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Cosmic Microwave Background
Today, in the here-and-now, a full 13.8 billion years have elapsed since the start of the hot Big Bang. But would that be true for everyone?
In theory, the fabric of space could have been curved in any way imaginable. So why is the Universe flat when we measure it?
Before we formed stars, atoms, elements, or even got rid of our antimatter, the Big Bang made neutrinos. And we finally found them.
Our great hope is that today's indirect, astrophysical evidence will someday lead to successful direct detection. What if that's impossible?
Outer space begins just over 100 kilometers up, but what we can see extends for billions of light-years. Here's what all of it looks like.
Particles are everywhere, including particles from space that stream through the human body. Here's how they prove Einstein's relativity.
Wavelengths stretch, distances grow, and temperatures cool as the Universe expands with time. How are the various cosmic parameters related?
We've long known we can't go back to infinite temperatures and densities. But the hottest part of the hot Big Bang remains a cosmic mystery.
Observations with the Hubble space telescope helped cement dark energy and reveal the Hubble tension. How are these two things so different?
If you think of the Big Bang as an explosion, we can trace it back to a single point-of-origin. But what if it happened everywhere at once?
The hot Big Bang is often touted as the beginning of the Universe. But there's one piece of evidence we can't ignore that shows otherwise.
As we gain new knowledge, our scientific picture of how the Universe works must evolve. This is a feature of the Big Bang, not a bug.
Just 13.8 billion years after the hot Big Bang, we can see 46.1 billion light-years away in all directions. Doesn't that violate...something?
The relic signal that first proved the Big Bang has been known and analyzed for 60 years. Join us at the frontiers of modern cosmology!
The CMB has long been considered the Big Bang's "smoking gun" evidence. But after what JWST saw, might it come from early galaxies instead?
For hundreds of millions of years, a cosmic fog blocked all signs of starlight. At last, JWST found the galaxies that cleared that fog away.
Different methods of measuring the Universe's expansion rate yield high-precision, incompatible answers. But is the problem robustly real?
In our Universe, dark matter outmasses normal matter by a 5-to-1 ratio, shaping the Universe as we know it. What if it simply weren't there?
It rotates on its axis, revolves around the Sun, moves throughout the Milky Way, and gets carried by our galaxy all throughout space.
If it weren't for the intricate rules of quantum physics, we wouldn't have formed neutral atoms "only" ~380,000 years after the Big Bang.
It took nearly 400,000 years, after the Big Bang, to first form neutral atoms. The imprints from that early time can now be seen everywhere.
Since 1998, we've known our Universe isn't just expanding, but the expansion is accelerating. Could the Big Bang itself be the reason why?
It's difficult to project a sphere onto a flat, two-dimensional surface. All maps of the Earth have flaws; the same is true for the cosmos.
Since the dawn of history, humans have pondered our ultimate cosmic origins. Now in the 21st century, science has gone beyond the Big Bang.
The CMB gives us critical information about our cosmic past. But it doesn't give us everything, and galaxy mapping can fill in a key gap.
Dark matter doesn't absorb or emit light, but it gravitates. Instead of something exotic and novel, could it just be dark, normal matter?
Only 5% of the Universe is made of normal "stuff" like we are. Could there be dark matter or dark energy life, or even aliens, out there?
Historically, astronomers have often named things creatively, bizarrely, and often inaccurately. But which terms are the most egregious?
First discovered in the mid-1960s, no cosmic signal has taught us more about the Universe, or spurred more controversy, than the CMB.
Since mid-2022, JWST has been showing us how the Universe grows up, from planets to galaxies and more. So, what's its biggest find of all?