All water on Earth put together in a single ball

The picture below illustrates the size of a sphere that contains all the water on Earth, in comparison to the Earth itself. The blue sphere sitting on top of the United States has a diameter of about 1,385 kilometres, with a volume of a colossal 1,386,000,000 cubic kilometres. The ball of water includes all of the water from the oceans, seas, lakes, rivers, icebergs as well as groundwater, water in the atmosphere, even the water in living beings, humans, animals and everything in your garden. 

Source: http://ga.water.usgs.gov/edu/2010/gallery/global-water-volume.html

Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution; USGS..
Data source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).





Disclaimer: I do not own anything in this post. All rights belong to the people linked above. 

Smartphones with X-ray Vision?

Four days ago, on the 20th of April, the University of Texas announced to the world that they have created a technology that will give smartphones the ability to see through walls, through the application of T-rays.
Of course, we know that cameras with see-through capability have been around for quite some time. Existing cameras with 'penetrating vision' detect infrared radiation which goes through cotton-based clothing.

So what does the aforementioned technology bring to the table?

Imagine the infrared technology we already have, vastly improved, minaturised and produced cheaply enough to make it usable for the everyday consumer, where it can help detect skin cancer and cracks through walls.

Read more:
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"CMOS is affordable and can be used to make lots of chips,” Dr. O said. “The combination of CMOS and terahertz means you could put this chip and receiver on the back of a cellphone, turning it into a device carried in your pocket that can see through objects

To answer lingering questions in your mind:
1. What exactly are T-rays?

T-rays were discovered way back in the 1960s, and were pushed to the forefront of the scientific page in 2005. Terahertz radiation(T-rays) refers to electromagnetic waves propagating at frequencies between the infrared band and the microwave bend. Technically, they can still be classified as infrared rays.

Terahertz waves can pass through everything sans metal and water. It's usefulness as a communication tool is severely limited by it's relatively short range, since Earth's atmosphere absorbs most of it.


2. So... smartphones with X-ray vision, where can I get one?

As a matter of fact, the application of terahertz radiation is pretty common. This CMOS + T-rays combination is still new, and there will definitely be some kinks to iron out before the corporate world can commercialise the technology.

3. Can I use this to spy on peop- I mean, isn't this an invasion of privacy?

It could be. The researchers at the University of Texas claim that for privacy reasons, their research will only focus on a maximum length of 10 centimeters. Terahertz radiation itself has a very short range, but with the CMOS detectors, who knows?
The only thing that I can safely say (for now), is that there is no chance of you sneaking up on someone and... you know.

What do you mean, this isn't the Tray you're looking for?

Edit: Apparently people are only concerned about 'can it see through clothes?' Technically, yes, but the resultant images aren't viable for privacy invasion issues.

The Hardest Logic Puzzle in the World

Blue Eyes:
The Hardest Logic Puzzle in the World
A group of people with assorted eye colors live on an island. They are all perfect logicians -- if a conclusion can be logically deduced, they will do it instantly. No one knows the color of their eyes. Every night at midnight, a ferry stops at the island. Any islanders who have figured out the color of their own eyes then leave the island, and the rest stay. Everyone can see everyone else at all times and keeps a count of the number of people they see with each eye color (excluding themselves), but they cannot otherwise communicate. Everyone on the island knows all the rules in this paragraph.

On this island there are 100 blue-eyed people, 100 brown-eyed people, and the Guru (she happens to have green eyes). So any given blue-eyed person can see 100 people with brown eyes and 99 people with blue eyes (and one with green), but that does not tell him his own eye color; as far as he knows the totals could be 101 brown and 99 blue. Or 100 brown, 99 blue, and he could have red eyes.

The Guru is allowed to speak once (let's say at noon), on one day in all their endless years on the island. Standing before the islanders, she says the following:

"I can see someone who has blue eyes."

Who leaves the island, and on what night?


There are no mirrors or reflecting surfaces, nothing dumb. It is not a trick question, and the answer is logical. It doesn't depend on tricky wording or anyone lying or guessing, and it doesn't involve people doing something silly like creating a sign language or doing genetics. The Guru is not making eye contact with anyone in particular; she's simply saying "I count at least one blue-eyed person on this island who isn't me."

And lastly, the answer is not "no one leaves."

I've done my best to make the wording as precise and unambiguious as possible (after working through the explanation with many people), but if you're confused about anything, please let me know. A word of warning: The answer is not simple. This is an exercise in serious logic, not a lateral thinking riddle. There is not a quick-and-easy answer, and really understanding it takes some effort.

Source: xkcd.