Physics in Action by Topic

Space & the Universe

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Memory, Thermodynamics, and Time

New strides in explaining the arrow of time


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The Dawn of the Tetraquark

A new particle discovery requires some rethinking in particle physics


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First Detection of Elusive Gravitational Waves Explained

One of the biggest discoveries in decades.


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Whirling Skirts Reveal Steady Patterns

An unexpected application of the Coriolis effect


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Pluto's Neighbor Could Float on Water

A Kuiper Belt object less dense than water has piqued scientists' interest


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A Spin on Doppler

A twist on this physics principle can detect rotation in tornadoes, planets and more


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The Monkey and the Hunter

Test your knowledge of gravity with this thought experiment.


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There and Back Again: An Asteroid's Tale

Scientists analyze asteroid dust retrieved by spacecraft


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Galactic Cannibalism

The Andromeda Galaxy, is one of the most distant objects that can be seen with the naked eye and it's on a collision course with our home galaxy, the Milky Way.


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Diamond planets are a girl’s best friend

What's better than a diamond engagement ring? An entire planet made of diamonds!


The first six flight ready James Webb Space Telescope's primary mirror segments are prepped to begin final cryogenic testing at NASA's Marshall Space Flight Center in Huntsville, Ala.

A Mirror Built for Space

How do you design a mirror with a diameter of 6.5 meters that can survive a rocket launch into space, orbit the Earth at a radius of about one million miles for 5-10 years, and hold its shape at temperatures near -220˚C? And why would you want to?


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Landing on Mars

When NASA’s next generation rover Curiosity reaches the red planet next summer, it will rely on an array of new technologies to slow itself down as it enters Mars’ gravity, survive the intense heat of falling through the atmosphere and then be dropped onto the surface by a futuristic floating “Sky Crane.” Any one error could easily result in a loss of the spacecraft, which represents $2 billion in taxpayer funds and years of hard work.


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Imaging the Invisible: The Dark Energy Camera

The average digital camera is great for taking embarrassing pictures of friends and capturing a couple’s first kiss, but taking pictures of really faint galaxies that are millions of light years away requires some serious modifications or the Dark Energy Camera.


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Galaxy Demographics

As observation techniques of distant objects advance, so does our knowledge about the universe. One recent observational study led by Pieter van Dokkum (Yale) and Charlie Conroy (Harvard-Smithsonian Center for Astrophysics) indicates that there may be three times as many stars as previously thought!


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Physics of Colonizing Space

Our planet has long sheltered humanity from the harsh climates of outer space. The Earth's electromagnetic field protects us from a barrage of harmful particles and its atmosphere allows us to breathe freely while destroying small inbound space rocks.


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Infrared Light

What do night vision goggles, land mine detectors, and studies of the universe have in common? In some way, all of them are connected to a small range of light sandwiched between visible light and microwaves on the electromagnetic spectrum—infrared light.


Artist's rendition of Centaur upper stage rocket approaching the moon with the Lunar CRater Observation and Sensing Satellite (LCROSS), 'shepherding satellite,' attached

Finding Water on the Moon

How do you find water that is frozen beneath the surface of the moon? Send a high-speed satellite to plunge into the lunar surface like a man-made meteor and then examine the debris. When it comes to finding water in an extraterrestrial desert, NASA doesn’t mess around.


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Dark Matter

In 2006, an investigation of the Bullet cluster, which is composed of two colliding clusters of galaxies, provided important evidence for the existence of dark matter.


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Planet Pluto Goes Poof

Pluto—now reclassified as a "dwarf planet"—was discovered after American astronomer Percival Lowell predicted that a "Planet X" was perturbing the orbits of Uranus and Neptune.


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Our Very Own Black Hole

The Milky Way is a vast spiral, similar to our neighbor the Andromeda galaxy.


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Neutrino Astrophysics

Very large stars can end their lives in a cataclysmic explosion called a supernova. The photographs show a supernova in the Large Magellanic Cloud, a satellite galaxy of the Milky Way located only about 160,000 light years away.


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Space Weather

How's the space weather today? Quiet enough for a safe trip to the moon? Quiet enough to operate your GPS navigation system accurately? So active that it would crash your power grid? Like our everyday weather, space weather can change suddenly, become violent, and interfere with our lives.


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Old as the M4 Planet

In the universe, we may or may not be alone, but at least there seem to be plenty of planets. Over the last decade, extra-solar planet-finding has become a growth industry, with some 100 already identified by their effect on the motion of their central star.


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Hubble Goes Deep

As residents of the Milky Way galaxy, we live in a huge spiral system of about 10 11 stars.


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Far Out Planets

Are we alone in the universe? To begin to answer this question, we could first ask if Earth is unique in the universe.


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Fluids in Space

We have all seen images, such as the one at the right, of astronauts floating inside a spacecraft. If these astronauts used a spring scale to weigh themselves, they would detect no weight at all. Does no weight mean no gravity?


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GRACE Under Fire

Remote and beautiful, Antarctica is covered by an ice sheet averaging several kilometers in thickness that locks up some 70% of Earth’s fresh water—if it all melted, the oceans would rise about 70 meters.


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The Little Constant that Couldn't?

Physicists measure the values of basic quantities like the speed of light and the charge of the electron. Cosmologists use the results in studies of the origin of the universe, some 12 billion years ago, and they assume the numbers have not changed over this time.


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Catch a Cosmic Microwave

A trio of recent findings on cosmic microwave background radiation lends strong support to the idea that the entire observable universe was once smaller than an atom and underwent a "super-charged" Big Bang.


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Deep Impact

Comets are relics from the origin of the solar system, carrying material about 4.5 billion years old.


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Waving Back

Of the forces in nature, gravity is by far the weakest.


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What the WMAP!

Cosmology is one of the great success stories of contemporary physics. A few investigators began theorizing about the history of the universe in the 1940s, but there was precious little observational evidence to work with.


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Big 'G'

In 1665, Isaac Newton recognized that all matter attracts all other matter, but he also recognized that the gravitational attraction of everyday objects for each other was far too small to be measured in his time.


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Gravitational Waves

In our everyday world, we observe all sorts of waves, including sound waves, water waves, and radio waves. But what about gravitational waves?


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Black Holes

A star exists in a delicate balance between the crushing force of gravity, on the one hand, and the push of incredibly hot gases on the other.


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Solar Flares

You may have seen the “northern lights” in the fall of 2003, even if you live as far south as Texas or Italy.


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Nuclei Knockdown

At RHIC--the Relativistic Heavy Ion Collider, located at the Brookhaven National Laboratory in New York--gold nuclei traveling at nearly the speed of light smash into each other, destroying themselves and producing a spray of other particles.


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You are My Shining Star

To a star, size matters. The more massive the star, the higher the pressure and temperature in its core, the brighter it shines, and the sooner it exhausts the hydrogen fuel supply for its fusion reactions.


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An Especially Elegant Universe

Joe McMaster, producer, director, and writer of Nova's The Elegant Universe, is not a physicist. Fortunately, he had the patient help of the show's star and narrator, physicist Brian Greene, as he put together the PBS production delving into String Theory.


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Saturn's Rings

Saturn’s rings have posed a big challenge ever since Galileo first laid eyes on them in 1610 through his 20-power telescope.


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AMANDA, Light of my Ice...

An underwater telescope called AMANDA, frozen deep in Antarctic ice, peers down at ghostly neutrinos that pass through Earth from above the Northern Hemisphere.