Hacker News Reader

Comment by mrfusion | Hacker News Reader

I’ve got a flat earth family member and I thought it would be easy to go out to the beach and get a photo of a ship appearing over the horizon to disprove them.

But it just won’t seem to work out. They seem to get smaller and smaller and too small to see if the botttom is disappearing first. I’m going to have to try it with a telescope. It’s kind making me question my own beliefs.

Also they made me watch some of those YouTube videos about the eclipse going in the wrong direction. I still haven’t been able to explain that. :-(

I guess my point is don’t expect an easy debate if you engage them. Some of this stuff just isn’t as easy as you’d expect.

View on HN

> Also they made me watch some of those YouTube videos about the eclipse going in the wrong direction.

You mean a video that's flipped or running backwards? Why would you question your whole worldview before questioning the reliability of the alleged evidence?

I just mean the moon moves from east to west in the sky but the eclipse went from west to east.

There are lots of videos and article with explanations but none of them clicked for me.

Here's a clean explanation from NASA's eclipse site (https://eclipse2017.nasa.gov/why-do-eclipse-tracks-move-east...).

The moon actually moves much faster than the Earth spins -- it just seems to move westward to humans on the ground because it's so far away from Earth (takes 28 days to go around Earth). During a solar eclipse though, we see the effect of its true blisteringly fast orbital speed.

"Because the Moon moves to the east in its orbit at about 3,400 km/hour. Earth rotates to the east at 1,670 km/hr at the equator, so the lunar shadow moves to the east at 3,400 – 1,670 = 1,730 km/hr near the equator. You cannot keep up with the shadow of the eclipse unless you traveled at Mach 1.5."

So why would the moon rise in the east and set in the West? That’s the part I’m confused by.

All the stars in the sky are also rising in the east and setting in the west. Our own sun is rising in the east and setting in the west. The earth's spin causes stuff in space to appear to go in the same direction.

Stars in general appear to move across the sky (east -> west) faster than the moon does. Does this mean the stars are actually moving faster than the moon? Of course not. The sky is just a stationary backdrop, and the moon is moving along the same direction as Earth's rotation.

In the eclipse situation, the actual speed of the Moon matters, not the fact that its orbit is so long that it orbits the Earth about once a month.

The apparent relative motion with respect to the Sun is what matters. Of course, both bodies are rising in the East and setting in the West. But at the moment of the eclipse, the Moon is a little slower.

There's got to be an animation of this out there. Something like this, but I feel it can be done better: https://youtu.be/jnphuI7hyeM

Reply on news.ycombinator.com