# AST201H1 Study Guide - Midterm Guide: Length Contraction, Special Relativity, Dark Matter

**sky.h.kim**and

**37594 others**unlocked

24

###### AST201H1 Full Course Notes

Verified Note

24 documents

## Document Summary

Astronomy midterm review sketch of look back time : the further you look, the further in time you are looking. Dark energy and dark matter: it was first observed through rotation curves. Speed of light : constant and invariant. The fact that everyone agrees of law of physics then weird stuff happens: length contraction, clock dilation etc . Issue of the twin paradox: but there is a solution to it. Seems like a paradox but it"s not. Two twins traveling shows that what one sees is not necessarily what"s happening. Based on the fact that light takes time to travel while the twins travel. The twin that is moving is young because clock runs slower when moving. Gravity: as a way to introduce general relativity. 4 forces of nature. Newton"s law of motion and law of gravity (classical physics) In general relativity: anything with mass bends space time. Gravity is a force (newton) or spacetime curvature (einstein)