1. 03:00

20 Plays / / 0 Comments

Full text at http://howfarawayisit.com Until the 1900s, based on Young’s results, it was understood that light was a wave. And because waves were known to need a medium to propagate through (like water waves or sound through air), it was assumed that all space was filled with a massless substance that was given the name aether. Then in the mid-1800s, James Maxwell who was studying electricity and magnetism proposed that the existence of an electric charge filled empty space with an electric field. Here’s a NASA picture of small threads suspended in an oil aligned with the electric field of a charge. Accelerating the charge causes the electric field to change. Furthermore, he showed that a changing electric field created a magnetic field. And a changing magnetic field created an electric field. So the accelerated electron creates a disturbance in the electric field that propagates itself through space as an electromagnetic wave. Earlier, Michael Faraday and Andre Ampere had measured the resistance of empty space to the forming of an electric field called permittivity and the resistance of empty space to the forming of a magnetic field called permeability. Using these numbers, Maxwell calculated the speed of his wave and found that it was exactly the speed of light! He had discovered that light is an electromagnetic wave! There’s one more thing to point out about electromagnetic waves that will become important as we move inside atoms. Mathematically, waves can be described by a generalized wave equation that describes a vast number of different kinds of waves. For waves like this one, the solution to the wave equation provides valuable information about the wave’s characteristics, including its amplitude at any point in time. The idea of an aether filling otherwise empty space was rendered un-needed for light propagation once electromagnetic radiation was understood. So it faded from our vocabulary - replaced by the idea that empty space supported magnetic and electric fields and light represented a disturbance in the electric field. The exact characteristics of so called empty space will be a recurring subject for us as we approach our segment on the Higgs Boson.

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• 29:52

from Julia Cain Wide Eye Video / Added

10 Plays / / 0 Comments

This educational video on groundwater is the third video in a series on water commissioned by the Water Research Commission of South Africa. Once again, Erald Felix takes his viewers to varied landscapes around South Africa. As part of this journey, we gain an introduction to the following: - Permeability and porosity - Groundwater flow in the hydrological cycle - Importance of groundwater to our eco-systems - Groundwater aquifers in South Africa - Groundwater use and technology - Groundwater for municipal, rural and agricultural users - Groundwater management for sustainable supply - Protecting groundwater for use in the water mix - Artificial recharge of groundwater

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• 06:06

Pressure transient analysis response for a horizontal well showing the matching process and source of uncertainty. Two examples of horizontal well responses are presented. All at http://TestWells.com

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• 00:30

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Hydraulic fracturing market research report estimates the global market in terms of volume and value, where the volume in terms of million hydraulic horse power (million hhp) and value in terms of \$million. For more info visit : http://goo.gl/TpDXVA

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• 00:41

15 Plays / / 0 Comments

Installation work by Harald Hofmann from "Stay Hungry" in Berlin

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• 00:22

30 Plays / / 0 Comments

I'm trying to figure out how frogs can breathe inside a quart size storage bag. Herpetologists collect them this way. Three to five frogs can live zipped inside a bag for days. First thing to test, does the zipper leak? Maybe carbon dioxide gets out and oxygen gets in through the zipper. Smoke test shows there aren't any holes big enough for smoke in a zipper bag. Must be smaller scale than that then.

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• 05:18

from Giatec Scientific Inc. / Added

31 Plays / / 0 Comments

Giatec Perma™ is a laboratory test device for the measurement of the electrical resistance of concrete against the penetration of chloride (RCPT) according to the standard methods such as ASTM C 1202, AASHTO T 277 and ASTM C 1760. The measurements can be used to estimate the chloride diffusion coefficient of concrete, which enables predicting the service life of concrete structures. Perma™ could also be used for durability-based quality control purposes. Perma™ is electrically certified for rapid chloride penetrability test in concrete laboratories and its measuring cell sizes are according to the ASTM and AASHTO specifications.

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• 00:36

306 Plays / / 0 Comments

KinectをofxOpneNIで動かしつつ、アミッドスクリーンのテスト

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• 00:26

115 Plays / / 0 Comments

ポリッドスクリーンの素材テスト

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• 03:48