I normally get up around six o’clock AM for school and am out the door by 6:50. When I got outside yesterday, it was already getting light out. However, the folks on the news put the sunrise at around 7:21. I’m assuming they mean the time the sun comes up over the horizon, but if that’s the case, which horizon do they use? The horizon itself is just an illusion, so how do they set an exact time? 
Argh, and that’s supposed to be “decide” and not “dicide” in the title. Funny how you notice these things after you post :smack: .
The use something like this from theNaval Observatory.
You have to go to Frequently Asked Questions, Sun and Moon, and follow on further links to sunrise and sunset times.
And it is only accurate for a particular place. Your sunrise may be different from someone else in the same timezone.
The horizon isn’t just an illusion. For any particular location on the globe, you can calculate at which point of time the sun will be visible for the first time on a particular day after being concealed by the earth during night.
Or you could just link it. 
Previous posts have provided the information on sources available on line today.
Prior to some time shortly after 1983 an annual edition of “he Astronomical Almanac” was publiched in Washington DC and London. This was THE BOOK for navigators on ships and planes. Also used extensively by land surveyors.
QUESTION FOR YOU: What takes it’s place today?
My Cajun barometer…it’s a piece of rope hanging in the back yard.
If it’s wet, it’s raining outside…if it’s flopping from side to side, it’s windy. If I can see it, the sun’s up and if I can’t see it, the sun has set.
Good one. You should have gotten the deluxe long model though. It is hard to calculate sunrise times with it unless it is a very long piece of rope. I am from Louisiana so I know all about these things.
And everyone has to calculate it.
New Question: " Why are the sunrise and sunset curves shifted and not colinear?
Well, as a naval officer, I still use it (or a version of it) to work out sunrise/sunset. You can generally get to within 30 seconds of the correct time.
Why, the celestial horizon, of course, which is a projection of the equator onto the celestial sphere!
Nay, nay–published sunrise and sunset calculations use the astronomical horizon, which allows for 34 minutes of atmospheric refraction, rather than the celestial horizon, which makes no allowance for refraction.
It’s real fun when you’re somewhere where the geography to the east isn’t flat. Albuquerque has a mile-high mountain to the east, meaning that there’s sunrise, and then there’s the time when the sun actually clears the mountain. That time is a quite a while after sunrise.
Well, first of all, “getting light out” isn’t “sunrise”. The atmosphere refracts the sun’s light to your eyes well before the disc of the sun peeps over the horizon.
To be precise, the atmosphere scatters light to your eyes during twilight. This should be distinguished from atmospheric refraction, a slight bending of light rays as they pass through the atmosphere which causes the disk of the Sun to become visible when it is still 34 minutes below the celestial horizon. (The atmosphere acts like a giant, weak, fish-eyed lens.) Published sunrise and sunset times do take refraction into account, but (naturally) not twilight–twilight is considered to be before sunrise or after sunset.
What he said. :smack:
I think I might be asking the same question in my new thread . I invite everyone to come over and help me figure this out.
To back up Bernard’s personal experience, the simple answer is that The Astronomical Almanac is still published.