Where are You Going in 2018 (Cosmically Speaking)?

By Corey S. Powell | January 24, 2018 12:13 pm
Rotation of the Earth as seen from the DISCOVR spacecraft, 1.6 miles sunward of our planet. (Credit: NASA/NOAA)

Rotation of the Earth as seen from the DSCOVR spacecraft, located 1.5 million kilometers sunward of our planet. (Credit: NASA/NOAA)

A while back, I wrote a column for Discover analyzing your place in space: astronomers’ best look yet at where you fit into the big, crazy, cosmic scheme of things. Any discussion of where you are inevitably brings up the related question of not just where you are, but where you are going. And there’s no better time to think about where you are going that at the beginning of the year–right around the time when you realize that, once again, this isn’t going to be the year you keep all your January 1 resolutions.

How to answer the question Where are you going? depends entirely your reference frame. There is no master set of coordinates for the universe (thanks a lot, Einstein), so you can only answer the question by addressing the subordinate question, In relation to what? Fortunately, that’s exactly when things start to get interesting.

Astronomy textbooks typically depict our motion through space in terms of vector arrows pointing in different directions, indicating the direction of Earth’s orbit around the Sun and the like. A recent question on Quora got me thinking about things a different way, however. What if you were suddenly motionless relative to the various cosmic reference frames about you? What would you see and experience if you made yourself the center of the universe, and let everything else move around you?

To make this thought problem work, you will need to add a couple more very important fantasy elements: You have to imagine that you can survive in space without a suit, and that you can pass like a ghost right through the solid body of the Earth if necessary. Caveats in place. Let’s go!

If you were motionless relative to the center of the Earth. In this case, you’d no longer participate in Earth’s rotation. The planet would rotate beneath you eastward at a velocity that would depend on your latitude. Specifically, it would move at 1,674 kilometers per hour at the equator, and at a velocity equal to this rate times the cosine of your latitude everywhere else. At 45 degrees north, for instance, your speed would be 1,184 kilometers per hour, or about three kilometers west every 10 seconds, relative to the spinning globe beneath your feet.

If you were motionless relative to the Sun. Now you would no longer participate in Earth’s orbital motion. Earth would fly past you at 29.8 kilometers per second, on average. The exact speed varies a little over the course of the year, because Earth’s orbit is an ellipse. At sunrise (roughly), your ghostly form would fly straight down through the ground. At sunset (roughly) you would fly straight up into space relative to the Earth.

OK, now get ready for a big leap.

Rotation, solar orbit, and galactic orbit of the Earth, beautifully depicted by Jim Slater307 (based on a diagram by ESO/S.Brunier).

Rotation, solar orbit, and galactic orbit of the Earth, beautifully depicted by JimSlater307 (based on a diagram by ESO/S.Brunier).

If you were motionless relative to the center of the Milky Way (as defined by the supermassive black hole Sagittarius A*).  Things get very disorienting once you no longer participate in the Sun’s orbital motion through our galaxy. Earth would fly past you at about 245 kilometers per second–and mind you, even at this rapid pace it takes the Sun and its planets 230 million years to complete one course around the Milky Way. As if that is not dizzying enough, note that half of the year Earth’s orbital motion would add to your galactic speed, and the other half it would reduce it. To visualize what’s happening, we’re going to need a bigger map:
The Sun's grand orbit through the Milky Way, dragging us all along with it. (Credit: NASA/JPL/R.Hurt/Cmglee)

The Sun’s grand orbit through the Milky Way, dragging us all along with it. Look sharp–you are at the little red circle in the center. (Credit: NASA/JPL/R.Hurt/Cmglee)

If you were motionless relative to the Andromeda Galaxy. The Andromeda Galaxy makes a handy deep-space reference point, since it is is the nearest major spiral galaxy to us (about 25 Milky Way diameters away). In this case, you would no longer participate in our galaxy’s slow-motion fall toward its larger neighbor. Or not so slow-motion: Our galaxy as a whole is falling in that direction at about 110 kilometers per second.

That velocity largely lines up with the Sun’s orbital motion around the Milky Way, though, so the net effect is that you’d be left behind at a rate of about 290 kilometers miles per second (plus annual variation from our cute little orbit around the Sun) as Earth and the rest of our solar system hurtles toward Andromeda.

Fun fact: You’d fly off roughly in the direction of Alpha Centauri, but even at this breakneck speed you’d need about 5,000 years to get there.  Space is really, really vast.

Map of the microwave background shows that half of the sky appears "hotter" than the other because Earth is moving in that direction relative to the background radiation itself. (Credit: NASA/WMAP)

Map of the microwave background shows that half of the sky appears “hotter” than the other because Earth is moving in that direction relative to the background radiation. Technically speaking, the red areas are blueshifted and the blue areas are redshifted…because astronomers are confusing like that (Credit: NASA/WMAP)

If you were motionless relative to the cosmic microwave background. This is the closest thing we have to a master answer to “where are you going?” relative to the universe as a whole. The cosmic microwave background is the relic radiation from the Big Bang. You can think of it as the reference frame of the birth of the cosmos. Studies show that we are moving at a velocity of 371 kilometers per second (plus annual variation, again) relative to the radiation background.

That motion is interpreted as the result of the gravitational pulls of a vast supercluster of galaxies (primarily the crowded downtown of our own supercluster, Laniakea), tugging on our Milky Way and the rest of our local cluster of galaxies.

If you want to take the most complete version of the question, that is your answer. You’d watch the Earth and the rest of the solar system fly away from you at 371 kilometers per second toward a point near the constellation Leo, falling toward thousands of distant galaxies. After 10 seconds, you would have traveled 3,710 kilometers through the solid Earth or 3,710 kilometers up into space, depending on the time of day. You can look up the current location of Leo in the sky to figure out your path.

Or you could just wait 100 seconds, and by then you would be far off in space no matter which direction you started out relative to the Earth. Per the rules of this imaginary game, you don’t need a space suit. But I hope you brought a flashlight, a good book, and a lifetime supply of snacks.

Follow me on Twitter for science news and other fun geeky stuff: @coreyspowell

  • OWilson

    I just looked around me, got tired of the hate, blame and division that corrupt politicians use to get elected, and found my tropical island paradise.

    Not for everyone though. Liars, dupes and fools are identified early on, and marginalized!

    Make sure you can qualify before you leave your Swamp!

    Then, c’mon down!

    • Corey S Powell

      So uh…where are you going in the universe?

      • OWilson

        Wherever this speck of dust, one of trillions is destined to go, and realizing that it has been on this journey for 4,500,000,000 years or so.

        Providing a living habitat for some 3,000,000,000 years or so, and not expecting any major changes or major changes in Al Gore’s puny lifetime?

        And you folks?

    • Mike Richardson

      It must be very peaceful there for you, with nobody bothering you. I’m happy for you, Wilson! :)

      • OWilson

        Thank you!

        Enjoy your gummint pension that is being borrowed from generations yet unborn!

        • Mike Richardson

          Well, getting paid by the “gummint” is something we both have in common, but don’t let that little fact detract from your pleasant marginalized stay in paradise. 😉

          • OWilson

            The difference is as an appointed Consultant, they pay me to save them (and the taxpayer) money that their “employees” are incapable of doing!

            The screening process to hire someone like me who is responsible for million dollar budgets, is a lot more rigorous than hiring a “me too” socialist who doesn’t have the brain power to heed government warnings and rebuilds his house exactly where he got flooded out before :)

            Liberal/socialist government officials are not always comfortable having to hire a conservative businessman, but sometimes when the rubber hits the road they really have actually get things done!

            On time and under budget!

            They are still calling me back!

          • Corey S Powell

            Folks: I carefully curate this blog to focus on the wonder of science, and to touch on politics only as it directly relates to the discovery process. I’d appreciate your help in keeping the tone here consistent with that: no political insults, no gratuitous left-right smears. There are plenty of other forums for such battles. Let’s keep this as a preserve for discussions rooted in curiosity, not divisiveness. Thank you!

          • OWilson

            Please don’t censor my factual post, yet leave the inference that I am a government employee, which is a lie!

            Can we at least clear that up?

          • Corey S Powell

            I took that earlier reply to mean that we all benefit from government services, but of course if you want to clarify that you are not a government employee that’s fine. Just please keep things civil here. And I sure would love to get back to science.

          • OWilson

            Thank you!

            I’ll take that to mean ALL posters including those who have nothing on topic to post, but troll those that do! :)

          • Mike Richardson

            Sorry for that, but the other poster did mention past employment on contract to the Canadian government, so I’m not lying, and not a big fan of double standards. Back on topic, I’m pretty happy to remain rooted in reality on this globe as my point of reference. Until such time as routine space travel is safe, we’ve got a pretty good view of the cosmos here at home. And thanks for keeping us informed on new discoveries related to our place in the universe!

          • OWilson

            Thank you for finally posting something on topic.

            It’s not much, but then, I don’t expect much! :)

  • http://www.mazepath.com/uncleal/EquivPrinFail.pdf Uncle Al

    Rotation of the Earth as seen from the DISCOVR spacecraft, 1.6 miles sunward of our planet.” 1.6 miles? Wouldn’t that be more of a closeup? “8^>) Excellent shot of the South Pacific Gyre. I can’t quite see the Chatham Islands.

    • Alex Sander Santos

      1.6 million kilometers, not miles, from Earth. And NASA spells it DSCOVR, without the “i’.

    • Corey S Powell

      I think I was eager to publish the piece, and typing way too fast at that point! I fixed the multiple errors in the first caption. Thank you for your careful reading.

  • Ken Albertsen

    Like a fly buzzing around inside a speeding car (it’s not flattened against the back wall by momentum) – I’m not feeling the effects of traveling hundreds of Km/second, ….unless, possibly, I’ve ingested some mind-altering drug (which I haven’t done since Flower Power daze). Serious Q: Are cosmic rays zipping thru my body affected by all these cosmic motions?

  • Sandeep koppu

    thank for giving nice information



Out There

Notes from the far edge of space, astronomy, and physics.

About Corey S. Powell

Corey S. Powell is DISCOVER's Editor at Large and former Editor in Chief. Previously he has sat on the board of editors of Scientific American, taught science journalism at NYU, and been fired from NASA. Corey is the author of "20 Ways the World Could End," one of the first doomsday manuals, and "God in the Equation," an examination of the spiritual impulse in modern cosmology. He lives in Brooklyn, under nearly starless skies.


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