Here's an example:
SPEED OF LIGHT: The anomaly here is that in any other scenario, velocities can be added and subtracted, except the velocity that’s known as the speed of light. Within Relativity Theory, if there is anything unintuitive it is the fact that in the entire Universe, it is the speed of light alone that is absolute or fixed, not something like space or time. It’s unintuitive in that all other bits and pieces that are in motion can be added or subtracted. So, if you are in a train that is moving at say 100 km/hour and you throw a ball at 10 km/hour in the direction at which the train is moving, to an observer outside the train, your ball is travelling at 110 km/hour. If you throw the ball towards the rear of the train, an outside observer will measure the ball as moving at 90 km/hour. If on the other hand, you shine a flash-light in the train, an outside observer will see the velocity of the resulting light beam moving at the speed of light – not the speed of light PLUS the velocity of the train, or the speed of light MINUS the velocity of the train, but at the speed of light! That’s nuts, but it’s scientifically nuts and been proven again and again in any experiment you care to devise.