Shall I compare thee to a summer's solstice?

By Phil Plait | June 20, 2012 6:01 am

Today, June 20, at 23:09 UTC (7:09 p.m. Eastern US time), the Earth’s north pole will be tipped over toward the Sun as far as it can for the year. There are other ways to describe it — the Sun reaches its maximum declination, its annual northern movement in the sky peaks, it’s the longest day of the year — but most folks just call it the summer solstice.

You can use this event to measure your latitude the Earth’s tilt, if you have a stick and a protractor and clear skies and the ability to take an inverse tangent. Or you can read about past summer solstices here, here, here, and here (or the winter solstice here, here, here, here, here, here and here).

Or you can celebrate by checking out the gallery below of some of my favorite pictures of the Sun. If it’s cloudy where you are, or you’re in the southern hemisphere where it’s the winter solstice today, then maybe that’ll help spill a little golden glow into your day.

And finally, think on this: the Earth has had well over 4.5 billion summer solstices since it formed. And it’ll have billions more! Just a little perspective to your day, care of the Universe.


Use the thumbnails and arrows to browse, and click on the images to go through to blog posts with more details and descriptions.

glennschneider_eclipse2010
alanfriedman_proms_halpha
alanfriedman_sun_halpha
atlantis_hst_2009may13crop
hst_wfpc_sun_610
iss_sunset
schneider_eclipse_plane
sdo304_dec62010
sdo_aia94_xrayflare
sdo_loopsflare
sdo_lunar_transit
sdo_prominence
sdo_solareclipse
stereo_flare
stereo_transit
sunpillar
sunspot_model
tenthings_sun_flare
thierry_iss_atlantis_2010
thierry_transit_iss

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (27)

  1. fredR

    I’m pretty sure my friends from South Africa don’t call it the “Summer Solstice”. Yes, most humans live in the Northern hemisphere, but in the global society we live in, shouldn’t we use less ambiguous terms?

  2. dcsohl

    Gotta agree with fredR here… I’m surprised to see a professional astronomer still calling this the summer solstice… Isn’t the proper term these days “the northern solstice”? I’d also go for “June solstice”.

  3. ElmarM

    I always thought that this would be on the 21st of june?

  4. Mr. Moody

    I really, really like the “long days” of summer. Some years the Summer Solstice actually bums me out knowing that each day’s daylight time will be getting shorter. Ironically, I find I am usually buoyed by the Winter Solstice for just the opposite reason – the anticipation that each day for the next six months will have more sunlight.

    This year, I think I will be outside on my deck, watching the sun at 7:09PM, with a beer in my hand (appropriately, it will be a Corona), not bumming out but just enjoying the minute…

    PS – concerning the use of the term “summer solstice” referenced by comments #1&2, please note the fine doctor’s comment of “If it’s cloudy where you are, or you’re in the southern hemisphere where it’s the winter solstice today, then maybe that’ll help spill a little golden glow into your day.” ;-)

  5. Wzrd1

    As the reference points for both time and the metric system are in the Northern Hemisphere, shouldn’t the seasonal reference be also? ;)
    Seriously though, I’d go with the June solstice over northern solstice. It’s more accurate and “plays” better to the ear.

  6. clm

    Just a quick correction: the National Geographic article seems to be saying that your latitude can be measured at the equinoxes, but that you can use the solstice today to measure the tilt of the earth’s axis (provided you already have your latitude).

  7. david

    Wouldn’t you more easily measure your latitude during an equinox? During a solstice, you’d also need to know the earth’s tilt. Of course you can look it up, but if you’re going to do that, you may as well just look up your latitude.

  8. Marco

    when we are in “Summer”, all humans on this planet are in summer (even if in the southern is colder). The same, when there is a soltice, the Earth has a soltice. So today is a “summer solstice”. There is no north and south racism in astronomy :)

  9. Nigel Depledge

    @ david (7) –
    True, but the Earth’s axial tilt is the same number no matter where you are on the Earth’s surface, so, unlike one’s latitude, does not change as you travel north or south. Hence, measuring the angle of the sun at noon on the solstice allows you to derive your latitude. Similarly, it is not a vastly onerous calculation to work out one’s latitude from the angle to the sun at noon on any day of the year – IIUC, you just need to incorporate the sun’s analemma.

  10. Robert Gibson

    @ ElmarM (3)

    Generally the solstice does occur on June 21. But this is a leap year, so every date after Feb. 29 would have been one day later in every other year. That is, Feb. 29 would normally have been Mar. 1, and June 20 would have been June 21.

    Having said that, it is not uncommon for the solstice to be a day early or late. According to http://www.timeanddate.com/calendar/june-solstice.html, “In the Gregorian calendar the June solstice dates vary. For example, it was on June 20 in 2008 and falls on 21 Jun 11:08pm UTC in 2012. A June 22 solstice will not occur until June 22, 2203. The last time there was a June 22 solstice, was in 1971.

    “The varying dates of the solstice are mainly due to the calendar system – most western countries use the Gregorian calendar, which has 365 days in a year, or 366 days in a leap year. As for the tropical year, it is approximately 365.242199 days, but varies from year to year because of the influence of other planets. A tropical year is the length of time that the sun takes to return to the same position in the cycle of seasons, as seen from Earth. According to Swinburne University of Technology, the exact orbital and daily rotational motion of the Earth, such as the “wobble” in the Earth’s axis (precession), also contributes to the changing solstice dates.”

  11. cope

    Ethan Siegel at the “Starts With a Bang” science blog explains how to determine both latitude during an equinox and axial tilt during a solstice.

    http://scienceblogs.com/startswithabang/2012/06/19/measure-the-tilt-of-the-earth-on-the-solstice-this-wednesday/

  12. OneofNone

    @3. ElmarM:

    I always thought that this would be on the 21st of june?

    In fact it is on June 21st. If you for example live in Germany, as I do. +1 hour to UTC, +1 extra for daylight saving time.

    But in general, that’s why we have leap years. We just are in one, so we already had one extra day before the solstice. Which makes the number on the day one less. Without looking it up, I bet next year it will indeed be on June 21st at Greenwich. Because it will happen roughly “6 hours later”.

  13. Matt B.

    A term like “June solstice” makes it sound like solstices can happen in any month. There’s a reason they’re named after seasons.

    Since we use the Latin-derived terms “vernal” and “autumnal” for the equinoxes (or equinoctes), we could use “(a)estival” and “hibernal” for the solstices. Then we would just understand that those are technical terms that have a history of referring to one hemisphere’s seasons, but don’t have to be taken as indicating particular seasons in modern times. Just like “cervix” is Latin for “neck”, but…

  14. pblz

    @10

    This is what confuses me…I was baffled by the solstice posts today, and another blog gave the leap year explanation, but that seems counterintuitive to me because if it’s a leap year, shouldn’t the days leap forward? Like the days of the week leap forward one day after Feb 29, so surely the solstice should too?

  15. truthspeaker

    “Marco Says:
    June 20th, 2012 at 9:21 am

    when we are in “Summer”, all humans on this planet are in summer (even if in the southern is colder”

    Not really…

  16. truthspeaker

    pblz, the sun and earth don’t care how we number our days. This year’s summer (Northern Hemisphere) solstice occurs roughly 365 days after last year’s summer (Northern Hemisphere) solstice. June 21, 2011 to June 20, 2012 is 365 days because of the extra day in February.

  17. KC

    @pblz No, the solstice is occurring at the same time every year – its our calendar that’s changing. The solstice is not fixed to particular day or date.

    If say the solstice was noon on the 21st, once you insert a day at the end of February all the days are going to be shoved forward one day. The 21st is then shoved 0ne day after the solstice so that the solstice is now at noon on the 20th. Does that make sense?

    @Fredr

    I see no reason not to call it “Summer Solstice” – I personally so not get offended when the Aussies call it the Summer Solstice. Calling it the June or December Solstice is not a good solution if you don’t use the Gregorian calendar.

    No matter what you do someone’s going to get bent. So I say go with whatever the local custom is, but keeping in mind the other hemisphere is celebrating the start of a different season.

  18. Muz

    I prefer June solstice and looking out my north facing window I see a VERY low sun on this crisp winter day. Must light a fire outside and run around it naked. Sometime.

  19. StuartG

    @3 ElmarM

    Here in New Zealand it is the 21st June!

    It’s also Matariki. http://en.wikipedia.org/wiki/Matariki

  20. Naomi

    It’s the 21st here in Australia!

    It’s also winter. How about that. (If I was sitting any closer to the heater, I’d possibly be on fire.)

    I much prefer June solstice and December solstice – ‘Northern solstice’ doesn’t quite sound right to me, since a) we’re having a solstice down here as well, and b) the one in December is a solstice too, and that takes place in your winter. It’s not like solstices are exclusive to June! ‘Northern summer solstice’ and ‘Northern winter solstice’ are more accurate, but still terribly Northern-centric. The Southern hemisphere does exist too, you know!

    On a happier note – this time next year I’ll be on a cruise ship above the Arctic Circle in the vicinity of Nordkapp. Yay! Midnight sun on the June solstice!

  21. Phil:
    In the caption of the partial eclipse image, you say: “Technically, this is a transit, not an eclipse”.
    Technically, there is of course no such thing as a “solar eclipse”, or “eclipse of the Sun” at all! A total or partial eclipse is really an occultation of the Sun by the Moon, and an annular eclipse is really a transit of the Moon.
    On 14 November in Australia, I’ll be making my fifth attempt to observe a total occultation of the Sun by the Moon… :-)

  22. beer case

    Making the solstice a battleground for political correctness is pointless. As others have said, using the name of the month, is neither a good solution. Calling it “The northern solstice” would work better. But then, you’ll still have the “Northern Hemisphere bias”, and a much bigger discussion on why we define north as “up”.

    As some wise man (or woman?) once said: Pick your fights.

  23. Alan

    How many people spotted the booboo on spaceweather.com?

    http://spaceweather.com/archive.php?view=1&day=20&month=06&year=2012

    “Today, the sun crosses the celestial equator….”

  24. Teacher Al

    One misconception some people hold is that the Earth’s axis tilts radically to cause the seasons rather than being a result of Earth’s travel in its orbit. This phrasing may exacerbate the problem: “the Earth’s north pole will be tipped over toward the Sun as far as it can for the year.” I’m getting vertigo from the change in tilt.

  25. Lars Bruchmann

    23: OH!!! I NEVER thought of it that way… people think the Earth is actively changing its tilt. Like the northern hemisphere is being pushed towards the sun as if a big finger touched the ‘pole’ at the north and gave it a shove?? OMFSM. That never occurred to me. My brain does not work that way. Probably why most people think I’m weird and do not understand what I’m talking about. That’s fine with me.

  26. Lars Bruchmann

    I worked with an Australian woman in Italy (not relevant really) and in 1999 she complained that the summer solstice was on the wrong day. She said when she was a little girl it was always on the 21st of June. I tried to explain to her that the Earth and Sun and cosmos really don’t care what names or numbers we give any particular point in time. To no avail.

  27. ElmarM

    Ahhh, darn it is a leap year of course!
    Thanks for the reply Robert and all! Man, I feel really stupid now ;)

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