The combination of charge conjugation, parity, and time-reversal symmetry is known as CPT. And it must never be broken. Ever.
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With a massive, charged nucleus orbited by tiny electrons, atoms are such simple objects. Miraculously, they make up everything we know.
Yes, dark energy is real. Yes, distant galaxies recede faster and faster as time goes on. But the expansion rate isn't accelerating at all.
The Universe certainly formed stars, at one point, for the very first time. But we haven't found them yet. Here's what everyone should know.
Perhaps the whole Universe is the result of a vacuum fluctuation, originating from what we could call quantum nothingness.
There is no such thing as a void in the Universe.
By probing the Universe on atomic scales and smaller, we can reveal the entirety of the Standard Model, and with it, the quantum Universe.
In many ways, we are still novices playing with toy models seeking to understand the stars.
With no other galaxies in its vicinity for ~100 million light-years in all directions, it's as isolated and lonely as a galaxy can be.
Empty space itself, the quantum vacuum, could be in either a true, stable state or a false, unstable state. Our fate depends on the answer.
What would become the Big Bang model started from a crucial idea: that the young Universe was denser and hotter.
The Big Bang is commonly misunderstood, warping our understanding about the Universe's size and shape.
After 15 years of monitoring 68 objects known as millisecond pulsars, we've found the Universe's background gravitational wave signal!
From a photon's viewpoint, the Universe is timeless and dimensionless.
As far as we can tell, there's no limit to how far it goes on; only a limit to how far we can see. Could the Universe truly be infinite?
Ever since the Big Bang, cataclysmic events have released enormous amounts of energy. Here's the greatest one ever witnessed.
The answer to this question is key to understanding why anything exists.
The first observational evidence showing the Universe is expanding is 100 years old now: in 2023. Here's the story of its 100th anniversary.
Every time our Universe cools below a critical threshold, we fall out of equilibrium. That's the best thing that ever happened to us.
Uncertainty is inherent to our Universe.
The image you're seeing isn't a hole in the Universe, and the cosmic voids that do exist aren't hole-like at all.
A proponent of panpsychism argues moral truth is inherent in consciousness.
A cute mathematical trick can "rescale" the Universe so that it isn't actually expanding. But can that "trick" survive all our cosmic tests?
It's been 100 years since we discovered that the Universe was expanding. But if it's expanding, then what is it expanding into?
There might be a hard limit to our knowledge of the Universe.
From quarks and gluons to giant galaxy clusters, everything that exists in our Universe is determined by what is (and isn't) bound together.
With a finite 13.8 billion years having passed since the Big Bang, there's an edge to what we can see: the cosmic horizon. What's it like?
We can't go back to the Big Bang, nor ahead to the heat death of the Universe. Nevertheless, here are today's natural temperature extremes.