salem6sci

How the Eye Functions - Diagrams of structure of the human eye. How light waves are refracted by lens of eye & focused on the retina. The lens, its position & changes in curvature. Monocular & binocular vision, retina and function.

What does Pikachu have to do with your eyes? Find out in 10 things you didn't know about your eyes.

Music= Around the World by Terry Devine-King

A 2013 meteor explosion above Chelyabinsk, Russia injured more than 1,700 people. It was completely unexpected -- and it could happen again. Here's what NASA's doing to make sure we know how to act when (not if) the next one hits.

This got us thinking: What happens when smaller (and bigger) objects fly into our atmosphere? We used Purdue University's "Impact: Earth!" simulator to find our answers. Our own Bob Al-Greene illustrated the results, as seen in the gallery above.

Some highlights: Rocks the size of basketballs enter our planet about once a month; most burn apart in the atmosphere before they reach the surface. Objects as long as standard school buses (roughly 12 meters around) only sneak into the Earth every 20 years or so - but, as seen in Chelyabinsk, the damage can be much greater.

All results assume the object is traveling at a 45-degree angle, with a density level of 3000 kg/m^3 and a velocity of 11 km/s. Everything is assumed to be seen from 100 kilometers away from the direct impact zone.

Click "Show As List" on the bottom-left of the gallery to view larger images. And check out our Google Hangout with asteroid experts to learn more about what's being done to fend off space rocks, from basketball-sized to London-sized.

A great overview of the reasons that space exploration is worth the money from the Riding on Robots blog.

The first color pictures from the NASA space probe expedition to Mars have now been published. They look like -- well, they look like pictures of a lifeless, distant planet. They show blank, empty landscapes. They show craters and boulders. They show red sand. Death Valley, the most desolate of American deserts, at least contains strange cacti, vicious scorpions, the odd oasis. Mars has far less than that. Not only does the planet have no life, it has no air, no water, no warmth. The temperature on the Martian surface hardly rises much above zero degrees Fahrenheit, and can drop several hundred degrees below that.

I like to point out that the space program technology transfer is two-way. Many NASA engineers give their expertise and spare time to apply space program technology to problems facing the developing world. In doing so, they learn valuable lessons that will allow us to push space exploration beyond low-earth orbit. The highly efficient engineering approaches that are required in the developing world - robust solutions that do not require a lot of maintenance, resupply or training - are the same approaches we need to employ if we are going to break out of the bounds of low-earth orbit.

Read any debate about space exploration, and this question will invariably come up. "Why should we be spending money exploring space when there are so many problems here on Earth that we need to solve first?" It's a tricky one. I've got a simple answer; space exploration is awesome. Come on, think of space ships traveling to other worlds - that's really cool.

Okay, perhaps I've got too simplistic an argument, so I turned to the astrosphere and posed the question to other space bloggers. Here's what they had to say…

In an interview with the Daily Telegraph, Mr Baumgartner, who became the first man to break the sound barrier after leaping from 128,100ft above the Earth almost two weeks ago, urged the US Government to divert the money it spends on Mars toon environmental projects on Earth.
"A lot of guys they are talking about landing on Mars," he said. "Because [they say] it is so important to land on Mars because we would learn a lot more about our planet here, our Earth, by going to Mars which actually makes no sense to me because we know a lot about Earth and we still treat our planet, which is very fragile, in a really bad way.
"So I think we should perhaps spend all the money [which is] going to Mars to learn about Earth. I mean, you cannot send people there because it is just too far away. That little knowledge we get from Mars I don't think it does make sense."

The Internet's favorite astrophysicist talks about saving NASA, putting a person on Mars, and why he thinks every tweet is "tasty."

This is one of those questions which four year old's ask all the time. Also i would like to point out that there are plenty of other videos which address this question. However many of those fail to explain it in detail. This video covers many of those small details. I have been reading a lot about it. And while i was at it, many more questions came into picture, like why is the sun yellow, why are clouds white, why are oceans blue, etc. I have tried to cover up as much as possible in this video. I'll include all useful links below.

As you probably know, astronomers use the distance that light travels in a year as a standard measuring stick for calculating the largest distances in the Universe. The nearest star to Earth, Proxima Centauri, measures 4.22 light-years from Earth. The center of the Milky Way Galaxy is 26,000 light-years away. The nearest large galaxy, Andromeda, is 2.5 million light-years away.

This is a difficult number to know for certain, since we can only see a fraction of the Universe, even with our most powerful instruments. The most current estimates guess that there are 100 to 200 billion galaxies in the Universe, each of which has hundreds of billions of stars. A recent German supercomputer simulation put that number even higher: 500 billion. In other words, there could be a galaxy out there for every star in the Milky Way.

A Steve Spangler video experiment that might be good for teaching students about the Law of Conservation of Energy. Involves making a solar powered oven to convert light energy to heat energy to cook S'mores.