In the shadow of the invisible

I have suddenly realised thay I have forgotten a detail of Ars Magica physics/optics, namely what do you see if you stand in the shadow of an invisible person/item, and look towards the light source?

We know invisible people/items still leave shadows and reflections, even though you can't see the person/item, yet you can see everything that should be hidden behind them.
But say you have an invisible tower, with 1PM bright sun behind it. If you are standing in the shadow of this invisible Tower, and then look towards it, you won't see the tower. But what of the light source - the bright sun?
Can you see the sun, and will doing so send you blind?

After a little thought, I have come up with - the light from the Sun is blocked, not any species it produces.
Hence in the shadow you can't see the light of the sun.
If something is illuminating the sun, then the species from the sun may be seen.

But is anything illuminating the sun?

So an invisible object can't be seen, unless there's a light source behind it, in which case it appears as a shadow to the viewer on the other side of the object from the light source?

This seems strange.

Not so strange. It works because of

, while

, hence


My understanding is no, the object remains invisible. You can still see the iconic species of what is behind the the invisible person/object, but not be affected by any light sources behind the invisible person/object.

I have been finding it greatly difficult to separate the concepts of light emitted versus iconic species emitted.
Now, I think I have it sorted out in my head. The way I explain it to myself goes like:
Mythic Europeans can not directly see Light, merely the secondary iconic species when light interacts with gross matter. The light from the sun is different from the iconic species from the sun. It is the intense light that damages our Mythic European eyes, while the iconic species lets our Mythic European see the sun. If the sun is behind something invisible, our Mythic European still sees the sun, but the damaging light is blocked.
Normally the iconic species of a solid object block the iconic species from behind it, just as the matter blocks the light. Unless the object is invisible, then the iconic species get through.

So if your mage is looking at the sun, and it appears normal but is not blinding, then there is something invisible between the magus and the sun.

Of course, my modern mind keeps wondering how an invisible person can see if they are not intercepting iconic species.

Are there primary iconic species? I might not understand you here.

Right. But the sun's iconic species are carried by its light: see HoH:S p.61 Species.

The light of a candle is governed by Ignem and casts shadows - but does not damage eyes when looking into it.

That image of the sun would not cast shadows then, right? And the light to carry the species of the sun - see HoH:S p.61 Species - would have to come from somewhere else in the shadow of the invisible person, right? From where?


Sorry, didn't mean to imply that there were different sorts of iconic species.
I was trying to say light comes first, then light interacts with matter, therefore the iconic species are generated second.

I overlooked your quote from earlier on.
And just like that I am now back to the first post in this thread, not understanding how invisibility affects light sources.

Is it not possible to make a lit candle invisible, but it still illuminates?
Seen in reflections?

Unlike the sun, candles don't generate light intense enough to do damage. Or cause sunburn.

  • Perdo Imaginem spells cannot destroy shadows (ArM5 p.146 box) or direct light, but otherwise can make a candle invisible. Mirror images are affected by invisibility (ArM5 p.146 box): that invisible candle would not be seen in reflections either.
  • It requires an Ignem requisite (ArM5 p.142 box) to extinguish the light in a candle flame: in this way it does neither illuminate nor create shadows or reflections, but still burns.

Light not carrying any species at all, hence illuminating and invisible at the same time, is a topic for natural philosophers in Mythic Europe.

But there are some thought experiments about the shadow of invisible things and light which might help:

  • If you turn a solid wall of a dark completely lightless room invisible with Perdo Imaginem, there will still no light enter that room - so you cannot see into it.
  • If in the same room there is a lit candle, its light can still not pass through the invisible wall - as the Perdo Imaginem spell cannot destroy the wall's shadow: it still blocks the candle's light, and the species that are carried in it.


The following post is worth linking at this point:



Thanks for the reference, Mark. I didn't have that at hand now, and had no time to search.

I still should continue the thought experiment from my above post now:

Assume that there is light falling onto the outside of the wall you turned invisible. That wall - once invisible - shows what is behind, but is limited by both the light inside the room, and the light falling upon its outside.

  • If the room is lightless, looking from the outside through the invisible wall shows the lightless inside: quite a magical view, as the light from the outside does not illuminate the inside.
  • If there is a candle burning inside the room, its light cannot pass through the shadow of the invisible wall. But there is light on the outside wall, so the Perdo Imaginem spell moves the iconic species from the illuminated room onto the light on the outside wall, making the wall - in a way - transparent to iconic species and showing the room's inside. This is limited by the amount of light available on the outside of the wall, though: if there is little, the image of the candle will not be very bright. Imagine a cinema screen, whose images are three dimensional, but limited by the power of the projector's lamp, light bulb or LEDs.


Another hypothetical example.

A bucket is made invisible, then placed over a person's head.
By my understanding, the person should still be able to see through the invisible bucket, but their face (and head) should be in shadow.

I don't have my ArM5 book in front of me. What happens if a magus casts the CrIg spell (level 20?) that I think is called "Flash of Scarlet Flames" and is designed to temporarily blind people, onto the invisible bucket wearing person. So the flash occurs just outside the bucket?

This is correct, as long as the bucket still does allow sufficient light to come under it - likely from a space between the chest and the bucket.
A full helmet without visor slits, and worn firmly fixed to breast and back, will let no light come between it and the wearer's eyes, so even if invisible will still blind its wearer. It will also make the space around his head look spookily black and lightless even in bright light.

To blind someone, ArM5 p.140 CrIg 15 Flash of the Scarlet Flames must be targeted on the person's face. Targeting it onto the invisible bucket makes the person see flames, but not be blinded by them.

In practice this requires further considerations, though:
Does the caster of Flash of the Scarlet Flames see in time the continuous deep shadow on the head of the intended target?
Does he have enough Magic Theory to suspect an invisible helmet, headdress or even bucket?
Does he have enough Finesse to target Flash of the Scarlet Flames under the bucket and close to the target person's eyes?