Ever wonder why there is a plethora of pigeons frequenting most downtown areas and not a bunch of smaller, nicer, or prettier birds? It turns out that pigeons are smart. Recent research has revealed that most birds that are urban, meaning they live in the city, have bigger brains than birds that live in the country. And, big-brained birds have a greater potential for what we like to call street smarts.
Of course, people who own pigeons, nice domesticated ones as opposed to the trash-eating ones on the street, have known this for a long time. Pigeons are highly trainable and have been used to carry messages during wartimes for many countries, including the US. In fact, 32 individual birds have actually been awarded medals for their service to the British military. Pigeons are also bred for sport, such as racing, and we have attributed many a romantic tradition to doves, even though doves really are just small pigeons (in fact, the name ‘pigeon’ and ‘dove’ are used interchangeably by scientists)
Why study bird brains? Alexei Maklakov and his European colleagues were actually interested in the effects of increased urbanization. As our human population booms, more and more areas are going to be urban instead of rural. They wanted to know which sorts of species fared well in this steadily enlarging urban setting. Brain size was linked to the ability to survive in novel and changing habitats, such as the city.
So, if city birds are smarter than country birds, does this mean the country birds are in trouble? The research shows that smaller brained birds tended to avoid urbanized areas. This means that as these areas get smaller, the available habitat for such birds is shrinking. That we are losing much of our wild lands is nothing new. However, the notion that bird brains just cannot cope with the change, is new. This research suggests that the smaller birds simply have trouble adjusting to change.
Makalov and colleagues suggest that street smarts ‘help birds find innovative solutions to problems such as a lack of trees, ubiquitous plate glass windows, and deciding whether or not to eat street-cart hot dogs off the sidewalk’.
Thursday, April 28, 2011
Thursday, February 17, 2011
Cat got your tongue?
Most of us who have pets have, at one time or another, watched them lap up water or some form of liquid from a bowl. Cats and dogs, unlike us, do not have complete cheeks, therefore they cannot form suction to draw the water out of the bowl the way we can, for instance with a straw. It is also why they cannot give us a big smooch and we have to accept a sloppy swipe of the tongue as a ‘kiss’. In order to drink, we have assumed that they use their tongues much like a soup ladle and scoop water from the bowl. Judging from the mess of water constantly spread around our dog’s bowl, this is certainly true, at least for dogs.
But, recently, a scientist from MIT (in Cambridge, Mass), sat at breakfast watching his own cat drink from her bowl. And, he was intrigued. Subsequently, he recruited a few colleagues and, on their own time (not funded by university time or funds), they filmed the cat, and later nine others, drinking. The high-speed video revealed that cats do not make ladles with their tongues.
Instead, they employ a tricky combination of physics principles, inertia and surface tension pitted against gravity.
Cats simply dip their tongue into the water and pull it back up. The water tends to adhere to the tongue and be drawn upward into the mouth because 1) the tongue has imparted some upward motion onto the water, called inertia, and 2) because water molecules like to stick together. The ‘stickyness’ of water is due to molecular forces holding the atoms together. Water likes to adhere to itself, a simple phenomenon we know as ‘surface tension’. We see surface tension all around us. For example, when water beads up and runs down our windshields, it is the surface tension forming the beads. The beads readily contact and merge with other beads, forming larger droplets.
In the cat’s case, gravity will eventually win out, and impart a force larger than the forces maintained by surface tension. And, the water will fall back into the bowl. But, hopefully not before some of the water has made it into the cat’s mouth along with the tongue. A careful trick of timing maximizes the amount of water that makes it into kitty’s mouth.
A trip to the local zoo revealed that all felines may in fact use this unique physics trickery to get a drink. Lions and tigers both showed this same behavior. Just goes to show you, even our household pets have something new to teach us if we pay attention!
But, recently, a scientist from MIT (in Cambridge, Mass), sat at breakfast watching his own cat drink from her bowl. And, he was intrigued. Subsequently, he recruited a few colleagues and, on their own time (not funded by university time or funds), they filmed the cat, and later nine others, drinking. The high-speed video revealed that cats do not make ladles with their tongues.
Instead, they employ a tricky combination of physics principles, inertia and surface tension pitted against gravity.
Cats simply dip their tongue into the water and pull it back up. The water tends to adhere to the tongue and be drawn upward into the mouth because 1) the tongue has imparted some upward motion onto the water, called inertia, and 2) because water molecules like to stick together. The ‘stickyness’ of water is due to molecular forces holding the atoms together. Water likes to adhere to itself, a simple phenomenon we know as ‘surface tension’. We see surface tension all around us. For example, when water beads up and runs down our windshields, it is the surface tension forming the beads. The beads readily contact and merge with other beads, forming larger droplets.
In the cat’s case, gravity will eventually win out, and impart a force larger than the forces maintained by surface tension. And, the water will fall back into the bowl. But, hopefully not before some of the water has made it into the cat’s mouth along with the tongue. A careful trick of timing maximizes the amount of water that makes it into kitty’s mouth.
A trip to the local zoo revealed that all felines may in fact use this unique physics trickery to get a drink. Lions and tigers both showed this same behavior. Just goes to show you, even our household pets have something new to teach us if we pay attention!
Friday, January 14, 2011
Black Holes and White Galaxies
The largest black hole that we know of, at least in nearby galaxies, is the black hole in galaxy M87.
M87 is not our galaxy. Earth and the other planets we know and love are part of the Milky Way Galaxy, so named because of the dense band of stars that passes through it creating a milky-white colored path. This milky white band of stars is only apparent as such from a certain vantage point. From here on Earth, all of the stars we see in the night sky are actually a part of the Milky Way. As such, our galaxy is a relatively light place.
Black holes are areas of the universe so dense that not even light can penetrate them. Thus, these areas appear as black regions, and appear to literally suck the light from surrounding regions inward. The idea that black holes such everything inward is a bit of science fiction. However, they are literally so dense that they can in essence have their own level of extreme gravity. Once objects get close enough to the black hole they can only go onward into the hole because of this gravitational effect. The point of no return, beyond which light or other objects will go forward into the hole, is called the Event Horizon, so named because any event (light emission or other) that happens beyond this point will not be observable outside the hole. Therefore it is impossible to determine if the event occurred at all.
The black hole in the Milky Way Galaxy is a mere 2 billion solar masses, or 2 billion times the mass of our sun. Some estimates place this at closer to 4 billion. But, even that number pales compared with the black hole in M87. The black hole in M87 is now estimated to be 6.6 billion solar masses.
These super massive black holes are probably formed by merging smaller black holes. Smaller black holes are commonly formed by collapsing stars. Once a star runs out of fuel to burn, it cannot maintain itself and collapses in on itself, succumbing to its own gravity. If the star was dense enough, it will form a stellar black hole as a result of this event.
M87 appears to be the result of hundreds or more mergers of smaller black holes, and could now swallow our whole galaxy. In fact, it could swallow more than 4 of them. But, we are in no danger. The M87 black hole is also more than 50 million light years away from Earth.
In addition to being the largest black hole on record, M87 provides physicists their best chance to study black hole physics, which, by and large, is still only theory at this point.
M87 is not our galaxy. Earth and the other planets we know and love are part of the Milky Way Galaxy, so named because of the dense band of stars that passes through it creating a milky-white colored path. This milky white band of stars is only apparent as such from a certain vantage point. From here on Earth, all of the stars we see in the night sky are actually a part of the Milky Way. As such, our galaxy is a relatively light place.
Black holes are areas of the universe so dense that not even light can penetrate them. Thus, these areas appear as black regions, and appear to literally suck the light from surrounding regions inward. The idea that black holes such everything inward is a bit of science fiction. However, they are literally so dense that they can in essence have their own level of extreme gravity. Once objects get close enough to the black hole they can only go onward into the hole because of this gravitational effect. The point of no return, beyond which light or other objects will go forward into the hole, is called the Event Horizon, so named because any event (light emission or other) that happens beyond this point will not be observable outside the hole. Therefore it is impossible to determine if the event occurred at all.
The black hole in the Milky Way Galaxy is a mere 2 billion solar masses, or 2 billion times the mass of our sun. Some estimates place this at closer to 4 billion. But, even that number pales compared with the black hole in M87. The black hole in M87 is now estimated to be 6.6 billion solar masses.
These super massive black holes are probably formed by merging smaller black holes. Smaller black holes are commonly formed by collapsing stars. Once a star runs out of fuel to burn, it cannot maintain itself and collapses in on itself, succumbing to its own gravity. If the star was dense enough, it will form a stellar black hole as a result of this event.
M87 appears to be the result of hundreds or more mergers of smaller black holes, and could now swallow our whole galaxy. In fact, it could swallow more than 4 of them. But, we are in no danger. The M87 black hole is also more than 50 million light years away from Earth.
In addition to being the largest black hole on record, M87 provides physicists their best chance to study black hole physics, which, by and large, is still only theory at this point.
Consider donating to Wikipedia, the source of information for many of the links found here.
Thursday, December 16, 2010
Can we still make a difference?
Global warming, climate change, rising sea-level…oh my. Some believe it is real, some believe it is a myth. Regardless of what you believe, it seems we hear about it constantly these days. You cannot escape it.
I personally think that some level of global climate change is real. We just cannot possibly be emitting that much pollution and smoke and carbon products into the atmosphere and not have some impact. How big is the impact? I don’t really know. But I am willing to try to do my bit to make the impact a little less. Whether you believe the earth is a gift from a Creator, or that it was created by the Big Bang, either way it is now ours to care for and we should indeed do our best to do so.
The problem is that this global climate change stuff is so hyped up by the media that we have become numb. The ‘doom and gloom perspective’ is that things are so bad, you just cannot think about the repercussions of all this global change without basically wondering why we should even bother. It is the only alternative. If you believe the doom and gloom, and lets face it, the media is driven by such extremes, then it almost paralyzes you with fear. If you think about it too hard, it could send you into a full on panic. What will our kids’ lives be like? Our kids’ kids?
And, so, we are largely numb to the problem. So numb that it has become almost hip to not care. It is like a defensive mechanism we collectively have evoked.
So, it is wonderfully reassuring to read a story where we find we can still make a difference. Recent research into the fate of the polar bears and the retreating sea ice gives us that hope. Polar bears, as a species, were given a fatal diagnosis a couple of years ago. With the loss of sea ice, they were losing their habitat, and were predicted to be extinct by 2050.
The most recent models still support that result, as reported by the National Center for Atmospheric Research in Boulder, Colorado. However, they also have begun to experiment with the effects of reductions in green house gasses. The good news is that rather moderate reductions, like those being planned by some countries, would actually slow the ice loss to a point that major areas of polar bear habitat would be protected.
Are we going to be able to do that – to reduce emissions? Only time will tell. But it is sure reassuring to know that we can still stop the effects of what is so often pitched as ‘the end of the world’
I personally think that some level of global climate change is real. We just cannot possibly be emitting that much pollution and smoke and carbon products into the atmosphere and not have some impact. How big is the impact? I don’t really know. But I am willing to try to do my bit to make the impact a little less. Whether you believe the earth is a gift from a Creator, or that it was created by the Big Bang, either way it is now ours to care for and we should indeed do our best to do so.
The problem is that this global climate change stuff is so hyped up by the media that we have become numb. The ‘doom and gloom perspective’ is that things are so bad, you just cannot think about the repercussions of all this global change without basically wondering why we should even bother. It is the only alternative. If you believe the doom and gloom, and lets face it, the media is driven by such extremes, then it almost paralyzes you with fear. If you think about it too hard, it could send you into a full on panic. What will our kids’ lives be like? Our kids’ kids?
And, so, we are largely numb to the problem. So numb that it has become almost hip to not care. It is like a defensive mechanism we collectively have evoked.
So, it is wonderfully reassuring to read a story where we find we can still make a difference. Recent research into the fate of the polar bears and the retreating sea ice gives us that hope. Polar bears, as a species, were given a fatal diagnosis a couple of years ago. With the loss of sea ice, they were losing their habitat, and were predicted to be extinct by 2050.
The most recent models still support that result, as reported by the National Center for Atmospheric Research in Boulder, Colorado. However, they also have begun to experiment with the effects of reductions in green house gasses. The good news is that rather moderate reductions, like those being planned by some countries, would actually slow the ice loss to a point that major areas of polar bear habitat would be protected.
Are we going to be able to do that – to reduce emissions? Only time will tell. But it is sure reassuring to know that we can still stop the effects of what is so often pitched as ‘the end of the world’
Wednesday, December 1, 2010
Wikipedia – Why you should care…
Today’s column is not so much a scientific rant, like I normally provide, but a plea:
Support Wikipedia.
What is Wikipedia? It is an on-line encyclopedia of sorts. It is the 5th most visited site on all of the internet. More than 400 million people use Wikipedia and its sister sites every month, so they claim. It has information on just about everything. I use it often when I teach, admittedly checking the facts against my own understanding of a subject before referring students to the site, but it is nearly always correct. It has a level of accuracy, I think, that shames the entire rest of the internet, all sites combined.
Why is Wikipedia amazing? It provides information, for free, to anyone and everyone that wants access. And, after all, that is my motto, Science Is For Everyone. Although wikipedia is not just science, it is a collection of facts that has the same appeal as science, at least for me.
John Goma, an editor for Wikipedia, recalls “I found a Wikipedia article on a topic that I had studied when I was a math student. I noticed that a few important points were missing. I hit the edit button, made some changes, and I've been writing and editing ever since. “ He states “Wikipedia is the sum of all those moments of discovery by millions of editors like me. People across the world add their time and energy to the vast, ever-growing store of knowledge that Wikipedia has become. But what's really remarkable about Wikipedia is that it's the product of volunteers working one entry at a time. And because Wikipedia is free of advertising, those of us who create and use Wikipedia have to protect and sustain it.”
Imagine a world in which every single human being can freely share in the sum of all knowledge. That's Wikimedia’s commitment. The Wikimedia Foundation is the foundation raising the funds to keep Wikipedia alive.
Want to know where your money would go? A donation to Wikipedia/Wikimedia supports technology and people. The Wikimedia Foundation develops and improves the technology behind Wikipedia and nine other projects, and sustains the infrastructure that keeps them up and running. The Foundation has a staff of about fifty, which provides technical, administrative, legal and outreach support for the global community of volunteers who write and edit Wikipedia.
Many people love Wikipedia, use it every day, but a surprising number don't know it's run by a non-profit.
Just type Wikipedia in your browser search bar and you’ll be there. Support the quest for knowledge and free access to it.
Support Wikipedia.
What is Wikipedia? It is an on-line encyclopedia of sorts. It is the 5th most visited site on all of the internet. More than 400 million people use Wikipedia and its sister sites every month, so they claim. It has information on just about everything. I use it often when I teach, admittedly checking the facts against my own understanding of a subject before referring students to the site, but it is nearly always correct. It has a level of accuracy, I think, that shames the entire rest of the internet, all sites combined.
Why is Wikipedia amazing? It provides information, for free, to anyone and everyone that wants access. And, after all, that is my motto, Science Is For Everyone. Although wikipedia is not just science, it is a collection of facts that has the same appeal as science, at least for me.
John Goma, an editor for Wikipedia, recalls “I found a Wikipedia article on a topic that I had studied when I was a math student. I noticed that a few important points were missing. I hit the edit button, made some changes, and I've been writing and editing ever since. “ He states “Wikipedia is the sum of all those moments of discovery by millions of editors like me. People across the world add their time and energy to the vast, ever-growing store of knowledge that Wikipedia has become. But what's really remarkable about Wikipedia is that it's the product of volunteers working one entry at a time. And because Wikipedia is free of advertising, those of us who create and use Wikipedia have to protect and sustain it.”
Imagine a world in which every single human being can freely share in the sum of all knowledge. That's Wikimedia’s commitment. The Wikimedia Foundation is the foundation raising the funds to keep Wikipedia alive.
Want to know where your money would go? A donation to Wikipedia/Wikimedia supports technology and people. The Wikimedia Foundation develops and improves the technology behind Wikipedia and nine other projects, and sustains the infrastructure that keeps them up and running. The Foundation has a staff of about fifty, which provides technical, administrative, legal and outreach support for the global community of volunteers who write and edit Wikipedia.
Many people love Wikipedia, use it every day, but a surprising number don't know it's run by a non-profit.
Just type Wikipedia in your browser search bar and you’ll be there. Support the quest for knowledge and free access to it.
Thursday, October 28, 2010
For the love of Chocolate
Continuing with the Halloween theme, today I write about candy. And, not just any candy - chocolate. Almost everyone likes chocolate, and some of us love it. I know I am certainly guilty of raiding my kids’ trick or treat bags in search of the good stuff; which in my book is the solid chocolate without anything else getting in the way. No peanuts, no nuts, no crispies, no crunchies, no wafers, and not even caramel. Just chocolate.
What is it about chocolate that makes so many of us crave it. Turns out there is some solid science behind this apparent madness.
First of all, there is the chemistry. Scientists have discovered several properties of chocolate that literally lead us to crave it. One, it has opioids. Opioids are also found in opium. So, not surprisingly, chocolate, like opium, serves to dull pain and give a general feeling of calm and happiness. Of course, it is present in pretty small doses, so chocolate is a lot safer way to get these feelings! Two, chocolate has caffeine, which is an upper, which tends to make your heart beat just a little faster.
Second – the psychology. Because we tend to give gifts of chocolate to people we love, some theorize that eating chocolate can induce feelings of comfort and/or love for purely psychological reasons. Given the chemistry above, and the biological responses, it is no wonder people have associated chocolate with love. But our resulting cultural association of chocolate with love has trained our emotional responses as well. Even without the underlying chemistry, giving, receiving, or just eating chocolate tends to induce happiness.
Third – the biology. Chocolate really is good for you, at least in moderation. Chocolate contains antioxidants, and flavenoids, both of which are thought to increase your life span through their cardiovascular benefits. In simpler terms, chocolate is good for your heart, biologically-speaking. And, we know that our bodies tend to crave the things that are good for us. It is our bodies’ way of telling us we are short on particular nutrients.
Of course, we also routinely crave what is not so good for us, and too much chocolate definitely falls into that category as well. Chocolate has lots of fats, and sugars. The fact that it contains all those fats, which make it smooth, may also explain some of why we like it so much - the sensation of eating it.
So whatever the reason, enjoy!
What is it about chocolate that makes so many of us crave it. Turns out there is some solid science behind this apparent madness.
First of all, there is the chemistry. Scientists have discovered several properties of chocolate that literally lead us to crave it. One, it has opioids. Opioids are also found in opium. So, not surprisingly, chocolate, like opium, serves to dull pain and give a general feeling of calm and happiness. Of course, it is present in pretty small doses, so chocolate is a lot safer way to get these feelings! Two, chocolate has caffeine, which is an upper, which tends to make your heart beat just a little faster.
Second – the psychology. Because we tend to give gifts of chocolate to people we love, some theorize that eating chocolate can induce feelings of comfort and/or love for purely psychological reasons. Given the chemistry above, and the biological responses, it is no wonder people have associated chocolate with love. But our resulting cultural association of chocolate with love has trained our emotional responses as well. Even without the underlying chemistry, giving, receiving, or just eating chocolate tends to induce happiness.
Third – the biology. Chocolate really is good for you, at least in moderation. Chocolate contains antioxidants, and flavenoids, both of which are thought to increase your life span through their cardiovascular benefits. In simpler terms, chocolate is good for your heart, biologically-speaking. And, we know that our bodies tend to crave the things that are good for us. It is our bodies’ way of telling us we are short on particular nutrients.
Of course, we also routinely crave what is not so good for us, and too much chocolate definitely falls into that category as well. Chocolate has lots of fats, and sugars. The fact that it contains all those fats, which make it smooth, may also explain some of why we like it so much - the sensation of eating it.
So whatever the reason, enjoy!
Friday, October 15, 2010
Spooky Spiders…
October seems the appropriate month to continue on the theme of spiders and other creepy crawlies who happily decorate our homes right now in larger-than-life form. Last time I wrote about spider silk, and its amazing strength. Spiders are biological wonders from several other perspectives as well. Notably, their long and leggy legs.
First, have you ever noticed that when you find a dead spider, that its legs are all curled up (so long as it is not smashed, that is)? Their legs roll inward towards their bodies and form a sort of ball. This is because spider legs are hydraulic, like pistons. They are held rigid by the fluid inside them, and that fluid must be maintained at pressure in order for them to hold the spider up and allow it to move around. Once the spider dies, the pressure cannot be maintained, and the legs collapse.
To move, the spider has muscles within the legs that allow the seven (yes seven) sections of each leg to bend inward a coordinated manner. But, to straighten the leg, there are no opposing muscles in most spiders, because there is nothing to attach them too. Remember spiders have no bone, just their tough exoskeleton that makes up what we think of as their crunchy skin or shell. The fluid pressure in the leg is changed via changes in the spider’s blood pressure. Increases in pressure straighten the leg, decreases allow it to bend.
Jumping spiders are by far the best at this feat. They can quickly change the blood pressure in the legs which allows them to spring upwards, travelling as far as 25 times their body length. That’d be 25 to 30 feet for the average human. None of us can pull that off.
Running spiders are special again in their own way. They have given up web building entirely for the purposes of capturing food, and obtain their meals hunting them down and then overtaking them with sheer speed. Our common wolf spiders often hunt this way. Luckily, even the largest of wolf spiders is only about an inch long, because spiders running you down is enough to unnerve just about anyone. They play an important role in the control of other insects, however, so be thankful that they are there.
Fishing spiders, however, win the award for amazing legs. Fishing spiders can literally walk on water. They do this by abusing the laws of physics, and taking advantage of simple surface tension. Surface tension is the tendency of particles of water to stick together. This is why you see a drop of water form a round, bead-like drop, and not just scatter into its infinitesimally small molecules. Fishing spiders have tiny leg tips, and light bodies, and when they press these leg tips to the surface of the water, they are able to stay atop the surface, and not break the surface tension. This is due largely to a waxy coating on the legs. You see a small dimple form on the water from the pressure of the leg, but the tension does not break, unless the spider wants it to. These spiders can dash out onto the water to grab prey such as insects, or reach below the surface to grab even small fish. And, when they really need to move, they can rise up on two legs and gallop across the water, reaching speeds of about 30 feet per second, or 2 miles per hour. The average running speed for a person is 6 miles per hour. The world record 100 m dash clocked in at 28 miles per hour. But, when they are just hanging around, or casually need to move from place to place, fishing spiders can also place their legs on the water and sail with the wind.
Not a bad way to get around.
First, have you ever noticed that when you find a dead spider, that its legs are all curled up (so long as it is not smashed, that is)? Their legs roll inward towards their bodies and form a sort of ball. This is because spider legs are hydraulic, like pistons. They are held rigid by the fluid inside them, and that fluid must be maintained at pressure in order for them to hold the spider up and allow it to move around. Once the spider dies, the pressure cannot be maintained, and the legs collapse.
To move, the spider has muscles within the legs that allow the seven (yes seven) sections of each leg to bend inward a coordinated manner. But, to straighten the leg, there are no opposing muscles in most spiders, because there is nothing to attach them too. Remember spiders have no bone, just their tough exoskeleton that makes up what we think of as their crunchy skin or shell. The fluid pressure in the leg is changed via changes in the spider’s blood pressure. Increases in pressure straighten the leg, decreases allow it to bend.
Jumping spiders are by far the best at this feat. They can quickly change the blood pressure in the legs which allows them to spring upwards, travelling as far as 25 times their body length. That’d be 25 to 30 feet for the average human. None of us can pull that off.
Running spiders are special again in their own way. They have given up web building entirely for the purposes of capturing food, and obtain their meals hunting them down and then overtaking them with sheer speed. Our common wolf spiders often hunt this way. Luckily, even the largest of wolf spiders is only about an inch long, because spiders running you down is enough to unnerve just about anyone. They play an important role in the control of other insects, however, so be thankful that they are there.
Fishing spiders, however, win the award for amazing legs. Fishing spiders can literally walk on water. They do this by abusing the laws of physics, and taking advantage of simple surface tension. Surface tension is the tendency of particles of water to stick together. This is why you see a drop of water form a round, bead-like drop, and not just scatter into its infinitesimally small molecules. Fishing spiders have tiny leg tips, and light bodies, and when they press these leg tips to the surface of the water, they are able to stay atop the surface, and not break the surface tension. This is due largely to a waxy coating on the legs. You see a small dimple form on the water from the pressure of the leg, but the tension does not break, unless the spider wants it to. These spiders can dash out onto the water to grab prey such as insects, or reach below the surface to grab even small fish. And, when they really need to move, they can rise up on two legs and gallop across the water, reaching speeds of about 30 feet per second, or 2 miles per hour. The average running speed for a person is 6 miles per hour. The world record 100 m dash clocked in at 28 miles per hour. But, when they are just hanging around, or casually need to move from place to place, fishing spiders can also place their legs on the water and sail with the wind.
Not a bad way to get around.
Subscribe to:
Comments (Atom)
Posts
