National Radio Astronomy ObservatoryGreen Bank, WV
Measuring the Size and Age of the Universe
You are an astronomer who has just made this image of the sky.
As you study this image, what questions do you ask?
What are these “fuzzy” objects?
Are they moving?
Are they part of a system? How far away are they?
What are they made of? How were they formed?
Neon
Sodium
Hydrogen
Radio Spectral Line
Hydrogen
NGC 628
Doppler Shifts
The Expanding Universe
If we assume:
•All spiral galaxies are similar in size to the Milky Way.
•Spiral galaxies are 10 kpc in radius.
Then we can estimate the distance to these galaxies.
TAN angle = Opposite Adjacent
R
Angular size
Distance
Distance = Radius
TAN angle
= Radius Distance
half angle in degrees tan Distance(kpc) distance(lightyear) Velocity(km/s)1.5 0.025 0.000436 22918.31035 74690773 2100
2 0.033333333 0.000582 17188.73191 56018077 15902.5 0.041666667 0.000727 13750.98466 44814459 1350
4 0.066666667 0.001164 8594.363048 28009029 680
0
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0 20000000 40000000 60000000 80000000
Distance (lightyears)
V (km/s)
Hubble Constant
1/T = H1/H =
Time!!!
Slope = V/D
T=
1x
D
D0
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0 20000000 40000000 60000000 80000000
Distance (lightyears)
V (km/s)
distance(lightyear) Distance (km) Velocity(km/s) H=V/D (km/s/km T (years)74690773 7.10468E+20 2100 2.9558E-18 1118776173056018077 5.32851E+20 1590 2.98395E-18 1108221626144814459 4.26281E+20 1350 3.16693E-18 1044190977028009029 2.66425E+20 680 2.55231E-18 12956410213
0
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0 20000000 40000000 60000000 80000000
Distance (lightyears)
V (km/s)
So, What is the Age of the Universe?
About 11 BY
August, 1999
October, 1999
Distance LadderDistance Ladder
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