Questions you'd like answering, regardless of how trivial they may seem

[laurentian]

Who says it has stopped?

If it slows by just a metre per second per year, that is probably beyond our current capability to measure.

Universe is approximately (and, I guess, arguably) 13.8 Billion years old so slowing at 1 m/s per year down to where we are now would mean it would have been, well, bloody fast at the beginning of the universe!

I am far from an expert on this but I would imagine that even a small reduction in the speed of light (and all electromagnetic waves) would have been detected and probably have caused us lots of problems . . . but then its all relative so . . .

 

[ebikeerwidnes]

but if it slows down, then how long is a metre?

basically, it is one of the fixed constants of the Universe
so other things are measured by it

so a meter is the distance travelled by
The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of ⁠1/299792458⁠ of a second, where the second is defined by a hyperfine transition frequency of caesium.[2]

so if light slows down then the metre shrinks as it is a man made definition rather than a physical constant based on nature

 

[Profpointy]

Who says it has stopped?

If it slows by just a metre per second per year, that is probably beyond our current capability to measure.

I'd have thought that would easily show up in observations of the distant, ie a long time ago, universe as the physics would show very differently if one of the key (so say) constants of nature varied significantly. I've not done the calculations, and would struggle to think of where to start, but I would he surprised if this wouldn't have been the subject of papers pretty much as soon as the constancy of the speed of light was mooted

 

[FishFright]

in a vacuum

true

So there is an arguement that in the very early universe whcih contained alll matter/energy already was much denser than a vacuum so the speed of light was indeed different .

I've not seen any models that show this yet so it remaind conjecture on my part

 

[Ming the Merciless]

wouldn't that imply that it is constantly slowing over time?

It would imply nothing about a rate of decline in the speed of light. Why assume it’s a constant deceleration? We have not been measuring the speed of light for that long in the scheme of things. How many times have we actually measured it?

 

[laurentian]

So there is an arguement that in the very early universe whcih contained alll matter/energy already was much denser than a vacuum so the speed of light was indeed different .

I've not seen any models that show this yet so it remaind conjecture on my part

Would that not be a different speed due to the interaction of light with the matter (refractive index) as opposed to a change to the speed of light itself?

 

[FishFright]

Would that not be a different speed due to the interaction of light with the matter (refractive index) as opposed to a change to the speed of light itself?

Honestly I don't know .

 

[laurentian]

Honestly I don't know .

Nor me! Though I do find this stuff fascinating and try my hardest to understand it all

 

[laurentian]

It would imply nothing about a rate of decline in the speed of light. Why assume it’s a constant deceleration? We have not been measuring the speed of light for that long in the scheme of things. How many times have we actually measured it?

From "the internet":

"The speed of light is no longer measured; it is a fixed, defined value of exactly 299,792,458 meters per second since 1983. Before 1983, it was measured countless times using various experiments, with each new measurement providing more accurate results, such as those by Fizeau in 1849 and Michelson in 1879".

 

[DRM]

From "the internet":

"The speed of light is no longer measured; it is a fixed, defined value of exactly 299,792,458 meters per second since 1983. Before 1983, it was measured countless times using various experiments, with each new measurement providing more accurate results, such as those by Fizeau in 1849 and Michelson in 1879".

It's the recorded speed of a BMW/Audi going from the motorway entrance slip road to lane 3, or lane 3 to the exit slip road!

 

[Ming the Merciless]

but if it slows down, then how long is a metre?

It’s circular, the metre is defined by speed of light in vacuum, the speed of light is defined by m/s. If light slows down, then the metre is shorter, the m/s remains constant.

 

[Animo]

Why was there a guy wearing nothing but a pair of underpants running alongside the A167 near Durham this morning?

 

[raleighnut]

Why was there a guy wearing nothing but a pair of underpants running alongside the A167 near Durham this morning?

@Drago out for a jog ?

 

[stephec]

Why do touchscreens on phones and tablets never need calibrating?

I work with machinery that all use a HMI with a touchscreen, every now and again the screen needs a calibration, so why is it that phone screens never go out, and if they don't why not make the industrial HMIs to the same design?

 

[stephec]

Why was there a guy wearing nothing but a pair of underpants running alongside the A167 near Durham this morning?

Speedo Mick?