Mike Murphy's Blog

Last post of 2023.

If you look at a river, you will quickly realise that the water flows at different speeds depending on where you’re looking. Near the river banks it usually flows quite slowly, whereas it will typically flow much faster near the centre, if unimpeded.

A closer inspection reveals that the currents in a river flow at different rates, all across the river. They slow down when the water encounters any obstruction or where the river is shallower.

There will be ‘eddies’ where the water changes direction completely, or, sometimes, comes to a near standstill. So, the fact is, the water in a river flows at many different rates, depending on the very local conditions.

Picture here

This is how I view the flow of time in the universe. Einstein’s General Relativity tells us that time slows down near massive objects due to gravitational dilation.

If you go near a massive star or a black hole, time will slow down for you, although you will not be aware of it yourself (since everything will slow down!)

So, if you are in deep space, far from any matter (stars, planets etc) the flow of time will be at its maximum. This is similar to being in the middle of a river, far from the banks or other objects. The water flows more freely and rapidly here – just like time far from massive objects.

Whereas, as you approach a river bank, or an island, the water slows – like time near massive objects.

This means that the rate of time changes constantly depending on how far or close you are to any massive object. The more massive it is, the slower time flows. Time virtually stops at the event horizon of a black hole.

So, when looking at the universe, you are essentially peering into the ‘river of time’. Near stars and large planets, time will slow. Whilst, in the deep space between galaxies, time will flow freely.

But it doesn’t stop there…

Einstein’s first great theory – Special Relativity – tells us that time ‘appears’ to slow down when travelling at very high velocities (approaching the speed of light).

This is purely due to relativistic effects and is not connected to gravitational dilation. The faster you travel, the slower your flow of time appears to a stationary observer.

So, if you are travelling very quickly towards a large star or black hole, to an external observer, you will appear to slow down as you get closer to the object – due to both gravitational and high velocity time dilation. In fact, as you approach the event horizon of a black hole, you will appear to slow down so much, that you never actually reach it – but only to an outside observer…

Very interesting.

Happy New Year and all the best for 2024.

Ciao for now,

Mike.