What causes cluster headaches?

How do we fuel cars more sustainably? What causes morning sickness during pregnancy? Why does California have a sunny Christmas? Why are some smells able to summon powerful memories? Why can I hear fluid flowing when I move my neck? Is premature ejaculation nature's way of hastening reproduction? And what's the physics behind why stars twinkle? Dr Chris Smith and Clarence Ford have the answers... Like this podcast? Please help us by supporting the Naked Scientists