Como astrônomo amador fico fascinado com as surpresas que o céu nos reserva. Por exemplo, ver de dia o planeta Vênus é uma delas. Vc pode vê-lo de 10 h da manhã (25/08/2010) até a meia-noite. Ele aparece mais ou menos 15 ou 20 graus de distancia do sol, ao meio-dia ele esta bem no meio do céu. Nosso amigo John Walker tirou uma foto dele com um telescópio, mas este pode ser visto facilmente a olho nu sem problemas. E ainda mais, consegui ver além de Vênus a formação estelar da Via-lactea durante o dia, é fantastico poder ver estes astros durante o dia, uma dica, para ver Vênus durante o dia, use fios de postes ou casas proximas para que seu olho tenha algo como referencia para vc ver melhor o céu distante ou então olhe para o horizonte e depois olhe rapidamente para o local onde esta o planeta Vênus. Ok. Boa observação! Segue aqui o texto em inglês para vc praticar!
Viewing Venus in Broad Daylight by John Walker
For almost twenty years I lived near the Pacific coast of California, north of San Francisco (in Marin County). While the climate is superb (if you don't like hot weather, which I detest) and the scenery is magnificent, for an amateur astronomer like myself, there's one huge drawback: the fog. Mark Twain once remarked that the coldest winter he recalled was a summer in San Francisco. Although it rarely rains in the summer, almost every evening dense fog rolls in from the Pacific, reducing visibility to next to nil. On many days which dawn enveloped in fog, the Sun does manage to burn it off in the middle of the day, but come the evening the fog rolls right back in, much appreciated, no doubt, by the huge slimy slugs which outnumber primates in the region, but distinctly less so among said primates who amuse themselves by peering through telescopes.
I mean, astronomers are stargazers, and if the only time the sky isn't shrouded in fog is mid-afternoon, that kind of pares down the list of things at which one might direct one's gaze. Daytime optical astronomy seems a subject uniquely devoid of objects: the Sun, Moon, Venus, the occasional comet, the exceptional bolide, and the odd supernova pretty much exhaust the list of potential targets.
Venus? Yes. When Venus is bright and far from the Sun in a clear sky, you can observe this planet in broad daylight with the unaided eye. Here's how.
I've found that the best way to spot Venus in the daytime is to first note the angular distance between the Sun and Venus by observing Venus shortly after sunset. Then, the next day, find an observing site where the Sun is blocked from view (essential both for eye safety and to allow the iris to dilate and see Venus better against the sky). From that location, sweep the sky in overlapping fields with binoculars pre-focused at infinity by observing an object on the horizon. Sweep along the ecliptic in the area with the angular separation from the Sun noted the previous night. Since the Sun is blocked from view at your observing site, you can freely scan the sky without fear of damaging your vision by inadvertently sweeping past the Sun.
When you sweep past Venus, you'll know it. Even with my battered, poorly collimated, and cheap 6×30s, Venus is a brilliant speck of white against the blue sky. Once you've found Venus with binoculars, put the binoculars down and observe that area of sky with the naked eye. If the sky is perfectly clear your eye has no reference to focus upon so if you've learned the trick of consciously focusing your eyes, changing the focus may help Venus pop out from the sky.
Another trick I use to spot Venus in the daytime sky with the naked eye is to focus on the horizon, then quickly look up to the area of sky where Venus shines—the eye tends to remain focused at infinity, and Venus is found more readily. Looking up from a head-level position also seems to minimise interference from material floating within the eye. If the Moon is visible in the daytime sky, I've found that observing it to focus the eye, then sweeping over to Venus also works well.
The more transparent the sky, the more visible Venus will be; I've spotted Venus on afternoons with a very light haze, but anything more than that makes naked-eye observation extremely difficult, if not impossible. You can estimate the transparency of the sky by observing how close to the Sun the sky remains blue—the smaller the white dazzle around the Sun, the clearer the sky. Don't, of course, stare directly at the Sun unless you want to permanently conclude your astronomical career.
I find the sight of Venus shining forth from a brilliant blue mid-afternoon sky not only inherently beautiful (when else can you see a pinpoint of light piercing the daytime sky?), but rewarding to the observer in the sense that you're seeing a sight that billions of people could see if they bothered to look, but which only a very few people will ever observe in their lifetimes.
It's also possible to photograph Venus in broad daylight. The photo at the top was taken at 14:30 Pacific Standard Time on March 13th, 1988, with Ektachrome 200 film through an 80mm Brandon apochromatic refractor with the image projected onto the film plane of a Nikkormat camera by a Brandon 20mm focal length wide-angle eyepiece. The shutter speed was 1/250 second. The slide from which the above image was scanned was taken from Muir Beach, California (37°52'N 122°35'W).
So far, I've failed to capture Venus through a normal lens when the Sun was unobscured in the sky, though I've taken several slides which, if summed, might possibly reveal Venus. The problem is that the image of Venus through a normal lens is on the order of the grain size of Ektachrome film, so it's hard to dig the image of Venus out of the random grain pattern of the resulting slides. Using finer grain films such as Kodachrome 25 and red filters which enhance the contrast of white Venus against the blue sky may help. If you succeed in photographing Venus in the daytime with a normal lens, let me know; I'll be happy to publish your pictures here with full attribution and/or link to your page containing the photos.
Once you've found Venus in the daytime sky, it's a rewarding telescopic object at high magnifications. Waning gibbous Venus against a brilliant blue sky is a sight few people have seen. The bright background actually makes the phase easier to see than at night when the glare of Venus against a black sky often makes one reach for a neutral density filter.
Quando vc vê um jornal na banca de revistas, geralmente uma manchete chama sua atenção e aí vc chega e compra este jornal porque havia algo escrito que vc considerou importante. Justamente esta manchete sensacionalista é um screamer, assunto apelativo que atrai a atenção do leitor. Para vc praticar seu inglês mais um texto informativo que disponibilizo para os queridos leitores do blog.
A screamer is a distinctive headline which has been written with the goal of drawing attention to the article beneath it. While all headlines arguably serve this function, screamers demand attention, insisting that readers turn to the article in question immediately and without delay. Screamers are typically sensational, and sometimes specifically designed to be provocative. For some good examples of screamers, peruse the tabloids at the checkout stand, which often have a plentiful array of screamers to choose from. Screamers appear on the front page, because the idea is to entice consumers into buying the newspaper or magazine to read what's inside. In newspapers, screamers are always above the fold, ensuring that they will be visible, and they are often larger than the surrounding headlines so that they really stand out. Screamers may also be italicized or underlined for extra effect, and some companies also allow the use of punctuation marks in screamers; exclamation points, for example, will really make a screamer stand out. This term is most commonly used in print journalism, in reference to newspaper and magazines. Screamers also appear in online journalism, however, and at more adventurous sites, they may literally scream at the viewer, with the use of an embedded sound file. Screamers also show up on television, in the scrolling news feeds at the bottom of some network feeds. Urgent breaking news may show up as a screamer while the network prepares to cut to a journalist, for example, ensuring that viewers stay pinned to the network for an update. Some newspapers eschew the screamer, preferring a more stately and elegant look; the New York Times is probably the most famous for its staid, unremarkable appearance. More stately papers prefer descriptive headlines which sum up the content of an article, like "Politician X Speaks at Union Rally," allowing readers to get a quick idea of the coverage on the front page, while screamers highlight the sensational content of a news item, as in "Politician X Claims 'Oil Companies Should be Nationalized'." Writing a screamer, or any headline, takes talent. Headlines need to be succinct, clear, and to the point, and editors need to be careful about unintentional double entendres and glaring mistakes such as the infamous "Dewey Defeats Truman" headline of 1948, which the Chicago Tribune may never live down. In the case of a screamer, more journalistic license is involved, and the editor may generate a headline which punches up tension to draw the eyes.
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Como astrônomo amador, a teoria sobre a existência de buracos negros nunca me agradou. Depois de 30 anos de controversias e teorias absurdas, muitos físicos hoje admitem que os buracos negros não existem. Boa notícia, já estamos começando a fazer progresso neste campo, porque quando os cientistas abandonam uma teoria e seguem para outra é sinal que tem a mente aberta para outras possibilidades e é assim que a ciência evolui ao longo dos séculos. Neste texto da Sciencia Now, já se admite que o fenomeno do suposto buraco negro nada mais é o que sobrou de uma estrela outrora ativa que agora possui um grande poder gravitacional mas não infinito e que agora atrai objetos ao seu redor. Algo muito mais sensato, simples e plausível de se entender. Para vc praticar seu inglês segue este excelente texto informativo.
Black Holes Don’t Exist, Say Physicists
Well-known science commentator and intelligent design foe Lawrence Krauss has published an intriguing paper that dispenses with a major contradiction in black hole theory by arguing that black holes as commonly described cannot exist.
Black holes are presumed to possess infinitely strong gravity, a property that gives rise to a famous problem first pointed out by Stephen Hawking in 1974. Due to random particle movements posited by quantum theory, black holes should slowly evaporate as particle-antiparticle pairs flit into existence at a point straddling the event horizon, where gravity is so strong even light can’t escape.
In Hawking’s scenario, one partner in the pair should fall into the hole, while the other should make it free, if only barely. Thus, over billions and trillions of years, the block hole should lose mass.
This predicted phenomenon, dubbed Hawking radiation, has never been observed; but it has stumped physicists for more than three decades. "How can black holes be both airtight and leaky?" asks ScienceNOW, in a report published Wednesday.
Krauss’s answer: Hawking’s riddle is a trick question. Due to the relative nature of time under Einstein’s general theory, time should stop at the event horizon. Anything that approaches, therefore, should come to a halt before it falls into the black hole, effectively preventing the black hole from forming in the first place.
What we think are black holes, says Krauss in a paper co-authored with colleagues at Case Western Reserve, could be misidentified remnants of stars possessing a tremendous — but not infinite — amount of gravity
Em português "espelunca" significa •cavidade profunda no solo; caverna, cova, o mesmo se aplica em inglês, então spelunker é o termo usado para explorador de cavernas, mas sem preparo técnico, um simples amador ou melhor um amante de cavernas, aquele que explora por hobby, segue aqui mais um texto para vc praticar seu inglês e enriquecer seu vocabulário. Boa leitura!
A spelunker is a person who explores caves as a hobby. Two other terms applied to those who partake in cave exploration are caver and speleologist. However, the latter two terms are generally reserved for those with extensive training and education in the science of caving. Spelunkers are usually amateurs who don't follow any specific guidelines for traversing the passages of caves to retrieve data for scientific study. Drawn to the mystery of the unexplored and uncharted, spelunkers seek caves for their own pleasure and not necessarily with any specific goals in mind
Many who are interested in becoming a spelunker join clubs or groups organized by more experienced cave explorers, such as the National Speleological Society (NSS). The NSS organizes caving clubs that promote the preservation of caves, interest in the science of caving, and advancement in the study of caves. These clubs also plan caving trips that allow for safer exploration, as a lone spelunker would be taking a huge risk. It is always best to have a group large enough to allow for some to remain outside the cave, lest the participants inside the cave run into trouble and require a rescue.
Safety is a primary concern for spelunkers. The biggest risks are falling, being hit by a falling object, and hypothermia. Caves are dark and often damp, making surfaces slippery and range of vision limited. This means a spelunker must move carefully and deliberately and ensure proper footwear and gear is worn at all times. A helmet is required to reduce the risk of injury from falling objects, and warm clothing is essential in case a spelunker gets separated from the group and stuck in a cold cave for a longer time than originally anticipated. Spelunkers should also be sure to bring a first aid kit, food, water, and light.
Some of the basic tenets of safe and responsible cave exploration are to form groups of four to six spelunkers, establish a time limit before entering a cave, and tell additional parties about the caving trip. Spelunkers must be in relatively good shape as many caves require climbing, squeezing through tight passages, and sometimes using ropes to descend into pits. Novice spelunkers should always include more experienced cavers in the group and start with well known caves that are less likely to have surprise obstacles. Most importantly, new spelunkers should remember to stay with the group at all times.
É um assunto bastante interessante! Nunca concordei com a existência dos buracos negros. Pois, acho tudo isso um absurdo e me admira muito porque tantos cientistas concordam com este disparate. Mas um alivio e uma luz no fim do tunel começam finalmente a aparecer e muitos cientistas estão agora contestando esta teoria absurda. Muitos já dizem que eles não existem, que são fisicamente impossíveis! Então para a nossa alegria, este fenômeno que há no espaço que muitos astrônomos já observaram precisa ser revisto e outra explicação deve ser elaborada para responder nossas indagações sobre o que realmente esta ocorrendo no universo. Com isso posso afirmar aqui que não há um buraco negro no centro da via láctea, o que existe lá é simplesmente uma grande energia acumulada e que sofre uma grande pressão por causa da rotãção imensa da galáxia. Tudo isso explica os fenômenos observados lá pelas sondas de rádio, raios x e gama, etc. Queira deus que num futuro não muito distante poderemos ter uma prova irrefutável da não existencia de buracos negros e poderemsos jogar definitivamente por terra toda esta crença absurda propagada nos últimos 30 anos. Seguem trechos abaixo confirmando minhas suspeitas sobre esta teoria ridícula.
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