Questions regarding electromagnetic radiation in the visible spectrum.

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18
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3answers
4k views

Why can't moon light (reflected sun light) turn the sky blue?

Does turning the colour of the sky blue need more luminous light? Does it depend on luminosity or some other factors are also responsible for this phenomenon? Why can't the moon light turn the sky ...
0
votes
1answer
30 views

V838 Monocerotis Supernova images morphed into nice video, but why so few original images?

This NYTimes video shows what I think is a series of real Hubble images which have been "morphed" artistically to appear to be continuously expanding. (also see The V838 Monocerotis Star Still Has ...
0
votes
1answer
32 views

How high does light pollution reach into the sky?

I want to know how high does light pollution typically reach into the sky STRAIGHT UP? Has anyone ever researched this because I wonder if being at 10000ft elevation would reduce the amount of light ...
2
votes
1answer
65 views

Given a collection of pixels, how to deduce the flux from them?

I've obtained the coordinates of brightest pixels from different images (.fits files) using Python. I want to get the flux of each pixel. How do I go about finding out the flux?
0
votes
1answer
35 views

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.
3
votes
5answers
390 views

Could light be dark matter?

Is it possible that light itself is dark matter? I am speaking of photons (e.g. visible light, infrared, ultraviolet, etc...). I realize light is understood to be massless, but it is obvious it at ...
24
votes
2answers
4k views

Why doesn't the moon twinkle?

Stars twinkle because their light has to squeeze through several different layers of the Earth's atmosphere. So why doesn't the moon twinkle as well?
3
votes
1answer
48 views

Gravitational Waves and the Big bang

The Ligo website says "Detecting the relic gravitational waves from the Big Bang will allow us to see farther back into the history of the Universe than ever before." I find this puzzling. How can a ...
0
votes
2answers
56 views

Regarding the age / size of the Universe [duplicate]

I believe the current estimated age of the Universe is around 14 billion years. I just read in another post on here that the diameter of the Universe is around 90 billion light years. This doesn't ...
1
vote
2answers
50 views

What is the longest observable wavelength of light using an optical telescope?

How far outside the visible spectrum could an optical telescope feasibly operate?
3
votes
1answer
213 views

How can light reach us from 14 billion light years away?

One thing that I can't quite wrap my head around is how light is traveling to Earth from 14 billion light years away, aka the beginning of the universe. The way I see it, the universe itself was very ...
2
votes
1answer
49 views

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 ...
0
votes
1answer
86 views

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 ...
2
votes
2answers
37 views

Is the colour of a wave from a far galaxy the same for us as for a galaxy which lies between?

Because of the expansion of the universe, light from a far galaxy is redshifted. The expansion of the universe will make the wavelength of light longer. But is the colour of such light the same for ...
16
votes
5answers
3k views

By putting a mirror in space, would we be able to see into the past?

I only ask this because of how fast light travels. The question remains in the title. Why, or why not, would this work?
0
votes
2answers
49 views

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 ...
6
votes
3answers
320 views

How does light affect the universe?

When light is emitted by for example a star, that star loses energy - which causes it to reduce its gravity. Then that energy begins a journey for potentially billions of years, until it reaches some ...
4
votes
2answers
50 views

Which planets have abundant amounts of photoluminiscent matter?

Which planets have abundant amounts of photoluminiscent matter? Photoluminiscent or chemoluminiscent whatever the glow-in-the-dark stuff it may be. Planets or bodies which have good enough the ...
3
votes
1answer
88 views

Would I actually be able to see Ceres without shining a really bright torch onto it?

NASA's put out a semi-CGI video of a Ceres flyby using material from the Dawn mission. Now I realise that visibility is relative, even on Earth: I can walk into my basement and not be able to see ...
0
votes
2answers
2k views

Star like light moving in the sky, what could it be?

I was camping this weekend away from the city, so my friends and I decided to spend one of the nights watching the sky, since it's impossible to see anything around where we live. After a little ...
2
votes
2answers
124 views

Why isn't everything yellow(ish)?

I understand that - although appearing yellow - the sun is white. And that this is because the other light colours are scattered by the atmosphere. For example: Google image search for "The Sun from ...
1
vote
1answer
74 views

What was James Bradley's calculation to calculate the speed of light?

Looking into the history of how the speed of light came to be determined, to what we know it to be today, James Bradley is often mentioned. He was credited with the discovery of the aberration of ...
2
votes
1answer
108 views

Is Darkness Faster Than Light?

I've been looking around, and can't find a solid answer. Many websites say darkness is the speed of light due to the fact it is the absence of light, but other sources say otherwise, that in some ...
14
votes
6answers
3k views

Are we still going to have rainbows if Sun is replaced by another star?

Rainbow is a property of light splitting due to the water molecule present in the clouds and is related to the light emitted by our Sun. Our sun is a yellow star. Now if we replace sun by a blue giant ...
-1
votes
2answers
78 views

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 ...
1
vote
1answer
88 views

What's the difference between the apparent horizon and event horizon of a black hole?

The Wikipedia page for apparent horizon is pretty sketchy and requires some GR knowledge. Is there any simple definition?
0
votes
1answer
59 views

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?
4
votes
3answers
318 views

Is a black hole a perfect sphere?

I know all about how black holes form and why their gravity is so strong. However, is the gravity equally powerful in all directions? Will the event horizon appear as a perfect sphere?
10
votes
1answer
232 views

How did New Horizons take such well-lit pictures of Pluto?

The photos of Pluto from New Horizons are truly beautiful. But considering that Pluto is so far away from its nearest start - our Sun - how is it so well lit up? Did the New Horizons have a massive ...
6
votes
4answers
478 views

Does Sun have a reflection on Earth?

The new Google Maps1 presents an actual view of Earth, with the current position of Sun illuminating half part of Earth in real time. It is quite an exquisite view. My question is based on the ...
3
votes
3answers
422 views

How does gravity interact with a photon?

If photon is mass-less and gravity can interact only with matter, then how does gravity alter the trajectory of light?
3
votes
0answers
78 views

How does light so travel so fast?. [duplicate]

I've read that photon's have zero mass, hence no force is needed to accelerate them. But then the second question. How can gravity affect something which has 0 mass?. Yes, gravity(black hole) can bend ...
2
votes
5answers
693 views

How far away is the light that would reveal the Big Bang?

I guess theoretically if we could go faster than light, which we clearly cannot, at some point we'd be able to see the big bang itself. Just curious - how far away is that light?
2
votes
1answer
72 views

Travelling at light speed(inside water) [closed]

It is a said fact that 299792458 m/s is the speed limit,nothing can go faster than this speed, or it will take an infinite amount of energy for propulsion.What we perforce in vacuum is one thing.Can ...
2
votes
1answer
34 views

how to assess a periodical signal?

After folding a light curve, we may get some kind of shape. How to tell whether there is a real periodical signal quantifiably? The fluctuation may be small, and the folded shape may not be perfect. ...
3
votes
1answer
153 views

How much illumination do the background stars provide?

I'm trying to get a better understanding of what things look like in "outer space." The main problem I'm trying to solve right now, is how much illumination is provided by the background stars. Is it ...
3
votes
2answers
298 views

Is the ratio between earth's distance from the sun and the speed of light just a coincidence?

I was doing some calculations to see how hard it would be to observe the speed of light and discovered an interesting correlation between the speed of light and the average distance from the earth to ...
3
votes
3answers
110 views

What is the average color of the universe?

Our Earth, being a beautiful blue orb, has an overall perceived wavelength of somewhere near 470 nm, that being the wavelength of light blue, because the oceans play an enormous role in the weighted ...
5
votes
1answer
63 views

Why do some artificial satellites decrease and increase in brightness multiple times?

I just observed a satellite almost directly above me travel for a few minutes while constantly dimming and then getting brighter. It did this for about 3 minutes until it faded out. I also observed a ...
4
votes
1answer
50 views

Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...
1
vote
0answers
85 views

Energy required for light speed [closed]

It is said that in order for us to travel at the speed of light, there has to be an infinite amount of energy. Light is made up of photons but photons themselves do not have an infinite amount of ...
2
votes
1answer
85 views

What is the ratio of cosmic microwave background radiation to normal radiation?

I would like to know the ratio of cosmic microwave background radiation to normal radiation in the universe. I am considering cosmic microwave background radiation to include the microwave, and any ...
11
votes
4answers
9k views

What is the difference between our time and space time?

I am trying to understand the phenomenon of space-time. But, everything on internet seems to be too complicated for me since I do not have a background in physics. Can anyone give me simple ...
4
votes
1answer
260 views

How to calculate the limiting magnitude of Hubble?

I've found various sources on the web stating that the limiting apparent magnitude of the Hubble Space Telescope is about 31 or 31.5. Wikipedia lists that here and it has a cite to a pdf about it. ...
9
votes
5answers
4k views

What would the effects be on Earth if Jupiter was turned into a star?

In Clarke's book 2010, the monolith and its brethren turned Jupiter into the small star nicknamed Lucifer. Ignoring the reality that we won't have any magical ...
3
votes
3answers
1k views

What's in the center of a Galaxy?

Ok, so it's supposed that there is a black hole in the center of any galaxy, that makes my head explode because: There is light in the center of the galaxy, but it is supposed that black holes, also ...
3
votes
2answers
254 views

Could someone see anything while being inside black hole?

If we managed to survive in a black hole and move inside the event horizon then could we see the surroundings of the black hole inside the event horizon by source of light? Can the light not come up ...
2
votes
3answers
381 views

Longest and shortest wavelength

What is the longest and what is the shortest wavelength of light? How fast would a light-emitting object have to recede in order to shift the frequency of light to increase the wavelength from the ...
0
votes
1answer
42 views

Sunsets: Mars/Earth

I understand why our sky is blue and turns red when the sun sets or rises. I know why the sky on mars is red, but why does it turn blue during sunsets and rises? Shouldn't this actually not work due ...
0
votes
0answers
124 views

How strong does a light source on the Moon have to be to be visible from Earth?

Flashes from some meteoroid impacts on the Moon can be seen with the naked eye. How much light must a future lunar base emit in order to be visible as a dot in the lunar night (like the flag of ...