• Wavelengths(emiEed(by(objects(moving(away(
are(shi^ed(to(lower(frequency((towards(reds)(
• Wavelengths(emiEed(by(objects(moving(
towards(us(are(shi^ed(to(higher(frequency.(
• Example(of(sound(–(pitch(of(fire(engine(is(
higher(as(truck(moves(towards(you(and(lower(
as(it(moves(away)(
• For(galaxies(outside(our(group,(the(redshi^(is(
known(as(hubble(expansion((a^er(Edwin(
Hubble(who(discovered(this(phenomenon(in(
1929).