Reskin Menu

Why doesn't a mirror reverse top to bottom?

John Bell, iPad app

This seemingly tricky question has caused arguments since at least the time of Aristotle, 2,300 years ago. But in essence, the explanation is simple. Mirrors don't reverse up and down – and, in fact, they don't reverse left and right either. They simply show us our reflection, and that appears to reverse the direction we're pointing. The reason this also seems to reverse left and right is because these two directions are defined relative to our own direction.

Don't believe it? Then stand opposite someone else and both lift your right arms: you'll initially think that the other person has lifted the 'wrong' arm. They haven't: it's just that they're pointing in the opposite direction to us – so their idea of left and right no longer agrees with ours. It's the same when you're looking in a mirror; your reflection created the illusion of reversing your direction.

Comments: 0
Q&A Tabs
Is time real or an illusion?

Diverse thinkers, from the ancient Greek philosophers through contemporary quantum cosmology and eternal inflation theory, have called time an illusion. For them, the perception of time passing...

Is swallowing your own phlegm harmful?

Phlegm is the mucous secretion of the respiratory passages. The cilia cells that line these passages are continually driving the phlegm upward to the throat, where it triggers the swallow reflex...

Can I get sunburnt through glass?

Ordinary glass absorbs 97 per cent of the UVB rays that cause sunburn and some skin cancers, and 37 per cent of the less harmful UVA radiation. This translates to a protection of about SPF30, so...

What is the record for the most languages spoken by one person?

It depends on how high (or low) you set the bar of fluency. Ziad Fazah, born in Liberia, brought up in Beirut and now living in Brazil, claims to be the world's greatest living polyglot, with a...

Why do we salivate before we vomit?

Vomiting is a deliberate response by the body that evolved as a purging mechanism to remove toxins or foreign bodies from the stomach and oesophagus. Since stomach contents are highly acidic,...

Is time real or an illusion?

Diverse thinkers, from the ancient Greek philosophers through contemporary quantum cosmology and eternal inflation theory, have called time an illusion. For them, the perception of time passing...

Why don't passenger seats on aircraft face backwards?

Air crash investigators have found that flight stewards in rear-facing seats have suffered less severe injuries in accidents than forward-facing passengers. This is because the energy from the...

Does Britain still lead the world in anything?

While Britons have pioneered all sorts of things from the steam engine and the computer to passenger jets and rugby football, we have dismally failed to maintain world dominance in much at all...

Why does time seem to go faster as we get older?

Most people agree that the years seem to pass at an ever-accelerating rate. That’s because traditions, anniversaries and celebrations gradually accumulate and merge, so that the difference...

Can I get sunburnt through glass?

Ordinary glass absorbs 97 per cent of the UVB rays that cause sunburn and some skin cancers, and 37 per cent of the less harmful UVA radiation. This translates to a protection of about SPF30, so...