4 ms·
The wild thing to me, assuming I understand it correctly, is that the expansion speed can exceed the speed of light.
by 762236 6y ago
The wild thing to me, assuming I understand it correctly, is that the expansion speed can exceed the speed of light.
- k_sze 6y agoYep. That’s why we talk about the observable universe. Objects outside the radius of the observable universe are moving away from us so quickly that any light or gravitational effect from those objects have no chance of reaching us any longer.
- cdumler 6y agoYou correct, but in the details. Travelling through space is limited to the speed of causality (the speed any massless particle travels) but space between itself is not limited to any particular speed. Think of it this way: A balloon is space and the speed of sound is the limit at which waves can travel across it. This normal for sound waves. If every bit of the balloon expanded at 1 inch per second, a small balloon would be getting bigger, but wouldn't exceed the speed of sound. A sound wave will outrace the expansion. Once the balloon as expanded to about 2500 feet in diameter, the expansion along the balloon will be greater than the speed of sound. A sound wave will never make to the other side. That said, no one place is expanding more than 1 inch per second. Nothing in part violates the speed of sound.
- Erlich_Bachman 6y agoIf you choose your relative objects that you compare carefully, even much simpler systems can be seen as expanding much quicker than the speed of light, relative to some specific theoretical observer. But nothing can travel faster than the speed of light (no matter or energy or information), relative to the source point.