Mathematical genius required

[ban-all-sheds]

Please do.

A diagram showing the direction(s) incoherent light goes having been emitted by a source would be very helpful.

 

[EFLImpudence]

Is the Earth's shadow the same size as the Earth outward into space for ever?

 

[ban-all-sheds]

That depends on the relative size and position of the light source in which it is casting a shadow, doesn't it.

 

[EFLImpudence]

Exactly.

Is the Sun (and other stars) larger than the Earth?

 

[ban-all-sheds]

Yes.

You do know that this is all heading towards a bad outcome for you, don't you?

Why don't you just draw a diagram with a light source which shows what is making that light converge on a point some distance away from it.

 

[EFLImpudence]

Well, if I draw lines from the edges of a big ball to the edges of a small ball which are converging, what technical term will you tell me I have misused - and why?

 

[ban-all-sheds]

First draw the diagram showing light from a source converging on a distant point.

Light from other stars does not converge on The Earth. Why would it, in preference to all the other planets in the universe? That's why they are so faint.

The light from the Sun does not converge on the Earth, fortunately, or we would be dead. Did you never experiment as a child with a magnifying glass making an infinitesimally small amount of sunlight converge?

 

[rsgaz]

The 'rays' are a mixture of all of them though.

Converging to a point
Diverging
Parallel

edit: I've not drawn diverging from a single point on the sun, so there's two diverging types.

 

[ban-all-sheds]

Jolly good.

Please tell us what optical devices are making those rays converge, or become parallel, or what effects are responsible for any of them not being orthogonal to the surface of the star.

 

[ban-all-sheds]

Converging to a point
Diverging

No - those are the same, it's just that the focal points are different.

 

[rsgaz]

or what effects are responsible for any of them not being orthogonal to the surface of the star.

Because photons are thrown out at all angles across the whole surface of the sun...

Here's a tiny diagram taken from a NASA article on the path a photon takes from the centre of the sun. When it escapes it is not orthogonal.

How come we can see the sides of the sun then?

 

[Mike53]

Fascinating. When I first noticed the word "converging" in this thread I was a little confused. I have always understood light from stars was diverging and have never before read any reference to it converging. For all practical purposes I will still consider that light diverges from stars but also now understand if it is possible to focus a scientific instrument for example a telescope on one side of a star and then the other side of the same star as far as that telescope is concerned the light is converging.

Mike

 

[Robbox]

From my school years learning about umbra and penumbra, we interpreted light from our sun (or a near star) as a reduction to individual photons setting off from the edges in exactly our direction. Obviously, a bucket load of photons coming from everywhere else on the surface in our direction. But for physics, the edge photons were only considered to show how umbra/penumbra worked. Also to show how Polaris is used to navigate, it was reduced to a point source of light. For navigation using the sun, either the top edge or the bottom edge is used to make measurements.

 

[durhamplumber]

Light rays aren't parallel in a light bulb in your house because we can walk around the light bulb by only walking a short distance. At say 10 feet away from the light bulb every 2 inches is a degree. 2 inches is not very far so we can easily notice the non-parallel nature of the light rays.

 

[gasbanni]

This is beyond me but why would the earth be smaller if it was further away?

If I park my car at the end of the road it looks smaller but it’s really the same size.

You absolutely sure ?