Maybe this is a dumb question. How do we know that time slows down when you move faster? And maybe it is just that things/atoms move slower when you are going fast. And at very fast speeds the ways we measure time fails
Maybe this is a dumb question. How do we know that time slows down when you move faster? And maybe it is just that things/atoms move slower when you are going fast. And at very fast speeds the ways we measure time fails
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Because, all theoretical formulas aside, GPS satellites’ onboard clocks keep suffering the expected delays…
If things/ atoms move slower at high speeds, then that’s time slowing down.
This is observable. Airplanes with clocks synced to clocks on the ground come out of sync after a while. We need to allow for this with satellites.
There are actual experiments done to verify this. One was taking 2 synchronized clocks, leaving one on the ground and flying the other on a jet plane around the world.
There are also corrections done on GPS satellites to take this effect into account. Since GPS works very well, these adjustments are necessary and therefore time dilation is demonstrated. Without the adjustments, GPS wouldn’t work at all.
Because we know that light (really causality) has to move the same speed no matter how fast you’re going.
This is required for Maxwell’s equations, which do a REALLY good job of explaining how electromagnetism works properly. They use the speed of light as a constant. For everyone in motion to see light as going the same speed, you need to have space contract (get shorter) as you go faster and time dilate (times get longer), as described by the Lorenz Transformations.
If time didn’t slow down, if you ran alongside a photon you would observe that photon going slower than someone who was standing still.
With the invention of ultra precise clocks we have been able to measure this effect.
This thought experiment helped me a lot back when I was in school:
Imaging a clock that is made from bouncing a photon up and down between a two mirrors, one on the floor and one on the ceiling. To make the numbers easier, let’s say it’s 4 meters.
Now imaging the whole setup is moving, so that for each bounce, the whole setup moves 3 meters to the right. This means that the setup is moving a decent fraction of the speed of light!
Light always travels at the same constant speed, but as a stationary observer you see that it now has to travel 5 meters (3 meters along, 4 meters up, the other side of this right angled triangle by Pythagoras is 5 meters).
This means that the clock is ticking at 4/5ths the speed that it was before! When the clock accelerated to near the speed of light, it slowed down
Particles at the collider exist a lot longer at high speeds.
There are some particles that decay really really fast. However when we accelerate them around particle accelerators to large fractions of the speed of light they take significantly longer to decay.
So, some experiments in the 1880s by scientists Albert Michelson and Edward Morely showed that the speed of light didn’t change depending on what direction you were traveling, meaning that everyone in the universe would see light traveling at the same speed, no matter how they are moving relative to that light. Various scientists like Hendrik Lorentz proposed solutions on how the measuring apparatus changing shape etc. based on their movement could result in the observations that Michelson and Morely made until about 15 years later Albert Einstein brought it all together and published his Special Theory of Relativity where the speed of light is an universal constant and what keeps the perceived speed constant is the contraction and expansion of space and time relative to your movement.
And this is not theoretical at all. Scientist have measured the differences in timing with atomic clocks and GPS requires adjustments to the clocks in the GPS satellites because of both special and general relativity, precisely in the amounts predicted by Einstein’s theories.
It’s both. Time is the measure of how fast things move relative to each other. If there were no things, there would be no time.
An easy way to get your head around it is to imagine that we are always moving at a constant speed through spacetime.
If you are stationary in space, then all that speed is in time. But if you start moving through space, your speed through time is reduced to maintain the constant speed. And if you travel through space at near the speed of light, you are nearly stationary in time.
It’s not an accurate metaphor but it’s enough to get your brain to accept the concept.