Astroquizzical: A Curious Journey Through Our Cosmic Family Tree

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What Do We Encounter Going Straight Up Out Of The Solar System?

So if our solar system is more or less flat in terms of the planetary rotations around the sun (I’m using typical pictorial depictions of the solar system), what is up and down from our solar system and galaxies? It doesn’t seem like above and below of light years in space is ever explored. Or are the (for example) constellations examples of up and down in space?
 "Draco and Ursa Minor", plate 1 in Urania's Mirror, a set of celestial cards accompanied by A familiar treatise on astronomy. Jehoshaphat Aspin,  Public domain

"Draco and Ursa Minor", plate 1 in Urania's Mirror, a set of celestial cards accompanied by A familiar treatise on astronomy. Jehoshaphat Aspin, Public domain

Originally posted on Forbes! 

The solar system is indeed pretty much a flat sheet, with the major planets all orbiting in a very thin plane surrounding the Sun. Part of the reason we don’t tend to send spacecraft in the 'up' direction, out of this thin plane, is simply that there’s not very much...

The solar system is indeed pretty much a flat sheet, with the major planets all orbiting in a very thin plane surrounding the Sun. Part of the reason we don’t tend to send spacecraft in the 'up' direction, out of this thin plane, is simply that there’s not very much there! Now, that’s not to say that there isn’t anything out that direction, but you have to travel for a while before you reach it.

Closest to the solar system, but at its outermost fringes, the orbits of the objects in the Kuiper Belt deviate from this extremely flat plane, but still tend to orbit mostly in a disk surrounding the Sun. Instead of an extremely flat plane, you have something more like an inner tube - inflated, with some vertical height to it, but still mostly lining up along the plane of the rest of the major planets. This area is where Pluto falls - its orbit is tilted out of the plane of the major planets by 17 degrees, but it’s not so far tilted out of the plane of the rest of the planets that it’s really traveling overhead the other planets.

 A drawing of the solar system shows Pluto's tilted orbit. Pluto's path is angled 17 degrees above the line, or plane, where the eight planets orbit. Pluto's orbit is more elliptical than the planets’ paths. Image credit: NASA

A drawing of the solar system shows Pluto's tilted orbit. Pluto's path is angled 17 degrees above the line, or plane, where the eight planets orbit. Pluto's orbit is more elliptical than the planets’ paths. Image credit: NASA

What you do get overhead the planets is a much more distant object, the Oort Cloud. This is a reservoir of comets, incredibly distant from the Sun, which are arranged in a roughly spherical distribution around the Sun. The objects out here are small, dimly lit chunks of ice and rock, and so far from the Sun that they are extremely difficult to observe, even with high end telescopes.

If we travel further away, and look for even more distant objects, then suddenly we run into a proliferation of stars within our own galaxy which are 'up' above the plane of our solar system. Part of this is that the galaxy is much thicker than the solar system, and so even if the plane of the galaxy and the plane of the solar system were perfectly aligned, we would see stellar neighbors of our Sun, both above and below our solar system. However, our solar system isn’t perfectly well aligned with the Milky Way galaxy- those two are off from each other by 63 degrees. What this means is that we see far more stars 'up' or 'down' out of our solar system, as we look through part of the densely populated disk of the galaxy, than we would if we were looking directly 'up' out of the plane of the galaxy.

 A star chart oriented so that the center of the image is directly perpendicular to the plane of the solar system. The constellation Draco falls in the center of the image, with the Little Dipper slightly to the right of center. Image credit: Tom Ruen, public domain

A star chart oriented so that the center of the image is directly perpendicular to the plane of the solar system. The constellation Draco falls in the center of the image, with the Little Dipper slightly to the right of center. Image credit: Tom Ruen, public domain

The constellations are a good example of things that exist 'above' our solar system. Our planet spins on an axis that’s tilted by 23 degrees relative to the plane of the solar system, so looking at the stars at the exact North Pole isn’t quite pointing us in the right direction, but it’s pretty close! If you find the North Star, Polaris, and then wander about twenty degrees (about two fists, held at arm’s length at the sky) away from the path the Moon travels, now you’re pointing 'up' out of the solar system. The constellations in this region of the sky are plentiful. This is roughly where the cup of the Little Dipper is, though exactly 'up' is in the much fainter constellation Draco (illustrated at the top of the article). The stars that hang 'above' our planet remain roughly stationary in our night skies as our planet rotates beneath them - if you’re far enough North these stars will never set.

Since the direction of 'up' away from the solar system doesn’t also point you directly out of the Galaxy, if you want to face a direction that aims you at the center of the galaxy or 'up' out of the Galaxy, you need to point yourself in a different direction.  The center of the galaxy is in the direction of the Sagittarius constellation, which looks a bit like a very pointy teapot in the sky. To point your face out of the galaxy, you must aim yourself at the lesser-known constellation Coma Berenices, which is surrounded by other constellations you’ve probably heard of - Virgo and Leo border it, as does Ursa Major (which contains the Big Dipper). If you take the last three stars in the curve of the handle of the Big Dipper, and imagine them creating a long, pointy pizza wedge, you’ve gotten pretty close to Coma Berenices. What's in that direction? Not much that's visible to the naked eye, but if you have a well-equipped telescope, you run into the Coma Cluster, a very dense collection of galaxies - an environment very unlike the galaxy our own Milky Way finds itself within. 

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What Would We See If The Moon Rotated Every 24 Hours?

If the Moon rotated as fast as the Earth, would we only see one side of the Moon?
 Framed by the Earth's horizon and airglow, the full moon floats in the blackness of space in this photo from the Expedition 10 crew on board the International Space Station. Image credit: NASA

Framed by the Earth's horizon and airglow, the full moon floats in the blackness of space in this photo from the Expedition 10 crew on board the International Space Station. Image credit: NASA

Originally posted on Forbes!

The Earth rotates around its own axis once every twenty-four hours. The Moon, on the other hand, rotates once around its own axis every 28 days, and once around the Earth in that same 28 days. The end result of this combination is that the same side of the Moon is always facing the Earth. As the Moon moves to be directly above a different portion of the earth, its face also turns at exactly the same rate, so that only one hemisphere of the Moon is ever visible from our home here.

If the Moon turned at any other rate (either faster or slower), we would eventually see all sides of the Moon, and what is currently the lunar far side would be a much more familiar sight to us. If we spun up the Moon to one rotation every 24 hours, how dramatic would this be?

I’m assuming that we’re not changing the Moon’s orbit here - so that the Moon would still orbit the Earth once every 28 days. This means that the rising and setting of the moon would happen in the same way as they do now - slightly later every day, and the phases of the moon would remain the same, because the phases are simply the combination of the Moon’s location in its orbit around the Earth, and what fraction of the near side of the Moon is illuminated by the Sun. So we would still have a new moon and a full moon about once per month. What would certainly change is which portion of the moon is illuminated.

Speeding up the Moon’s rotation so that it spins once every 24 hours is a pretty dramatic change. That means the Moon has to rotate the full 360 degrees of a circle in 24 hours, which puts us at 15 degrees of rotation every hour. That may not sound like a lot, but over the course of an evening, which we’ll say is an average of 12 hours (half of our Earth’s 24), that means that the Moon has rotated by 180 degrees. A full moon could rise with the familiar near side facing us, and by the time it sets, 12 hours later, we’d be looking at the unfamiliar jagged territory of the lunar highlands - what is currently the lunar far side. In a six hour period, you’d expect the Moon to rotate by 90 degrees. If you were in a half-moon phase, where only half of the Moon’s face is illuminated, you would expect that illuminated portion to change completely, twice over, every time the Moon rose above the horizon.

However, if the Moon truly did rotate once every 24 hours, the two sides would probably look much more similar to each other than they do now. Part of the intense cratering of the far side of the Moon is because it is constantly facing “outwards” towards space, and it’s an easier target for interplanetary fragments of rock to hit, than the somewhat protected, Earth-facing side. If the Moon rotated faster, these meteoroids would have a pretty even chance of hitting any face of the moon, and the cratering would probably be more evenly distributed.

It’s fun to think about how this kind of situation might have influenced our calendars - since our months are roughly based on the lunar cycle, perhaps we would have used the appearance or disappearance of certain features of the moon as a smaller unit of time. But we certainly wouldn’t have grown attached to one side of the Moon - what we see now as the near side would be just as normal to us as the far side.

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Astroquizzical book cover reveal!

Hello all! I have a very exciting announcement!

In conjunction with the lovely folks at Icon Books, I am pleased to unveil the cover for Astroquizzical: A curious journey through our cosmic family tree. This book is based on the content of Astroquizzical over the past few years, and will be coming out in the UK on March 8th, and in the US on June 12th! 

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How did the Earth get to be the way it is? Just like all of us, it’s a product of its ancestors.

In this enthralling cosmic journey through space and time, astrophysicist Jillian Scudder locates our home planet within its own ‘family tree’. Our parent the Earth and its sibling planets in our solar system formed within the same gas cloud. Without our grandparent the Sun, we would not exist, and the Sun in turn relies on the Milky Way as its home. The Milky Way rests in a larger web of galaxies that traces its origins right back to tiny fluctuations in the very early Universe.

Following these cosmic connections, we discover the many ties that bind us to our Universe. Based around readers’ questions from the author’s popular blog ‘Astroquizzical’, the book provides a quirky layperson’s guide to how things work in the Universe and why things are the way they are, from shooting stars on Earth, to black holes, to entire galaxies.

For anyone interested in the ‘big picture’ of how the cosmos functions and how it is all connected, Jillian Scudder is the perfect guide.

The book is available for preorder on Amazon in both the UK and the US, and if you check the Icon Books page, there are links to sources for the rest of the world (and non-Amazon options)! 

I hope you all enjoy it!

Can A Slow Shuttle Leave A Fast Ship Safely?

I am traveling in a Generational spaceship that has, over time, been accelerated to 0.4 light speed. The ship can not slow down until it nears its destination in 50 years. The ship has a small, conventionally powered shuttle craft whose top speed is 0.1 light speed. Can that shuttle leave the ship and maneuver about the ship without being left behind? I am thinking that when it leaves the ship it is moving at the same relative speed as the ship, and as long as it does not ever go below that speed, it can safely return.
 The Space Shuttle orbiter Atlantis, framed by the California mountains, as it rides on the back of one of NASA's Boeing 747 Shuttle Carrier Aircraft (SCA) en route from California to the Kennedy Space Center, Florida. Image credit: NASA

The Space Shuttle orbiter Atlantis, framed by the California mountains, as it rides on the back of one of NASA's Boeing 747 Shuttle Carrier Aircraft (SCA) en route from California to the Kennedy Space Center, Florida. Image credit: NASA

Originally posted on Forbes!

It’s easier to get your head around this scenario if we start with a much simpler version of this, moving at much slower speeds. So let’s say we have a convertible, driving at 40 miles an hour, and a passenger in that car can throw a ball at 10 miles an hour. If the passenger throws the ball straight up while the car is moving, the passenger can catch that ball when it comes back down. Someone observing this scene from the side of the road would say that the ball is moving to the side along with the car, while the passenger inside the car would tell you that the ball didn’t move horizontally relative to the car. (This means that when the ball came back down, it landed in the hands of the person throwing it, instead of hitting the front or back of the car.) Both statements are perfectly correct, and both the side of the road watcher and the passenger in the car would tell you that the ball flew upwards at 10 miles an hour, and then back down.

This kind of thought experiment illustrates an important point in physics - motion in the horizontal direction and motion in the vertical direction can be treated completely separately from each other. If I’m just interested in describing the motion of the ball up and down, that can be done regardless of what the horizontal motion of that ball is doing - any horizontal motion simply takes a vertical path up and down and stretches it out sideways.

Once we speed things up to fractions of the speed of light, the concepts of special relativity begin to apply, but this basic division of motion remains constant. Two things do change, though, and the first is that we need to be much more careful with where our watchers are when we describe what it is that they see. The other change is that the conversion from what the passenger in the convertible sees to what the person on the side of the road sees is more complex than simply remembering to add in the motion of the car.

 Flying some 500 feet behind NASA's DC-8 flying laboratory, NASA Langley's heavily instrumented HU-25 Falcon measured chemical components of the exhaust streaming from the DC-8's engines burning a 50/50 mix of conventional jet fuel and a plant-based biofuel during the 2013 ACCESS biofuels flight tests. Image credit: NASA/Lori Losey

Flying some 500 feet behind NASA's DC-8 flying laboratory, NASA Langley's heavily instrumented HU-25 Falcon measured chemical components of the exhaust streaming from the DC-8's engines burning a 50/50 mix of conventional jet fuel and a plant-based biofuel during the 2013 ACCESS biofuels flight tests. Image credit: NASA/Lori Losey

If our shuttle exits the larger spaceship, and has two rockets on it, one on each end, so that it can move at a speed of one-tenth the speed of light at a perfect 90 degrees, and then stop, and go in reverse back to the spaceship, we have effectively replicated our slower situation. A person on the spaceship would say that the shuttle isn’t moving at all horizontally (in the direction the spaceship is traveling) but is bouncing outwards and back without shifting along the spaceship from its berth. Because it’s moving at 90 degrees to the direction the spaceship is traveling, there isn’t anything that would prevent the shuttle from coming straight back to its dock on the main spaceship.

An observer on a nearby planet would see the spaceship passing by at four tenths the speed of light, and they would see a shuttle leave the main craft, appear to drift outward at an angle, and then drift back inwards, meeting back up with the main craft. That planet based observer would measure the speed of the shuttle to be higher than 0.1c, because it’s got a horizontal speed that the observer on the spaceship doesn’t see, along with its motion at a right angle to the spaceship.

But what if the shuttle doesn’t go out at a right angle to the spaceship’s direction of travel? In that case, what the watching people see on the spaceship and on the planet they’re zipping past might differ a little more. If our shuttle can reverse directions instantaneously, going from 0.1c “forwards” with the spaceship to 0.1c “backward” right away, then someone on the spaceship would simply see the shuttle moving at 0.1c relative to the ship, which is stationary under their feet. As long as the shuttle is always moving at a fixed speed, it should be able to reverse course and catch back up to its dock.

The planetary observer, meanwhile, would observe a whole host of things changing. (And if we wanted to make things super complicated, we could look at how much time each set of observers is dealing with.) Velocities don’t add in the same way when you’re moving at significant fractions of the speed of light, and so the shuttle would appear to be moving at different speeds relative to the planet, depending on whether the shuttle was moving against the flow of the spaceship (0.29c) or along with it (0.48c).

The shuttle could wind up in a situation where it couldn’t reach the spaceship again if it could slow itself down enough. In the above scenario, I’ve assumed that that shuttle is always moving at a fixed speed, but if the shuttle could change its speed so that instead of being stationary relative to the spaceship, it were stationary relative to the planet, it would not be able to accelerate back up to the speed of the spaceship. Then it would be stuck, lagging ever further behind the spaceship it came from.

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