from the world's big
Gravity is not uniform. It varies geographically.
As this map of Bouguer's gravity anomaly shows, the pull of the earth varies considerably by region.
- The law of gravity may be universal, gravity itself varies considerably across the earth.
- Most factors can be mathematically accounted for; local geology is the odd one out.
- Bouguer gravity anomaly maps like these show regional gravitational variation.
Apple and tree
Isaac Newton's apple tree at Woolsthorpe Manor, Lincolnshire. In the background: the house where he was born.
Image: arthurmarris, CC BY-SA 3.0
What a weird place this planet is. But especially southern Illinois, according to this map of gravity anomalies across three Midwestern states.
Gravity is what made the apple fall from a certain tree (in Woolsthorpe, Lincolnshire), causing Newton to wonder why it fell down straight. But the law of universal gravitation he formulated (and published in 1687) by way of explanation is a lot less uniform than you'd think.
For gravity does vary across the earth, meaning Newton's apple has a slightly different weight in various other parts of the world and falls at slightly different speeds. That's due to a combination of four factors.
- First, there's a latitudinal effect. The earth is not perfectly round: it's flatter nearer to (and flattest at) the poles and bulges more towards (and most along) the equator. As a result, the distance from the earth's center to sea level is 13 miles (21 km) greater at the equator than at the poles. The latitude you're at has an effect on gravity, with polar and equatorial extremes: Newton's apple (and you) weigh 0.5% more at the poles than at the equator.
- Secondly, there's a rotational effect. That difference in gravity between the poles and the equator is only partly due to gravity itself; it's also caused by the fact that the earth spins faster at the equator.
Bouguer gravity anomaly map of Illinois, Indiana and Ohio. Red means higher than average anomalies, blue means lower than average ones.
- Then there's an altitudinal effect. Earth's gravitational pull depends on your distance from its center. Gravity diminishes with altitude – but again, with fairly limited effect. If you're 16,400 feet (5 km) up a mountain, you weigh 99.84% of what the scales would say at sea level.
- Fourth differentiator: the tidal pull of the moon and sun. Although this has visible, repetitive and significant effects – the ebb and flow of sea levels – the variations this causes in the earth's gravity are very small indeed.
- Final factor: an area's geological makeup. The density of certain rock types has an effect on the force of gravity. Areas with higher subsurface rock density have higher than average gravity, and vice versa. Mountains increase gravitational density, ocean trenches decrease it. The effect is usually not greater than 0.01%.
While the first four factors can be compensated for mathematically, it's the local geology which produces random gravity anomalies of the kind mapped here.
This is a Bouguer gravity anomaly map, showing gravity variations resulting from lateral density variations in the earth. It looks like a relief map of invisible elevations and imperceptible depressions, grouped together in plateaus and peaks of higher-than-average pull and valleys and troughs of lower-than-average gravity.
Of course, gravity anomalies are not exclusive to Illinois, Indiana and Ohio. Here's a gravity anomaly map of the entire earth, in two hemispheres.
The Bouguer (pronounced boo-gay) gravity anomaly is named after French scientist Pierre Bouguer (1698-1758), a prodigy who succeeded his father as professor of hydrography at the tender age of 16. Among his many discoveries was the fact that small regional variations in the earth's gravity field could be related to the varying density of subterraneous rocks in the subsurface.
The values on this map are expressed in milligals, 1/1000th of a Gal (short for Galileo), which is the unity of gravity, equal to 1 cm/sec2. Positive anomalies (i.e. greater density than average) occur in areas colored red. Negative anomalies (less density than average) are found in areas colored blue.
It looks like Newton's apples weigh a bit more in southern Illinois than they do on average, and a bit less in central Indiana and large parts of Ohio. While these anomalies may only account for variations in decimal points, the difference is big enough to have measurable effects: these gravitational anomalies cause the sea to bulge in certain places, and throw pendulum clocks out of sync.
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A recent study on monkeys found that stimulating a certain part of the forebrain wakes monkeys from anesthesia.
- Scientists electrically stimulated the brains of macaque monkeys in an effort to determine which areas are responsible for driving consciousness.
- The monkeys were anesthetized, and the goal was to see whether activating certain parts of the brain would wake up the animals.
- The forebrain's central lateral thalamus seems to be one of the "minimum mechanisms" necessary for consciousness.
Pixabay<p>When the team electrically stimulated a part of the brain called the central lateral thalamus, located in the forebrain, the monkeys woke up: they opened their eyes, blinked, reached out, made facial expressions and showed altered vital signs. </p><p>"We found that when we stimulated this tiny little brain area, we could wake the animals up and reinstate all the neural activity that you'd normally see in the cortex during wakefulness," Saalmann told Cell Press. "They acted just as they would if they were awake. When we switched off the stimulation, the animals went straight back to being unconscious."</p><p>This area of the brain may function as an "engine for consciousness," Redinbaugh told Inverse. Although past studies have shown that electrical stimulation can arouse the brains of humans and animals, the new findings are unique because they reveal which specific neural interactions appear to be minimally necessary for consciousness.</p><p>"Science doesn't often leave opportunity for exhilaration, but that's what that moment was like for those of us who were in the room," Redinbaugh told <a href="https://www.inverse.com/science/first-squid-mri-study-brain-complexity-similar-dogs" target="_blank"><em>Inverse</em></a><em>.</em></p>
Future applications<p>The team said the findings could have many applications down the road, but more research is needed.</p><p>"The overriding motivation of this research is to help people with disorders of consciousness to live better lives," Redinbaugh told Cell Press. "We have to start by understanding the minimum mechanism that is necessary or sufficient for consciousness, so that the correct part of the brain can be targeted clinically."</p><p>"It's possible we may be able to use these kinds of deep-brain stimulating electrodes to bring people out of comas. Our findings may also be useful for developing new ways to monitor patients under clinical anesthesia, to make sure they are safely unconscious."</p>
The coronavirus pandemic has brought out the perception of selfishness among many.
- Selfish behavior has been analyzed by philosophers and psychologists for centuries.
- New research shows people may be wired for altruistic behavior and get more benefits from it.
- Crisis times tend to increase self-centered acts.
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