Neil deGrasse Tyson | Photons | Stars | Speed of Light | Time

[0:00]what travels at the speed of light? Light does. Okay. I was about to say light. So, if photons had a clock, the clock would never tick. Nice. Which means, when I go to a mountaintop as I did in graduate school, to observe the center of the Milky Way galaxy for stars that emitted their light 30,000 years ago, traveling through the gaps of interstellar space and they move through space come through Earth's atmosphere, they come down into the telescope, they reflect, go back to my detector and land on my CCD chip. that photon when it was born at the star that emitted it, was detected at my telescope in the same instant. Wow. according to the photon itself. Live fast, die hard. the photon has no knowledge of that trip because time did not exist for it.