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"http://yt.cl.nr/iQOHRKKNNLQ" In this segment I ask why astronauts in the space station are weightless. The most common answer is because there is no gravity in space. But of course there is gravity in space, especially where the space station is located (only about 400km from Earth's surface). So astronauts still experience a gravitational pull - it's just that they and the space station are in free fall so they are accelerating together towards the Earth. The space station doesn't crash into the Earth because of its orbital velocity - it's going 28,000 km/h so as it falls, the Earth curves away from it.

Spectacular vision of earth from the Space Station.

" Dim Lights Share a clea.nr URL: Hide Comments, Favorites, Suggested Videos, etc. There is a common perception that weight and mass are basically the same thing. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter that means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force. Subscribe 109 videos 32,519 Like Add to Share Uploaded by 1veritasium on Feb 7, 2011 There is a common perception that weight and mass are basically the same thing. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter that means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force. 320 likes, 14 dislikes Show more Uploader Comments ( 1veritasium ) Actually, it is the friction which is causing difficulty in moving the car. Ideally if there is no friction, whether rolling or sliding, even the slightest of the force would make the car move. You could actually be able to move the car with a push of your little finger if there is no friction at

"http://yt.cl.nr/yxFazy_vDhE" The ocean -- it is the most prominent feature on Earth, and of immeasurable importance to life on the planet. But what would it look like if all of the water was drained out of it? Mountains and valleys that dwarf Everest; shifting plates and undersea volcanoes; seams, ripples, and plains.

Journey back in time to the Ice Age and witness one of the world's deadliest animal killers - the tar pit. With enough force and consistency to kill a fully grown mammoth, was crude oil the biggest threat to species survival in early Earth?

"http://yt.cl.nr/_mCC-68LyZM" If you drop a heavy object and a light object simultaneously, which one will reach the ground first? A lot of people will say the heavy object, but what about those who know both will land at the same time? What do they think? Some believe both objects have the same gravitational pull on them and/or both fall to the ground with the same constant speed. Neither of these things is true, however. The force is greater on the heavy object and both objects accelerate at the same rate as they approach the earth, i.e. they both speed up but at the same rate.

Suitable for Preliminary Biology - Life on Earth Topic

"It's the dream of kids all around the world to see giant beasts walk the Earth again. Could -- and should -- that dream be realized? Hendrik Poinar gives an informative talk on the next -- really -- big thing: The quest to engineer a creature that looks very much like our furry friend, the woolly mammoth. The first step, to sequence the woolly genome, is nearly complete. And it's huge. (Filmed at TEDxDeExtinction.)"

"http://yt.cl.nr/6kXIo_lcvzE"

Genetically modified animals: questions and answers

Easy version.

Easy version

Fun, interactive, research-based simulations of physical phenomena from the PhET project