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Ephemeris: 11/03/2025 – Why is the universal expansion speeding up?

November 3, 2025 Comments off

This is Ephemeris for Monday, November 3rd. Today the Sun will be up for 10 hours and 4 minutes, setting at 5:28, and it will rise tomorrow at 7:25. The Moon, 2 days before full, will set at 6:15 tomorrow morning.

The Big Bang, nearly 14 billion years ago set the universe to be expanding. All the mass of ordinary matter and the dark matter I talked about last week should be slowing that expansion. However, about 20 years ago it was discovered that the universal expansion is not slowing down. Instead, the expansion rate is increasing! Astronomers don’t really know why. Since expansion requires energy, this new property is called dark energy. It is actually the expansion of space itself. The galaxies are not fleeing by their own motion through space. They are carried by the expanding space around them. It turns out that objects with mass cannot exceed the speed of light, but the expansion of space itself has no speed limit. At least that’s how I understand it.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

This is an infographic of the evolution and expansion of the universe from the Big Bang to the present day.
This is an infographic of the evolution and expansion of the universe from the Big Bang to the present day showing the inflationary period when it increased in size extremely rapidly, faster than the speed of light, actually. About 380,000 years later light was finally decoupled from matter. Before then the universe was opaque. Light could not travel very far before hitting another particle. At 380,000 years the universe became cool enough so that electrons and protons in this Big Bang soup could find each other and become atoms. This caused the universe to become transparent. At that point is where we see, with our radio telescopes, the cosmic microwave background radiation. After that there’s a period where stars are being formed. There’s not much light being emitted because the stars are not radiating brightly because the hydrogen fusion in their cores had not started. This period is called the dark ages and may have lasted up to 400 million years. The period of the first stars and galaxies is the area that James Webb Space Telescope was primarily built to investigate. It is only visible in the infrared. All this happened 9 billion years before the Earth was formed. It is evolution on a scale Darwin could not have imagined! Click or tap on the image to enlarge it. Credit: NASA

Categories: Cosmology, Dark energy, Ephemeris Program