Hacker News new | past | comments | ask | show | jobs | submit login

https://en.wikipedia.org/wiki/William_Anders

He took the Earthrise photo, which Nature photographer Galen Rowell described as "the most influential environmental photograph ever taken": https://en.wikipedia.org/wiki/Earthrise

https://www.abc.net.au/science/moon/earthrise.htm




> Joni Mitchell sings on her 1976 song "Refuge of the Roads": "In a highway service station / Over the month of June / Was a photograph of the Earth / Taken coming back from the Moon / And you couldn't see a city / On that marbled bowling ball / Or a forest or a highway / Or me here least of all …"

Great lyrics

https://youtu.be/VfLH0xJByiI?si=W953IQPO98QSSq0K&t=284


Wikipedia links to a nice visualization on youtube of the moments when the photo was taken, synced with the recording of the actual conversation of the Astronauts as recorded by the Apollo 8 equipment:

https://www.youtube.com/watch?v=dE-vOscpiNc


"calm down, Lovell!"

That's a fun listen.


> He took the Earthrise photo, which Nature photographer Galen Rowell described as "the most influential environmental photograph ever taken": https://en.wikipedia.org/wiki/Earthrise

Heh. I'd never read/heard that quote before. But no one's photos have touched me more than Galen Rowell's, so it bears an incredible amount of weight to read.

Thank you for sharing it.


I don't know how true this story is but here is one version of the creation of the photo.

https://www.coquelicot-translation.com/picture-earth-earthri...


The shutter speed was 1/250th of a second, so the earth rotated about 4 miles or 6 kms while the shutter was open. Not enough to blur the photo obviously, but crazy to think about.


I have no idea how to calculate it, but I interpreted this to mean not that the earth rotated (which everyone is trying to calculate) but that the earth was crossing the horizon of the moon such that four miles of earth crosses the horizon during the shot causing earth blur for a moon-stable reference frame.


From the moon's reference, the Earth orbits around it, traveling 2 × π × distance_moon_earth per orbit. Divide this by 27.3 days (sidereal orbital period) to get the Earth's speed. Multiply by 1/250th of a second. And we find this is, again, much less than 4 miles. Using GNU units:

  $ units "2 * pi * moondist / (27.3 day) * (second / 250)"
        Definition: 4.0958765 m
which is only 0.0025450597 miles.


Revolved I think would be the correct term for that.


I’m confused. Does this math check out?

Circumference is 24,901 - so about 1000 mph at equator.

1000 mph / 3600 s / h = 0.27 mps

0.27 * (1/250) = 0.001 miles?

Doing this math on my phone but am I missing something here?


You are correct. Using GNU units:

    $ units '2 * pi * earthradius / day * (second / 250)' 
        Definition: 1.8532517 m
Which is 0.0011515572 miles...


I think the parent comment was confusing/misremembering the rotational speed value in miles per hour as miles per second.


Even if we stretch out and look at how fast the Earth orbits the sun, it still doesn't explain the 4 mile figure.

Earth's orbital speed: 66,200 mph

66,200 mph / 3600 s/h = 18.38 mps

18.38 * (1/250) = 0.07 miles


I got the same answer


I think it's relative and phrased poorly, since the orbiter has to circle the earth at a certain faster speed. But quick googling shows Apollo 8 was traveling about a mile a second?


rotation:

360/86,400=0.0041667deg/sec

0.0041667 * 0.004sec = 000016667degR

circumference:

2pi * 6371km = 40,030km

land covered by rotation:

40,030 / 360 = 111.194km/deg

0.000016667deg × 111.194 km/degree = 0.001854 km

km to m:

0.001854km × 1,000 meters/km = 1.854 meters

more like 0.001 miles. ... oh, woops. I see your answer is in kms.

it was something like 0.46km/s.


If the orbital period was 80 minutes then that is 1/1,200,000th of a period and with Earth's circumference being ~25,000 miles that should only be about 0.02 miles.

Or if the orbital velocity was 17,000 mph and neglecting the height of the orbit, 17000 / 3600 / 250 = 0.018 miles.

So either way, about 100 feet.


It was taken from the moon, not low earth orbit.


Oh right, those numbers made so little sense I assumed we were talking about a different picture, and I wasn't even thinking about the name.




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: