Tag: magnetic fields

The 50th anniversary of Starfish Prime: the nuke that shook the world

By Phil Plait | July 9, 2012 6:05 am

On July 9, 1962 — 50 years ago today — the United States detonated a nuclear weapon high above the Pacific Ocean. Designated Starfish Prime, it was part of a dangerous series of high-altitude nuclear bomb tests at the height of the Cold War. Its immediate effects were felt for thousands of kilometers, but it would also have a far-reaching aftermath that still touches us today.

In 1958, the Soviet Union called for a ban on atmospheric tests of nuclear weapons, and went so far as to unilaterally stop such testing. Under external political pressure, the US acquiesced. However, in late 1961 political pressures internal to the USSR forced Khrushchev to break the moratorium, and the Soviets began testing once again. So, again under pressure, the US responded with tests of their own.

It was a scary time to live in.

The US, worried that a Soviet nuclear bomb detonated in space could damage or destroy US intercontinental missiles, set up a series of high-altitude weapons tests called Project Fishbowl (itself part of the larger Operation Dominic) to find out for themselves what happens when nuclear weapons are detonated in space. High-altitude tests had been done before, but they were hastily set up and the results inconclusive. Fishbowl was created to take a more rigorous scientific approach.

Boom! Goes the dynamite

On July 9, 1962, the US launched a Thor missile from Johnston island, an atoll about 1500 kilometers (900 miles) southwest of Hawaii. The missile arced up to a height of over 1100 km (660 miles), then came back down. At the preprogrammed height of 400 km (240 miles), just seconds after 09:00 UTC, the 1.4 megaton nuclear warhead detonated.

And all hell broke loose.

1.4 megatons is the equivalent of 1.4 million tons of TNT exploding. However, nuclear weapons are fundamentally different from simple chemical explosives. TNT releases its energy in the form of heat and light. Nukes also generate heat and light, plus vast amounts of X-rays and gamma rays – high-energy forms of light – as well as subatomic particles like electrons and heavy ions.

When Starfish prime exploded, the effects were devastating. Here’s a video showing actual footage from the test, 50 years ago today:

As you can see, the explosion was roughly spherical; the shock wave expanding in all directions roughly equally since there is essentially no atmosphere at that height. Another video has many more views of the test; I’ve linked it directly to those sequences, but if you start at the beginning it’s actually an hour-long documentary on the test.

Nuke ‘em ’til they glow

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Mesmerizing visualization of a geomagnetic storm

By Phil Plait | December 7, 2011 12:00 pm

When the Sun belches out an eructation of subatomic particles, they can travel across the solar system and interact with the Earth’s magnetic field. This can make our field ring like a bell, shaking the particles trapped within, and generating electromagnetic noise and signals across the radio spectrum. The CARISMA radio array can detect these emissions and learn about how the Sun’s and Earth’s fields interact.

That’s the science. But there’s art here, too: the Lighthouse agency commissioned artists to create digital artwork based on science, and one group, Semiconductor, used the CARISMA data to do so. Based on the data, they translated the radio waves (which are like the light we see, but less energetic) and converted them to sound. This has been done many times before, but what’s cool is that they then created an animation based on the converted sounds, an astonishing and odd and mesmerizing animation. Watch:

How wild is that? It reminds me of the movie "Forbidden Planet". The vibrating patterns are wonderful, and while I’m not sure how much scientific insight can be gained from them, the aesthetics are riveting. And I can hope the underlying purpose of this will be seen: to show that science is beauty, science is art, and that if this gets someone who might not otherwise be interested to poke a little further into it, then mission accomplished.

Related posts:

- Cosmically creepy chords
- Listen in on the Perseid meteor shower
- Saturn, the forbidden planet
- Phoenix sings

CATEGORIZED UNDER: Cool stuff, Geekery, Science

Summer solstice 2011

By Phil Plait | June 21, 2011 6:30 am

Today, June 21, 2001, at 17:16 UTC (1:16 p.m. Eastern US time), the Sun will reach its peak in its northward travels this year. This moment is the summer solstice — I describe this in detail in an earlier post. Technically, that article is for the winter solstice, but the idea’s the same. Just replace "winter" with "summer" and "December" with "June" and "south" with "north". That should be clear enough. It might be easier just to multiply the entire article by -1. Or stand on your head.

Since for the majority of people on the planet this day marks the start (or more commonly the midpoint) of summer, enjoy the gallery below that shows our nearest star doing what it does best: giving us light, giving us beauty, and sometimes, blowing its top.

Use the thumbnails and arrows to browse, and click on the images to go through to blog posts with more details and descriptions.


CATEGORIZED UNDER: Astronomy, Pretty pictures

Followup: Sunspot group's loopy magnetism

By Phil Plait | April 20, 2011 7:00 am

Yesterday I posted a video showing a cluster of sunspots forming on the Sun’s surface. As it happens, a new video was released last night from NASA’s Solar Dynamics Observatory satellite showing this same sunspot group, but this time, along with the visible light images, we also get X-ray images. X-rays are emitted by plasma trapped in magnetic fields, so in a sense you can actually see the magnetism of the sunspots as they evolve. Watch!

How awesome is that? The full disk picture on the left combines visible and X-ray light, the lower right shows the spots in just visible light, and the upper right is just X-rays. You can see the magnetic field lines looping from one part of the sunspot cluster to another as the plasma follows them. If you look carefully, you’ll see flashes of brightness, too: those are solar flares!

The magnetic field stores energy. If the loops get tangled together, they can snap and release their energy in one sudden burst (like a box full of mousetraps, if you happened to see my episode of "Bad Universe" on Discovery Channel yesterday). What’s interesting about this video is that it shows that the rotation of the sunspots plays into this too.

Imagine a bunch of magnetic field lines coming from a spot, going up above the Sun’s surface, then back down to another spot. If the spot is rotating, that cluster of loops will get twisted up, just like a rubber band gets twisted when you rotate one end (do you kids these days still play with balsa wood airplanes that use a rubber band to spin the propeller? It’s just like that).

If the loops get too twisted, they’ll snap, too, and kablam! Solar flare. Remember, this was the biggest flare seen in several years, so apparently having several rotating spots feeding into the system really pumps a lot of energy into the loops. That makes sense, and it means that clusters of spots may be the ones we should keep our eyes on if we want to catch big flares in the act.

Video credit: Movie produced by D. Brown (UCLan). Data courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.

Related posts:

- The birth of a sunspot cluster
- Incredible solar flare video
- Sunlight and a spot of calcium
- One solar piece of flare

No, a pole shift won't cause global superstorms

By Phil Plait | February 9, 2011 6:30 am

[Note: I may have to start a series of "No, a blank won't blank" posts; there's been a spate of nonsensical doomsday pseudoscience lately. Sigh.]

So the latest doomsday fearmongering I’m hearing about are global superstorms caused by dangerous shifts in the Earth’s magnetic field. Maybe you’ve heard: the Earth’s magnetic field is wandering around, and may be about to reverse. When this happens, incoming radiation will affect our weather, causing gigantic storms the likes of which have never been seen except in Hollywood movies.

Panic! Death! Higher gas prices! Cats and dogs, living together!

Yeah, right. I’ll be up front right away: this claim is baloney. Garbage. Nonsense.

The article in question is pretty long, and as usual debunking something takes more time and effort than it does to simply say wrong things. So for the TL;DR (too long; didn’t read) crowd: the article makes basic science errors, attempts to link totally unrelated phenomena, states things as facts that are pure conjecture, and generally gets almost everything wrong. Bottom line: his claim of a link between the Earth’s magnetic field and superstorms is totally wrong.

OK, so you want details? I got details.

The source

As far as I can tell, the source for this silly claim is an article titled "Magnetic Polar Shifts Causing Massive Global Superstorms", first seen online at helium.com, but also reprinted widely (I’m getting lots of emails from people who read it at the Oregon Salem-Online site). The author, Terrence Aym, wrote at least one breathlessly overblown and grossly inaccurate doomsday article without doing the necessary basic research; that one was about Apophis hitting the Earth in 2036 — and you know how I feel about that sort of thing.

This one is more of the same. Aym makes scientific claims that are completely unfounded in reality, and sometimes says things that are simply dead wrong.

For example, some of the basic science Aym claims is way off:

Worse, what shields the planet from cancer-causing radiation is the magnetic field. It acts as a shield deflecting harmful ultra-violet, X-rays and other life-threatening radiation from bathing the surface of the Earth. With the field weakening and cracks emerging, the death rate from cancer could skyrocket and mutations of DNA can become rampant.

Bzzzzt! Nope. The Earth’s magnetic field protects us from charged particles like fast electrons and protons in the solar wind. If we didn’t have a magnetic field the Earth’s air would stop these particles anyway. The radiation he’s talking about — UV and X-rays — are totally unaffected by magnetic fields. That type of radiation is also absorbed by the air (including the ozone layer). Ironically, I will note that without the magnetic field protecting us, subatomic particles in the solar wind could erode the ozone layer, causing an increase in skin cancer rates from UV, but Aym doesn’t say anything about the ozone layer. And it takes X-rays to affect DNA [UPDATE: I've been made aware that some forms of UV light can affect DNA], which can’t get through our air no matter what. So that last statement of his is still wrong.

When something as basic as that is wrong in an article, it should make you at least a little suspicious about bigger claims. As well it should. But perhaps it’s an honest mistake. We all make ‘em, right?

But then he says this:
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