Stories tagged gravity

Here is footage from a helmet cam of a base jumper who leaped off 1 World Trade Center in lower Manhattan last fall. This is an illegal activity and three of the four people involved in this jump were arrested yesterday. But the footage is so cool.

Oct
02
2013

Gravity: Do they get the science right in the new action film Gravity?
Gravity: Do they get the science right in the new action film Gravity?Courtesy Wikipedia
Film goers will have the chance to travel through space this weekend with the blockbuster movie "Gravity" hitting the theaters. Its a ficticious story about two American astronauts dealing with disaster during a space shuttle mission.

I've come to expect Hollywood to place loose and easy with actual science when it comes to movies with scientific themes. And then today I stumbled upon this article in Time by Jeffrey Kluger, the co-author, with astronaut Jim Lovell, of Lost Moon: The Perilous Voyage of Apollo 13, which was the basis of the Apollo 13 movie released in 1995.

He applies his extensive space knowledge to fact check what's depicted in the new George Clooney/Sandra Bullock film. Here's his analytical summary: "So, that’s a lot that Gravity gets wrong. But you know what? So what? The shuttle, space station and spacesuits are painstakingly recreated; the physics of moving about in space—thrusts requiring counterthrusts, spins requiring counterspins, the hideous reality that if you do go spiraling off into the void your rotation never, never stops—are all simulated beautifully, scarily and accurately."

Click on the link above to get detailed analysis of what's scientifically right and wrong with Gravity.

Have you seen the film? What do you think about its accuracy in portraying the science of living and traveling in space?

Apr
04
2011

We often hear about gravity being different on other planets--the Moon is an oft-cited example of how weaker gravity makes you weigh less. But did you know that gravity actually varies on our own planet?

There's this thing called a geoid. It sounds like something out of a sci-fi story, but it's quite real. The geoid is a map of the Earth's gravitational field. And since gravity impacts things like sea level and currents, it's important to understand how it varies.
Welcome home: I think that's South America on the left there...
Welcome home: I think that's South America on the left there...Courtesy ESA/HPF/DLR

Luckily, those crafty Europeans came up with the GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite, which has painted the clearest picture yet of the geoid. With its variations exaggerated, it makes the Earth look like a giant potato. The variations come from unevenness in earth's mass and shape. Its wobbly surface represents what shape the oceans would take without current, wind, or tide to move them. The satellite also studies ocean circulation and the movement of ice.

This information is particularly important to understanding sea level rise. Scientists predict that, on average, sea level will rise 3 feet overall by 2100. But those three feet will be distributed differently throughout the world, and studying that distribution is pretty complicated. There's the impact of the geoid and of gravity from large ice sheets, but winds and water circulation, water temperature, salinity, meltwater from ice sheets, rainwater runoff, and land changes all leave their marks.
Home sweet tuber: Aww
Home sweet tuber: AwwCourtesy Lumbar

Some of these changes redistribute water (ex. geoid), others add to the volume of seawater (ex. temperature increases), and still others modify the land's height relative to the water (ex. land changes, such as sedimentation and oil extraction). Some changes leave a lasting impact (ex. meltwater from glaciers), while others can vary by the hour or the season (winds).

By developing this most-accurate-to-date geoid and ocean circulation model, researchers have created a picture of sea level at its natural state and modeled some of the processes that alter that state, so that we have a reference point for understanding many of the less-defined factors in sea level rise. And that, my friends, will help us better anticipate and plan for the changes ahead.

Plus it's just kinda cool to see how the Earth is really shaped, huh?

Gravity Sim: You can enable path tracing too. The shapes traced are pretty awesome.
Gravity Sim: You can enable path tracing too. The shapes traced are pretty awesome.Courtesy Joel Bonasera
Check out this awesome gravity simulator (you'll need Flash and a decent processor). You can introduce objects of different mass and watch how their gravitational pull moves them through space. My personal favorite is the "proto disk" button. Protoplanetary disk theory is one explanation for planetary development, and you can investigate it on your own on the site. Once I have a complex system started, I like to throw a huge mass through and see how it wrecks the balance of forces. Just don't tell my psychologist.

Dec
26
2009

GOCE Satellite: The Gravity field and steady-state Ocean Circulation Explorer
GOCE Satellite: The Gravity field and steady-state Ocean Circulation ExplorerCourtesy ESA
Can it be true? Yes, for a mere $5,544 dollars round-trip airfare to Greenland! In March 2009, the European Space Agency launched the Gravity field and steady-state Ocean Circulation Explorer (GOCE) into orbit around our planet, which is now transmitting detailed data about the Earth’s gravity. The GOCE satellite uses a gradiometer to map tiny variations in the Earth’s gravity caused by the planet’s rotation, mountains, ocean trenches, and interior density. New maps illustrating gravity gradients on the Earth are being produced from the information beamed back from GOCE. Preliminary data suggests that there is a negative shift in gravity in the northeastern region of Greenland where the Earth’s tug is a little less, which means you might weigh a fraction of a pound lighter there (a very small fraction, so it may not be worth the plane fare)!

In America, NASA and Stanford University are also working on the gravity issue. Gravity Probe B (GP-B) is a satellite orbiting 642 km (400 miles) above the Earth and uses four gyroscopes and a telescope to measure two physical effects of Einstein’s Theory of General Relativity on the Earth: the Geodetic Effect, which is the amount the earth warps its spacetime, and the Frame-Dragging Effect, the amount of spacetime the earth drags with it as it rotates. (Spacetime is the combination of the three dimensions of space with the one dimension of time into a mathematical model.)

Quick overview time. The Theory of General Relativity is simply defined as: matter telling spacetime how to curve, and curved spacetime telling matter how to move. Imagine that the Earth (matter) is a bowling ball and spacetime is a trampoline. If you place the bowling ball in the center of the trampoline it stretches the trampoline down. Matter (the bowling ball) curves or distorts the spacetime (trampoline). Now toss a smaller ball, like a marble, onto the trampoline. Naturally, it will roll towards the bowling ball, but the bowling ball isn’t ‘attracting’ the marble, the path or movement of the marble towards the center is affected by the deformed shape of the trampoline. The spacetime (trampoline) is telling the matter (marble) how to move. This is different than Newton’s theory of gravity, which implies that the earth is attracting or pulling objects towards it in a straight line. Of course, this is just a simplified explanation; the real physics can be more complicated because of other factors like acceleration.

Albert Einstein
Albert EinsteinCourtesy none
So what is the point of all this high-tech gravity testing? First of all, our current understanding of the structure of the universe and the motion of matter is based on Albert Einstein’s Theory of General Relativity; elaborate concepts and mathematical equations conceived by a genius long before we had the technology to directly test them for accuracy. The Theory of General Relativity is the cornerstone of modern physics, used to describe the universe and everything in it, and yet it is the least tested of Einstein’s amazing theories. Testing the Frame-Dragging Effect is particularly exciting for physicists because they can use the data about the Earth’s influence on spacetime to measure the properties of black holes and quasars.

Second, the data from the GOCE satellite will help accurately measure the real acceleration due to gravity on the earth, which can vary from 9.78 to 9.83 meters per second squared around the planet. This will help scientists analyze ocean circulation and sea level changes, which are influenced by our climate and climate change. The information that the GOCE beams back will also assist researchers studying geological processes such as earthquakes and volcanoes.

So, as I gobble down another mouthful of leftover turkey and mashed potatoes, I can feel confident that my holiday weight gain and the structure of the universe are of grave importance to the physicists of the world!

Sep
10
2009

Pshhhheeeewww!: Science everywhere!
Pshhhheeeewww!: Science everywhere!Courtesy SiamEye
I don’t even know where to begin today! All I can think is “OMG!!!!” And each exclamation point I think is like a blood vessel bursting in my brain!

OMG pop pop pop

So why is this a day of excitement, instead of quiet family tragedy? Because the biggest explosions today aren’t happening in little tubes in my head, they’re happening in the world of science! (I don’t consider the physiology of my head to be science. More like magic. Or trial and error.) I just don’t know what to do with all this science.

See, unlike your average Friday Extravaganza, a Thursday Explosion has no focus; it’s just kind of all over the place. A mess! There are all these stories, but we really have to stretch to fit them into a single post… so the loose theme of this explosion will, fittingly, be “flying things.” Am I not helping? Just wait, you’ll see.

Normal mouse becomes flying mouse, doesn’t care!
Check it out: a baby mouse was put into a little chamber and subjected to an intense magnetic field. What happened? All the water in the mouse’s body was levitated. And because those squishy little mice are so full of water, the mouse itself levitated along with the water.

Unfortunately, the first mouse wasn’t quite ready for life as an aviator, and upon levitation, he began to, as scientists say, “flip his Schmidt.” Lil’ mousey started kicking, and spinning, and with minimal resistance in the chamber, he started spinning faster and faster. He was removed from the machine, and put wherever little mice go to relax. Subsequent floating mice were given a mild sedative before flying (pretty much the same thing my mom does), and they seemed cool with it. Now and again the floating mice would drift out of the region of the magnetic field, but upon falling back into it they’d float right back up. After remaining in a levitating state for several hours, the mice got used to it, and even ate and drank normally. Afterwards, the mice had no apparent ill-effects from the experiment (rats had previously been made to live in non-levitating magnetic fields for 10 weeks, and they seemed fine too.)

Aside from the excitement normally associated with floating mice, the experiment is promising in that it may be a useful way to study the effects of long term exposure to microgravity without bringing a subject to space.
pop pop pop

Great tits are dangerous if you’re a sleepy bat!

It’s true! Forget everything you thought you knew about great tits and get schooled once again, my friends, for great tits are killers!

I’m not talking about the senseless murder of bugs, either—everybody already knew that great tits are primarily insectivores. A population of great tits in Hungary have been observed hunting bats!

As fun as it is to keep writing “great tits” with no explanation, I suppose we should be clear that great tits are a type of song bird common in Europe and Asia. Little, bat-hunting songbirds.

Meat eating great tits had been reported in other parts of Europe, but it was thought that those individuals had only consumed already-dead animals. The tits of Hungary were actually observed flying into bat caves, where they would capture tiny, hibernating pipistrelle bats and drag them out of the cave to devour them alive. It even appeared that the birds had learned to listen for the bats’ disturbed squeaking (or, as I like to think of it, their horrified shrieking)—when the same noise (which is too high for humans to hear) was played back for captured tits, 80% of the birds became interested (read: bloodthirsty) at the sound.

If it really is just the Hungarian population that engages in this behavior, the situation also brings up the possibility of culture in the birds. That is, if this isn’t some sort of innate behavior, but something learned and taught, and passed through generations that way, it could be considered culture. Amazing! Great tits are cultured!

pop pop pop

Flying velociraptors!

Well, not so much flying as falling. But falling with purpose. (What was it Buzz Lightyear said? Oh yeah, “I’m so lonely all the time.”)

We all know about how awesome raptors are. I think it’s part of kindergarten curriculum now, just between how not to accidentally poison yourself, and why you shouldn’t swear and hit. Well, I remember reading a news item a couple years ago about how some paleontologists were thinking that raptors’ famous giant toe claws may not have been for disemboweling their prey. Instead, the scientists proposed, raptors would lodge the massive claw into the skin of their prey with a kick, and then use it to hang on to the unlucky animal while the raptor went bite-crazy. The researchers had made a simulation of a raptor claw, and found that it could easily puncture thick skin and flesh, it didn’t seem to be sharp enough to actually cut the skin. (Cutting is necessary for a good disemboweling.) One might argue over the strength and sharpness of raptor claws, considering that the fossilized bone claws we see in museums would have been covered with a tough, horny substance, which did not fossilize, but whatever—the new scenario was still pretty cool.

Now, the same group of paleontologists is proposing that raptor claws were also well suited to tree climbing. Raptors could have waited on overhanging limbs, and then pounced on their prey from above. Pretty neat! The researchers point out that the microraptor a tiny relative of the velociraptor, had feathered limbs to help it glide down from high places, so it’s not a stretch to think that its cousins were comfortable in trees too. “The leg and tail musculature,” one scientist says, “show that these animals are adapted for climbing rather than running.”

I’ll take his word for it, I guess, but I do have some questions on that point. There’s a dromaeosaur (it looks a lot like a velociraptor) skeleton here at the museum, and I seem to remember that its tale was supposed to be very stiff—it has these cartilage rods running the length of the tail to keep it rigid. I feel like a long, stiff tail would be a pain in the butt up in a tree. It’s not the sort of thing arboreal animals invest in these days. Also, I wonder what sort of vegetation was around in the areas raptors lived. Plenty of big trees with good, raptor-supporting limbs? (I’m not implying that there weren’t, I’m just curious.)

The researchers do acknowledge that tree climbing wouldn’t have been every raptor’s cup of tea, however. Species like the utahraptor, weighing many hundreds of pounds, and measuring about 20 feet in length would have been “hard put to find a tree they could climb.”

pop pop pop

Pretty neat stuff, huh? Explosions usually are. But you see now why I couldn’t wait for three posts to get it all out there.

Jul
20
2009

Super Solar Ring: ...but remember, don't look directly at it or you WILL GO BLIND!!!
Super Solar Ring: ...but remember, don't look directly at it or you WILL GO BLIND!!!Courtesy Incredible India

Get ready, because one of Newton’s laws is about to be tested. A little thing called gravity is going into question during the total solar eclipse on July 22nd.

I’m sure most of you have heard of or know what a solar eclipse is. If not, here’s a refresher: “A solar eclipse occurs when the Moon lies between the Sun and Earth, casting its shadow on our planet. Depending on the location of the observer on the Earth’s surface, the observer may see a total solar eclipse, a partial solar eclipse or none at all. If the observer is lucky enough to be located in a position where the moon’s umbra contacts the Earth they will witness a total solar eclipse of the sun.”

Unfortunately for those of us in St. Paul, the only way for us to see the total solar eclipse would be to buy a one-way ticket to the eastern hemisphere. The path of the eclipse will start in eastern India and end about 2,000 miles south of Hawaii. During which it will be visible for nearly 6 minutes in China, and that’s where Newton steps in (not literally of course).

Researchers at the Chinese Academy of Sciences are about to test the controversial theory that gravity drops slightly during a total eclipse. Originally observed in 1954, the French physicist Maurice Allais noticed erratic behavior in a swinging pendulum when the eclipse passed over Paris. The shift in direction of the pendulum’s swing suggests a sudden change in gravitational pull. Though tests have occurred since, nothing has been conclusive.

The best chance to prove the gravity anomaly is this Wednesday during the longest eclipse duration of the 21st Century. This is why Chinese geophysicists are preparing six different sites with an array of highly sensitive instruments to take gravitational readings during the total eclipse. The head geophysicist Tang Keyun states, "If our equipment operates correctly, I believe we have a chance to say the anomaly is true beyond all doubt."

Okay, there's gravity involved in this story so that makes it scientific, right? Check out this video report from KSTP-TV about a brazen BASE jumper at the W Hotel (old Foshey Tower) and the trouble that ensued. Evidently there are quite a few people jumping off buildings downtown these days.

Sep
24
2008

Hi, All. This is another video from the "Do This At Home" video MASTER!If you like this one, once again, www.youtube.com and search "science experiments to do at home". Well, adios!

Sep
23
2008

i would count this video as a video that contains "current science". It's all in methods and g-force. If ya wanna see MORE videos like this, again, youtube.com. c ya all!