Questions tagged [light]
Questions regarding electromagnetic radiation in the visible spectrum.
6
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3answers
139 views
Universe isn't infinite theory
Forgive me if any of my terminology is off I am no physicist but I have wondered about this question for a while.
I have read in various books that if the universe was infinite, and uniformly created ...
1
vote
2answers
50 views
Why is it that night has a almost a bluish tint to it instead of red?
From my understanding/been told, the color red has the ability to travel the farthest in our atmosphere, being the reason why we have red sunsets and such. But with this in mind, why is it that at ...
47
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5answers
13k views
If light has no mass, why is it affected by gravity?
Light doesn’t accelerate in a gravitational field, which things with mass would do, because light has a universally constant velocity. Why is that exception?
0
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0answers
7 views
Could we use a narrow paradigm, say laser, to get info faster from New Horizons? [migrated]
There was just a question about why the data rate from New Horizons is low.
Of course, even with the most directional radio antennas, the spread is enormous.
I guess conceptually, some sort of laser ...
1
vote
0answers
40 views
Can you go blind if you look at the sunrise and sunset? [duplicate]
Everyine knows its dangerous to look directly at the sun, but can you look safely at sunrises and sunsets without going blind? Because the uv radiaton and the light is much weaker. Or is it still very ...
2
votes
2answers
135 views
What fraction of starlight, seen from Earth, is actually reflected light?
Thanks to reflected starlight, many planets and comets in the Solar System have been visible to humans since long before the development of modern astronomy.
Some of the starlight from outside the ...
2
votes
1answer
102 views
Is there enough light to grow plants in the ocean of Europa?
What is the underwater temperature of Europa?
I know Jupiter emits infrared light but does it emit any light able to support plant life of any type on near by Moons? Can under water volcanic activity ...
6
votes
1answer
184 views
What is the underwater temperature of Europa?
If Europa has an oxygen atmosphere with a water mantle, is it possible that there could be life under the crust of Europa ice on the ocean where it is warmer? What could be the temperature under the ...
5
votes
1answer
291 views
Are there any examples where the transverse doppler effect is applied in astronomy?
Are there any astronomical examples where the transverse doppler effect(Horizontal doppler effect) is applied (Derives a meaningful result)?
4
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1answer
90 views
How does V838 Monocerotis look today? Any subsequent light echo images, or is the party over?
This answer to the question V838 Monocerotis “light-echo” images morphed into nice video, but why so few original images? contains the following information below. There are other answers and more ...
1
vote
1answer
83 views
Light pollution and apparent magnitude of objects in solar system
Dust along the ecliptic scatters light, causing “light pollution” throughout the orbital plane of the solar system. If an object like, say, the sun's corona, had its brightness measured from above the ...
1
vote
1answer
35 views
Source of mirror reflectivity data
I am trying to find a source of mirror reflectivity versus wavelength for the typical protected overcoat Aluminum mirrors used in astronomy. I need this to cover the whole visible range (300-1200nm) ...
2
votes
0answers
30 views
What is the advantage of taking monochrome photographs in standard lenses
I've readen "When photographing faint objects monochrome photos will resolve more than RGB pics"
Is this really a thing? If yes, how?
-1
votes
2answers
70 views
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 ...
-1
votes
1answer
131 views
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 ...
4
votes
1answer
549 views
Does Time Exist for Photons? [closed]
If time slows down the closer you get to the speed of light, does it follow that time does not exist for photons. Do photons - even if they travel across billions of light years of space - arrive at ...
1
vote
1answer
37 views
What unit is used for region Surface brightness in DS9?
The value of the surface brightness is in what unit? I hope it is in Rayleighs. Is that true?
1
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0answers
52 views
Almost unseeable light moving over nightsky. What is it? [duplicate]
Sometimes when I look up at the sky at night, I can see something moving. It’s so small that I barely can see it, but I can’t see it when I look directly at it. I need to look beside it to see it. It ...
2
votes
1answer
492 views
Strange bright light in the sky flying fast [closed]
I was out with my dad on our porch watching the stars with our telescope. after awhile of looking and taking pictures I noticed something strange in the sky. There were two airplanes flying close to ...
0
votes
2answers
172 views
Does the edge of the Universe travel faster than the speed of light?
The Universe is expanding faster than the speed of light then does that mean matter at the edge of the universe is also traveling at the speed of light or are ether opposite sides of the universe are ...
0
votes
1answer
78 views
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 ...
2
votes
2answers
104 views
Are galaxies expanding away from us at more than the speed of light? [duplicate]
If you go to the following video, at this certain time:
https://youtu.be/Iy7NzjCmUf0?t=435
you will see that the narrator says:
"We simply don't know what else is out there because the light from ...
2
votes
2answers
99 views
How far away is this galaxy?
Arp 299 is in the news, with most sources reporting it as 140 or 150 million light-years away. But what kind of distance is this?
The paper which is trhe source for the news item has Supplementary ...
6
votes
1answer
196 views
How much do starlight and artificial light illuminate the Moon?
The Moon receives most of its light from the Sun, either directly through sunlight or indirectly through Earthshine. However, there are many other dimmer sources of illumination.
Starlight. This is ...
5
votes
2answers
109 views
What's the difference of the oldest light and newest light?
Excuse an amateur question, as inspired by this question: "How old is the oldest light visible from Earth?", how to determine the age of light? Does light get old? Does light have characteristic ...
2
votes
1answer
41 views
Scattered Intensity of Light vs Angles of Incidence and Emission
So I just derived an expression for the scattered intensity of light from an atmosphere with ideal isotopic scattering: $I/F=\frac{cos(i)}{4(cos(e)+cos(i))}$, where $I$ is intensity, $F$ is flux, $i$ ...
40
votes
5answers
12k views
How old is the oldest light visible from Earth?
Because light can only travel so fast, all of the light we see in the sky was emitted at a previous moment in time. So if for example we see a supernova or some other great stellar event, by the time ...
3
votes
2answers
103 views
Bright light in the sky, in the '90s, what could it have been?
Sometime in the summer months during the years from 1993 to 1998, my friend and I saw what looked like a gamma-ray burst (or what looked like an artist's impression of it). It looked like a star that ...
1
vote
2answers
491 views
Sunlight intensity during a day
What simple mathematical function would reasonably well simulate sunlight intensity (disregarding weather) from dawn till dusk in relative numbers, 0-100 %. Are there significant differences (apart ...
4
votes
1answer
154 views
Can light be trapped in orbit?
Could rays of light be ever trapped in a constant orbit around a black hole if approached from a certain angle ? Like light hitting a glass or liquid with critical angle.
2
votes
1answer
57 views
Spectrum of star
I constructed a telescope and fixed my mobile's camera to the eye lens. I then viewed the sky via the mobile and I captured this image.
This is the magnified version of it:
I'm not sure if this ...
26
votes
1answer
3k views
How did Ole Christensen Romer measure the speed of light?
How did Ole Christensen Rømer, who in 1676, shortly after Galileo's death, was said to have measured the speed of light as 220,000 km/s by timing the orbits of Io around Jupiter?
My only guess is ...
4
votes
3answers
168 views
What would a terraformed Mars look like from Earth?
Question in the title. Currently, Mars is a small orange dot in the sky. But what if green, blue, and some white were added? I wouldn't expect it to be too different- a large portion of it will remain ...
2
votes
1answer
165 views
What is the light that we see from a neutron star come from?
What hold the electrons in orbit? Is it gravity or the atomic attraction between the protons and neutrons?
I asked this question on Physics SE I hope I improved on the quality enough to do better ...
8
votes
1answer
3k views
Why do stars twinkle but the Sun doesn't (I'm asking this because the Sun is also a star) [duplicate]
My friend asked me
"Sun is also a star then why doesn't it twinkle like other stars"
I brought this question here so that I have (and have more) infomation on this topic.
0
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0answers
30 views
Space expansion speed vs Light speed [duplicate]
How is the space expanding at a speed greater than the speed of light, while nothing is moving faster than light?
3
votes
1answer
64 views
minimum size for a black hole to capture a photon
If a photon is moving past a black-hole, what is the minimum size of the black-hole that will capture the photon and prevent the photon from going onto orbit around the mass? Do black-holes exist that ...
2
votes
0answers
52 views
How do I measure occultation for the upcoming lunar eclipse?
I'm trying to simulate the lunar eclipse on Jan. 31, similar to this simulation I made of last year's solar eclipse, using Three.js. I have the minute-by-minute coordinates for the Sun and the Moon in ...
3
votes
0answers
77 views
What is the science behind the polar light shapes
Is there any scientific explanation that causes polar lights (aurora borealis/australis) to have their unique shapes?
Specifically:
Rayed Arcs
Dual Bands
Corona
(Images on NASA Pdf)
This site (by ...
4
votes
1answer
479 views
How bright would it be on the “face” of Titan
If you were planing a maned mission to Titan and wanted to find a landing site that would get the most visible light for the longest amount of time, your first logical choice would be the dark side of ...
1
vote
1answer
126 views
Are there clouds/clusters of gas in space that have red and blue color adjescent to one another?
In artistic renditions of space scenes, there were stunning depictions of gasses or galaxies with bold red and blue colors immediately adjacent to one another, in contact as water is with oil in a ...
2
votes
0answers
39 views
Finding individual band magnitudes: Why and how is the integration of individual flux values for each wavelength used?
What differentiates the distance modulus equation to find the difference between two apparent magnitudes? For example,
$$ m_1 = -2.5\cdot log_{10}\left(\frac{F_1}{F_2}\right) + m_2$$
leads to the ...
2
votes
2answers
128 views
How close to a brown dwarf would a planet need to be to receive as much light as Earth?
How close to a brown dwarf would an orbiting planet need to be in order to receive as much sunlight as Earth receives from the Sun?
1
vote
3answers
149 views
Will we be able to see our galaxy if we travel far enough?
Will we be able to see our galaxy if we travel far enough? When we leave earth far enough, we'll be able to see Earth from distant, is it same with the galaxy? if we travel far enough, will we see the ...
3
votes
3answers
444 views
How can the universe be expanding faster than speed of light? [duplicate]
So the story goes like this:
A long time ago, 13.799±0.021 billion years to be exact, something happened. It was a big bang, loud explosion and universe came to existence. It grew and grew, and now ...
3
votes
2answers
141 views
A [very basic?] question about light scattering and colors
Since the night two days ago, the moon here in Israel appears to be orange as it rises, and then gradually becomes white as it continues travelling across the sky.
This phenomenon comes in a great ...
1
vote
2answers
272 views
Is an expanding universe equivalent to a universe in which everything is shrinking?
Why do we always think of the universe as expanding?
Surely, from our perspective an expanding universe would look exactly the same as a universe in which everything is shrinking away from ...
2
votes
2answers
640 views
Does Absolute Velocity Exist?
It seems everyone is on the same page about there being no "absolute velocity" due to the fact that everything is relativistic. However, this leaves me confused. This seems to be disconnected with the ...
8
votes
2answers
680 views
Is the age of the universe relative to an observer's location in that universe?
According to Wiki the age of the universe is 13 billion years old, and I was taught that background radiation made the universe uniform in all directions.
Doesn't this define a sphere of space in the ...
35
votes
6answers
12k views
How do we have photos of galaxies so far away?
A possible answer for this is that, light emitted from the galaxies travelled a billion miles all the way to earth, where the hubble space telescope picked up this light through its sensors, and was ...
