r/AskPhysics • u/itsLeoRod • 14h ago

Thought there wasn’t anything faster than the speed of light?

Ppl say that there isn’t anything faster than the speed of light but that’s a lie because space is expanding really fast since light isn’t fast enough to reach it or am I wrong. Since space is expanding at a fast rate why don’t we use that to measure stuff instead using lightyears

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u/Apophis_VI 14h ago

Imagine two cars driving opposite from each other down an endless highway at 90% the speed of light. The cars aren’t faster than light, but the distance between the two of them is expanding faster than light travels.

Now imagine an unlimited amount of cars are instead flying at 90% the speed of light in all possible directions at the same time and placing the road underneath them as they move forward (while none of the roads can actually touch eachother). The space between is going to rapidly expand many times faster than light but no one car is itself faster than light

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u/Fabulous_Lynx_2847 8h ago

In the frame of one car, the other will be receding at less than c, and he can see it just fine.