I sort of get the idea of how nothing can go faster than the speed of light but it always bugged me in the back of my mind and seems like it shouldn’t be how the universe works
In: Physics
Speed of light can decrease depending on the medium it’s travelling through. So it’ll move slower in water than it would in a vacuum, but it’ll never exceed C since that’ll require infinite energy
We don’t know.
What we do know is that what’s usually called “the speed of light”, is better thought of as the maximum speed at which information can travel. Light can carry information, so it’s capped at that speed. So is gravity (if the sun disappeared, the earth’s orbit wouldn’t change immediately, it would take time for the change in gravity to reach us). But that just moves the question–why would the speed of information be what it is, and not some other speed?
There’s a Nobel prize for you if you figure it out.
Our understanding of physics leads us to *describe* what we observe, which is “the speed of light”, and we seek to *understand* it, but at the time, our understanding is limited, and we can only describe that there appears to be a limit of “the speed of light.”
>seems like it shouldn’t be how the universe works
By all scientific evidence we have, that _is_ how the universe works. Matter can’t really get usefully close to that speed because of how much energy is required. Light can only go that speed. It’s not some arbitrary limit someone made up, it’s the truth as observed and demonstrated in countless experiments.
If light was a different speed, it would mess up the formulas that use the constant c e.g. E=mc^2. Suppose light was slower. Maybe stars would always collapse because fusion wouldn’t provide enough energy for them to overcome their own gravity. Or maybe if light were faster, stars wouldn’t form at all because they would blow apart from too much energy.
The super-simple, ELI3 answer I gave my son when he asked was: The speed of light is how fast you go when you weigh nothing. Asking why you can’t go faster is like asking why you can’t weigh less than nothing.
If there were no brakes, if there was no matter weighing stuff down, then everything would travel at that speed. But there is “stuff,” and stuff is heavy. So when you’re made of stuff, you get weighed down and can’t go as fast. We all grew up in a world made of stuff, so we made measurements of how fast stuff travels under certain conditions. We came up with measurements like miles-per-hour or whatever. We came up with ways to measure how much energy it takes to move stuff at a certain speed, and we discovered formulas and equations, like *F=ma,* and we attached numbers to those measurements.
And once you have equations, you can plug in different numbers and play with them, and it turns out that if you weigh zero, then you would move at about 300,000km/second^(1) according to the measuring system we use. There’s nothing magical about the number 300,000kn/sec, I’m sure some people on another planet somewhere call it something else, but it’s just how fast nothing goes.
The reason this all got so confusing is because of Einstein and his friends. People started noticing that you could set up an equation where light (or nothing) could be measured differently depending on where you were standing. The famous “Twins Paradox.” Einstein was the guy who finally realized–and proved–that time itself was malleable. If things reach the top limit speed-wise, then there’s no more room for movement, so something else must change. And this turns out to be a scientific fact. Time is different depending on your situation.
But the speed of light is just “speed.” It’s how fast everything wants to go, but it’s weighed down with all this stuff.
^(1. This is a huge oversimplification, but it’s an ELI5 question.)
People often think the speed of light is weird and arbitrary because we use weird and arbitrary human- and Earth-based units to measure it. So we get values like 299,792,458 meters per second and 5.88 trillion miles per year, which are messy and don’t seem “right” for such a fundamental constant in the universe. But meters, miles, seconds and years are just human creations. You could measure the speed of light in banana lengths per fortnight and it would be no more or less legitimate.
A computer have a clock speed that it is born with and uses as long as it exist. Older models are slower and today model are faster, but once created it can never change
The speed of light is the clock speed of this universe. Maybe other universes could have different speeds, but this one was born with this speed and it will not change.
Your brain evolved to understand things that are about the right size to throw, and move about as fast as you can throw them. Those things are nice and linear and predictable.
Bigger things, smaller things, faster things, far away things are weird. They need math to understand how they work, and sometimes the math isn’t even enough. You rarely if ever see things moving that way, so it’s not going to make intuitive sense.
That said, the speed of light isn’t some specific value, it’s a fundamental property of the universe. It’s not just the speed of light, it’s the speed of anything that doesn’t have mass. It makes more sense to use the speed of light as a unit, and measure your speed as a fraction of it. And we kind of do, because our definition of the meter is a fraction of the speed of light.
The speed of light can’t be faster or slower, because it scales all of our physics that works near that speed. It’s like asking what if we made the spaces on the Monopoly board bigger, you’d still move seven spaces when you roll a seven. You wouldn’t notice the difference. What matters is how your speed compares to the speed of light. And most of the time you’re so much slower that it doesn’t affect you and you’re back in the comfortable linear domain of stuff you can throw.
A light particle traveling at the speed of light does not experiance time. It arrives at it’s final destintion at the exact moment it is created by whatever creates it (from the frame of reference of the photon itself). To the light photon, time does not exist, so therefore how can it have speed?
We on the other hand do experiance time, see a lag between creation of the photon and it’s arrival at it’s destination. Time is an illusion created by <insert Nobel Prize winning thesis here>.
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