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Can One Measure the Expansion of the Universe Within Our Solar System?

-- Gerald | February 5, 2021

Diagram depicting the major milestones in the evolution of the Universe since the Big Bang

Question:

The universe is expanding. The space occupied by the Solar System is therefore also expanding. This being the case, the distance between the components of the Solar System should be increasing with time. Has such an effect been detected?

-- Gerald

Answer:

The universe is currently expanding at a rate of about 75 kilometers per second per mega-parsec. If we consider how much the expansion of the universe is stretching the distance between the Sun and the Earth, we first need to determine what fraction of a mega-parsec (10^6 parsec) that Earth-Sun distance is. Since one mega-parsec is about 2.06×10^11 times the Earth-Sun distance (which is called an Astronomical Unit), then we can say that the distance between the Earth and the Sun is being stretched by about 75/2.06×10^11 km/s, or about 3.6×10^(-10) km/s, which is about 36 billionths of a kilometer each second. As you can see, the distance between the Earth and the Sun is being stretched by an incredibly small amount due to the expansion of the universe, an amount of stretching that we would have great difficulty measuring.

-- Jeff Mangum

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