Does time really exist, or is it a persistent illusion? |
Imagine you are sitting on a train, moving at a constant speed. The blinds are drawn so you can’t tell you are moving. A light bulb hangs on a chain in the centre of the car. When someone turns it on, your human eye perceives the whole carriage lighting up.
What actually happens is that light first reaches the two sides of the car simultaneously. A moment later, the light reaches the front and back of the car, again simultaneously. The light has travelled at the exact same speed in all four directions.
Albert Einstein wondered how this situation would be described from the perspective of someone outside the train who was not moving with the car. For a drone hovering over the train, for example, the light still reaches the two sides simultaneously but the back of the car lights up before the front. This is because the train is moving forward, so in the moment it takes the light to travel to the front and back of the car, the back has moved closer to the light source and the front has moved further away.
This phenomenon, discovered by Einstein in 1905, is called the “relativity of simultaneity.”
On the basis of this phenomenon, scientists have argued that in reality there is no objective “now” and that time does not truly pass. Some have even suggested that the apparent passage of time may be psychological.
Modern cosmological observations, however, suggest that time is more than a mere........