@Science
Interesting fact of the day:

Despite popular belief it is not really correct to say the speed of light is a universal speed limit in the universe. It would be more correct to say one object can never go faster, relative to another object by the speed of light.

In other words, no matter what speed I am going relative to the earth (or anything else) doesn't matter; if there is some object going the same speed and direction as me I can still accelerate up to the speed of light faster than it.

All that matters is that nothing can go faster than the speed of light relative to me the observer.

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@freemo

All that matters is that nothing can go faster than the speed of light relative to me the observer.

More generally, since this is true for all observers:

All that matters is that nothing can go faster than the speed of light relative to any observer.

Which is exactly what is meant by saying the speed of light is a “universal speed limit”.

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@khird

Indeed, that is the intended meaning of course.. but often grossly misunderstood by people.

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@freemo

I don’t know it’s a misunderstanding as much as just a carelessness or lack of rigour with the vector math (mixing observers without accounting for time dilation when adding velocities leads to errors at relativistic speeds). The sum of the velocity of B as observed from A and the velocity of C as observed from B is not necessarily the velocity of C as observed from A.

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@khird

I’m not sure we can say its carelessness if they dont understand the math to begin with. Most people who misunderstand it likely arent even doing or considering it in vector math terms. I am more interested in the purely conceptual understanding that a lot of people are curious enough that they do consider it, but often get it wrong.

Understanding it really doesn’t require anything nearly as complex as vector math, and even if you do vector math you don’t even need to touch or incorporate time dilation directly (you can use energy equations and ignore time dilation and it works out correct). Sure if you want to calculate exact numbers in a complex scenario with multiple objects moving at different speeds and directions then vector math is going to be your go to (with or without time dilation).

Simply understanding intuitively as I have already done in some of the comments or even doing the math without consideration fo vectors by limiting our talks 2D is possible with just a basic intuition and very little rigour (the numbers I cited in some of my comments i just did simple math in my head, there wasnt a vector in site or anything to do with time dialation to cite those numbers).

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