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[-] treesquid@lemmy.world 16 points 13 hours ago* (last edited 13 hours ago)

In the same way that two cars driving away from each other at 60 mph have relative speeds of 120 mph with regard to each other, two bodies moving away from each other at less than the speed of light have relative speeds exceeding it. Everything in the universe is moving away from everything else and sometimes at relative speeds that exceed the speed of light. Nothing is individually exceeding the speed of light in absolute terms.

[-] NigelFrobisher@aussie.zone 1 points 1 hour ago

I fucking hate that aspect of Special Relativity when I did l A-Level Physics (wait, shouldn’t that be “Physic” in the US to go with “Math”?). Two spaceships head off in opposite directions at light speed - from the frame of reference of each spaceship, the other is moving away at C, not 2C, because the Universe would rather slow down time itself than let anything move faster than its stupid precious C!

[-] Objection@lemmy.ml 12 points 6 hours ago* (last edited 6 hours ago)

That's intuitive but actually completely wrong. There is no "absolute" reference frame, and nothing can move faster than light in any relative reference frame.

The only thing that gets around that is the expansion of space itself. It's not that the objects are moving away from each other, it's that the distance between them is expanding, causing them to become farther apart.

The best analogy is to picture an ant crawling on the surface of an expanding balloon.

[-] Rooster326@programming.dev 3 points 6 hours ago

Okay but the ant can still only go at the speed of ant.

[-] Allero@lemmy.today 9 points 4 hours ago* (last edited 4 hours ago)

Exactly! That's why we have a concept of observable universe.

As the universe expands (think of it not as ants moving, but more space created between ants as balloon gets inflated), at some distance away from us it starts doing so faster than light.

The light, however, can only travel at, well, the speed of light. As such, we will never see or reach anything that is beyond this light speed horizon. And as the expansion of the universe speeds up, more and more objects that we can still observe will disappear beyond this point.

[-] Luna@ani.social 5 points 7 hours ago

Relative speeds also cannot exceed the speed of light. Since there's no absolute reference frame, if this were possible it would be no different than exceeding the speed of light on "absolute" terms. Once you get up to speeds where this would matter, funny dilation effects that I'm too dumb to understand would prevent this.

[-] childOfMagenta@jlai.lu 1 points 6 hours ago* (last edited 6 hours ago)

Cars are not driving away from each other at more than the speed of light relatively. The road is stretching faster than the speed of light.

this post was submitted on 25 May 2026
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