Sunday, March 20, 2011

Vernal Equinox Today!

At 23:21 UT (19:21 PM Eastern Standard Time), spring will officially be here for the northern hemisphere! It's been nice spring weather here for the past couple of days, but it's nice to have it be official. Although, I guess some people argue that it's really the middle of spring. I suppose both could be right, it's a matter of perspective and seasons are loosely based anyways. Wintery days can occur in Fall or Spring, and Fall can have Summer or Wintery days, and so forth. It tends to be more of an 'I know it when I see it' concept.

That said, what makes the Vernal Equinox special is that it is a midpoint in the Sun's journey across the sky. The Sun appears to travel against the sky throughout the year due to the Earth's tilt as it orbits the sun. On the equinox's (there is also the autumnal equinox in September), the sun sits over the equator, day and night are roughly the same length (12 hours) all over the Earth.

The term equinox means equal day and night. Ver is latin for spring, and autumnus is autumn, so these terms have a general bias for the northern hemisphere. Down below the equator, I'm sure you guys are getting ready for your colder months, since this is in reverse for you.

Also, I suppose I should dispel some incorrect notions about seasons. I have heard people tell me before that the reason for the seasons was because the Earth got closer and further away from the Sun due to Earth's non-circular orbit, or because the tilt of the Earth made one hemisphere closer then the other. It should be noted that distance from the Sun has nothing to do with the seasons, the temperature difference really is not that huge over Earth's orbit. In fact, during winter in the northern hemisphere, we are closer to the Sun!

The Earth's tilt is the reason for the seasons. And not because one hemisphere is closer to the Sun then the other, but because of it's angle in the sky. When you are in summer, your hemisphere of the Earth is tilted towards the Sun, meaning it is high in the sky with plenty of direct sunlight. When it is winter, you're tilted away from the Sun, it is low in the sky and there isn't a lot of direct sunlight, more of it reflected by the atmosphere.

Here's an infograph from NASA:

How Seasons Work

Another interesting fact about the Earth's tilt is that it's cause is thought to be the same collision that created our moon!

That's all I have for winter, I'll have a fresh spring post tomorrow. I have a wealth of information that I learned from my visit to the Applied Physics Lab at John's Hopkins. I'll probably do an over view post tomorrow and might have a couple posts over the next week to share the information.


45 comments:

Chris said...

lol i was one of those who used to think it was because the earth was closer to the sun :P

skinned sheep said...

awesome. thanks for the information

Jason said...

very informative thanks!

Robert Fünf said...

I always took the "closer to the sun" thing to mean that one hemisphere is closer (see also: angled) to the sun. Not that the entire Earth was closer to the sun. So apparently I mistook a mistaken teaching, and came out on top. wrong + wrong == right.

Jay.CA said...

wow! and so close to the supermoon we had a few nights ago. :D

Astronomy Pirate said...

Ha, not quite right, but sure. The angle has to do with it, but it is because of direct and indirect sunlight, not distance.

Matt said...

It's about time; I'm done with winter. Great explanation!

Christophe said...

I knew the thing about the seasons at one point, but it was shuffled from my mind to make room for other stuff.I also think the words Vernal Equinox are awesome!

Astronomy Pirate said...

Jay.CA, pretty much the 'supermoon' was a non-issue to me and most of the astronomical community. Most of the news reports about it were full of it. There is an illusion that occurs when a full moon is low on the horizon, but it is a fairly common event. Then again, so are equinoxes (they happen twice a year), but there was so much about it in the news I just refused to make a post about it here. Sure, its good to look at the moon, but it wasn't as special as it was made out to be.

Every Day said...

Always an interesting read. Thanks for sharing!

THUNDERCAT832 said...

I wonder why the weather is always crazy as hell where I am from (Houston, Texas) Does this have some thing to do with it?

Jordan Vargas said...

Sweet info.

Lemmiwinks said...

good info

Chris said...

Excellent writeup

Astronomy Pirate said...

It could be TC, with the interactions between warm and cold air, there tend to be storms. I'm not the greatest person at atmospheric sciences, but seasonal changes tend to be fun weather-wise.

ankmanpro said...

Great info! Thanks!

The Wired said...

Please do share what you learned! If I wasn't studying Computer Science, Physics is where I would be!

Shelby Fox said...

The recent earthquake slightly deviated Earth's orbit around the sun. Crazy eh?

Bubi said...

thanks for the info!

Josh said...

Hooray for spring!

glivin said...

That's crazy man!! Astronomy...

Necroticism said...

I feel like a wolf staring at this enormous moon, looks beautiful :)

Triper said...

I heard about this many times so it must be true, good post!

Patrick Holton said...

I used to think the Earth got closer and farther away with the seasons haha.

Eiriklol2k said...

its all about the rotating.

Tyler Steele said...

i refuse to believe this is some hobby.. this must be somehow connected to your work? if not DAMN SON you're drowning in esoteric knowledge

Astronomy Pirate said...

Tyler, read my About Me section, I have a degree in Astronomy. It is my life. I am currently trying to afford to go to grad school.

Buckaroopopcorn said...

Great explanation, it left me spinning... OK bad joke but I had to ;)

Patti D. said...

awesome, thanks for the heads up, did know this was going to happen

mac-and-me said...

awesome, the more you know

-DO- said...

great info, thx!

Alphabeta said...

Seasonal change is definitely putting a 'spring' in my step. Thanks for the science.

Zombie said...

Spring has sprung!

ScottD said...

great post

Banacek said...

I'm still waiting for spring to start!

Merlyy said...

Awesome blog! FOllowed!

Kim Anders said...

nice! x

eXo said...

Very interesting, thanks for the post.

AnthropoSeptic said...

Dammit, missed another opportunity to dance around a fire wearing the horns of Cernunnos.

PenDRaGoN said...

THank GOd, finally, now it only gets "less hot" in the south hemisphere.
+follow

Sam said...

Nice image, going to save it :)

Daily01 said...

Nice post, I am bit smarter now. I will follow!

Zakk said...

I didnt know that! cool!

Biff Tanner said...

About time I hate cold.

G said...

great info and easy to follow explanation

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