Where are you going? That is, how fast and in which direction are you being transported through space?
Four months ago (exactly!) a reader (David Keys) asked whether I had put out information about these space motions, and this gave me the idea of fitting them into some sort of diagram. I imagined vectors – an arrow from the surface of the Earth representing our motion as it spins, and built on that a larger arrow for Earth’s travel along its orbit, and then a larger arrow in another direction for our solar system’s travel around the Milky Way.
I found it a tough programming problem, and delayed between attempts. Eventually I found it could be fitted into a “sphere” kind of picture, like those that run through the Astronomical Companion.
The sphere of space is slightly wider than the Earth’s orbit. The Sun is exaggerated 10 times in size, the Earth 500 times so as to be able to show its equator. The dashed ellipse is the plane of the ecliptic, in which Earth moves. The dashed line with ram’s-horns symbol is the vernal equinox direction. On the surface of the imaginary sphere are painted a band of dots, representing the midline of the Milky way; and the boundaries of three selected constellations.
And indicated are four velocities. As you can see, they differ so enormously in magnitude that they couldn’t possibly be lines in one picture. (It occurred to me to make them logarithmic, like the first sphere in the Companion, but – even more tangled programming.)
Look at the equator on the Earth. Standing on it, you are being carried all around in 24 hours, at about 1,700 kilometers an hour (less fast at higher latitudes). No wonder Galileo’s critics objected that there would be a thousand-mile-an-hour wind!
But the whole planet is hurtling along its orbit about 54 times faster. We show its travel over one month.
But the whole solar system is in a vast orbit around the disk of the Milky Way galaxy, at a speed more than 7 times faster again. The direction, in this part of the orbit, is toward the northern constellation Cygnus.
And our galaxy is a member of a group (along with an even greater one, Andromeda, and a number of dwarf galaxies), and this Local Group has been found to be moving in a direction relative to others. It’s apparently being pulled toward a remote concentration of mass, called the Great Attractor, and it’s going there at a speed nearly 3 times faster again. The mass is due to a swarm of galaxies in the direction of the southern constellations Norma (the “carpenter’s square”) and Triangulum Australe (the “southern triangle”).
In our picture, a band of dots all around the sphere is the midline of the Milky Way’s disk. The Cygnus direction is in this plane, and the Norma direction is close to it – it is in what astronomers call the zone of avoidance, because the teeming stars and nebulae in the Milky Way make it difficult to observe things beyond; hence the difficulty in detecting the Great Attractor. The Milky Way seems to be tipped into a plane edge-on to the Great Attractor, and one wonders whether there is a vast-scale reason for that.
Wrong direction down on Earth
Our beloved planet is microscopic in the universe. So it doesn’t matter (does it?) if it self-destructs because a few rich men, the bosses of Shell, ExxonMobil, Chevron, and BP, secretly plan enormous increases of fossil fuel production so as to rake in even more trillions of dollars in their personal lifetimes.
That attitude to the future is like an ant’s-eye view of a galaxy.
Misplaced modifier of the week
“Ivo Delingpole filmed Keir Starmer drinking beer through the window of Durham Miners Hall” – caption for a photo in the Guardian, May 10.
A broad gulp!
This is a badly placed phrase of the “Bath for baby with enamel bottom” type, rather than the “Hurtling through the sky he saw a rocket” type.
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You wrote that there may be a reason the Milky Way is edge on to the Great Attractor. I would assume that we we spun off of the great Attractor and are now being pulled back in.
Repeating patterns and cycles are a hallmark of nature. DNA shows a repeating pattern in all mammals. with a few changes here and there to make the different species. There is the cycle of mountains forming from plate tectonics and mountains degenerating through weathering. Water goes through repeating cycles of evaporation / condensation. Another feature of plate tectonics is that we alternate from one big landmass (Gondwana) to the breaking apart of continents and the eventual return to one big continent. There is also the political cycle: Tyranny, societal anger, rebellion, freedom, prosperity, complacency, weakness, tyranny.
Nothing is static in our universe unless you consider things on the Earth as being relatively stable such as the lumber, nails and plaster keeping your house in one piece, though even that is undergoing entropy, as any homeowner can attest to.
Yes, but not everything is cyclical: you ended by mentioning entropy (loss of order), which physcusts say is remorselessly one-directional except in relatively small closed systems.
I wouldn’t just place the blame on those plutocrats running those oil companies.It’s all fueled by the great car economy that is breaking the planets back so also those who make cars,sell them and more importantly buy the things! They’ll try and worm out of it by saying that they’ll get electric cars but the take up just as much space,are just as deadly and drain the planets resources to make an service.
Can you add all these speeds of motion and say we are travelling at 3,069,700 km/hour?
Love you posts, thank you for sharing
Thank you, Janett.
I’m sure you can’t simply add the speeds, because they are in different directions, and the first two, at least, keep changing direction. I think there must be mathematical formulae for combining vectors, which I don’t know. I would love it if someone who does know explains a little to us!
and here all this time I’ve been thinking that we were being pushed away from the Camelopardalis direction by the Great Repeller!! It makes your head spin LOL. My own ant’s-eye view of astronomy is more focused on hoping I have clear skies for the lunar eclipse on Sunday night.