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The speed of light isn’t even really a speed, it’s a property of space itself.
But it’s also a speed
When sailing boats pushed for speed they ended up hitting an unexpected speed barrier. As you increase velocity the break wave created by the bow of the ship elongates until the length of the ship is at 1 wavelength, then the hull drag prevents further acceleration. For a 50 meter ship it’s about 17 knots. You can get much faster lifting the boat from the water as you gain speed with an underwater wing, the current max speed was set 47 years ago at ~276 knots. But that’s only because they can remove the hull from the high drag environment and is extremely dangerous to attempt to break. The speed of light is nothing like that because spacetime itself can stretch and squish, I just wanted to talk about boats for a bit.
You have two observers, moving directly opposite each other.
Each has a flashlight pointing back at the other.
The speed of the light from those torched is the same for both observers.
(Instead the light would be red-shifted.)
Add a third observer, stationary to one and moving towards the other. As the third observer passes that observer, the speed of light from their flashlight never changes, and it’s the same speed as from the other two. (Instead it would go from being blue shifted to red shifted.)
This adds substantially more questions than it answers.
-Scientists after discovering General Relativity
Different phases (colours of light) move at different speed, and have different longevity, I think. So how they always thought those pretty galaxy nebula photos, were red? Actually turns out that phase of light just travels for a longer time. Lasts longer. OK, now someone correct me, because I have absolutely no idea what I’m talking about. Just bring up vague floating memories from an article i read once.
I think it’s neat that Newton is taught first. As in: gravity is a function of mass. Because that works in so many scenarios.
But then you learn that gravity bends light and that photons have no mass.
So… Gravity isn’t a force, it’s more like going downhill… in the dimension of time.
If they have no mass, how do they push solar sails?
A bit late to the party, but I’ll try anyway!
So, first, speed is distance over time. Miles per second, kilometers per hour, whatever.
Consider a person rocketing by a planet in a little spaceship at a good fraction of the speed of light. To amuse themselves, they’re bouncing a ball between two paddles on opposite walls of their craft. The ball describes a path like:
O--------O
–O----O
-----O
Of course, to a person on a planet they’re blasting past, the path looks different - the ship moves a long way between each bounce, so they see:
O----------------------------------O
-------O------------------O
----------------O
The thing is, both of these are correct from each point of view - from each reference frame. For the shipboard person, the ball moves the width of the ship, and for the planetside person, it covers the distance the ship traveled in the bounce (plus some for the width).
Now, swap the ball for a photon, which always moves at the same speed. The distance the photon travels from the two points of view - the two reference frames - is different, so the time component of the photon’s measured speed must change as well because the photon’s speed remains the same! Each side sees the photon moving at the same speed, despite the difference in distance traversed each pov sees - which means each must also have a different measurement of the time involved!
So, time is compressed on the spaceship relative to the planet - from the ship, the planetside observer is moving very fast, while to the planetside observer, the space pilot is moving in slow motion. The speed of the photon is universal - it’s the distance it travels between bounces, and therefore how long it takes to bounce, that differs between their perspectives.
I want to know why it works that way. I’m pretty sure we don’t actually know why that is a law of nature, just that it is. Some of these things I learned in physics I was frustrated that we can’t explain the why. We just kind of know this is what experiments tell us, and the math.
If you mean the relativity part, to my understanding space and time are basically a shared dimension, so the faster something is moving in space the slower it’s moving in time. Why it’s shared, I have no clue.
We don’t actually know that space and time are a shared dimension though. Relativity treats it that way mathematically, but we don’t know what space and time are. I’m also just one of those people who want to know the answer to everything, so when the answer is we don’t know, or it works that way bcz it works that way frustrates me.
Even the idea that space and time are interconnected seems like an incomplete explanation to me.
To me, there’s no reason space and time have to be connected. But they obviously are.
My favorite theory is that time isn’t real, just an extremely stubborn illusion. Fun to think about, really difficult to prove.
Well strangely a lot of things are “it just works that way,” at least to our current understanding, like gravity, electromagnetic forces, things tending towards lower energy states. We could conceivably live in a universe where a ball doesn’t roll down a hill, it just stops where it is and retains its energy.
I saw something called the “fine tuning argument” that said there must be some higher power because our universe could not exist without those constants being what they are, but we also wouldn’t exist to experience it otherwise so ¯\(ツ)/¯
You mean Aristoteles? Many of your questions belong to philosophy not physics, give it a try when you need answers!
And that is what is meant by time dilation, and why Matthew Mcconaughey was younger than his grandkids. His balls took longer to bounce…
Okay, but what if I go the speed of light minus 1m/s and shine a flashlight, can I catch the photons?
You can catch the photons just fine without needing to go absurdly fast. Just put your hand in front of the flashlight beam, and you’ll catch lots of them.
Physicists hate this one weird trick
