Intergalactic Voyages (Narration Only)
Science & Futurism with Isaac Arthur
00:00
The Intergalactic Medium Is Not Empty
A photon of light can travel at light speed, but its internal clock does not tick. It gets emitted and one day may also get absorbed. In a nanosecond or several quintillion years there was no passage of time between those moments. The larger the percentage of their total energy is their mass or rest mass, the faster time moves for them. A billion lightyear trip would feel like only a year to those on board. But we have one more fundamental maximum that is very important to intergalactic travel: space is not empty,. Even intergalactic space still has stuff in it."
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