Scientists on Reddit

Craig DeForest

Solar physicist, NASA PUNCH mission lead

u/Craig_DeForest ↗AMA only

How we know it's theirs

The 2017 r/science AMA, posted from this account

We retrieved 1 post and 22 comments from u/Craig_DeForest, all from 2017, most often in r/science.

Best moment

A redditor wrote in r/science

On “Science AMA Series: I'm Craig DeForest, a solar astrophysicist. I’m here to talk about next week’s eclipse: how to view it safely, what to look for, why you should plan to be in the path of totality, and logistics of getting there.”

Dr. DeForest, thanks for doing the AMA. We're driving down from NY to South Carolina for a family science road trip, and I was wondering if you had any thoughts on how I can explain the sun's corona to my kids (3 and 7)?

u/Craig_DeForest replied

The corona is the largest, brightest object in the sky -- other than the Sun. The problem is that you can never really see it, because the Sun is so bright. An eclipse is a great chance to see it…

Read all of itShow less

The corona is the largest, brightest object in the sky -- other than the Sun. The problem is that you can never really see it, because the Sun is so bright. An eclipse is a great chance to see it.

The corona is the Sun's atmosphere. It is very, very hot, and many times larger than the Sun itself. The Sun may seem hot, but the surface is only about as hot as the inside of the projector at a movie theater. The corona is about a thousand times hotter than that. Nobody knows why. You can see the corona mostly because it scatters sunlight. Sort of like the air does, so you see blue sky when the Sun is up, but the corona is wrapped around the Sun instead of around the Earth. There isn't much material in the corona. It's many, many times larger than the Sun, which itself is about a million times larger than Earth -- but the whole thing weighs about as much as the water in Lake Michigan.

Around the corona you'll see planets come out. You will be able to see four planets, all lined up across the sky. That is the shape of our solar system. All the planets orbit the Sun in a flat plane, like the surface of a table. An ant on a picnic table would see all the other ants on the table lining up in a straight line (the horizon). Since the planets are all in a flat plane (the "plane of the ecliptic") and we're standing on one, they all line up in the sky.

More moments

A redditor wrote in r/science

I live about 4 hours from the direct eclipse, how different will it be for me?

u/Craig_DeForest replied

Read all of itShow less

If you're a 4 hour freeway drive away from totality, you'll see about a 90% partial eclipse (90% of the Sun occulted). If there are no clouds, you will see some optical effects -- like "gloomy sunlight" that feels a little odd. (The day will appear normal, but without the strong heat and glare of the Sun.) You'll notice that shadows appear sharper. Near maximum eclipse for you, you might be able to pick out four planets lying along a straight line across the Sky -- the plane of the ecliptic, which forms the main shape of our solar system. It's best to be above 95% totality to catch the full view, though.

This is one of the few chances you'll ever get to see the whole inner solar system lain out across the sky like that, and it is quite spectacular.

On the other hand, from the standpoint of the visceral wonder of a total eclipse, 90% is very small potatoes. The difference has been compared to the difference between kissing someone and marrying that person.