When a distant star explodes, its light travels toward us for billions of years. Astronomers measure how dim it appears and use that to calculate the distance. Usually, this involves complex models with dark energy and other mysteries. But now a simple pattern has been found: if you take the supernova's brightness and subtract five times the logarithm of the distance, you get a straight line.
This line is described by just two numbers: one sets its height, the other its slope. The slope turns out to be related to how fast the universe is expanding. Surprisingly, this simple formula works out to distances of 11 billion light-years and matches complex models. Moreover, it doesn't need data from nearby supernovae — distant ones alone suffice.
The scientists tested this pattern in eight patches of sky. All gave the same values for the two numbers, meaning the universe looks the same in all directions. This confirms that accelerated expansion is not a local quirk but a general property of the cosmos.
Type Ia supernovae are so bright that at the moment of explosion they can outshine an entire galaxy, even though they are comparable in size to Earth.
In Carl Sagan's novel 'Contact,' a signal from space makes humanity rethink its views of the universe, just as these supernovae push us to seek simpler laws.