The size of the universe is incomprehensibly big. Similarly, the particles that make of the universe that we know are incomprehensibly small. Just imagining how big the solar system actually is, which is just a small dot in the universe as a whole, is nearly impossible. In order to have any type of understanding of the size of the universe, we must compare objects throughout the universe against the size of objects we already know.
The observable universe is estimated by scientists to have a diameter of over 8.8*10E^26 meters, or 96 billion light years. For comparison's sake, the Milky Way Galaxy, which is the home of planet Earth, is a tiny fraction of that size, 120,000 light years across.
Source: Number Sleuth
A tiny grain of rice measures at 0.008*0.0025 meters big. Skin cells and viruses are thousands of times smaller than the smallest observed objects to the human eye. Yet, a single atom of hydrogen is billions of times smaller than that.
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