Ice Cave

Two weeks ago, my friend Alex and I decided to go snowshoeing at Castner Glacier. The goal was to spend some time outside in the wonderful spring weather and, if we could, find a way inside the glacier.

The parking area is just a wide bit of gravel shoulder where the Richardson Highway crosses Castner Creek. It's not marked, so you have to know this is the place to stop, and start walking upstream. Or, what would be upstream if the creek wasn't under 10 feet of snow and ice. I was here in summer and it was difficult going, you have to push for a bit through thick alders, which seems sketchy so you constantly yell and clap so you don't surprise any nearby bears. It's much easier this time of year as you can walk in the flat wide open of the creek itself. After about 1.5 miles of that, you come to a steep hill. Looking back from the top:



At this point, you're actually standing on Castner glacier: the hill is the terminus. This isn't entirely obvious in any season - even when there isn't a layer of snow, this part of the glacier is covered by a layer of rocks and even plants from upstream. But there are clues, such as this 20 foot ice wall sticking out of nowhere:



I was here last spring and found a cave entrance right at the base of the glacier's foot here, but now it is completely buried under the snow and I couldn't even tell where to start digging. So Alex and I decided to go further up-glacier to see what else we could find:



Up to the top of the terminus, there was a nice packed trail for us to follow, but going further required us to break new trail as no one had been out there. We came to the top of the next hill and found a large collapsed cave entrance in the valley below us. The gaps between the ice blocks looked possibly big enough to squeeze through, but there was no easy way down there, so we followed a set of animal tracks up a ridge line to the next hill:



There, we found another entrance, this time easy to get to:



Stepping inside:





This was a surprisingly large cavern - see the picture at the top of this post, which has me standing in it (did you miss that?), for scale. The cave continued back around a corner, and we could see a hint of light coming from back in the depths somewhere: Probably the other, collapsed entrance we saw earlier. Alex walked a bit down the corridor with a flash and I took a picture of the entrance lit by natural light and the passage lit by flash:



It was starting to get late out, and we had a ~3 mile slog through snow to get back to the car (finding a new route rather than going back over the top where we came from). So, time to go:



Back outside, the Sun was already set in our little valley, though it still lit the mountains nearby:



There was a bright aurora in the sky for the entire drive home.

Worlds: Mars, Saturn

It's time to finish off the March tour of other worlds you can see with just your eyeballs. Last time was Venus and Jupiter. This time it's Mars and Saturn. Together with Mercury, those are the five 'wandering stars' known to the ancient world.

Mars first. It's visible basically all night right now, and you can find it with a sky map. Perhaps the easiest thing to do is look outside at midnight, when Mars will be pretty much due south. Mars will be conspicuous as one of the brightest 'stars' in the south, with a distinctive reddish color - Mars is named for the Roman god of war. The red color is due to a dusty surface, and though Mars is dry and cold today, large amounts of liquid water may have once existed on its surface. It has weather, too - this picture of 'tornadoes on Mars' recently made the rounds on the internet:


Huge source.

That was taken by the University of Arizona's HiRISE imager in orbit over Mars. It produces some really incredible images, like this impact crater:


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Huge source.

Or this one:


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Huge source.

Or these sand dunes:


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Huge source.

Hint: The images above have been massively downsized to display properly here, HiRISE is a very high resolution imager, click the 'source' link below any of the above pictures for a big version, or the 'huge source' for a ridiculously large version you can zoom in on. It's worth it.

HiRISE has an image gallery of over 21,000 images like these, you can find it here. If you have your red-cyan 3D glasses*, you can find 3D images of Mars from orbit (HiRISE) here, and from the ground (Spirit and Opportunity rovers) here and here.

*You don't have red-cyan glasses? I told you, they're free.

On to Saturn:


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You can find Saturn just east of Mars, right next to the bright star Spica. Here's a screenshot from Stellarium (you should download Stellarium if you like astronomy, it's free) to show how to find Saturn. Click for bigger:



Saturn's most obvious feature is those lovely rings, made primarily of dust. If you have a very nice pair of binoculars (you need about 25x magnification) and good eyes, you may be able to make them out, but most likely you'll need a small telescope. The good news is it doesn't need to be anything fancy, just about any small telescope will do. It's one of the most surreal things you can see in the night sky. I highly recommend it, A++, would look at again.


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That's the Moon in the foreground with Saturn peeking out behind. That's about what you can expect Saturn to look like through a typical consumer telescope. If you were in a space ship, you could get a much closer view, like this one from Cassini:


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Taken with the Sun hidden behind Saturn, so the planet is seen in silhouette and the rings are lit up by the sunlight passing through. Notice the bright dot just above and to the left of the bright inner rings - that's Earth.

And because we're all about auroras here, this is a shot of an aurora on Saturn:


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And that wraps up the tour of the naked eye worlds. Except... don't forget the Moon! It's so obvious it's easy to take for granted, but even with a basic pair of binoculars, it's really something else:


Huge source.

Same deal as above, click the 'huge source' button and zoom in.

Look what I can do!

I balanced a broom. I got a text message on March 9 that said: "Something is making brooms balance by themselves. It has to be gravity or magnetic pull." Attached were these two pictures:



I've never heard of balancing brooms, and my first thought was 'What?'



So I googled it, and found several 'explanations', which were mostly variants of:

1. Gravitational pull due to either the equinox or an alignment of planets.
2. Something nondescript having to do with solar flare activity and/or the planet's magnetic field.

Both of those sound like nonsense. I mean, why brooms? Why not shovels? The fact that it's only brooms people are balancing tells me the explanation should have something to do with the broom rather than being external to the broom.

I must admit, it looks really wrong for the broom to be standing there all leaned over like that. Before we go on with the broom, let me propose something else to think about:



That's my reading light on its charging stand. It also leans quite a ways over past the base, but it doesn't seem out of the ordinary. Just looking at it, it's intuitive that all the weight is down in the base, and it doesn't seem weird for it to stand up like that. The physics is, if you have an object, no matter if some of it leans out quite a way, as long as the center of mass is still over the base, it stands up.

Back to the broom. The broom is really long, but all the weight is down by the brushy end, the rest is just a hollow plastic tube. We can figure out where the center of mass is by using this simple trick:



If you like people sliding their hands under a ruler set to piano music, here's a longer video. At the end, they unbalance the ruler by taping washers to one end, to show that fingers still meet at the center of mass, even when the center of mass is no longer at the middle.



So I did that, attached a tag where the center of mass is on my broom, and stood it up again:



And what do you know, the center of mass is completely over the base of the broom. So this is really no more strange or mysterious than my reading light standing up - the problem isn't that the broom stands up, the problem is that we think it shouldn't. It's like that thing they tell you in elementary school about how you can balance an egg standing up on the equinox. That's true, but only because you can balance an egg on any day of the year if you're careful enough. The equinox doesn't have anything to do with it.

For the broom, an additional effect comes from the fact that the broom is standing on bristles, which are basically little springs. For it to tip to either side, the bristles on that side have to compress, and their springiness helps push the broom back upright. It's a small push, but it probably accounts for people's reports that they can 'feel' some force trying to make the broom stand up. So not only does a broom balance, but it has a small restoring force to make it more stable.

I left the broom standing almost an hour ago; it's still there. It's just not that hard to balance a broom.

Remind me in a month, when we're away from the equinox and any kind of planetary alignment, and I'll do it again.

Winter Wrap Up Day

Tomorrow is the spring equinox, which is when day and night are equally long. After tomorrow, the day will be longer than the night (in the northern hemisphere).

This is because of the way the Earth is tilted with respect to the Sun: As the Earth goes around the Sun, it ends up with the north pole either tilted towards or away from the Sun. On the summer solstice, the north pole is tilted as far towards the Sun as it can be, and so the northern hemisphere gets pretty direct sunlight and the longest day of the year, which warms things up and we have summer. At the winter solstice, the north pole is tilted as far away from the Sun it can be, so we get indirect sunlight and the shorted day of the year; things cool off - winter. Note that the opposite is true in the southern hemisphere: The south pole is tilted away from the Sun while the north pole is tilted towards, so southern hemisphere winter is during northern hemisphere summer.

In between the solstices we have the equinoxes, when the Earth is tilted neither toward nor away from the Sun. The spring (vernal) equinox is when the days are getting longer and the fall (autumnal) equinox is when the days are getting shorter.


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Tomorrow, on the spring equinox, the Sun will rise (more or less) due east and set due west, and it will be up (more or less) the same amount of time as it's down. I say more or less because there's atmospheric lensing effects, but it doesn't make much difference.

The seasons are defined like this:
Spring - day is longer than night, and days are getting longer
Summer - day is longer than night, but days are getting shorter
Autumn - night is longer than day, and nights are getting longer
Winter - night is longer than day, but nights are getting shorter

So autumn and winter are the dark nighttime seasons, and spring and summer are the bright daytime seasons. Each season is 3 months long. Works for me.

Ah, and since tomorrow is the first day of spring, that makes today Winter Wrap Up Day! Have a video:

Worlds: Venus and Jupiter

In the first installment last Friday, I told you to start with Mercury because it would be gone soon. Did you see it? I didn't :(. If not, you're not alone. Many people who have lots of experience with the night sky (myself included) have never seen it. Heck, I TA'd astronomy labs and worked in an observatory for years! I asked a few of my physicist-buddies these past few days if they've seen it, and no one could give me an unambiguous 'yes'. So don't be too discouraged, that was a tough one.

This time will be super easy. Go outside pretty much any time after dark but before midnight and look to the west. Venus is the brightest 'star' over there, and Jupiter is the second brightest 'star', right next to Venus. The easiest is about 30 minutes to an hour after sunset, when the sky is still blue. Venus and Jupiter will show up before any other stars are visible. Again, no telescope necessary, just use your eyeballs. Here's some pictures I took which show you what to expect:



Later on:



That second photo was used in this Huffington Post UK article about the conjunction. That's what you call it when two or more astronomical objects get close together in the sky - a conjunction. The two planets were closest together Monday night and will be very close all week, so now's the time. But check again on the 25th: They'll be noticeably further apart, but the crescent Moon will be right between them, so that's cool too.

Venus' most notable feature is its thick atmosphere: The surface pressure is about 93 times higher than Earth. All that gas in the atmosphere came from geologic activity, i.e. volcanoes. Venus has 167 volcanoes more than 100km across. Earth only has one that size: Hawaii. It's size and mass are similar to Earth. The surface temperature is around 800ºF, thanks to a runaway greenhouse effect due to carbon dioxide in the atmosphere. Yes, the very same greenhouse effect responsible for climate change here on Earth.


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Jupiter, on the other hand, is huge: 1300 times the size of Earth and 300 times the mass. But it's much further away than Venus, so it looks smaller and dimmer in the sky. It has rings, like Saturn, but much thinner and fainter.


Source - Cassini satellite


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So I said you could see these with the naked eye, where they look like bright stars. But do you happen to have a nice pair of binoculars or a small telescope around? If so, break them out and use them here. You'll see something like this:


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That's what Jupiter looks like through a pair of binoculars. Notice the bright dots to the side? Keep track of them for a while, and you'll notice something interesting happening:



Those are moons! Going around Jupiter!

Now hold on a minute, Galileo. This is crazy. Let's move those binoculars over to Venus for a little while, and see what we can see there:



Wha... it's not round. It has phases, going from crescent to full, just like Earth's moon.

Well congratulations Galileo, you just discovered the two key bits of evidence that the solar system is centered on the Sun, not the Earth. Galileo, seriously. He was the first person to make these observations through a telescope, and used them as support for Copernicus' heliocentric model. The heliocentric model is a major step in the history of human thought - The universe does not revolve around us. 400 years later, we're still trying to come to grips with that. Back then, the Catholic Church threatened Galileo with torture and execution for telling people he saw this.

Today's telescopes, even amateur ones, are much, much nicer than what Galileo used. With the right combination of equipment and experience, you can take a picture like this from your back yard:


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And of course we have spacecraft that can go out there and take pictures up close. Here's a view of Jupiter's moon Io in front of Jupiter. Colors are different because it's infrared:


Source - New Horizons spacecraft.

Io is volcanically active, and if you zoom in you can see a red spot on the top of it (a volcano erupting!) with a blue cloud above (the plume from the eruption!). Wow!

Here's the other three Galilean moons. Images are from... I don't know. I'd guess Voyager or Galileo (the spacecraft, not the guy). They are all worlds of their own.

Europa:



Ganymede:



Callisto:



Now that you know what you're looking at, get out and see Jupiter and Venus this week. No equipment is needed to see the planets, but bring a pair of binoculars or a telescope and you might see some of the most important sights in human history.

Sunspot 1429 is still acting up.

Sunspot 1429 is large enough to see without a telescope. Try looking at the Sun through a welding mask, if it's still too small you can put the welding mask in front of a pari of binoculars, just be careful. If you don't have a mask, it's safe to look at the Sun directly (even with binoculars) in the last minute or so as it sets. Or, if there's thick enough fog or dust around, that can work too. These shots were taken through a cloud of dust. Credit for both of these photos to David Tremblay.



So I wrote Tuesday about an X5 flare from this sunspot, following an X1 flare a few days prior. Both of those were pointed slightly away from Earth so we only received a glancing blow from their CME's, but it was enough to spark a geomagnetic storm both times. The CME from the X5 flare arrived last night and apparently made quite an aurora show, but sadly it was cloudy in and around Fairbanks.

1429 produced an M6 class flare (M-class is just below X-class) late Thursday night, and this time it was pointed almost directly toward Earth. That CME should arrive tonight, and the sky is clear right now, so this might be a good night. It caused a plasma-tsunami on the Sun, around 100,000km (60,000 miles) high and moving at 250 km/s (half a million miles per hour). The Sun is a crazy place...

This morning the sunspot produced another flare, an M8 class, also pointed at Earth, and we should expect that one to arrive on Monday. Here's an animated forecast track, in the left-hand panel watch the big blog fly out to the right and hit Earth (the yellow dot).



Spring break auroras!

Worlds: Mercury

If you think of Earth as home, then they're our next door neighbors. If you rather like to think of Earth as whizzing around the galaxy (at half a million miles per hour!), then they're our fellow travelers. Either way, this month is one of the best in years for viewing the other planets in our solar system. All five planets known to the ancients - Mercury, Venus, Mars, Jupiter, and Saturn - are visible in the sky this month, and you don't even need a telescope. All but Saturn and Mercury are easy to find just by going out at the right time and looking up in the right spot. And so I'm going to try to spot them all this month: You should give it a shot, too. Priority one is Mercury.


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Taken by Mariner 10 in 1974. Until the 2008 visit from Messenger, only half of Mercury had ever been seen.

Mercury stays close to the Sun, so it's only visible when the Sun is far enough below the horizon that it's kind of dark, but not so far that Mercury is also below the horizon. This means you can theoretically see Mercury from about 30 minutes after sunset to about an hour and a half after sunset, but 30 minutes after sunset the sky is still too bright unless you know exactly where to look, and an hour and a half after sunset Mercury is so low on the horizon to be obscured by hills or trees. Realistically, you have about a 15 minute window about an hour after sunset. Get somewhere with as clear a view to the west as you can find, and look low, where the Sun was just before it set. Since all the planets are in the ecliptic plane, you can use Jupiter and Venus to help: They'll be the brightest looking 'stars' on that side of the sky, fairly close together. If you were to draw a line between them and extend it toward the horizon, they point to Mercury. Like this:


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Mercury is going to be hard to find: I've never seen it myself. How the heck did ancient astronomers find this thing in the first place? A good pair of binoculars should make things easier. All you can do is try.

The window of opportunity ends in a few days, then Mercury will be below the horizon before it gets dark enough to see, so make this planet the first priority or you'll miss your chance.

Happily, all the other planets will be much easier to find, and the window of opportunity is longer, so I'll save those for another night. Get after Mercury ASAP.

The fun has been doubled!

And I just posted about a solar flare. That one was an X1 class. Today, the same sunspot blasted out an even more powerful X5 class flare. Video:



I like the ripples across the Sun's surface. This one is large enough to possibly cause some trouble with communication satellites. Hope for clear skies around the 8th and 9th.

Random space-related stuff

From out in the tubes.

1. A stereographic image of the Sun:


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Click for larger.

Put on your red/cyan glasses and check it out. Don't have red/cyan glasses? You can get a free pair here, and you should probably go ahead and do that, because there's lots of neat stereoscopic stuff on the web, and I'm going to try making my own at some point, so it'll come up here again.

2. A time lapse filmed from the space station:



The smooth, ruddy green glow over the horizon is airglow, which is light emitted due to chemistry in the atmosphere. This is different from auroras, and happens all over the world, but is usually too dim to see with the eye. After about 1:20 there's auroras in the shot too, and the difference is obvious. There are pulsating patches directly below at 1:44.

This water is too damn cold!

I really only like to drink very cold water. Like 75% a block of ice, and you drink the slushy stuff it's floating in. So I've gotten in the habit of setting a water bottle just outside the front door for a while so it gets really cold. Last night, I left one outside too long, and it froze so solid it split a seam down the middle of the aluminum water bottle:



I guess 6 hours at -12ºF was a bit overkill.

Today, the Sun exploded

Here's the video:



This solar flare came from a very active sunspot that's just rotated around to our side of the Sun. Sunspots look like dark spots on the Sun, they're areas of increased magnetic activity which keeps the hot material from rising to the surface, so it's cooler than the surrounding areas. Here's a picture of the sunspots on the Sun right now, the one labeled 1429 is our culprit. Note it's about 4 times larger than the Earth (see the scale at the bottom right).



The magnetic field lines coming out of a sunspot are shaped like long tubes, called flux tubes, and they're connected back to another sunspot. As the Sun rotates, the tubes connecting a pair of sunspots gets twisted up, storing magnetic energy in the twist. Eventually, they twist up so much they 'break' - the field lines reorganize to a less twisted shape, and the stored up magnetic energy is released. There is a sudden brightening as the energy is released - a solar flare - and big clouds of plasma can be thrown off into space - a Coronal Mass Ejection, or CME. Sometimes, those clouds of material get thrown in the direction of Earth, and this happens.

The flare above wasn't directed at Earth, but it was close enough that we'll receive a glancing blow from it. It's expected to hit on Tuesday or Wednesday. The thing is, the same sunspot spit out a flare on Sunday that's also expected to arrive on Tuesday. We might get hit with a double whammy here! I'm hoping for clear skies, maybe we'll get a good show.

Sunspot 1429 is producing multiple strong flares and currently rotating to face Earth, so we should expect more excitement over the next two weeks or so.