Questions tagged [light]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
4 votes
0 answers
41 views

Which transparent mineral has the highest IOR? natural or lab made

I do apologize if this is the wrong place to ask this question. It's a rather simple question, but google gave me rather vague / random results, so I thought it might be better to ask somewhere like ...
3 votes
1 answer
34 views

Where may I find spreadsheet data on the spectral density of daylight at various times throughout the day from morning to evening?

I want to know the precise spectra density of light we humans (and plants) are exposed to at various times throughout the day from morning to evening. I'm searching for spectral density graphs/...
2 votes
1 answer
96 views

Why does the camera do this and what does the sky really look like around 87,000 ft altitude?

When watching this high altitude balloon video I stumbled across a weird thing: Go to 6:08 and watch as the black sky suddenly turns to blue due to a different camera position. This is an image from ...
2 votes
1 answer
165 views

What are the risks of developing geoengineering?

Wikipedia page for geoengineering entry list a lot of proposals to decrease global temperature: Solar radiation management methods[5] may include: Surface-based: for example, surface-based mirror ...
16 votes
2 answers
11k views

Is spectrum of sunlight the same in the summer as in the winter?

Of course we receive less sunlight in winter, because the sun is lower in the sky, so the light has to travel through more atmosphere, and loses strength. Does this mean that the blue light is more ...
0 votes
0 answers
941 views

Identifying circle of light in night sky

I was recently reminded of when, while with some friends 20some years ago, we happened to look up and see a circle of what seemed to be light (in the sky of course). The circle was "empty" (only the ...
4 votes
2 answers
39k views

Why was the sky SO yellow?

Today, I was coming back from music school, and it was raining heavily. An hour after I came back, the sun started coming out from one side, and the sky wa very brighr yellow. The lighting effects ...
8 votes
2 answers
2k views

Light at the coast - is it different?

I have heard artists talk about the unique quality of light near the sea, and now I live near the coast I want to know if there's any truth in it. Does being near the ocean affect light inland? I'm ...
29 votes
1 answer
5k views

Why does glacier ice look blue?

The color of the ice observed in glaciers, icebergs and crevasses is often blue. However, ice cubes and industrial ice blocks are perfectly transparent or white if not. So. Why does glacier ice look ...
6 votes
2 answers
391 views

Can I just walk around Greenland with a UV light and find rare Earth minerals on the ground?

The NPR.org news article and podcast Greenland Is Not For Sale. But It Has The Rare Earth Minerals America Wants is interesting, and it includes a few large GIFs (too large to post here) that appear ...
1 vote
3 answers
78 views

What does it mean when polar nights have twilight?

My family and I want travel somewhere with polar night. I looked up Tromsø, Norway. "Down all day" beneath means 24 h darkness, no sun and thus no sun-light. Right? But if no sun and sun-light, ...
6 votes
1 answer
122 views

What actually happens to reduce the perceived color in a 'white rainbow" or "fog-bow"?

The image below is included in the BBC article Amazing white rainbow snapped over Scottish moor. Apparently this phenomenon is sometimes called a "fog-bow" and is characterized by the washing out of ...
1 vote
2 answers
306 views

Why does chlorophyll only come in green? [closed]

Plants do not only come in green but chlorophyll does. The pigment in the plant creates other colored plants other then green. Could a plant grow under an alternative light spectrum like a green sun ...
3 votes
2 answers
209 views

Database of color wavelengths of minerals

I was wondering about the physics of color, and now am interested in finding out if there are any resources (databases, text files, html tables, or pdf listings) of minerals and their associated ...
2 votes
1 answer
273 views

At what point are water droplets too small to make a rainbow?

This question asks How to tell if fog is made out of water droplets or ice crystals? I know that ice fog makes a rainbow where fog does not. Ice crystals aside: How does the water droplet size ...
3 votes
1 answer
2k views

Where can I find weather data on ambient outside illumination?

I am looking to analyze outside lighting data and its implications on human health regionally, but I can't seem to find a ubiquitous database that contains outside lux illumination data throughout the ...
8 votes
1 answer
69 views

Is moonlight a significant condition for making life possible on earth?

We know of course that light from the sun is a fundamental component to making life possible on earth because of the energy it provides. Does the light that is reflected off of the moon make a ...
1 vote
0 answers
322 views

Why is the sky blue? Due to the ozone layer or due to ''light scatterization in atmosphere''? [closed]

I've found several answers to the question of why the sky is blue. Basically the title. Elaborate however you want...
2 votes
1 answer
200 views

Calculating a cloud cover index based on comparison of horizontal and tilted irradiance from pyranometers

I have data from 2 pyranometers, one in the horizontal plane and one in a tilted plane. The relevance of the tilting relates to their useage in solar-power plants whereby the tilt is in the same plane ...
2 votes
0 answers
193 views

Why are all rainbows are not the same? [closed]

How does these rainbows water drops differ? I know it has to do with the size of water drops refracting light. Is there a formula that determines the type of rainbow? Icebow Unlike this questions ...
3 votes
0 answers
64 views

How could a 9 hour rainbow be possible?

The BBC article Taiwan rainbow 'lasts record-breaking nine hours' also mentions that Guinness World Records lists six hours as the current record. See also Taiwan News Taiwan shatters world record for ...
7 votes
2 answers
10k views

Why does the intensity of sunlight depend on your latitude? [duplicate]

People at the equator get to bask in more sunlight than Santa Clause and other inhabitants of the arctic regions. Not quite as pronounced, but they get more than me too. Why is the sunlight more ...
11 votes
2 answers
2k views

How can daily brightness be quantified or measured?

It occurred to me that there might very will be a metric out there that measures and quantifies "daily brightness". Meaning, how bright any given day is, taking weather conditions and cloud coverage ...
2 votes
1 answer
1k views

US Naval Observatory Sunrise/Sunset Data: Blank Sunrise/Sunset Times?

The US Naval Observatory has a webpage that allows a user to enter a year and a latitude/longitude pair, and then produces a table of sunrise and sunset times for each day during that year at that ...
10 votes
1 answer
313 views

Does this optical phenomenon have a name?

Last summer, I snuck out with a row boat around 4am. Eventually with the sun risen but still quite low in the horizon, I was rowing in the middle of the absolutely still lake when I witnessed an ...
9 votes
1 answer
2k views

What causes the colors seen during a sunset / sunrise?

What causes the typical red, pink or orange colors seen in sun-rises and sun-sets? How come the sky doesn't just turn a darker blue?