I've decided to revive an old thread format from long ago as it's always good to have a repository of obscure trivia here for easy access. Please add your own.

The speed of light is not impossible to exceed according to Einstein's theory of special relativity, but matter is divided into that below the speed of light which theoretically can't reach beyond it as it requires infinite energy, and tachyon energy which may exist beyond the speed of light, always travelling faster. In theory this could imply an alternative dimension and universe where everything is moving beyond light speed and could not be seen by us as (bringing to mind various episodes of Star Trek) beyond our level of vision.

Mars bars are simply named after Forrest Mars, the original company owner, M&M's being for Mars and Murries, his partner at the beginning. Similar company names are based on the owner's name such as Hoseasons holidays and Converse boots.

David Bowie was not born with eyes of different colours, one is due to an injury.

Guano is not just bird droppings, it includes all nitrogenous dung able to be used as fertiliser, and made by bats and seals as well as the more familiar birds.

Healthy urine is sterile and used for medicinal purposes in many cultures.

Plum pudding has no plums and mincemeat has no meat. This was not as a joke, unlike Welsh Rabbit which has no rabbit in it, but because the meanings of the words have changed since the 17th century, where plums were any small fruit like raisins, and what are now plums were more likely to be called prunes. Meat also referred to a wider version of food in general and became narrower over time to only refer to dead animals' flesh.

I will continue to add more as they come to me.

Admiral Nelson didn't wear an eye patch. It was made up by Hollywood to 'improve' his image.

A human embryo's heart starts to beat at about 3 weeks of age (5 weeks of pregnancy)!

Mincemeat used to include animal flesh. It still includes suet.

That's what I tell myself each time my daughter pees on me!

We heard our daughter's a week later. At 5 weeks pregnant, we saw just a shadow that was the yolk sac - she was too small to see. Only a week later her heart was beating and we could see a mass of cells. Was amazing she grew so much in a week!

I'll add one of my own: a bagpipe is a double reed instrument. The reed is found inside the instrument.

Capt Kirk never said 'Beam me up Scotty'.

I thought it was "Welsh rarebit." Nowhere in Britain is more than 75 miles from the sea. Boggie never says "Play it again Sam." in casablanca. The insane policy when entering an iceflow during the Titanic times was to go faster to get out of it faster.

I just finished a course on embryology (where I found out about the heartbeat) and I think most people would be pretty surprised at how much happens in the tiny embryo in just a week or two!

My dictionary of word origins (Adrian Room, author of one of my original trivia posts here when I arrived but long gone) says it's Welsh rabbit because it's not, rarebit has been used because the irony didn't make sense to many people. I go back way before you could post links and relied on the library! 11 years later however Wikipedia has much of the similar information, rarebit being a word never seen elsewhere and first recorded 60 years after rabbit.
Welsh rabbit

Great stuff everyone (especially the pee observation Beth), I'm learning a lot and will add some more when it comes to me.

One criterion to decide if a biscuit or cake (important in UK as each has a different purchase tax class) is biscuits are hard and get soft when stale while cakes are soft and go hard. I'd have suggested one is sponge and the other biscuit, but I don't make the rules. And what about wafers?

I also think so.

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