Just as the spaceship was traveling faster than light, you are traveling faster than snail-mail, so you beat some (or all) of your mailed selfies home. The day after your homecoming, the mail carrier delivers two of your pictures: one from the trip out, and a second from your trip back.
Ongoing research has shown that oral melatonin supplements can promote the dipping process. They can reduce nocturnal systolic blood pressure by about 6 mm/Hg, and diastolic pressure by 4 mm/Hg. Not surprisingly, the studies also indicate that melatonin improves sleep quality, which allows the body to relax more.
As a result, melatonin levels in the blood rise sharply and you begin to feel less alert. Sleep becomes more inviting. Melatonin levels in the blood stay elevated for about 12 hours-all through the night-before the light of a new day when they fall back to low daytime levels by about 9 am. Daytime levels of melatonin are barely detectable.