Twin paradox: the real explanation
12:05
Twin paradox: the real explanation (no math)
8:16
Does acceleration solve the twin paradox?
15:37
Spacetime rotations, understanding Lorentz transformations
9:46
If the universe is only 14 billion years old, how can it be 92 billion light years wide?
10:29
What are virtual particles?
10:13
How fast is gravity?
21:52
I never understood why speed of light is a constant (c)... until now!
16:20