Redshift and the expanding universe

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   A galaxy's hydrogen line (656.3 nm in the lab) is seen at 662.9 nm. Using speed ≈ z × 300,000 km/s, about how fast is it receding, by Bo's math?

   • About 3,000 km/s
   • About 3,000 km/s toward us
   • About 1,980,000 km/s
   • About 6.6 km/s
2. 2.

   A galaxy's hydrogen line at 486.1 nm in the lab is seen at 491.0 nm. About what is z, by Esme's math?

   • About 0.010
   • About 4.9
   • About 0.10
   • About −0.010, a blueshift
3. 3.

   A galaxy has z = 0.02. Where should its hydrogen line (656.3 nm in the lab) appear, by Jun's math?

   • About 656.3 nm, unchanged
   • About 669.4 nm
   • About 643.2 nm
   • About 13.1 nm

4. Read this first

   Galaxies (model data)

   Galaxy	Distance (Mpc)	Speed away (km/s)
   P	20	1,400
   Q	50	3,500
   R	100	7,000
   S	200	14,000

5. 4.

   Using the table, about how fast is galaxy S (200 Mpc) moving compared with galaxy R (100 Mpc), by Kira's reading?

   • About half as fast
   • The same speed, since everything stretches equally
   • About twice as fast
   • About 100 times as fast
6. 5.

   Speed = H0 × distance; H0 about 67 to 73 km/s/Mpc; distance 100 Mpc. Sources put H0 at about 67 to 73 km/s/Mpc. A galaxy is 100 Mpc away. In what range is its speed, by Luz's math?

   • About 67,000 to 73,000 km/s
   • About 0.67 to 0.73 km/s
   • About 67 to 73 km/s
   • About 6,700 to 7,300 km/s
7. 6.

   Distance = speed ÷ H0; speed 7,000 km/s; H0 about 67 to 73 km/s/Mpc. A galaxy recedes at 7,000 km/s. With H0 about 67 to 73 km/s/Mpc, about how far away is it, by Milo's math?

   • About 100 Mpc (96 to 104 across the range)
   • About 1,000 Mpc
   • About 10 Mpc
   • About 490,000 Mpc
8. 7.

   Why do distant galaxies all appear to rush away from us, by Noah's reading?

   • They are falling toward a central point
   • Their light is turning red as they age
   • Space itself is stretching between the galaxies
   • They were thrown out from our galaxy
9. 8.

   Galaxies in a nearby cluster stay together while distant clusters move apart. Why, by Ren's reading?

   • The cluster is at the center of the universe
   • The cluster is moving toward us
   • Gravity holds the cluster together
   • Everything expands, but too slowly to see

10. Galaxies (model data)

    Galaxy	Distance (Mpc)	Speed away (km/s)
    P	20	1,400
    Q	50	3,500
    R	100	7,000
    S	200	14,000

11. 9.

    Galaxy Q (50 Mpc) and galaxy P (20 Mpc): how many times faster does Q recede, by Zee's math?

    • 0.4 times
    • 2.5 times
    • 30 times
    • 70 times
12. 10.

    What is the slope of the table's speed-against-distance line, by Ari's math?

    • 0.014 Mpc per km/s
    • 70 km/s/Mpc
    • −70 km/s/Mpc
    • 7,000 km/s