My son asked me this theoretical question, and I had to confess that I couldn’t answer it. So, I’m turning to my fellow Dopers, hoping someone might already know the answer.
How fast would someone (or something) have to travel to stay in sync with daylight? In other words, if I started driving west (at theoretical speeds, of course) from Point A at, say noon, at what speed would I have to travel to remain in daylight in perpetuity? For the purpose of his question, I don’t think he cares if it remains noon, as long as it’s still “daylight” out.
Hope the question makes sense. Obviously, there aren’t real strict standards - he’s only 8 years old.
On the spring or autumnul equinox, in miles per hour…
2pi3963.19*cos(latitude)/24
~= 1037*cos(latitude)
or 861 mph for, say, Los Angeles
(spherical Earth approximation)
---- or ----
Just remember that you’re standing on a planet that’s evolving, and revolving at 900 miles an hour;
that’s orbiting at 19 miles a second, so it’s reckoned, a sun that is the source of all our power…
Which means your typical airliner can keep pace with the sun at about 58 degrees latitude, or a couple hundred miles North of the US/Canada border.
As a jet driver I’ve seen that effect hundreds of times. By departing a US city westbound with the sun already low in the sky you can “enjoy” the spectacle of staring into the setting sun for 2 or 3 hours before it finally pulls far enough ahead of you to get below the horizon. Some days it’s very beautiful; other days it’s just a pain in the a**. If you ever wondered why pilots often wear dark glasses, now you know.
Ummm… I just got out my looooonnnng tape measure, and the circumference of the earth at the equator is closer to 25,000 miles, so your speed would have to be a tad over 1,000 mph, say 1,040 or so.
Another factor is altitude. The greater your altitude, the faster you would have to go due to your greater radius from the Earth’s center. For example, consider geosynchronous satelites (sp).
Ha! Hf he had ever settled for such an easy out, my life so far would have been much easier. As SCSimmons says, the fact that he’s asking in the first place should show you that he’s not going to settle for what I assume you meant to be “vewwy vewwy” fast.
Thanks for all the info so far guys, even if it is conflicting - it at least gives me a good way to explain to him how we can figure it out, and what the different variable factors would be.
Quick, someone give me a better way of saying “variable factors”
Of course, you are also looking at (with the above answers) trying to do this indefinitely. I was intrigued by your comment above that “he doesn’t care if it remains noon, as long as it’s still daylight out”. If you want to keep up your travel indefinitely, this is hardly a difference; but for shorter journeys, it’s different.
Just for fun, how about a hypothetical trip from Danbury, CT to Los Angeles, CA, trying to keep in the daylight?
I popped over to this site to find out that, for today (April 21, 2004), the sun rose at 6:04am Eastern time in Danbury, and will set at 7:30pm Pacific in Los Angeles. I’m willing to give your son that 4 minute headstart in the morning twilight, so let’s call it 16.5 hours.
I checked MapQuest for the shortest route. We’re driving this time, because if we take an airplane we have to account for the longer distance above the ground, and I didn’t want to make that calculation. MapQuest told me it was 2853 miles, from and two whatever points it chose in those two cities.
Therefore, you would have to travel at about 173 miles per hour – still pretty fast, but a lot slower than those airplanes in the previous calculations. Do try not to get pulled over, and mind the school zones.
Here’s a good way for you to help your son figure it out for himself:
You may want to pull out a globe or an Atlas for this one, preferably one with longitude lines.
To keep up with the sun, you must circle the Earth once every 24 hours. The Earth has 360 degrees of longitude. 360 degrees/24 hours = 15 degrees per hour.
Now you pull out the Atlas. Turn to the map of North Carolina (why? Because I actually know that geography.) Raleigh and Ashville are approximately 5 degrees apart, so in order to keep up with the Sun, you would have to travel from Raleigh to Ashville in twenty minutes.
i was assuming an 8 year old might understand but not really appreciate what traveling at 1000 mph really means. not sure if i should envy or pity the two of you.
vawwiable factors?
Yeah, it was stupid. I don’t know where I pulled that from - I know the circumference is about 25,000 miles. What’s embarrassing is I used to do stuff like this for a living. I got it right then.
