Red ShiftBlue Shift The Doppler Effect with Light

Red Shift/Blue Shift The Doppler Effect with Light

Scientists Say: The universe started like this: Here we look at some java applets: 2 D big bang 3 D big bang Today we’re going to learn why.

Electromagnetic Spectrum Increasing λ In which direction does the wavelength increase? In which direction Increasing does the frequency f increase?

Stationary Wave Sources L Q: Does either eye (left or right) observe a different wavelength light? A: No. Both eyes observe the same wavelength, yellow, light. R

Moving Wave Sources L R Q: Does either eye (left or right) observe a different wavelength light? A: Yes. The left eye will see longer wavelength light and the right eye will see shorter wavelength light.

Red Shift / Blue Shift, Notes: L R b. Wave source approaching (blue shift) i. wave fronts are squished together ii. wavelength is shorter, frequency is higher iii. so it appears bluer a. Wave source moving away (red shift) i. wave fronts are spread apart ii. wavelength is longer, frequency is lower iii. so it appears redder Q: What happens to the light the left righteye eyesees? see? Red Shift Blue Shift No Shift

What Color Does Ashley See? What Color Does Jessica See?

A Person Stands on a Planet The Planet is Flying Away The person is holding a red and a blue light bulb. A green light bulb grows out of their head.

Draw What You’ll See: Label the colors of the light bulbs! The person is holding a red and a blue light bulb. A green light bulb grows out of their What colors will you see? head. green ? red ? ? blue

Green Yellow Red Infrared* You Would See * Note: Human Eyes Can’t See Infrared Blue Green

The Sun & The Stars • The sun is a star. • The sun and the stars are all made out of hydrogen. • Light from hydrogen leaves a distinctive pattern of black lines (an absorption spectrum).

What We See Close Star Nearby Galaxy This is Faraway Galaxy Really Faraway Galaxy the absorption spectrum (pattern of black lines) from a close star like our sun.

What We See Close Star Nearby Galaxy Faraway Galaxy If the nearby galaxy wasn’t moving, the absorption spectrum (the pattern of black lines) would be in the same place. Really Faraway Galaxy

What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy Is the pattern red shifted or blue shifted?

What We See Close Star Nearby Galaxy Faraway Galaxy The pattern is red shifted since it is shifted towards the red side of the spectrum. Really Faraway Galaxy

What We See Close Star Nearby Galaxy Faraway Galaxy Really Is the Faraway Galaxy The pattern is red shifted. — So — nearby galaxy moving towards us or away from us?

What We See Close Star Nearby Galaxy Faraway Galaxy Really The Faraway Galaxy bigger the shift, the faster the light source is moving.

What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy Which is moving away faster: the nearby galaxy or the faraway galaxy?

What We See Close Star Nearby Galaxy Faraway Galaxy Really Faraway Galaxy

Your Turn The further away a galaxy is, the bigger the ______ shift. red blue So far away galaxies are moving away _______. slower faster

Your Turn The further away a galaxy is, red shift. the bigger the ______ red blue So far away galaxies are moving away _______. slower faster

Your Turn The further away a galaxy is, red shift. the bigger the ______ red blue faster So far away galaxies are moving away _______. slower faster

The further away a galaxy is, the bigger the red shift. So far away galaxies are moving away faster. Scientists’ Conclusions • The galaxies must have been close together in the past. • A tremendous explosion (a big bang) must have made everything explode outward. • That’s why the fastest galaxies are the furthest away.