My Dad has this recurring dream... He is running impossibly fast and comes on a smooth lake... "Why not?" - and he starts running across it almost effortlessly getting only the bottom of his feet wet. He can run for miles like this and wakes up happy and exhilarated.
I have flying dreams and a different sort of running dream. I'm running very fast with longer and longer strides. I begin to increase the length of my strikes and start to pull my legs up a bit as I'm heading back towards the ground on each so the strides seem longer and longer. At some point I'm totally avoiding the ground.
Such dreams are probably common, but what about some athletes like basketball players who appear to float in the air for awhile? It can look particularly impressive as part of a slam dunk I've also seen it in soccer, er, football and volleyball. A volleyball playing friend told me sometimes she does it at the net so to keep herself well positioned to put together a block. She can touch a bit over 11 feet, so the ability to linger for a few tenths of a second at a slightly lower level can give an advantage. Plus "it feels neat!"
But the real masters are probably ballet dancers.
There seems to be something a bit wrong here - after all - high school physics teaches us that someone jumping will propel themselves in a parabolic arc. That is still true for a complicated object like a human body. The trick is that the its center of mass follows the parabolic path. You can move the rest of your body into any position you can muster while this is taking place. The physics is all very simple even though the motion of any of the given points can be very confusing.1 As its motion slows near the top of the trajectory the dancer can move her limbs so as to keep some of her body in a stationary vertical position. Adjustments are constantly made as her vertical speed slows, stops and then begins to increase in the other direction. As some point her center of mass is moving too quickly to compensate.
I watched a video of a dancer performing a grand jeté. In it she raises her legs into a nearly horizontal position and raises her arms above her head dropping the level of her head relative to her center of mass as it rises. She reverses the process as she begins to fall earthward again. I timed it at 0.44 seconds - a very long illusion. I also timed a basketball player in a slam dunk contest at about 0.3 seconds. In theory he could probably do it longer with his longer limbs, but he lacked her technique and 0.3s still looks startling and even beautiful to the audience. In volleyball it is more on the order of basketball. I'm sure it must feel wonderful when probably executed.
Using the fine print and the fact that we notice heads a lot to "cheat" gravity.
There is another use of this in sport. If you are standing normally, your center of mass is about 55% of your height from the ground and inside your body. If you bend forward at your hips your center of mass moves forward. It is possible to move it outside your body.2 A high jumper can arrange for his body to move so that it completely soars above the bar even though the trajectory of his center of mass might pass under the bar (or somehow cause some of him to collide with it). Dick Fosbury perfected the technique in the late 60s and revolutionized a sport - the Fosbury Flop.
Our sense of time is finely tuned to the environment we live in and that includes possible motions of our bodies. We can discern individual bits of motion down to about three hundreds of a second - our world is viewed at roughly video rate. A really fast tennis serve is a bit north of 65 meters per second. Air resistance quickly drops that, but the ball initially is travels about 2 meters before we can take in the next frame3 The receiving player must make a lot of assumptions about where the ball is going to go based on subtle information before the ball is hit. Clearly a lot of experience in understanding the biomechanics of how the trajectory of a tennis ball is created is built into any experienced player. The same can be said for many other sports - baseball, even though the ball's speed coming off the bat is somewhat lower than that of a tennis ball, is more dramatic as the ball has enough mass that it does not slow down as quickly..
Athletes are really good at Newtonian physics!
I'm better than Colleen sitting down with equations and working something out, but she has a much better ability to execute a series of those equations - equations that can be way to difficult for me to solve analytically - and not only come up with answers in real time, but convert the answers to values her muscles can use adjusting for real time position information of her own body. Even more impressive is the fact that her senses notice where her body was rather than where it is at any given time. We all have a neural time lag. Since she is very tall, she lives a bit more in the past than I do making the feat even more impressive.4
1 Take a hammer, or something else with an uneven mass distribution, and toss it with a bit of spin. (hopefully away from anything that can be damaged) The tends will form a tumbling pair of paths, but if you carefully watch the motion of the center of mass near its head. That will trace out a smooth parabolic trajectory.
2 You may have tried this as a student trying to pick up a chair with your head against a wall. Women tend to have lower centers of mass relative to their height than men - the net result can be the men are unable to pick up the chair, but the women can.
3 There is additional time used to register an event, but ignore that and assume you are watching the ball.
4 Neural impulses travel at speeds that are slower than you may think anywhere from a few to about 120 meters per second. Touch generally moves about 50 meters per second and pain much more slowly (hammer your finger and you notice you've done something really stupid fairly quickly, but the pain takes about a second to register - this is really useful to making an unencumbered choice when something really goes wrong)
The body tends to aggregate a few types of perception - touch your nose. You "feel" the touch with your finger tip and the tip of your nose even though the time delay on the path from your nose to your brain is much less (up to a few tenths of a second). People with longer bodies and longer neural path lengths perceive reality a bit later than shorter people. Colleen lives a few hundredths of a second more in the past than I do (probably about 0.05s or so - certainly more than a perceived image frame) and has to adjust the motion of her body appropriately. Of course we never notice any of that, but it is a fascinating new layer of complexity.
Anyway - you can probably figure out that I woke up after one of those wonderful dreams where I can adjust my stride so as to rarely touch the ground. Of course you might actually do that if you could dial back the force of gravity. For some fun, think about Olympic events on the moon where the force of gravity is about a sixth that of Earth (assume you are in a big stadium that has an atmosphere to make it a bit more interesting) ... what would the record book look like? And note that your reaction time is suddenly improved relative to how events transpire in some (not all!) sports...
This was really good the other night. Heirloom tomatoes are wonderful now and it that roasting them might be just wonderful. Some corn was lurking along with a very flavorful vegetable stock - enough to spark a soup. The quantities shown are very approximate - use your intuition and don't follow exactly.
Corn and Tomato Summer Soup
° 4 large very ripe heirloom tomatoes
° 2 ears of corn- cut off the kernels
° 4 cloves of garlic minced
° a small yellow onion
° a swish of olive oil
° a small chili finely chopped (I'll leave it up to you how hot or not, so pick your poison - you can leave it out)
° 700g or so of vegetable stock (about 3 cups)
° salt and pepper
° plain greek yogurt (I like Fage 2%, or the full test if you dare)
° Preheat your oven to 400°F
° Heat the olive oil in a large pan over a medium low heat .
° Add the onions, garlic, chili and some salt and sweat the onions (cook them 'til translucent - about 4 or 5 minutes for me)
° In another pot heat the stock
° Slice the tomatoes in half and cut out the cores, drizzle some olive oil on their flat sides and place them flat side down on a cookie sheet. Roast until they just start to caramelize, but don't let them burn (about 10 minutes for me)
° Dump the tomatoes into the pot with the onion and garlic. Pour a bit of the stock onto the yummy browned pan scrapings and scrape all of that into the pot.
° Cook on a medium heat for about 5 or 10 minutes until it starts to dry out a bit (depending on how much stock you have ladled onto it)
° Add the corn kernels and cook for another few minutes (maybe 3 or 4)
° Add the stock, bring to a boil and reduce to a simmer and cover. Let it cook "enough" - about 45 minutes for me.
° Put it into a food processor or use an immersion blender (much less dangerous). Strain off the debris
° Season to taste. You will need pepper and possibly more salt. Some herbs may be appropriate.
° Serve with a bit of yogurt and a drizzle of olive oil on each bowl. I added some chopped basil, but use your imagination.
Yesterday it was pointed out that it was "eat ice cream all day day" .. I decided to make something and picked up some heavy cream in the evening and then searched the pantry for inspiration. I ended up with a tried a true vanilla with some additions. Recommended. But try to get pasteurized heavy cream rather than the ultra pasteurized variety if you can (it isn't easy). Also use pasteurized eggs for safety as this is an uncooked method.
Lots of room for experimentation here!
Chocolate, Bing Cherry and Pecan Ice Cream
° 2 large pasteurized eggs
° 185g (about 3/4 cup) granulated white sugar
° 2 cups heavy cream (pasteurized rather than ultrapasteurized if possible)
° 1 cup whole milk
° half vanilla bean (optional)
° about 50g coarsely chopped semisweet chocolate (a mixture of chocolate types would be great!)
° about 50g bing cherries, pitted and cut into quarters
° about 30g coarsely chopped pecans
° chill the chocolate, cherries and nuts in separate bowls and get as close to freezing as you can
° whisk eggs until light and fluffy - a couple of minutes usually
° whisk in the sugar a bit at a time and then completely bend. Pour in the milk and cream and continue to blend.
° split and scrape the vanilla bean - mix in the goodstuff (I didn't have a bean and it worked out, but I think it would be better with)
° add to your ice cream freezer and start freezing
° a minute or so before it is ready add the nuts, chocolate and cherries