Euclid finds complete Einstein Ring in NGC galaxy
euclid-ec.org
euclid-ec.org
That's kind of surprising to me. I assumed in the newtonian picture gravity would not bend light.
I don't think there'd have been any reason to think it would act differently than any other small object passing near a more massive one?
Another key figure was Pierre-Simon Laplace, who, in the first editions of Exposition du Système du Monde (1796), independently proposed the existence of such massive celestial bodies that could trap light. However, he later removed this idea from later editions, possibly due to skepticism over the corpuscular theory of light.
The first real attempt to quantify how much gravity might bend light was made by Henry Cavendish (circa 1783–1784). Though unpublished at the time, his notes (discovered in 1921) contained the first calculations of the bending of light under Newtonian gravity. Later, in 1801, Johann Georg von Soldner formally published a paper calculating the deflection angle of light passing near the Sun under Newtonian mechanics, obtaining a result (~0.85 arcseconds) that was later found to be half of what general relativity predicted.
These early discussions framed gravitational lensing in a purely Newtonian context, treating light as a particle affected by gravitational attraction.
Given that, why shouldn't light also fall at 9.8 m/2^s as it passes the earth? That would be extremely hard to measure, but if you extrapolate the phenomenon, you get gravitational lensing.
18th century scientists wouldn't have known that light was a zero-mass particle. The results of the calculations are ambiguous with a zero-mass particle (a=F/m is a divide-by-zero error). But if you don't know about that, you can just wonder if light particles (or waves, or whatever) also gets deflected at the same acceleration as ordinary matter.
Light in fact doesn't accelerate at a, but at 2a in a gravitational field. The Eddington experiment in 1919 agreed with that figure, disproving the Newtonian version.
Minute Physics have a nice video on this: https://youtube.com/watch?v=tmNXKqeUtJM
And just to clarify to GP, the original dust was not in the same plane and the video explains why it ends up in the same plane.
So too with galaxies---which, from a cosmological perspective, are essentially infinitesimal dust.
Well that depends on what your intuition about randomness is, doesn't it?
Flipping a coin is not random, but you can't tell me the answer before it happens.
Similarly, galaxy orientation is not random, but predicting the world we perceive is perhaps not so easy.
If not, the forces that turn some solar systems and galaxies into rotating disks might not act the same at the supergalactic scale in time and space?
Because the light traverses regions of lower and higher density (made up mostly of dark matter), we see a gravitational lensing effect. Sources of gravity distort the image behind the "lens". The article describes a strong lensing effect, which is pretty self-evident. By analyzing correlations of galaxy ellipticities we can measure an effect which is only apparent as a statistical effect. You'd expect no intrinsic correlation of the apparent ellipticity between galaxies (because they can be millions of light-years apart), but this so called weak lensing effect does create a correlation. I basically think of it as observing perfect ellipses through slightly obscure glass and deducing from that the exact shape of the glass.
Thanks to Euclid's data, we will be able to create a sort of 3D map of the total matter distribution (dark and baryonic), which will in turn tell us how the universe evolved better than any other probe. We hope to learn more about dark energy in this way.
That's one way to put it, but a negative way. The other might be more humbling: how significant are we? Or, as a statement instead of a question, we are the only significant thing of which we know.
We can theorize about life elsewhere, and we can write space-opera fiction about life on other worlds, but, to the best of our knowledge, we are the only ones who can. We know there is other life on our world, but not as rational as we. We do not know for a fact that there is any equivalent, rational species in all that vast universe that we can see, let alone any more advanced than we are.
Asking the question that way makes me, at least, wonder if we comport ourselves in accordance with our knowledge of our exceptionalism. If we are the most advanced form of life that we know and can prove to exist, do we behave like it?
Its just one of those concepts or facts of life like our (im)mortality that each of us has to handle on their own terms since each of us is wired in pretty unique ways. Its perfectly fine to be in awe or even stunned by it, it means one actually started to grasp vastness of that topic and the fact we don't have it all figured out and during our lifetime this won't change.
Every time I look at starry night sky and realize those distances, thermonuclear furnaces glowing across vast distances in absolute cold (or their massive groups looking similarly yet being vastly further), I am in awe. It puts my efforts and happiness in my life in a good perspective, in similar fashion spending my time with my kids does. And I look at stars every night I can, its a beautiful calming sight for me.
I do believe we all must face these emotions to become aware. But the depression/nihilism trap is very real for many people (myself included), and learning to walk that line and stay curious is part of our emotional/psychological development.
We have no proof of extraterrestrial life. Yet.
If we were the only “rational” beings (all of past, present, and future), that would clearly be some feat!
However, if we’re to bet on our limited evidence that this is true, we’re likely not to flourish as we might.
Just remember, there are more stars than sand, and more time than not.
We are surely not the first observers of this reality (however “rational” or not), and likely not the last.
We may assume that we are the only intelligent life in the universe and that life on our planet is highly significant. Humanity itself faces a great challenge in finding its way. We are currently in a dark period of our evolution—one where we have mastered a great deal of technology to make our lives materially comfortable, yet we have not mastered the "demons" within our minds. We fail to control them as individuals, and even less so as societies. These demons were instilled in us by natural evolution, serving us well until the Neolithic age. But in the modern era, they have become our greatest enemy. At this point, the biggest problem facing humanity is human nature itself. We stand on the brink of destroying our planet in numerous ways. Humans have already caused one of the greatest mass extinctions of large animals in Earth's history.
One argument supporting the theory that Earth is the only planet with advanced life is the growing realization of how many rare conditions must be met for life to emerge. In the past, scientists believed it was enough for a planet to be located within the habitable zone of its star. We are now beginning to understand that this is merely one of the most basic requirements among many others.
Earth itself has come close to losing all its life on multiple occasions—such as during the Snowball Earth period—despite the Sun remaining stable and the planet still being within the habitable zone.
One crucial factor for sustaining life is a planet’s internal magmatic activity, which must be powerful enough to generate a stable magnetic field. This field protects the atmosphere from being stripped away by solar winds. Additionally, it seems that magmatic activity played a key role in warming the planet during its early years when the Sun’s radiation was weaker. In fact, the gradual increase in solar radiation over billions of years appears to have offset the decrease in Earth's internal heat, maintaining the planet’s temperature within a range suitable for life to thrive.
However, Earth's prolonged and vigorous magmatic activity appears exceptional, likely because a colossal collision with a rogue protoplanet—the event known as the Giant Impact Hypothesis—not only formed the Moon but also injected an enormous amount of thermal energy into the young Earth. This impact created a long-lasting magma ocean phase, effectively resetting the planet's internal heat and driving rapid mantle convection and differentiation. Such enhanced magmatic activity contributed to the early formation of a stable geodynamo, which has sustained Earth's magnetic field and, consequently, its atmosphere over geological time.
For all we know, Earth may be unique in the universe, but we are far from certain enough to make such a claim.
The other possibility is that intelligent life exists elsewhere, but the barriers imposed by the speed of light—combined with the unimaginable vastness of the universe—may render it impossible for advanced civilizations to find or communicate with one another. Who knows? Perhaps the universe was created by some form of intelligence that ensured life could develop, but only in such rare and distant pockets that no two civilizations could ever reach each other, or even communicate.
EDIT: expanded the paragraph about the big impact hypothesis.
It doesn’t make me feel like anything, other than trying to imagine the universes’ vastness - in an attempt at futility. I don’t think my mind (or any human mind) can ever truly fathom it.
The image in question is likely a blow up of a point in the sky that’s 1mmx1mm, about the size of a grain of sand, and it is rich with many many galaxies, way more than we can see - if you account for the vast and infinite depth. The Milky Way is said to have 400 billion stars. So if there are a 1000 galaxies present in the image, that’s trillions of stars in a square mm of the sky.
I think it’s pretty darn empowering to think your life’s problems mean that less, one part in numbers so large I can’t even pronounce. Don’t you think?
For those also morbidly curious (consider yourself warned) - https://en.wikipedia.org/wiki/Lingchi
He pointed out to the viewers that the amount of void in between stars that is visible is a bit misleading in all these super high res photos we see of our universe.
The video ended with some special effects/simulations of the night sky as seen from the South Pole. If the light pollution was literally zero, and you had eyes (or a camera) that could somehow see _all_ stars regardless of how far away they are, the night sky would basically look like a still picture of the color noise on an old analog TV. Hardly any black void anywhere, it’s just all stars. It was mind-boggling (and I hope true, not a scam video).
In particular, the scale of the universe just hurts my brain: If you were to scale down the Sun to the size of a coarse grain of sand (1 mm), then the orbit of the Earth would be about 20 cm across, with the planet itself being microscopic at this scale (10 micrometers). Jupiter would be a barely visible speck 55cm from the Sun.
At this incredibly tiny scale, the next nearest star in the galaxy is about 30 kilometers (18 miles) away! That's roughly the same as a trip across a typical city, but our Voyager probes at this scale have gone only 15 meters over a period of 45 years! That's comparable to the rate at which hair grows (1 mm/day).
Hence, a good mental model for thinking about the scale of our galaxy is: Stars are grains of sand separated by tens of kilometers on average across a circular space the size of the orbit of the Moon.
The “Sun is a beach ball” is great for solar system understanding, etc…
And with that, it’s possible that our universe is on collision course with another, but because it’s on physics level of “outside” universe, the speeds relative to size there are millions of times faster. And if collision occurs our universe will cease to exist in a moment. We will not know it happened.