What is light cone ?

Question

In books i dont understand

Answer 1

Imagine a camera with a special lens that took a picture all around it. Not just 360 degrees left to right all the way round, but above and below, too. You could put the picture on the inside of a ball or sphere to see what the camera saw. Now, imagine that instead of a camera, you could take movies. When you were done you could sit inside a giant spherical audiorium and watch the film. Now picture that by special arrangement when you started your movie camera some lasers out in space turned on at the exact same time (this is a little tricky because of the way time works, but we'll ignore this). One laser is out at the same distance as the Moon's orbit after seven seconds its light appears on your film because its finally arrived. Another laser is out by Jupiter and it takes 70 minutes to hit the camera and make it onto the film. As time goes by more and more little lights show up on your film as the laser lights arrive from further and further away. Since we know that nothing travels faster than light, that anything caught on film is inside the maximum distance light can travel since you turned on your camera. So nothing further away will be recorded. As time goes by the sphere in the theatre is getting light from further and further away, if you were to draw it on a map of our solar system or the Milky Way the circle (if the map wasn't a 3d holograph) would be getting bigger and bigger, expanding at the speed of light (which would be pretty slow on a map of the Milky Way and not that fast on a map of our Solar System. You're seeing things further and further away.
The outer edge of the sphere is the three dimensional top edge of the light cone that is portrayed in books as one dimensional (usually to the left and right with time going up).
We can't draw 4 dimensions, heck we can't even draw three AND we need to draw time and the other dimensions, we draw a triangle and call it the light cone. It should be a 4 dimensional "cone" starting at a tiny point and expanding as a spherical shell at light speed. If there were just two dimensions in space the cone would expand in circles at light speed. Everything you can see HAS to be inside your light cone (light sphere actually) because if it is outside, light hasn't had time to reach you from it yet so we can't really say it exists. There are actually two light cones one from the past getting bigger going down (into the past) and one towards the future getting larger up the page. The past light sphere (light cone) includes all the things the camera could have recorded if it had been on forever (since the big bang). But that doesn't mean a picture of everything! If the Volgons attacked the Klingons and blew up their home planet 20 years ago, if that planet is 100 light years from here, it will be another 80 years before it shows up on the film! If you drew circles around the point where the Klingon home world disappeared on a map of the galaxy, one circle for every ten light years the 8th circle would hit the Earth (or the place the Earth will be in 80 years). Another way to put it is to say that their light cone would hit the center of our light cone (where we are - or if its your light cone where you are, actually) on the vertical axis 80 years in the future. This all means that the most we can possibly see are things inside our (past) light cone and nothing can possibly see us (as we read this) until it is inside our (future) light cone. A light cone is about just one instant in time and just one place in space. Each moment and each place has its own light cones (light spheres) but we're usually only interested in a particular event (time and place) and when we will see it (or when it will see us). The diagonal edges of the light cone indicate the speed of light; every second vertically is 186,000 miles to the left and right. Hope this helps a little.

Answer 2

Complicated answers above. I'll try to be clearer.
Imagine "time" flowing from the bottom of the page (past) to the top (future). Two objects in space are separated by a horizontal distance (space), but their time lines are going up as parallel lines.
Now, from the center of the bottom line, trace two oblique lines at 45 Deg, going up, and put an "O" at the bottom center. That is the Sun.
Put an "e" at the bottom left: that is Earth. The distance between e and O is the distance between the Sun and the Earth.
The two oblique lines (at 45 degrees) represent the travel of light.
A flash of light emitted in "O" will go left and right, away from the source (remember space goes left and right, and time goes upward).
Anything that is WITHIN the two lines will see the flash.
Anything that is out of the lines will not.
At start, the Earth is at "e", and O is the sun. At that time, the earth is out of the V: we don't see the light yet.
Time goes by (we going up). When time reaches the top, earth (e') is within the lines: we see the sunlight.
Now, make the V a cone (to have the 3 dimensions).
Anything WHITHIN the cone will see the light. Out, we cannot see it.
This is to say that when an event occurs (ie at O), if we are not IN the cone, we cannot see, nor interfere, with the event.
Hope this helps.
(When will YA! will allow us to put a graph or a bitmap? Would make so many explanations easier).

Answer 3

In special relativity, a light cone is the pattern describing the temporal evolution of a flash of light in Minkowski spacetime. This can be visualized in 3-space if the two horizontal axes are chosen to be spatial dimensions, while the vertical axis is time.

Answer 4

Since the observed properties of light were so vastly important in reshaping the mathematical models of space and time in Special Relativity, the propagation of light occupies a very special place in this model.
Relativists like to speak of the behavior of light in terms of light cones. Light cones come in two kinds: past light cones and future light cones.
The future light cone of a spacetime event E consists of all the paths of light that begin at E and travel into the future. One could imagine a flash of light at event E. The future light cone of E would be everywhere the flash went in space and time after leaving E.
In one time and one space dimension, light cones are lines in spacetime. The future light cone of event E is shown in the figure as the blue diagonal lines to the future of E.
The past light cone of a spacetime event E consists of all the paths of light that begin at E and travel into the past. The past light cone of E would be similar to flashes of light all converging at the event E. The past light cone of event E is shown in the figure as the pink diagonal lines to the past of E.

Answer 5

ok shall we are saying there's a prepare outfitted all over the earth it could holiday on the value of sunshine at this velocity the prepare can pass around the earth 325 situations consistent with 2nd so if there are passangers on the prepare shall we are saying a sprint lady grew to become into working interior the prepare wouldnt she destroy the cut back of velocity? think of roughly that, so thats why nature slows time interior the prepare so as that the little lady working interior wont destroy the cut back so if the passangers expirience 5 weeks interior the prepare while they pop out of the prepare they have exceeded one hundred years of time so while they get out they could see an entire new earth so i dont think of the sunshine cone is grater than the value of sunshine and despite if this is it may vanish or it ought to even blow up, i'm hoping this replied your question

Answer 6

It is basically a graph of distance vs time. It is used in relativity to show places in space-time that can and cannot be reached. A simple way to show a really complicated idea.