Why Do Letters Appear Overnight in Mirrors? Explained Simply

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In summary, mirrors do not switch left-right or up-down. The letters in a mirror are not overturned on left-right, but rather appear in reverse order due to a front-to-back reversal. This means that a mirror image of a right hand looks like a left hand and vice versa. It can also be interpreted as a left-to-right reversal with a 180 degree rotation. This phenomenon may seem strange because it is not a turn that we are used to seeing people do.
  • #1
Numeriprimi
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Hello.
I have got basic question for you. Can you explain it simply?

Why are the letters in a mirror overturned on left-right and not upside-down?

Thanks. And sorry for my bad English.
 
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  • #2
They are not turned left-right. The left-most letter is still on the left and the right-most letter is still on the right.

When a person turns to face you the left-most letter is on the right and the right-most letter is on the left.

Mirrors do not switch left-right nor do they switch up-down. When people face you they do switch left-right but not up-down. That is why mirrors seem strange left-right but not up-down. They are strange because they do not do a turn that we are used to seeing people do.
 
  • #3
A mirror reverses front and back (*). This means that the three-dimensional symmetry of an image in the mirror has been reversed; a mirror image of a right hand looks like a left hand and vice versa.

A front-to-back reversal is identical to a left-to-right reversal coupled with a 180 degree rotation. Either interpretation is valid. As Dale points out, the interpretation that feels natural is a left-to-right reversal with a 180 degree rotation.

(*) Where "front" and "back" are referenced against the plane of the mirror.
 
  • #4
Numeriprimi said:
Hello.
I have got basic question for you. Can you explain it simply?

Why are the letters in a mirror overturned on left-right and not upside-down?

Thanks. And sorry for my bad English.

From the man himself:

 
Last edited by a moderator:
  • #5
Numeriprimi said:
Why are the letters in a mirror overturned on left-right and not upside-down?

We had a thread about this not too long ago:

https://www.physicsforums.com/showthread.php?t=647426

Take a look at the picture attached to post #8, and then re-consider whether the letters are really "overturned on left-right". :smile:
 

1. Why do letters appear overnight in mirrors?

This phenomenon is known as the "Bloody Mary" effect, where letters or words seem to appear on a mirror overnight without any explanation. It is often associated with the urban legend of summoning the ghost of a woman named "Bloody Mary" by saying her name three times in front of a mirror. However, there is a scientific explanation for this phenomenon.

2. What causes this strange occurrence?

The most likely explanation for letters appearing overnight in mirrors is a process called "ghosting". This occurs when moisture from the bathroom or surrounding environment gets trapped between the mirror and the wall, causing condensation or fog to form. When the moisture evaporates, it can leave behind residue in the shape of letters or words, creating the illusion of writing on the mirror.

3. Can this phenomenon be prevented?

Yes, there are several ways to prevent ghosting from occurring in your mirrors. First, make sure to properly ventilate your bathroom to reduce moisture build-up. You can also use anti-fog spray or a hairdryer to dry the surface of the mirror after showering. Additionally, regularly cleaning your mirrors with a vinegar and water solution can help prevent residue from forming.

4. Are there any other possible explanations for this phenomenon?

While ghosting is the most common explanation for letters appearing overnight in mirrors, there are a few other possibilities. It could be a prank by someone using a temporary marker or lipstick on the mirror, or it could be a case of pareidolia, where our brains try to make sense of random patterns and shapes and interpret them as letters or words.

5. Is this phenomenon related to the paranormal or supernatural?

No, there is no evidence to suggest that this phenomenon is related to the paranormal or supernatural. It is simply a natural occurrence caused by moisture and condensation on the surface of the mirror. However, the association with the urban legend of "Bloody Mary" may lead some to believe it is connected to the supernatural.

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