Shapiro time delay | What is the true meaning of constant speed of light?

Full video here: • What is the true meani...
Shapiro time delay confirmed massive objects can slow down light passing by. However, special relativity told us, the speed of light is a constant. So what is the true meaning of constant speed of light?

[@universeio]

Full explanatory video: kzbin.info/www/bejne/nqewcodnrcqll68

[@leftifornian2066]

Was it Ben Shapiro ?😂

[@MillionairesDiary]

Due to strong gravity fields, time itself ticks at a slower rate, which is measurable by the relative decrease of C compared to a vacuum. But I've always wondered, what if due to dark matter, our entire galaxy was a strong gravitational field?? That would mean we are living our lives under the same kind of time dilation and we wouldn't be able to measure it! Unless we went outside of the galaxy and then compared clock speed to earth.