3 ms·
The bit I find amazing in these galaxy fields is the apparent randomness of the orientation of each galaxy. Why is this? Are we seeing a remnant of chaotic beha
by jl6 2y ago
The bit I find amazing in these galaxy fields is the apparent randomness of the orientation of each galaxy. Why is this? Are we seeing a remnant of chaotic behavior where tiny random variations at the smallest scale in the early universe led to the wildly diverse objects that we see today? There is great variation in the color, size, and shape of galaxies too, but somehow it’s the apparent orientation that baffles my intuition.
- UltraSane 2y agoThe location of galaxies is thought to have been triggered by quantum fluctuations in the earliest moments of the universe that caused matter to be denser in some locations. But why would you expect galaxies to NOT be randomly oriented?
- jl6 2y agoI guess I shouldn’t have that expectation. Perhaps it’s because on Earth we see nearby objects aligning with each other because they have been shaped by similar forces, or because they influence each other. But perhaps galaxies don’t interact with each other enough to result in any kind of alignment.
- UltraSane 2y agoThe planets in our solar system all orbit on the same plane because they all formed from the same dust cloud that was rotating in the same plane.
- orra 2y agoIndeed. And to elaborate: the random collisions which flattened the solar system (or galaxy) over billions of years all conserved angular momentum. Minute Physics have a nice video on this: https://youtube.com/watch?v=tmNXKqeUtJM https://youtube.com/watch?v=tmNXKqeUtJM
- prerok 2y agoNice video, thanks for sharing. 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.
- evanb 2y agoMolecules of nitrogen and oxygen both have a distinguished axis (along the bond), but because they're gaseous there's no reason to expect them to align throughout the atmosphere. So too with galaxies---which, from a cosmological perspective, are essentially infinitesimal dust.
- kryogen1c 2y ago> why would you expect galaxies to NOT be randomly oriented? 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.
- jrootabega 2y agoMight be begging the question. Perhaps it's not really that random. We common people don't usually get pictures that convey depth and orientation, and probably wouldn't care even if we did. Might only be as random as a solar system with varying orbital inclinations and directions. 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?
- mr_mitm 2y agoFunny you should ask. Euclid specifically measures the ellipticity of billions of galaxies. 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.