Press enter or click to view image in full sizeThe ultramassive, merging dynamical galaxy cluster Abell 370, with gravitational mass (mostly dark matter) inferred in blue. Many elliptical galaxies are found inside massive clusters like this, as the result of major mergers that occurred billions of years ago. There are still a large number of spirals, too, as the total mass of this galaxy cluster may exceed a thousand times that of the Local Group. (Credit: NASA, ESA, A. Koekemoer (STScI), M. Jauzac (Durham University), C. Steinhardt (Niels Bohr Institute), and the BUFFALO team)
It’s the origin of our entire observable Universe, but it’s still not the very beginning of everything.
If you ask a scientist where the Universe got its start, “the Big Bang” is the answer you’re most likely to get, as for over 60 years now, the scientific evidence that’s come in favoring that theory has overwhelmed all alternatives. Our Universe may be full of stars, galaxies, and a cosmic web of large-scale structure, all separated by the vastness of empty space between them, but it born that way. It’s a profound realization that our cosmos hasn’t existed in its current form forever. Instead, the Universe came to be this way because it expanded and cooled from a hot, dense, uniform, matter-and-radiation-filled state with no galaxies, stars, or even simple atoms present at the outset.
Everything, as it exists in its current form, wasn’t the way it is today back some 13.8 billion years ago: at the start of the hot Big Bang. Moreover, all that we know today about our place in cosmic history was figured out only during the past 100-ish years (beginning in 1923). However, even with all of this, there are a whole slew of facts most people — even many scientists — don’t quite get right about the Big Bang.
