In an effort to understand how the simple robots.txt file works for crawling search engines and all of its uses I've run across a couple very interesting things.
Let's start with how a web search engine crawls. The crawler goes to the website and starts are the main page. Off this main page are normally many html links. The crawler follows all these links, which go to other links, and other links; the crawler develops a picture of the entire site. The trick here is this may not contain all the pages on the site.
Enter the Deep Web. This is a place where normal search engine crawlers don't see. A page that isn't linked off the main site can't be found by a crawler. There's no way for it to know what that page name is, aside from guessing, and that could be a very large number of guesses. The crawler program has other things to do, like mapping sites elsewhere.
There are attempts to find these hidden pages. Protocols developed by Google and others attempts to put the onus on website administrators. The owner of the site has to decide what content to advertise. They place this in a file, similar to the robots.txt file used for blocking content from indexing on search engines. This is the opposite of this. These are pages a crawler may not find, but want to make sure they find.
Other areas of untapped data are things like flight schedules, medical journals/writings, and basically search-able databases that don't have direct html links to them. Programs are being developed to place specialized search terms into these online databases to index them like the regular web.
Back to the beginning, as I mentioned I was researching robots.txt and how it works. This is an 'exclusion protocol'. It tells a crawler NOT to index and advertise the particular link or URL. One concrete example I found that would work well for this is redundant links on the site. If there are links for 'print only' formats which are the same as the article, this could junk up the search for the site. One misnomer is using this robots.txt file to keep pages hidden from hackers. This is patently wrong. The robots.txt is accessible by anyone. This lets crawlers figure out what one doesn't want indexed. However since it is accessible by anyone it is a stopping point for hackers to look and see what they can poke at. Robots.txt has its uses, but securing a particular part of the site from unwanted lookers should be setup with authentication that the web server offers.
References
http://www.sitemaps.org/protocol.php
http://www.deeppeep.org/
http://www.nytimes.com/2009/02/23/technology/internet/23search.html?_r=1&th&emc=th
http://en.wikipedia.org/wiki/Deep_Web
Saturday, January 8, 2011
Wednesday, November 25, 2009
Invention
New million dollar idea for minivans:
The double door addition to minivans doesn't hold a candle to this.
Like the limo has a window the driver can close between the front and
the cabin area the minivan needs the same addition. With the new
reverse video feed in cars you'd simply pipe a video of the cabin to
this so kids can be watched yet preserve the quiet to the front cabin.
This would sell like hotcakes.
--
Sent from my mobile device
"I have no special talent. I am only passionately curious." --Einstein
Saturday, November 14, 2009
Into November
2010 is coming. Lately work has been killer. Very busy. And I've been thinking it really is too bad. I'm trying to find time to reassess what's important and what's not. Even that is difficult to get to. So I guess this is what it means to feel stuck in a rut of sorts.
On a positive note I went duck hunting today. Joel, Ryan, and Christian were also there. We found a nice spot down on the coast and parked for duck. One flew in on us when we were setting up and almost landing on our heads. It was still dark so he didn't see us until he was on top of us. We didn't have the guns loaded so we missed him. We split into two pairs on the bank. Close enough to talk still. A number of duck came by. Black duck, which don't like to land it seems even near decoys. Very edgy duck. Not trusting at all. Some mallards came in; they landed a bit upstream and never got close enough to take a shot at. Teal duck flew by really fast, and a couple may have landed on the other side of some grass near us, but again, too far away to take a shot. There was a junk duck of sorts that was hanging around too. They eat other ducks eggs and have no limit to them. Mergansers (had to look it up again).
So I got to learn some duck species.
Oh...did I shoot any? No. :) Ryan got a goose with duck shot, which was impressive. But the ducks were too on top of their game today. I would have really liked to get a black duck. However when I hunt, as with the goose hunting we tried awhile back, we run into 'odd' days where people see things they've never had happen much like lack of duck, or lack of geese. I seem to have that effect. :)
On a positive note I went duck hunting today. Joel, Ryan, and Christian were also there. We found a nice spot down on the coast and parked for duck. One flew in on us when we were setting up and almost landing on our heads. It was still dark so he didn't see us until he was on top of us. We didn't have the guns loaded so we missed him. We split into two pairs on the bank. Close enough to talk still. A number of duck came by. Black duck, which don't like to land it seems even near decoys. Very edgy duck. Not trusting at all. Some mallards came in; they landed a bit upstream and never got close enough to take a shot at. Teal duck flew by really fast, and a couple may have landed on the other side of some grass near us, but again, too far away to take a shot. There was a junk duck of sorts that was hanging around too. They eat other ducks eggs and have no limit to them. Mergansers (had to look it up again).
So I got to learn some duck species.
Oh...did I shoot any? No. :) Ryan got a goose with duck shot, which was impressive. But the ducks were too on top of their game today. I would have really liked to get a black duck. However when I hunt, as with the goose hunting we tried awhile back, we run into 'odd' days where people see things they've never had happen much like lack of duck, or lack of geese. I seem to have that effect. :)
Monday, April 6, 2009
Thermite Fun
Yesterday I found sparklers, though a more crude fuse than magnesium,
also lights thermite.
also lights thermite.
--
Sent from my mobile device
"I have no special talent. I am only passionately curious." --Einstein
Sunday, October 19, 2008
Supertasters and tomographic reconstruction
Wikipedia is a fun place to browse for any subject you happen to be digging into. Perhaps better than howstuffworks.com, it has detail and links that can be very helpful in understanding something. Two recent subjects I looked at are listed in the title.
Tomographic reconstruction is the first. I was looking up the difference between radiologist and radiographer. Unless in or among the fields one probably wouldn't be able to tell the difference. My brother is in radiography, and that is the operators of X-ray equipment. This led me to different types of X-rays, MRI's, and something called CT scans. Standing for computer tomography, it led to another page named tomographic reconstruction. This is a mathematical method of constructing the picture of what you X-ray. For your geek reading pleasure:
http://en.wikipedia.org/wiki/Tomographic_reconstruction
The second is supertasters. Something I just heard of, it is on wikipedia as well! What on earth are they? People with a large number of fungiform papillae to be specific. They don't like particular tastes, being much more sensitive to bitterness in foods. Broccoli, spinach, brussels sprouts, olives, coffee, and alcoholic drink, are just a few supertasters may avoid. I've encountered a couple ways to test. One is take a spoonful of water with sweet and low (saccharin) mixed into it, and take a drop of that and place it on your tongue. If sweet you are a non-taster or perhaps a mid-taster. If bitter, you are more likely a super-taster. Another test involves litmus type strips of varying types. I didn't have either of these, so I took the last test. Take blue food coloring, drop 1 bit on your tongue and swallow. Try to keep your tongue a bit dry by keeping it out and look in the mirror to see. Near the tip end, you'll see a number of spots that are not blue. These are the fungiform papillae. Find a lot and you are more likely a supertaster. For your reading pleasure:
http://en.wikipedia.org/wiki/Supertaster
It has been awhile since I posted, and these seemed as interesting as anything to read about on a day off.
Tomographic reconstruction is the first. I was looking up the difference between radiologist and radiographer. Unless in or among the fields one probably wouldn't be able to tell the difference. My brother is in radiography, and that is the operators of X-ray equipment. This led me to different types of X-rays, MRI's, and something called CT scans. Standing for computer tomography, it led to another page named tomographic reconstruction. This is a mathematical method of constructing the picture of what you X-ray. For your geek reading pleasure:
http://en.wikipedia.org/wiki/Tomographic_reconstruction
The second is supertasters. Something I just heard of, it is on wikipedia as well! What on earth are they? People with a large number of fungiform papillae to be specific. They don't like particular tastes, being much more sensitive to bitterness in foods. Broccoli, spinach, brussels sprouts, olives, coffee, and alcoholic drink, are just a few supertasters may avoid. I've encountered a couple ways to test. One is take a spoonful of water with sweet and low (saccharin) mixed into it, and take a drop of that and place it on your tongue. If sweet you are a non-taster or perhaps a mid-taster. If bitter, you are more likely a super-taster. Another test involves litmus type strips of varying types. I didn't have either of these, so I took the last test. Take blue food coloring, drop 1 bit on your tongue and swallow. Try to keep your tongue a bit dry by keeping it out and look in the mirror to see. Near the tip end, you'll see a number of spots that are not blue. These are the fungiform papillae. Find a lot and you are more likely a supertaster. For your reading pleasure:
http://en.wikipedia.org/wiki/Supertaster
It has been awhile since I posted, and these seemed as interesting as anything to read about on a day off.
Tuesday, August 19, 2008
Moosehead Lake Adventure
I'm on vacation. A weeks worth of vacation. A couple days we decide
to spend it with some friends up at Moosehead Lake. They have a camp
up there, but instead of staying at camp, the more 'funner' thing to
do is to stay out on Moosehead island. We got out there in the
mid-afternoon, packed up the boat with our tents and gear, and took
our four kids out to the island. We setup the tents, then shot back
to the mainland to eat supper. The boat we were using was a Lunn, a
bass fishing boat with a low profile on the water. Moosehead is a
huge lake, the biggest lake in Maine, second deepest only to Sebago.
After we ate, evening was starting to approach, so we took a run back
on the boat to the island to settle in. As we are preparing to leave,
I peek at the radar. We know a cold front is moving in, and there is
the potential for thunderstorms. The radar confirms it. We've got
large storms rolling all around, so my friend and I are figuring we
have a limited window of fishing time after we drop everyone off at
the island. We get there, setup the fire for smores, etc, leaving the
wives and kids to figure that out while we go to find some trout.
I kept checking the radar and the storms are getting closer, and the
light is starting to fade. We shot across part of the lake at high
speed to get to an area my friend has seen trout rising for flies. We
saw some big black clouds a bit north, and know we are next. We
fished a bit, watching bats zip around our flies maybe 6 inches to 1
foot off the water. Finally the black clouds have obscured the
western sky. We tossed our poles into the bottom of the boat, and
cruised back to the island.
Lightning is flashing north, and north-west now. The wind has
started to pick up. We pull into the island's beach and tie up the
boat as best we can, secure the life jackets, and head up to the
tents. My wife takes 3 kids up to the outhouse, and I dive into a
tent with the 4th to get out of the wind and potential rain. While we
are hiding out there, the rain starts pouring down. I finally head
out to see where my wife is, and meet them halfway down the trail with
a towel over their head marching together trying to stay dry. As we
approach the tents, I hand a battery power fluorescent light to my
oldest son and get him and my oldest daughter into their tent. As
they jump in, somehow my boy slips and drops the light on the tent
floor. By then I've got the tent zipped up and I'm making my way to
the other tent. I climb in, close up, and hear them yelling that they
have no light. I jump back out into the rain, get into their tent
with my headlamp, and look for what happened. When the fluorescent
was dropped, the batteries popped out the bottom, and their tent went
black. I fixed up the light, and then stay with them until the rain
let up, which was after perhaps 5-10 minutes.
I went over to the other tent, where my wife and I made the decision
to sleep in separate tents so the kids wouldn't be scared. I swapped
my bed, which consisted of an air mattress, and now wet sleeping bag
(the bag was touching the edge of the tent during the rain and pulled
some in - I'm telling you, what ever happened to good old cohesive
liquids anyway? Touch a sleeping back to a tent when raining and
suddenly your sucking water up like a straw; anyway...). The pack and
play I dug out of the older kids tent, and dropped that off. I had
checked the radar before the rain slowed, and knew there was a lull,
albeit a short one, so I was moving as quick as I could. I dove back
into the tent I was sleeping in just in time. The rain started coming
down again, and this time it was going to be for a longer period.
Everyone got to sleep well enough and the morning was on its way.
7:30am - I get woken up by the older kids. I decide to get up and
check the damage. As I step onto the shore I realize the wind has
changed direction and large waves are pounding into shore. The boat
is totally swamped. "This should make things interesting" I think to
myself. "Back up to make a fire." I start sawing and collecting some
wood; the kids chip in. As our friends climb out of the tent I hear
that the husband has rolled over the lighter in his sleep and it is
done for. Thankfully I packed some wooden matches and tossed them in
a zip lock back. While we work on the fire, my friend works on the
boat. A Lunn doesn't sink so easily apparently, and with the back end
sunk down in the water, he gets it started and motors it across to
another nearby island where another boater helps bail out water enough
so the bilge pump can finish the job. He brings the boat back,
anchors it, and dives into the water. If he landed the boat, it would
just fill with water again. We have coffee and popcorn, plus we've
had some banana bread, all in all, a pretty good breakfast. Now we
are trying to figure out how to get everyone back to mainland. The
boat can't be brought into shore. Swim everyone out to the boat?
Brrr...
I take off with a compass up what looks kind of like a snowmobile
trail. I figure it I head west, I'll find another side of the island
with little waves and we can bring the boat over there to pick
everyone up. And success! A place is found. Most of the walk was on
the woods trail, but I did have to venture off a bit once I got near
the water, so I marked the trail with a few white birch branches,
making an arrow of sorts. I time myself coming back: 8 minutes. Not
bad. Time+kids=15-20 minutes maybe. When I show up at the campsite,
it looks like my friends father, staying back at the mainland camp,
has come with his boat as well, concerned with the big waves. The
kids and moms pack up what they can with the expectation that we'll be
coming back in the evening. We start up the trail while my friend
takes his boat around to pick us up, along with his dad's boat
following. They meet up with us, we split up into the two boats, and
start making our way back to mainland. When we can past the island,
some pretty big waves are all around us. Probably two foot swells at
this point. They really pick up going down the stretch of lake there.
We get pretty wet, but make it back in one piece.
After hanging around at the mainland camp for lunch, we look at the
weather and see that it doesn't look any better for the evening or
next day in terms of wind. We decide the camping is going to be cut
short by a day unfortunately. But we've got our stuff on the island.
So we pack up the vans, and send the wives off with the kids to a
playground down the road. Meanwhile we venture back across the lake
where the wind has since picked up, plus we are heading into the wind.
The waves are really smashing around us now, getting us drenched. My
friend's father is also following us in his boat to try and help as he
can. I'm feeling bad asking him to tag along now, because these waves
are pounding on us. I'm sure he isn't having a nice time. We get
around the island again, and the waves are not letting up. We try to
anchor so the two of us can go into shore, but the anchor won't hold.
I wade in while he tries to re anchor the boat. He can't get it to
stick, so he keeps the boat in place, semi-anchored, and I start
packing up the tents and gear. My friend's father has brought along
my friend's brother-in-law, who managed to get dropped off up shore a
bit and hike down to the campsite to help pack up. We get things into
plastic bags and all brought down to shore. From there I wade out to
the boat, which is repositioned in deeper water then when I originally
hopped in. Before it was waist deep, now I'm going up to my underarms
handing things to my friend. Meanwhile I'm bobbing over large waves
coming into shore. As I get up to rib level I have to jump up and
down with the waves, holding stuff over my head as best I can. While
I'm going back and forth I'm remembering a few things. First, you
lose 30% of your body head from your head. So while wading in cold
water, I pull on the hood of my raincoat. Second, you lose body head
600 times faster in water, so I'm glad I didn't wear my cotton jeans.
Last I put on the life jacket I had left on the shore and make my way
out to the boat. The boat is packed at this point. Barely room to
sit. I climb up to the front to pull in the anchor line while my
friend drives the boat. the two foot swells ave found us at this
point. My weight on the front of the boat is causing waves to crash
over the front of the boat, over me, and drain to the back where the
bilge pump has all the work. My friend is getting nervous and wants
me off the front. we head for a nearby island to get the majority of
the water out of the boat we've since taken on. After the bilge stops
pushing water out, we pray and then head out into the waves. They are
good size waves, causing a lot of jarring on our part. But we are
heading with the wind, which makes it a little more pleasant. Once we
get by the island and channel into the fully open water we come
against, not kidding, what have to be 4 foot swells. And they are
wide too. The boat goes down in them, and back up. Since leaving the
island, we've been looking for his dad's boat. He oddly enough
disappeared. At first we thought his dad was picking up his
brother-in-law, because the in-law parted ways when I started sloshing
into the water. I joked that he could hop in and help out, but he
wasn't interested. No worries. But now the boat has vanished, which
is very uncharacteristic of his dad. Back to the 4 foot swells on
open water past the island. We spot the boat, but can't tell if both
in-law and father are in the boat. So we go into the wind, into the
giant waves, to get a closer look. At one moment, my friend asks if I
can see them both in the boat. I've had water spraying in my face,
and even with a raincoat and sunglasses, my water soaked contacts have
limitations. I blink and blink trying to see past it all, and finally
spot both people in the boat. It probably doesn't help that my
prescription of contacts is a bit dated too. Then we turn around and
get to ride with the wind, thankfully, back to port. I keep looking
at these swells in amazement. Not just 4 feet high, but the width,
and trough size is huge. If you fell overboard, you'd go in and out
of view to someone even looking for you in another boat. I'm thinking
this lake is crazy, then I'm thinking I'm crazy. We did get back to
shore. My wife's first thought was the boat looked like the Grinch's
sleigh filled with toys stolen from whoville. We both were drenched,
and as quick as we got the boat onto the trailer, I was off to the
bathroom to change to try and counter the likely mild-hypothermia
setting in. On the way out of town we grabbed a nice warm cup of
coffee, which hit the spot. We swung into mcdonalds where I proceeded
to steal mcnuggets from my younger daughter who wasn't eating them.
They get a toy, I get fatter; it seemed like a win win, although the
calories burned during the days events may have taken care of those
pesky mcnuggets.
to spend it with some friends up at Moosehead Lake. They have a camp
up there, but instead of staying at camp, the more 'funner' thing to
do is to stay out on Moosehead island. We got out there in the
mid-afternoon, packed up the boat with our tents and gear, and took
our four kids out to the island. We setup the tents, then shot back
to the mainland to eat supper. The boat we were using was a Lunn, a
bass fishing boat with a low profile on the water. Moosehead is a
huge lake, the biggest lake in Maine, second deepest only to Sebago.
After we ate, evening was starting to approach, so we took a run back
on the boat to the island to settle in. As we are preparing to leave,
I peek at the radar. We know a cold front is moving in, and there is
the potential for thunderstorms. The radar confirms it. We've got
large storms rolling all around, so my friend and I are figuring we
have a limited window of fishing time after we drop everyone off at
the island. We get there, setup the fire for smores, etc, leaving the
wives and kids to figure that out while we go to find some trout.
I kept checking the radar and the storms are getting closer, and the
light is starting to fade. We shot across part of the lake at high
speed to get to an area my friend has seen trout rising for flies. We
saw some big black clouds a bit north, and know we are next. We
fished a bit, watching bats zip around our flies maybe 6 inches to 1
foot off the water. Finally the black clouds have obscured the
western sky. We tossed our poles into the bottom of the boat, and
cruised back to the island.
Lightning is flashing north, and north-west now. The wind has
started to pick up. We pull into the island's beach and tie up the
boat as best we can, secure the life jackets, and head up to the
tents. My wife takes 3 kids up to the outhouse, and I dive into a
tent with the 4th to get out of the wind and potential rain. While we
are hiding out there, the rain starts pouring down. I finally head
out to see where my wife is, and meet them halfway down the trail with
a towel over their head marching together trying to stay dry. As we
approach the tents, I hand a battery power fluorescent light to my
oldest son and get him and my oldest daughter into their tent. As
they jump in, somehow my boy slips and drops the light on the tent
floor. By then I've got the tent zipped up and I'm making my way to
the other tent. I climb in, close up, and hear them yelling that they
have no light. I jump back out into the rain, get into their tent
with my headlamp, and look for what happened. When the fluorescent
was dropped, the batteries popped out the bottom, and their tent went
black. I fixed up the light, and then stay with them until the rain
let up, which was after perhaps 5-10 minutes.
I went over to the other tent, where my wife and I made the decision
to sleep in separate tents so the kids wouldn't be scared. I swapped
my bed, which consisted of an air mattress, and now wet sleeping bag
(the bag was touching the edge of the tent during the rain and pulled
some in - I'm telling you, what ever happened to good old cohesive
liquids anyway? Touch a sleeping back to a tent when raining and
suddenly your sucking water up like a straw; anyway...). The pack and
play I dug out of the older kids tent, and dropped that off. I had
checked the radar before the rain slowed, and knew there was a lull,
albeit a short one, so I was moving as quick as I could. I dove back
into the tent I was sleeping in just in time. The rain started coming
down again, and this time it was going to be for a longer period.
Everyone got to sleep well enough and the morning was on its way.
7:30am - I get woken up by the older kids. I decide to get up and
check the damage. As I step onto the shore I realize the wind has
changed direction and large waves are pounding into shore. The boat
is totally swamped. "This should make things interesting" I think to
myself. "Back up to make a fire." I start sawing and collecting some
wood; the kids chip in. As our friends climb out of the tent I hear
that the husband has rolled over the lighter in his sleep and it is
done for. Thankfully I packed some wooden matches and tossed them in
a zip lock back. While we work on the fire, my friend works on the
boat. A Lunn doesn't sink so easily apparently, and with the back end
sunk down in the water, he gets it started and motors it across to
another nearby island where another boater helps bail out water enough
so the bilge pump can finish the job. He brings the boat back,
anchors it, and dives into the water. If he landed the boat, it would
just fill with water again. We have coffee and popcorn, plus we've
had some banana bread, all in all, a pretty good breakfast. Now we
are trying to figure out how to get everyone back to mainland. The
boat can't be brought into shore. Swim everyone out to the boat?
Brrr...
I take off with a compass up what looks kind of like a snowmobile
trail. I figure it I head west, I'll find another side of the island
with little waves and we can bring the boat over there to pick
everyone up. And success! A place is found. Most of the walk was on
the woods trail, but I did have to venture off a bit once I got near
the water, so I marked the trail with a few white birch branches,
making an arrow of sorts. I time myself coming back: 8 minutes. Not
bad. Time+kids=15-20 minutes maybe. When I show up at the campsite,
it looks like my friends father, staying back at the mainland camp,
has come with his boat as well, concerned with the big waves. The
kids and moms pack up what they can with the expectation that we'll be
coming back in the evening. We start up the trail while my friend
takes his boat around to pick us up, along with his dad's boat
following. They meet up with us, we split up into the two boats, and
start making our way back to mainland. When we can past the island,
some pretty big waves are all around us. Probably two foot swells at
this point. They really pick up going down the stretch of lake there.
We get pretty wet, but make it back in one piece.
After hanging around at the mainland camp for lunch, we look at the
weather and see that it doesn't look any better for the evening or
next day in terms of wind. We decide the camping is going to be cut
short by a day unfortunately. But we've got our stuff on the island.
So we pack up the vans, and send the wives off with the kids to a
playground down the road. Meanwhile we venture back across the lake
where the wind has since picked up, plus we are heading into the wind.
The waves are really smashing around us now, getting us drenched. My
friend's father is also following us in his boat to try and help as he
can. I'm feeling bad asking him to tag along now, because these waves
are pounding on us. I'm sure he isn't having a nice time. We get
around the island again, and the waves are not letting up. We try to
anchor so the two of us can go into shore, but the anchor won't hold.
I wade in while he tries to re anchor the boat. He can't get it to
stick, so he keeps the boat in place, semi-anchored, and I start
packing up the tents and gear. My friend's father has brought along
my friend's brother-in-law, who managed to get dropped off up shore a
bit and hike down to the campsite to help pack up. We get things into
plastic bags and all brought down to shore. From there I wade out to
the boat, which is repositioned in deeper water then when I originally
hopped in. Before it was waist deep, now I'm going up to my underarms
handing things to my friend. Meanwhile I'm bobbing over large waves
coming into shore. As I get up to rib level I have to jump up and
down with the waves, holding stuff over my head as best I can. While
I'm going back and forth I'm remembering a few things. First, you
lose 30% of your body head from your head. So while wading in cold
water, I pull on the hood of my raincoat. Second, you lose body head
600 times faster in water, so I'm glad I didn't wear my cotton jeans.
Last I put on the life jacket I had left on the shore and make my way
out to the boat. The boat is packed at this point. Barely room to
sit. I climb up to the front to pull in the anchor line while my
friend drives the boat. the two foot swells ave found us at this
point. My weight on the front of the boat is causing waves to crash
over the front of the boat, over me, and drain to the back where the
bilge pump has all the work. My friend is getting nervous and wants
me off the front. we head for a nearby island to get the majority of
the water out of the boat we've since taken on. After the bilge stops
pushing water out, we pray and then head out into the waves. They are
good size waves, causing a lot of jarring on our part. But we are
heading with the wind, which makes it a little more pleasant. Once we
get by the island and channel into the fully open water we come
against, not kidding, what have to be 4 foot swells. And they are
wide too. The boat goes down in them, and back up. Since leaving the
island, we've been looking for his dad's boat. He oddly enough
disappeared. At first we thought his dad was picking up his
brother-in-law, because the in-law parted ways when I started sloshing
into the water. I joked that he could hop in and help out, but he
wasn't interested. No worries. But now the boat has vanished, which
is very uncharacteristic of his dad. Back to the 4 foot swells on
open water past the island. We spot the boat, but can't tell if both
in-law and father are in the boat. So we go into the wind, into the
giant waves, to get a closer look. At one moment, my friend asks if I
can see them both in the boat. I've had water spraying in my face,
and even with a raincoat and sunglasses, my water soaked contacts have
limitations. I blink and blink trying to see past it all, and finally
spot both people in the boat. It probably doesn't help that my
prescription of contacts is a bit dated too. Then we turn around and
get to ride with the wind, thankfully, back to port. I keep looking
at these swells in amazement. Not just 4 feet high, but the width,
and trough size is huge. If you fell overboard, you'd go in and out
of view to someone even looking for you in another boat. I'm thinking
this lake is crazy, then I'm thinking I'm crazy. We did get back to
shore. My wife's first thought was the boat looked like the Grinch's
sleigh filled with toys stolen from whoville. We both were drenched,
and as quick as we got the boat onto the trailer, I was off to the
bathroom to change to try and counter the likely mild-hypothermia
setting in. On the way out of town we grabbed a nice warm cup of
coffee, which hit the spot. We swung into mcdonalds where I proceeded
to steal mcnuggets from my younger daughter who wasn't eating them.
They get a toy, I get fatter; it seemed like a win win, although the
calories burned during the days events may have taken care of those
pesky mcnuggets.
Friday, July 25, 2008
Rocks and Canoes
This is an attempted proof for the rock tossed overboard problem and what happens to the water level.
"You sit in a canoe with a rock. You throw it overboard, and it sinks. Does the rock make the water level go up, down, or stay the same when thrown in?"
Does the water level go up?
Archimedes principle states that when a body is immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid the body displaces.
Since the rock doesn't sink the canoe, its weight or downward force is being equaled by the buoyancy of the water, an upward force.
B = pgV
B - buoyancy force
p - density of water
g - gravity
V - volume of water displaced
So the weight of the rock is equal to B
w = mg
w - weight or downward force
m - mass of rock
g - gravity
So
B = w
pgV = mg
When the rock is thrown overboard, the rock sinks; it overcomes the buoyant force of water.
In canoe
pgV = mg
In water
pgV < mg
Now 'p', 'g', and 'm' do not change. That being, the density of water, the gravity, and the mass of the rock all stay the same. The only thing left to change is the volume of water displaced, 'V'. The volume of water displaced must go down, and so the water level must go down.
Could the water level stay the same?
The problem with this is the rock must sink as set by the question. To keep the water level the same the rock would need to be equal in density to the water. Water doesn't sink in water, and neither would an object of equal density.
m = pV
m - mass
p - density
V - volume
You can substitute pV for the rock's mass
Before
water rock
pgV = pgV
After
pgV = pgV
If the rock was going to sink the downward force would have to be greater. The left side doesn't change, and volume and gravity on the right don't, so the rock's density doesn't. Your force is still equal; the rock wouldn't sink.
However you look at it the water level goes down.
"You sit in a canoe with a rock. You throw it overboard, and it sinks. Does the rock make the water level go up, down, or stay the same when thrown in?"
Does the water level go up?
Archimedes principle states that when a body is immersed in a fluid, the fluid exerts an upward force on the body equal to the weight of the fluid the body displaces.
Since the rock doesn't sink the canoe, its weight or downward force is being equaled by the buoyancy of the water, an upward force.
B = pgV
B - buoyancy force
p - density of water
g - gravity
V - volume of water displaced
So the weight of the rock is equal to B
w = mg
w - weight or downward force
m - mass of rock
g - gravity
So
B = w
pgV = mg
When the rock is thrown overboard, the rock sinks; it overcomes the buoyant force of water.
In canoe
pgV = mg
In water
pgV < mg
Now 'p', 'g', and 'm' do not change. That being, the density of water, the gravity, and the mass of the rock all stay the same. The only thing left to change is the volume of water displaced, 'V'. The volume of water displaced must go down, and so the water level must go down.
Could the water level stay the same?
The problem with this is the rock must sink as set by the question. To keep the water level the same the rock would need to be equal in density to the water. Water doesn't sink in water, and neither would an object of equal density.
m = pV
m - mass
p - density
V - volume
You can substitute pV for the rock's mass
Before
water rock
pgV = pgV
After
pgV = pgV
If the rock was going to sink the downward force would have to be greater. The left side doesn't change, and volume and gravity on the right don't, so the rock's density doesn't. Your force is still equal; the rock wouldn't sink.
However you look at it the water level goes down.
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