Over the last few weeks ObSrv was often returning empty feeds.
I’ve fixed this bug.
If there are any further problems, please let me know.
 Baby Black Hole by Nasa This is an open question to anyone who might understand astrophysics better than me (which is probably most of the human race). Assume there is a really big black hole. So large, in fact, that its event horizon is more than one light-year across. If you do the sums, the gravitational force near the event horizon of such a large black hole would roughly be about 1g – the same as what it is on earth. Imagine coming close to this event horizon in a spaceship. It would be easy to accellerate away – after all, the gravitational force in the vicinity is only 1g. So any imaginary spaceship capable of escaping the gravity of earth – if it were near the event horizon of this super massive black hole, would be able to escape its gravity. One of the horrors you normally hear about black holes is the tidal forces that would “tear you apart”. This is caused by the difference in gravitational forces as you move closer to center of gravity of the black hole. The same thing happens near neutron stars. Your head is being pulled with a lesser force than your feet. So you get “stretched”. But in our thought experiment, the centre of gravity of our supermassive black hole is over a light-year away. My head won’t feel any different amount of attraction than my feet would. There would be no noticeable tidal forces to speak of. So imagine you’re sitting in your late-model spaceship, orbiting just outside the event horizon of this super-massive black hole. You don’t feel any tidal forces, and the black hole is exerting a similar gravitational attraction on your vessel as what you’d experience orbiting the earth. Apart from the huge black sphere blocking half of the sky, and the strange lense-like effect of light bending as we look across the horizon of the black hole to the numerous stars in the distance, there’s nothing to be afraid of is there? My point is it would only take a reasonable amount of thrust to move our vessel away from the black hole. BUT… imagine as we sit near the event horizon, we move slowly towards it until we have moved INSIDE it. What would happen? What would we experience? My meagre understanding of physics leads me to think that the escape velocity just outside the event horizon would be slightly less than the escape velocity just inside the event horizon. So the burning question then is why couldn’t you escape from this super-massive black hole, having visited the forbidden area just inside the event horizon? The gravitational attraction at this distance would be small enough for our ship to thrust away. And this leads me to another question. If the gravitational force near this super-massive event horizon is about 1g, why couldn’t light escape from an object just inside the event horizon? And if light could escape, would there even be an event horizon? The “Black Hole” appearance of this thing is based on the assumption that no light can escape from it because the required escape velocity exceeds the velocity of light. So please help me. I obviously know nothing about black holes. I must be making an incorrect assumption. I don’t mind asking stupid questions, and am hoping that a patient genius will take the time to reply and explain where I’m going wrong. Thanks in advance Update Since I know so little about astrophysics I decided to pull together some formulas to demonstrate what I’m talking about. First of all a few facts about black holes. For any black hole:
Here are a few formulas: Schwartzchild Radius, rs = 2Gm / c2, where G is the Gravitational Constant, m is the mass of the black hole, and c is the velocity of light in a vacuum. This means we can work out how big the event horizon of a black hole will be if we know its mass. And we can work out what the gravitational acceleration will be at any given distance from a black hole if we know its mass. This allows us to ask the question, is there any mass of a black hole at which the gravitational acceleration at the event horizon will be similar to what we experience on earth (10 m/s2)? I think there is. Lets assume there’s a galaxy about 50% larger than our Milky Way galaxy. It would have a mass very roughly equal to about 1.5 x 1012 solar masses. If we squashed this galaxy down into a small enough pile, so that it became a black hole, its Schwartzchild Radius, rs, would be about 4.5 x 1015 metres, or about 1/100th of a light year. If we stand 1/100th of a light year from this object, what would its gravitational acceleration be? Using the above formula for a,we arrive at 10 m/s2. The bottom line of all this rambling is that hypothetically I think you can have a black hole where the gravitational acceleration at the event horizon is similar to the acceleration that an object would experience at sea level here on earth. That black hole would have a mass of 1.5 x 1012 times that of our sun. And that means the question I raised at the start of the article is a valid one. I’ve added a mandatory “Safe Search” filter to all images served up by ObSrv. To most users, you won’t notice any difference, but the problem was that some people were using ObSrv to generate adult images, which got me in trouble with Google Adsense. This is a business decision, not a moral one. Using ObSrv to generate adult images would get my Adsense account cancelled. No Adsense income = No ObSrv. Everyone would lose. So the simplest solution I could find was to block anything that didn’t pass the Google “Strict Safe Search” test. If you find your image feeds aren’t generating images any more, please consider using less adult-related search terms.
Close your eyes and imagine a clock face with hands and numbers. Imagine the clock face as a whole. Try not to think of just parts of it. In your minds eye can you see the individual numbers on the clock face all at once? I can’t. I have to “zoom” in to each part of the clock to see all the numbers. I can’t see them all at once. If the brain can’t do this while we’re awake, then it’s no wonder we don’t have vivid details of items when we’re asleep and dreaming. If our brains imagery has such low resolution, why do we seem to have such hi-resolution memories? Maybe it’s different for you. But that’s how it is when I try it. This whole experience helps me understand how my brain visualizes things. It’s not like the “Pictures” folder on my computer. I don’t store high-resolution pictures in my head. I think it’s more like a short-hand way of reconstructing a picture. Without realizing it my brain says “A clock is a circle. And it’s got numbers around it from 1 to 12. And it has hands. And it ticks”. Perhaps it’s like that for someone’s face as well? Do you know every freckle, mole or scar on your partners face? When you think about it, how much detail of someone’s face do you actually remember? I think perhaps we actually store a low res “caricature” of a persons face in our brain, and when we see that person, we match what we see of their face with the low res memory of it, and somehow our brain can recognize that the two things represent the same person. I think our physical perception of reality is a lot less detailed than we realize. When we look at a page in a book, there’s only a small circle of our vision that can actually see fine detail – about the width of our thumb held at arms length. If you hold your thumb in front of a book held at arms length, and focus on your thumb, you’ll find it almost impossible to read the book. That’s because the Fovea (the bit that sees detail) in your eye only occupies a small part of your Retina (the bit that actually sees things). But our brain manipulates us to think that we can see everything in detail, because our eyes dart around, and our brain puts all the jigsaw pieces together. So next time you’re certain you saw something, remember that what you saw, what you thought you saw, and what you remember seeing are all totally different! Isn’t the brain an amazing thing? I have had problems Activating and Updating Windows 7. I have an Endian firewall appliance. The main error I was getting was 0x80072EFD – unable to connect. For me, the solution (after hours of heartache) was simple: Go into Control Panel / Network and Internet / Internet Options / Connections tab / LAN Settings, UNTICK “Automatically detect settings” and press OK. Activation then works. Updates then work perfectly. Sorry – I’m not sure why this happens. I suspect it’s a bug in Endian version 2.2 which is fixed in later a version, probably relating to the internal Endian Proxy server which in my case is disabled anyway. I hope this helps someone. Many thanks to my son, Lachlan, who also had this problem, and figured out how to fix it after several days of heartache. I’ve improved the load speed of the ObSrv home page. Sometimes it would take a long time to load. I’ve also improved the speed of the image feeds. It still can be sluggish at times – that’s because it’s heavily used, but to counteract this, the Image Feed will ignore requests from the same computer if they come more frequently than about once every 3 or 4 seconds. For most people this won’t be a problem, and the only time you really notice delays on the Image Feed is if you try and display it in your browser. If site performance is still an issue for you, please let me know. Here’s a brief description of each of the photos in the “Around Pine Rivers” theme for iGoogle. If you’ve got any suggestions, corrections or improvements, please let me know. Click on the images for a larger view.
Aaron asked a good question they other day. Why does ObSrv only ever return 21 images at one time? I thought it was a bug in my code, but it’s not. ObSrv pulls images from Google Image Search, and Google only ever returns 21 images in one go. But this is not a problem. The images are embedded into a MediaRSS feed. That feed is cached for a maximum of one hour. After this time if you request the same feed, ObSrv will search again, but it will add in up to 21 extra images that weren’t shown last time. So on subsequent calls you’ll get more than 21 images in the feed. In the unlikely event that it runs out of images, it starts searching from the beginning again. So although there’s nothing I can do about the 21 images at a time issue, it’s not a major problem because you will get more images after the feed refreshes – but remember, to save server resources (and to stop Google from banning me) it waits an hour between doing searches on the same terms. I took Steve and Harrison on a bike ride this morning, along the North Pine River, up to Lake Samsonvale, and then back along the North Pine Rover. It was a hoot! A little bit slower than normal, because Harrison is only 9 and his bike is a bit worse for wear. But it was fun all the same. And I got to try out a new program for my Nokia N95 mobile phone. Nokia Sports Tracker Uses the inbuilt GPS on the phone to record speed and height info. While you’re cycling, your N95 acts like a speedo, and odometer, showing you all the vital stats. But when you get home, you click the button, and upload the data to sports tracker. The really cool thing is that if you take any photos with the phone on your journey, it will upload and geotag them. So the map on the left here is where we went. You can drag and zoom it if you want more detail. But the fun part is that the data is also uploaded to the Sportstracker community. Here’s a link to the data for our ride today. If you tick the “altitude” box, you can see every hill, and how fast we were going. The thing I like most about this technology is that it adds to the fun of getting out and exercising. At times I’ve found it hard to overcome my inertia to regularly exercise. In regards to exercise, if it makes me think “Oh yeah! I want to do that again!” then I think it’s a great thing. Oh – and you can use Sports Tracker for running, walking, skiing, rowing – whatever floats your boat. P.S. I’ve ordered a mounting bracket to attach my phone to my handlebars. Till that arrives, I’m using some of Lilly’s hair ties Loading…
Loading…
In this article about using slideshows in wordpress I showed you how to embed slideshows in WordPress blog posts and sidebars using the Google Ajax Feed API. I prefer to use this facility to pull in Image feeds from Flickr. The problem with the images in these feeds is that they’re either too large or too small. The MediaRSS specification has a <media:thumbnail> tag which lets you have a thumbnail image in your feed. That’s great, but the image size of the thumbnail is 75×75 pixels, which is useless for a nice looking slideshow. It ends up looking terribly blurry with no detail. The Google Ajax Feeds API tries to get around this by letting you specify a “thumbnailTag” in the slideshow options object. Basically, you set this to “content” to tell the API to look for the image in the “content” section of the feed, rather than the <media:thumnail> section. This is also great, but the problem is that Flickr uses the LARGE (or even worse, ORIGINAL) image size in this section. So you get nice large detailed images in the feed, but they’re so large that they take ages to load, and your slideshow sits there for ages saying “Loading….” while it grabs the huge images and chews up your audiences bandwidth. So I wrote a simple PHP screen scraping utility which grabs the Flickr feed, and changes the ImageUrl…_L.jpg to ImageUrl….M.jpg – in other words, it modifies the feed to include the medium size image rather than the large size. Medium sized images are fine for slideshows, and they load quite quickly. Here’s the PHP code:
Just save this in a file named FlickrRSS.php in the top folder of your wordpress directory. Then instead of using your flickr RSS feed, pass the feed as a query parameter to the PHP utility. You’ll need to change the < and > tags in the file to < and >. So if your feed URL was this: Use this instead This will change the <media:thumbnail> tag to point to the lager sized image, so your slideshows will load quickly, and look nicer |
|
|
Copyright © 2012 Neil Ennis - All Rights Reserved |
|
