What is Shadow: Definition and 122 Discussions

A shadow is a dark (real image) area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light.

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  1. K

    Measuring intensity of a shadow

    Is there any relation to find it's strength? I have got some raw data - 1# it depends on distance of light source of the object 2# how big the luminous object really appears from that place 3# intensity of the luminous object 4# how opaque is the object whose shadow is being formed...
  2. CarlB

    The sociology of physics: Gravity's Shadow

    It's not everyday that I find an 864 page book hard to put down, but I've been really engrossed in Harry Collins' book on gravity waves (theory and experiment) titled "Gravity's Shadow": https://www.amazon.com/dp/0226113787/?tag=pfamazon01-20 Part of this is because I took two classes from...
  3. U

    Does a Geo-Synchronous Satellite Catch a Shadow?

    If a geo-synchoronise satelite(which has the same time period as that of the earth) comes in a straight line with the Sun. Does it catch the shadow on the earth? If not why?
  4. I

    Shadow Color: The Science Behind Blue LED Light and Yellow Shadows

    I noticed this when I was holding a piece of paper in front of my blue led computer light. when a object (finger) is placed in front of the paper wiht the blue led light shining on it the shadow of the object is yellow. why? I tried to explain it as yellow is the complementary colour of blue...
  5. H

    UFOs, Greys and My Shadow: Is There a Connection?

    I just woke up from a dream involving U.F.O.s, so aliens were on the brain. It seemed to me that my shadow bears an uncanny resemblance to a grey alien, particularly when the light source comes from behind. (So that, say, it's elongated, meaning its limbs appear long and thin) <humor> Of...
  6. D

    Speed of Shadow Moving 40 ft from Pole: Solving the Problem

    Q. A street light is mounted at the top of a 15-ft tall pole. A man 6 ft walks awsay from the pole with a speed of 5ft/s along a straight path.How fast is the tip of his shadow moving when he is 40 ft from the pole? What I've done so far: this scenario can be drawn as similar triangles. from...
  7. P

    Parallax Question and Shadow Q (Gnomon?)

    1) A student is standing on the east side of a building and notices that it casts no shadow. One hour later, she notices that the shadow of the building is about 3 feet long. Approx. how high is the building she is standing next to? In this problem I honestly just don't know where to start...
  8. B

    A Moire Pattern of Shadow: Reading the Medea in the Late Afternoon

    My hair is cut short enough so that it's pretty much straight, like a wiffle only longer, and the other day I was sitting waiting for the bus in the late afternoon and reading a book (the Medea). The sun was behind me and the hair on my head cast a shadow onto the book. As I turned my head...
  9. E

    So, to answer the question: Why is the shadow during a lunar eclipse not black?

    I want to ask if there is coloured shadow ??If so, how to make it??
  10. T

    Solving Ball's Shadow: Theoretical Analysis

    Suppose you drop a ball alongside an exponential curve. On the other side of the ball is a continuous light source that is always shining perpendicular to the ball's path, such as in view 1. As the ball drops, the edge of the balls shadow on the curve moves, while the curve is still...
  11. U

    Can Our Brains Predict the Future?

    How powerfull is the human mind, especially the sub-conscious? Getting up, out of ones chair and walking over to the fridge to get something to eat and returning (if only to read something, slightly less interesting than food,) takes a great deal of physics, spontainious calculation, timing...
  12. K

    How Do You Solve Sphere Inscription and Shadow Length Problems?

    I am having trouble with these two problems, I was wondering if anyone here could help me. 1. Given a sphere of radius 10 inches. Calculate the altitude of the inscribed right circular cylinder of maximum volume. 2. A man 6 feet tall walks away from a light 30 feet high at the rate of 3...
  13. S

    What's Behind the Shadow of a Crescent Moon?

    is the shadow on a crescent moon the earth, or is it the dark side of the moon. i was taught in science a while ago that its the dark side of the moon, and an eclipse of the Earth on the moon is something different and more rare. but what i don't get is, if we are seeing mostly the dark side...
  14. hitssquad

    Shadow Ops: Red Mercury - world's first 64-bit game

    “AMD Athlon 64 technology is revolutionizing game design and, given the tremendous power and freedom AMD64 offers to our game designers, we are able to create scenes, physics, artificial intelligence, map sizes and graphics detail that we only dreamed of on 32-bit platforms,“ said Wim Stocks...
  15. marcus

    Urs Schneider's allegations about the Ashtekar Shadow states paper

    Urs Schreiber's allegations about the Ashtekar "Shadow states" paper Urs has made serious allegations about the paper "Quantum gravity, shadow states, and quantum mechanics" by Abhay Ashtekar, Stephen Fairhurst, and Joshua Willis. However I've not seen any place where he openly refers to...
  16. marcus

    Ashtekar's Shadow states paper

    Ashtekar's "Shadow states" paper There is this paper by Ashtekar, Fairhurst, and Willis called "Quantum gravity, shadow states, and quantum mechanics" http://arxiv.org/gr-qc/0207106 Citebase lists it as having been cited 5 times, one of which was in a paper by one of the authors. The...
  17. H

    Find height of tree from shadow silhouette

    need help on physics problems 1)The silhouette of a Christmas tree is an isosceles triangle. The angle at the top of the triangle is 10.2 degrees, and the base measures 1.67 m across. How tall is the tree? 2) A person is standing at the edge of the water and looking out at the ocean (see...
  18. tandoorichicken

    How Fast Does a Man's Shadow Change as He Walks Towards a Street Light?

    Its been a while since I did something like this: A man 6 ft tall walks at the rate of 5 ft/sec toward a street light that is 16 ft above the ground. At what rate is the length of his shadow changing when he is 10 ft from the base of the light? And I forgot how. Please help. Thx.
  19. R

    Stargazing Lunar Eclipse and earth's shadow

    Hi, I was fortunate to be camping on November 8 and near a nice warm fire throughout the entire lunar eclipse. It was awesome! I have a question about the the apparent direction the moon appeared to travel through the Earth's shadow. This is kinda hard to put into words, so please bear...
  20. B

    What is the Evidence for Dark Energy on Small Scales?

    Well, apparently we have now found new and more direct evidence for the existence of the so called 'dark energy.' I find it quite remarkable. http://www.space.com/scienceastronomy/dark_energy_030805.html
  21. Siv

    News Article : The Shadow War : Euro vs. Dollar

    THE SHADOW WAR : EURO VS. DOLLAR Some Indian thinkers are interpreting the U.S.-led attack on Iraq as part of the "clash of civilisations" between the "Christian" West and the Islamic world. Such facile academic theories can mislead both the public and policy makers into thinking that the...
  22. Moni

    Discussing Roger Penrose's "The Shadow of Mind

    I have heard from my teacher who is abroad now, that he have read a book written by Roger Penrose title "The shadow of mind". I looked for it in our public library but didn't find it. Have anyone of you read it? What is this book all about? Physics or Mind? Will anyone discuss about it ?
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