How much does a kilogram of platinun-iridium weigh?

Could my genius students help me understand what this means? I'm eager to know!!!

A kilogram just isn't what it used to be… literally.

A kilogram weighs 1000 grams, right? Right? Well, no. A kg isn't actually a unit of weight at all, it's a unit of mass.

For the past 123 years, the kilogram has been arguably the most influential standard, affecting everything from the increasing numbers on your bathroom scale to the calculation of gravity, density, force and pressure. Unfortunately, it is losing mass, and scientists aren't sure why.

More info: http://bit.ly/15UZAkT

Translators

Watch it up to the end. It's really good.



Any comments?

Speed dating

Have you ever heard about "Speed Dating"? Watch this video and give your opions!

Would you like to take part in one of these dates?
Do you think it an effective way to meet a partner?
What are the pros and cons?

Optical invisibility or cloacking

Watch the following video and, without cheating, try to explain how they manage to achieve the "invisibility effect".

Had you heard about it before?

Who can answer this question?

Who are these women?

Here are a few female scientists that you might not have heard of (but definitely should have). Marie Curie hasn't bee included, because as much as we all love her, she is the automatic "female scientist" that always springs to mind and we think it's time we branched out!

I'll give you a few days to see if you recognize them and can give some info about at least one of them . . .

And the winner is . . . . . . DANILO!!!  

Yes, Danilo has been the only one who's guessed five of these female scientists. You can read his findings in "comments". 
Below, you'll read more about them:

1. Ada Lovelace
Analyst, metaphysician, and founder of scientific computing. Read more about her life here:http://bit.ly/V3im
2. Rosalind Franklin
Biophysicist and X-ray crystallographer who made critical contributions to the understanding of the fine molecular structures of DNA, RNA, viruses, coal, and graphite. She received no credit for her contributions to the discovery of the structure of DNA. More on her life:http://bit.ly/4CJMC0
3. Rachel Carson
Marine biologist and conservationist whose book Silent Spring and other writings are credited with advancing the global environmental movement. More on her life:http://bit.ly/16f4Hcm
4. Lise Meitner
A physicist who worked on radioactivity and nuclear physics. She was part of the team that discovered nuclear fission, but was overlooked for the Nobel Prize in favour of male colleagues. More on her life:http://bit.ly/3js4zk
5. Cecilia Payne
Astronomer and astrophysicist who, in 1925, proposed in her Ph.D. thesis an explanation for the composition of stars in terms of the relative abundances of hydrogen and helium. More on her life: http://bit.ly/n4RNqS
6. Mary Anning
A paleontologist who made many important finds in the Jurassic marine fossil beds at Lyme Regis in Dorset. More on her life: http://bit.ly/rGXKq