Redshift and the expanding universe

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   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 120 Mpc
   • About 7.5 Mpc
   • It cannot be found without H0
   • About 34 Mpc
2. 2.

   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 million years
   • Between about 13 and 15 billion years
   • About 67 to 73 billion years
   • About 6,000 years
3. 3.

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

   • Disagree: galaxies are moving toward one spot
   • Disagree: space stretches everywhere, with no center
   • Agree: galaxies fly out through empty space
   • Agree: the Milky Way is near that spot
4. 4.

   Milo's cousin says the Earth and Moon drift farther apart each year because the universe expands. Which response is best?

   • Disagree: the Moon is moving toward Earth fast
   • Agree: the Moon is redshifted
   • Agree: each distance grows with the universe
   • Disagree: gravity binds them, so expansion does not pull them apart
5. 5.

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

   • Agree: red galaxies alone move away
   • Disagree: redshift means its lines moved to longer wavelengths
   • Disagree: redshifted galaxies look blue, since they move toward us
   • Agree: redshift is the galaxy's color
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 about 350 km/s
   • It moves toward us at about 3,500 km/s
   • It recedes at exactly 3,500 km/s
   • It recedes at between 3,300 and 3,700 km/s
7. 7.

   Why do different methods give H0 values from about 67 to 73 km/s/Mpc, by Ren's reading (NASA)?

   • The universe is not expanding
   • Nearer galaxies recede faster than far ones, which shifts the values
   • One method measures blueshifts
   • Two careful methods disagree, and the reason is still being studied
8. 8.

   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 6,300,000
   • No: it gives 0.014

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 0.01 Mpc farther
    • About one-third as far
    • About 3 times 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?

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