I have to say that 4th May, 2008 was the longest day of my life till now, not just because it never seemed to get over, but also because I actually spent more than 24 hours (28.5, to be precise) in it. Well, the reason, of course, was that I started and ended the day in two different countries (India and Scotland, respectively). However it did make me think on two rather interesting questions – 1. Can one spend a day longer than this? 2. What would be the length of the longest day one can possibly spend being on earth? Obviously, the answer to the first one should be “yes”. It would be too much of a coincidence to unknowingly do something which cannot be outdone as long as you are on earth.
In any case, I did think on the aforementioned questions and after a cup of coffee and some discussions with Eliot Gehrt Setzer, it turned out that the interesting question had a simple answer. The answer, first of all, is 48 hours. Secondly, there are several ways to spend a 48 hours day, an approximate but intuitive way being as follows –
Go to this place called the International Date Line, which, according to wikipedia, “is an imaginary line on the surface of the Earth opposite the Prime Meridian which offsets the date as one travels east or west across it.” Wait there till the start of a new day and start traveling towards west as soon as a fresh day arrives. Remember to keep your speed equal to the speed of the sun (figuratively speaking, of course). This will ensure that its always midnight in the country you are presently in. After just a little less than 24 hours, you will be at a place just a little east of the International Date Line, where it will still be midnight and the date, surprisingly, the same as the one it was when you started. So now you stop and spend your next 24 hours there. At the end you will have spent 48 hours in the same day.
Starting at midnight isn’t really a necessity. The key idea is that you should spend some 24 hours of your 48 hours day without changing the time. This happened to be your first 24 hours in the previous case. It can be the last 24 hours too, or it can be just spread randomly across the day.
Starting at the IDL is a necessity though. That’s because if you don’t start there, then at some point of time you will end up crossing it, resulting in a sudden change of date. Of course, you will have progressed by only one day at the end of your 48 hours in this case too, but you won’t spend all of those 48 hours in the same day.
The above is definitely a good solution as long as you do not mind occasionally traveling to the past. Since the time zones change in a discrete way rather than continuously, even though you are traveling with the sun, so to speak, you will not always remain at midnight (in case you decided to choose the first of the ways described above). You will, depending on the width of the time zones you travel through, keep going back in time by a few hours every now and then. You can however, choose only very narrow time zones to keep such occurrences to the minimum.
Another interesting question arises if you restrict your idea of a “day” to only the time between a sunrise and the next sunset or a date change, whichever happens first. Realize that with this new definition of the day, normal days are less than 24 hours long. They can easily be made equal to 24 hours though, by being at one of the poles during summer. Can we do better? By being just south of the north pole (or north of the south pole) and doing the circle starting at the IDL will do the trick. Being exactly at the pole may lead to some elegant trick, but thinking about the date and time at the pole is scary and I will refrain from getting into it.
Things 
Must be a great post yet again. I failed to comprehend and do not fail to accept it although in as many words. But, ingenious. Clever. Thoughtful. Mighty smart.
i’m assuming you have absolutely no work in edinburgh
Why on earth would anyone want to do such a thing?
But I know you definitely would and for that I must say, What a ground work!!!
CHINMAYA
I like your way of replying to people’s comments and hence I am copying it, once again, a copyright infringement, which I am not going to pay for.
I don’t like the fact that you fail to comprehend some of my posts. Of course, I don’t mind if some people don’t “like” my posts – people are free to have their own respective tastes, but not being able to comprehend is a stronger thing to happen and I have to say that I will have to look into it more seriously.
BAFF
ok
ANURAG
I must say that I always tend to deviate from the point these posts are supposed to make. The point here was this – It is actually possible to be on earth for 48 hours straight without seeing a change of date at a single point of time. And NOT this – Let’s pack our bags and go around the earth in 24 hours.
KO
you still owe me two samosas
Although your analysis is true in principle, you can actually spend 50 hours in one day on Earth.
Fun thing to do: Find out how to get those extra 2 hours
BAFF
ok 😀
ROBIN
Even if we assume that the world follows Newtonian mechanics?
Yes, yes, with Newtonian Mechanics.
I would never try a “oh, thats because of Quantum Gravity, you wouldn’t understand” 😀
sorry for commenting so late but yeah, this was a wonderful observation and inspired enough interest for a lazy a**hole like me to wiki about a couple of things..
keep blogging..[:)]–these r the only source of frenz existing these days..
Hmmm
Hi… I couldn’t read the whole article… but the topic sure is interesting 🙂
We can spend infinite time in a day… by…
1) Taking a flight from point x at 01:00 … going around the earth at the rate of 1 revolution/24 hours… how many ever times you want… And stopping at infinite revolutions and then spending 23 hours on that point… hence spending infinite+1 days in a single day
Instead of goinig around the world 1once like you suggested… just do that infinite times…
Did you understand what I said?
Choices
1) I’m too lazy to think about this new possibility
2) Your definition(s) of a day and other terminology is not the same as mine
3) Your wrong. If you read my blog better… you’ll understand
Ok now focus on the point where you started. What’s the date there when you reach there your 3rd time? Is it the same as the date when you started? If you say yes in your next comment, then you will be wrong in your next comment. If you say no in your next comment then you were wrong in your previous comment.
I guess this post has become old news by now, but as I have only read this recently, here is an interesting observation.
You can, in fact spend 50 hours in a day.
The united states shifts back its daylight savings time by 1 hour at 2 a.m local time on the first sunday in november. That is the next secon after 1:59:59, the clock is set to 1:00:00 so you have 25 hours on that day.
Luckily, the US has some territories on either side of the date line (a quick map search showed some howland islands immediately to the west of the date line).
So, start the first sunday of november in howland islands, stay there for 3 hours until the time is 2.am (dst remember) and then go around the world in 24 hours, reach alaska by 2.am, the clock again is set back by 1 hour, so end the day there.
so you have spent 2 + 1 + 24 + 1 + 22 = 40 hours.
If, every country you come across on the journey revert from dst on the same day at same time, you could spend more than 50 hours, but for now 50 will do.
2+1+24+1+22 = 50
it was a typo
@Harsha,
https://vinayakpathak.wordpress.com/2008/05/24/the-post-after-the-previous-post/