Image credit: NASA / GSFC via medium.come.
Measuring an Expanding Universe
There may be problems with the idea, but apparently the universe is expanding.
I can’t follow how astrophysicists validate this, but on a (over) simplified level it seems to me that if the universe and everything within it is expanding, then so too is the measurement system that’s used to determine the expansion. And this means (again, on a very simplified level) that the spacing between the demarcations on the ruler we use to measure length is also expanding at the same rate. In short – we’d measure no change in length!
Since speed is defined by distance divided by time, what does expansion mean for the speed of light? In an expanding universe the absolute distance travelled is increased – but covered in the same absolute time – so the absolute speed must also increase?
The common explanation when dealing in such cases is that time must slow down in order to keep the speed of light constant. Hence we divide an expanded (larger) distance by a slowed (increase length of) time.
So in an expanding universe, am I correct in surmising that time slows down?
What is a day?
I can understand this.
I’ve recently reduced my contracted hours in a working week from 32 to 24. This gives me an extra day at home.
In the Netherlands a work day is defined as 8 hours. In reality we add an hour each side for commuting, plus a further hour each side for train delays / cancellations. And 4 hours each side for time dilation effects because let’s face it, no matter how the train companies make it out, when we’re
sitting standing in a cramped and stinky train we really just wish we were somewhere else.
In total this is 16 hours of a day that we need to hand over to work. Sounds tiring – so let’s treat ourselves to 8 hours sleep and we have our standard day of 24 hours.
Now here’s the thing.
I’m decreasing my work week by a day to 24 hours which I’m spreading over 3 days.
The question is…how can I increase my extra day at home to an extra 3?
Back to the beginning
Wikipedia describes how in the first 10-32 of a second after the big bang the universe suffered an expansion of distance equivalent to expanding an object 1 nanometer (that’s about half the width of a molecule of DNA) in length to one approximately 10.6 light years”.
This comes to a speed of expansion of about 1 * 1048 m/s which is about 3.34 *1039 times the speed of light.
And we know that nothing can travel faster than the speed of light!
The get out clause is that the universe is expanding under “metric expansion” – a kind of expansion completely different from that seen in daily life (paraphrased from Wikipedia) and is “valid only on large scales (roughly the scale of galaxy clusters and above).”
(Ahem, so greater than about half the width of a molecule of DNA…)
I’m reluctant to fall victim to being too stupid to realise that I don’t understand something. But it’s quite clear that I don’t understand this which is a personal struggle seeing as I can’t stand black boxes!
Not to worry – at least I’ll have some extra time at home to look it up! 🙂
The bottom line
So for now I have to accept that the universe is expanding, there’s no negative consequences on the passage of time, and I’ve still got to wait way too long for my train to take me to work tomorrow morning – and back home again if I’m lucky.
If only there was another way of traveling available in the Netherlands…
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