We can describe what we see happening, but we don’t understand why.
Despite our vast cosmic knowledge, enormous unknowns remain.
These five existential physics puzzles still elude explanation.
1.) Why won’t gravitation stop the Universe’s expansion?
Somehow, there’s a non-zero, positive energy inherent to space: dark energy.
It accelerates the Universe’s expansion, but its existence and magnitude are unexplained.
2.) Is gravity truly a quantum force of nature?
At higher energies — and shorter distances — the fundamental quantum interactions change in strength.
Does gravity exhibits analogous quantum effects? We don’t know.
3.) Why is the Universe filled with normal matter, but not antimatter?
Antimatter only exists in tiny amounts; all stars and galaxies consist of normal matter.
Many theoretical solutions create this cosmic asymmetry, but lack supporting evidence.
4.) Why do we have electric charges, but not magnetic charges?
Isolated magnetic poles don’t fundamentally exist; only moving electric charges create magnetism.
Nature is not symmetric between electricity and magnetism, with no underlying explanation.
5.) Will we ever reveal the “matter” behind dark matter?
From gravitational lenses to the cosmic web to the CMB, indirect evidence overwhelmingly supports dark matter’s presence.
But every direct detection effort continues to fail, with experiments revealing no robust clues.
Until experiment, observation, and theory all align, these cosmic mysteries will persist.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.