Standing on the Shoulders of Giants
(Source: cfedey)
There are probably more than 100 billion galaxies in the cosmos. Each of those galaxies has between 10 million and a trillion stars in it. Our sun, a rather small and feeble star (a “yellow dwarf”, indeed), weighs around a billion billion billion tons, and most are much bigger. There is an awful lot of visible matter in the Universe.
But it only accounts for about two per cent of its mass.
We know there is more, because it has gravity. Despite the huge amount of visible matter, it is nowhere near enough to account for the gravitational pull we can see exerted on other galaxies. The other stuff is called “dark matter”, and there seems to be around six times as much as ordinary matter.
To make matters even more confusing, the rest is something else called “dark energy”, which is needed to explain the apparent expansion of the Universe. Nobody knows what dark matter or dark energy is.
Things can travel faster than light; and light doesn’t always travel very fast The speed of light in a vacuum is a constant: 300,000km a second. However, light does not always travel through a vacuum. In water, for example, photons travel at around three-quarters that speed.
In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them.
When this happens, they cause a blue glow, known as “Cherenkov radiation ”, which is (sort of) comparable to a sonic boom but with light. This is why nuclear reactors glow in the dark.
Incidentally, the slowest light has ever been recorded travelling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate.
Light has also been brought to a complete stop in the same fashion, but since that wasn’t moving at all, we didn’t feel we could describe that as “the slowest it has been recorded travelling”.
“Find what you love and let it kill you.”
(via djoharijohariah)
cwl: Ten Times Around The Sun Without Carl (Letter From Ann Druyan)
20 December 2006
Dear Friends of Carl Sagan,
Chances are, if you have come here to join me in an act of remembrance on this tenth anniversary of Carl’s death, you are already well aware of the numerous scientific and cultural achievements of the man. It is likely that you know he…
(via kenobi-wan-obi)
Richard Feynman Quote
“I have a friend who’s an artist and has sometimes taken a view which I don’t agree with very well. He’ll hold up a flower and say “look how beautiful it is,” and I’ll agree. Then he says “I as an artist can see how beautiful this is but you as a scientist take this all apart and it becomes a dull thing,” and I think that he’s kind of nutty. First of all, the beauty that he sees is available to other people and to me too, I believe. Although I may not be quite as refined aesthetically as he is … I can appreciate the beauty of a flower. At the same time, I see much more about the flower than he sees. I could imagine the cells in there, the complicated actions inside, which also have a beauty. I mean it’s not just beauty at this dimension, at one centimeter; there’s also beauty at smaller dimensions, the inner structure, also the processes. The fact that the colors in the flower evolved in order to attract insects to pollinate it is interesting; it means that insects can see the color. It adds a question: does this aesthetic sense also exist in the lower forms? Why is it aesthetic? All kinds of interesting questions which the science knowledge only adds to the excitement, the mystery and the awe of a flower. It only adds. I don’t understand how it subtracts.”
(via galaxyclusters)
NASA Rockets Make Weird Clouds Near Edge of Space
1. Blazing a Trail
Photograph courtesy NASA
An ATREX rocket lifts off from NASA’s Wallops Flight Facility in Virginia Tuesday morning. The first rocket launched at 4:58 a.m. ET. Each subsequent rocket then took off 80 seconds apart.
Two of the rockets released their tracers over the Wallops facility, while the other three created clouds in a line over the open Atlantic. The multirocket experiment allowed scientists to track the jet stream winds hundreds of miles out—the farthest rocket made it from the U.S. East Coast halfway to Bermuda (map), NASA says.
2. Starry Show
Photograph by Jeffrey Berkes, My Shot
The ATREX clouds lighted up the predawn skies as far away as West Chester, Pennsylvania, as seen in a shot taken by resident Jeffrey Berkes, about 180 miles (290 kilometers) from the launch site.
“Once the chemical tracers from the rockets were released, the view was amazing,” observer Bryan Lauber of Frenchtown, New Jersey, told Spaceweather.com.
“The tracers were extremely bright and seemed to just fall out of the sky!”
(via scinerds)
“To those who do not know mathematics it is difficult to get across a real feeling as to the beauty, the deepest beauty, of nature. If you want to learn about nature, to appreciate nature, it is necessary to understand the language that she speaks in.”
One Hundred Nanoseconds.
Two 2” diameter acrylic rods were irradiated with a 5 million electron volt e-beam while they were rotated in a motorized fixture. The roots of the discharges were mounted facing each other in a frame with illuminates each end with a 5 watt white LED.
(via theaggiephysicist)
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