I'm writing a sci-fi story in which a group of people are stuck in an endless desert. While I've mostly figured out the philosophical aspects of the story, there are still the practical ones. It's a desert. No water, scarce food, hot during the day, maybe cold during the night. The people have arrived there wearing only their clothes and maybe carrying a few pieces of technology and some transportation. Is it realistically possible to survive this journey for long?
A human cannot live more than 3-4 days without drinking, especially in a broiling environment like a desert.
Their immediate chances of survival depend on the ability to find an oasis, where they can gather water, within 3 days at most.
Then comes the issue of clothing: a warm desert is a nasty place, one need to be protected from the sun and heat during the day, and from the freezing cold during the night.
No, the fancy bermuda and short sleeves shirt are not going to do a lot for them, it would be better if they would be dressed like the Tuareg, with wool to insulate them from the environment.
Last but not least, the problem of food: finding food in a desert is pretty difficult, but a human can survive some week without food as long as water is available. But if they manage to find an oasis, they might also find some food: birds, plants, rodents, insects.
Of course, the above figures are valid for healthy people in decent conditions. If they are older or younger, the survival span may drastically shorten.
Yes. But they need a guide.
Random humans in the desert will die, as prior answers lay out. But your castaways encounter a native who shows them how to survive. I envision this native as without speech, or at least speech the humans understand. Its motives are unclear but it becomes very clear that this alien desert is dangerous, and without the help of the guide the humans will rapidly die.
I like the idea that the alien guide is paid by the humans in song. The humans know a lot of songs. We all do.
Remember the "hierarchy of survival." Humans can survive for 3 minutes without oxygen, three hours without shelter (meaning naked in any extreme climate, hot or cold), 3 days without water and three weeks without food. Based on that hierarchy the heat could kill them in a few hours, and lack of water in a few days at most. Even if they overcome both of those issues, in whatever way, they're probably going to starve to death within weeks unless someone has the expertise and equipment to do some hunting or foraging.
You need to describe your setting well because depending on what kind of desert they're in they're possibly going to die a lot faster or last a lot longer; something like the Sonoran is far more survivable than the Empty Quarter's sand seas.
No water is enough: they will live up to three days before dying of thirst. And this implies very nasty things like drinking their own wastes and finally blood.