We meet again for another fun-filled edition of Ask ARSE.
We get truckloads of questions in our official Australian Space Society, but some just stick out.
Not because they're particularly abstract, or profoundly scientific...
Sometimes it's the things we take for granted, like this question from Dave.
"Hey guys, thanks for everything you do!
I read your email this week and it got me thinking about the size of the universe and how immense it is. It really puts the speed of light into perspective. Which made me also think we speed of light is the way it is? Looking forward to your answer while I keep spreading ARSE.
Great question mate and it is something we always talk about in astrophysics but always overlook.
To start at the start of our relationship with the speed of light, we need to begin at the beginning.
Which was way back in the 17th century.
Pictured: Ole Romer
A bloke by the name of Ole Romer was intently studying the moons of Jupiter and by chance found that the planet would sometimes block the path of our view with its moon, Io.
This created an eclipse, but Romer noted that the timing between Io becoming dark in an eclipse changed over the course of the year.
Years go by and the undeterred Romer kept at it, eventually discovering the connection between our position in orbit around the sun.
By the time we see another eclipse Earth is not int he same position it was when the previous eclipse was observed.
Maybe we're further away from Jupiter. Maybe we're closer.
If we're further away from Jupiter, we have to wait a bit longer to see the next eclipse as it takes much longer for the light to reach us.
The opposite being true.
If we're closer, we wait less time.
It does sound elementary as we know the relationship between light and time, which is the speed of light.
But it's very important to remember that NO ONE did back then and this as revolutionary thinking.
Light was just light *shrugs shoulders in 17th century*
Romer came to the logical conclusion that the only way to explain the variations in light is that it must have a quantifiable speed.
Pictured: James Maxwell
Centuries pass and measurements continue to calculate the speed of light off the back of Romer's work.
Until in the 1850s, a physicist by the name of James Maxwell takes up the mantle left by Romer (who we can only assume has died).
Maxwell "accidentally" invented light, much like how Romer accidentally stumbled upon the delay in light over distance.
When goofing around with a magnet and electricity (as you do), Maxwell found the basis of the electromagnetic forces.
And with it, changing electric fields can create magnetic fields and vice versa.
Eventually, he found that waves of electricity make waves of magnetism, which create waves of electricity and so on over and over again that are sable to travel distance.
These waves piggybacking and leaping over one another is what we know as light.
When Maxwell tried to measure the speed of light, he came to the same speed his predecessors had before him.
When Maxwell attempted to measure the speed of these waves he got the same number his predecessors had over the course of hundreds of years.
About 299792.458km per second.
Therefore, Maxwell accidentally built light from its components rather than deconstructing it.
Which is the more logical course of action yet much harder to actually do.
Enter Albert Einstein a handful of decades later with his eureka moment about "space-time" and the realisation that the speed of light had nothing to do with light at all.
In a nutshell, Einstein's theory of relativity describes the true nature of space-time, and not the actual speed of light at all.
Einstein realised the glue that binds space and time (think a meter and a second) was something he called "space-time".
Think of space-time as the exchange rate in the stock exchange like "How much space can I get with X amount of time?"
Eventually, Einstein found there was a constant, measurable speed that would tell us the "exchange rate" of space to time.
Or, how much space was equal to how much time, and vice versa.
Unfortunately, Einstein's theories didn't tell us what the number was.
But he DID apply relativity to the equations Maxwell used to calculate the speed of light...
And guess what?
The conversion rate was 299792.458km per second.
The exact "speed" of light from centuries before.
From Romer's accidental discover of light vs time to Maxwell stumbling into creating it, there was an understanding of an unseen force that dictates the passage of time over space.
This conversion rate, this unseen force in nature is what unites and drives space-time.
The number itself doesn't matter, it's simply a result of us justifying something happening in units we decide on like meters and seconds.
The number 299792.458km per second is simply how we describe what we are experiencing in order to communicate it to one another and justify what we are experiencing in its simplest form.
Example: we call meters "meters" as we all agree on its length instead of something ridiculous like "bananas". We'd say the tree is 3 meters tall instead of 80 bananas tall.
It's just better communication.
Psst! Clint the Intern here, just letting you guys know there's FREE SHIPPING on hoodies while they last. There's no better way to spread ARSE than to wear it.Have a look here and I'll see ya on the socials! - Clintern
The speed of light is the same.
That huge number is just a less complicated way of describing space-time.
And Maxwell discovered it thinking it was the speed of light!
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