Redshift and the expanding universe

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   “Rule card:” A galaxy's 656.3 nm line is seen at 662.9 nm. With H0 about 67 to 73 km/s/Mpc, about how far away is it, by Esme's math?

   • About 200,000 Mpc
   • About 41 to 45 Mpc
   • About 0.1 Mpc
   • About 41 to 45 Mpc, moving toward us
2. 2.

   Speed = H0 × distance; A at 30 Mpc; B 4 times as fast. Galaxy A is 30 Mpc away; galaxy B recedes 4 times as fast. How far is B, whatever the exact H0, by Jun's math?

   • About 7.5 Mpc
   • About 34 Mpc
   • About 120 Mpc
   • It cannot be found without H0
3. 3.

   1 ÷ H0 ≈ 14.6 billion years at 67 and 13.4 billion years at 73. If galaxies always moved at today's speeds, the time since they were together ≈ 1 ÷ H0. With H0 of 67 to 73 km/s/Mpc, this comes to about what, by Kira's math?

   • Between about 13 and 15 billion years
   • About 67 to 73 billion years
   • About 6,000 years
   • Between about 13 and 15 million years
4. 4.

   Luz's friend says the Big Bang means galaxies are flying away from the spot where an explosion happened. Which response is best?

   • Disagree: space stretches everywhere, with no center
   • Disagree: galaxies are moving toward one spot
   • Agree: galaxies fly out through empty space
   • Agree: the Milky Way is near that spot
5. 5.

   Noah's friend says a redshifted galaxy must look red in a telescope. Which response is best?

   • Disagree: redshifted galaxies look blue, since they move toward us
   • Agree: red galaxies alone move away
   • Agree: redshift is the galaxy's color
   • Disagree: redshift means its lines moved to longer wavelengths
6. 6.

   Speed = H0 × distance; distance 50 Mpc; H0 about 67 to 73 km/s/Mpc. Sources give H0 as about 67 to 73 km/s/Mpc. Which statement about a galaxy 50 Mpc away holds for every value in that range, by Pia's math?

   • It recedes at exactly 3,500 km/s
   • It moves toward us at about 3,500 km/s
   • It recedes at about 350 km/s
   • It recedes at between 3,300 and 3,700 km/s
7. 7.

   H0 = speed ÷ distance; 21,000 km/s; 300 Mpc. A galaxy at 300 Mpc recedes at 21,000 km/s. Is it consistent with H0 of 67 to 73 km/s/Mpc, by Tala's math?

   • Yes: 21,000 ÷ 300 = 70 km/s/Mpc
   • No: farther galaxies should be slower
   • No: it gives 0.014
   • No: it gives 6,300,000
8. 8.

   The Milky Way; two galaxies 500 Mpc apart; two galaxies 1,000 Mpc apart; two clusters 300 Mpc apart. Which object is held together by gravity and does not take part in the expansion, by Zee's reading?

   • Two galaxies 500 Mpc apart
   • Two galaxies 1,000 Mpc apart
   • Two clusters 300 Mpc apart
   • The Milky Way

9. Read this first

   Two galaxies

   Galaxy	z
   X	0.005
   Y	0.015

10. 9.

    Galaxy X shows z = 0.005 and galaxy Y shows z = 0.015. Without knowing H0, how does Y's distance compare with X's, by Ari's math?

    • About 3 times as far
    • About 0.01 Mpc farther
    • About one-third as far
    • The same distance
11. 10.

    Four evidence cards, labeled A to D. Which evidence best shows the universe is expanding rather than galaxies rushing from our galaxy, by Bo's reading?

    • Distant galaxies look red in color
    • The same speed-distance pattern would be seen from any galaxy
    • Nearby galaxies show the biggest redshifts
    • Galaxies are moving away from the Milky Way alone