Transcript Measuring Distances in Space

Measuring
Distances in Space
The Light-Year (ly)
Light-year (ly)
distance light
travels in one year
Reminders...

Light travels in a straight line.
 The speed of light is 300,000 km/s
 The Sun is 150 million km away
– by car @ 100 kph, 165 years to the Sun
– by 747 @ 600 kph, 27.3 years to the Sun
– by shuttle @ 28,000 kph, 215 days to the Sun
– by Apollo @ 53,000 kph, 113 days to the Sun
– by light speed, it would take 8 minutes to the Sun
Next Closest Star



Proxima Centauri
4.3 ly away
If it went supernova
today (it won’t)…
– You would see it at
graduation
* Takes light 4.3 years
to get here!
The Milky Way
Our galaxy…

~ 7,000 ly thick
 ~ 100,000 ly diameter
 Light takes 100,000
years to travel from
one side to the other
 Earth about 26,000 ly
from the core
Your Turn…

Just how far does light travel in 1 year?
 Your group will need paper & pencil (you
may use a calculator)
 With your team, calculate the distance to
Proxima Centauri, 4.3 ly away…raise your
hand when you think you are done and I
will check it.
 HINT: need to use Speed of light and time
distance light travels in 1 s
x 60 s in 1 min
300,000 km/s
x 60 s/min
18,000,000 km/min
x 60 min in 1 hr
x 60 min/hr
1,080,000,000 km/hr
x 24 hr in 1 day
x 24 hr/day
25,920,000,000 km/day
x 365.25 days in 1 year
x 365.25 days/yr
9,467,280,000,000 km/yr=1 ly
x 4.3 ly to Earth from PC
x 4.3 ly
distance to Proxima Centuari 40,709,304,000,000 km
Hubble Deep Field Academy:
Distance Wizard…
1. Explain why you arranged the objects as you
did. Be sure to mention any particular trait
upon which you based your decision.
2. Explain how the object labeled “F” can be
smaller, yet closer, than the object labeled “C.”
3. How is your explanation regarding estimating
distances in space similar/different than the
astronomers’ explanation?