How fast is the universe expanding?

Since the big bang 13.8 billion years ago, the universe has been expanding. The decisive question is: how fast? This speed is also called the Hubble constant – after Edwin Hubble, who first noticed the expansion of the universe.

Astronomers have come up with two methods to calculate this constant. Method 1 involves the measurements by the ESA’s Planck satellite. This satellite measured the precise structure of the cosmic microwave background, which was produced 380,000 years after the big ban...