Saturday, July 1, 2023

Euclid Starts Its Trip - and Gives Us the QoTD

As we talked about on Monday, the European Space Agency's Euclid telescope was launched this morning at 11:11 AM ET, right on time, on a Falcon 9 flying only its second mission.  

Euclid is an infrared telescope like the Webb, but since it's smaller than Webb (and smaller than Hubble), it can't have the resolution (ability to optically separate sources that are close to each other) or the sensitivity that the "big brothers" provide.  Still the telescope will observe billions of galaxies during its six-year survey of the sky, measuring their shapes and positions going back 10 billion years, more than 70 percent of cosmic history.  

Led by the European Space Agency, the Euclid mission has the ambitious goal of helping astronomers and cosmologists learn about the properties and influence of dark matter and dark energy, which are thought to make up about 95 percent of the Universe. The rest of the cosmos is made of regular atoms and molecules that we can see and touch.

From Henk Hoekstra, a professor and cosmologist at Leiden Observatory in the Netherlands anxiously waiting for the data from Euclid to start pouring in, we get the quote of the day, “It’s very difficult to find a black cat in a dark room, especially if there’s no cat.” 

The current "standard model" of cosmology postulates the existence of "dark matter" we can't see and an even more obscure "dark energy" that's filling space.  The ideas for dark matter and energy came from observations of galaxies; how they rotate and how the stars are distributed.  Astronomers eventually concluded that there had to be far more stars in galaxies than could be seen, to provide the gravitational attraction to hold everything together the way the stars are distributed. 

All the atoms in the universe only make up about 5% of its total contents. The rest is dark matter and dark energy. Dark matter, which is about 27% of the contents of the universe, provides the gravitational foundation for building galaxies and galaxy clusters. The large-scale structure of the universe is produced by dark matter, but we still don’t know what it’s made of. Dark energy, making up the remaining 68% of the universe’s contents, causes the expansion of the universe to accelerate. The push-pull of dark matter and energy are what makes the universe look the way it does, so understanding exactly what these mysterious substances are and how they work is a major challenge of modern cosmology. 

Together, dark matter and energy as currently envisioned say that 95% of our Universe is something that's totally invisible to us.  The stars, planets, and everything else we can see are the other 5%.  Together, dark matter and energy have been called, “[the] biggest embarrassment that we have currently in cosmology.”

Data pouring in?  

Euclid is expected to downlink about 100 gigabytes of compressed data every day, and over the course of its mission, will produce more than 100 petabytes of information after automated processing at nine ground-based data centers, said Gaitee Hussain, head of the science division at the European Space Agency. 

That's from a 600-megapixel visible light camera, a 64-megapixel near-infrared camera and a spectrometer. 

Euclid will take about a month to reach its L2 orbit and another few months for equipment checkouts after that. 

The regions Euclid will survey during its six-year mission, totaling about 36% of the sky.  ESA Graphic

Scientists say it would take Hubble hundreds of years to complete the same extra-galactic survey as Euclid, which will cover in a week the same area of sky that Hubble has observed in its 33-year mission.

Think of Euclid versus Webb or Hubble as a wide angle lens versus a telephoto.  As is often the case in photography, knowing which lens to grab for a picture makes all the difference.   


  1. "especially if there’s no cat".
    Can't help but think of Schrodinger...

  2. We can't see it, measure it, or even verify its existence, but it must be there because the current theory demands it be.

    Compare and contrast this with "climate change" and "global warming" from the last 50 years, "phlogiston" from the 19th century, "ether" from the 1st century, and "magic beans" from "Jack and the Beanstalk". Discuss.

    Veterans of sidewalk three-card monte games, stop me if you've heard this one.

    People to whom this is like explaining calculus in Mandarin, using an abacus:
    I have jars of Dark Matter for sale, only $30k per quart.
    Contact me at my blog for payment options.

  3. I have always considered the "dark matter/energy" position ridiculous. This is just a patched-in excuse covering for ignorance of the hidden nuances in the current theory of gravity. Wake up, physics theorists, Einstein was not the be-all and end-all genius of forever -- just as Newton proved not to be precisely correct.

    Every time we push out the scale and look hard, things come into play that we just didn't see until we averaged out the noise. Galaxies are pretty large scale.

    1. Something that has been going on for as long as people have been observing is that "when you look with something no one has ever looked with, you see things no one has ever seen." That goes not just for observing in space, observing with IR or UV or radio telescopes. Before optical telescopes were big enough to resolve individual stars, galaxies were thought to be nebulas - gas clouds.

      As for theories, someone I heard or read decades ago had brilliant analogy. Think of theory to explain something starting out simple, like a see-saw. A plank on hinge mounted to a pipe. Then something odd is observed and a little thing is added to it to make it work. Eventually, it goes from being a simple board on a hinge to some monstrosity with add-ons stuck everywhere and it gets harder and harder to get it to work. When it gets to looking like that, you know it's time to throw it out and build something new. Something simpler that accommodates what all the add-ons were put there for. That's the hard part.

  4. Wishing success to the Euclid / Hera mission, in whatever they may find.

  5. There's another (very old) analogy that comes to mind:
    The blind men examining the elephant trying to determine what sort of animal it is.

  6. Dark Matter is the Luminiferous Aether of the 21st century.

  7. Astrophysicist’s are very very smart people. And to a man they WOULD LOVE to solve this problem, a Nobel Prize awaits the person or team that does!

    But they are constrained by the paucity of evidence - just some anomalous galactic orbital speeds. Occam’s razor led them to initially assume matter we can’t see, hence the rather dull term ‘dark matter’. It turns out, after decades of investigation, that it’s a lot subtler than matter we just overlooked.

    It is invisible exotic stuff, probably, and Euclid is a step towards getting a solution.

    1. A step towards a solution would be admitting the obvious:
      "We DO NOT KNOW wtf is going on to account for the apparent anomalies we observe, so we're going to explore until we can explain it based on evidence, rather than @$$-gas and speculation."

      Absolutely precisely correct. Humble. Curious.
      Scientific trifecta, right there.

      Science that was humble and curious would eliminate all the blowhards spinning fabulist fairytales out of their underwear, back to time before recorded history, and force them to return to disciplines like phrenology, from whence they sprung.

      Not holding my breath there.