [closed]
So, I've been doing research on how no mass could pass the speed of light. So, I've always had a question in mind. What would happen if someone was going at 99.99% the speed of light and they decided ...
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Plausible? Brown Dwarfs are rogue celestial bodies because they absorb all light due to their thick layer of matte black soot [closed]
My theory of why Brown Dwarfs are the rogue celestial bodies that travel through galaxies without a set course. My first theory would be their matte black in color due to a layer of soot.Light does ...
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Can "dark matter" be the additional mass from the speed of the Galactic Cluster?
Considering that the Earth orbits the Sun at 100 000 km/h and that the Sun orbits the Milky Way at almost 1 000 000 km/h, could it be possible that the galactic cluster orbits some super cluster at ...
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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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Looking at ourselves with a powerful telescope?
Could a small curved mirror and/or lens in Earth's orbit be aimed at a different hemisphere from where you are be be viewed with a powerful telescope to see the ground through the mirror? Would a more ...
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Why do people say travelling at the speed of light or faster is impossible? [closed]
Impossible assumes we know everything there is to know about, well, everything. There was a time when everything mad knew said that traveling faster than the speed of sound was impossible. These same ...
