What’s Changed Since Ringworld?

Larry Niven's Ringworld came out in 1970, a whopping 56 years ago as I write this. I was five years old when it was published. It was one of the first novels I ever read, which would have happened in 1975 or '76. Since it's one of the classic novels of "hard SF," I thought it might be fun to look back and see how much the science has changed since then.

One of my first questions was whether physics changed more after Ringworld or before it. To make it a fair fight, I compared the same number of years on each side. Go back 56 years from 1970 and you land in 1914.

1914 to 1970

Turns out a physicist in 1914 would barely recognize physics in 1970.

In 1914, that physicist knew about atoms. The nucleus had been found just a few years earlier. Electrons were known, and light was understood mostly as a wave.

In 1915, Einstein published his General Theory of Relativity. Gravity became the shape of space and time.

Early ideas about quantum mechanics were around in 1914, but the full theory came together in the mid-1920s. Nearly all of modern chemistry and electronics comes out of it.

Spiral nebulae, those dim fuzzy patches in the sky, were the subject of an open debate. Were they clouds inside our own galaxy, or whole galaxies of their own? Edwin Hubble settled it in the 1920s, and by 1929 he had also figured out that the galaxies were moving apart. The universe was expanding.

The neutron was found in 1932. Antimatter was predicted and then found in the same few years. Nuclear fission came in 1938. By 1939, physicists understood that stars shine by fusion.

The Big Bang and the Steady State were the two main theories for how the universe began. In 1965, two radio astronomers picked up a faint hiss coming from every direction in the sky. They thought it was a problem with their antenna, but it turned out to be the leftover heat from the early universe, and the Big Bang had won.

Quarks were proposed in 1964, and the first experimental evidence for them came a few years later. Quasars were found in 1963. Pulsars were found in 1967, and they turned out to be neutron stars. Niven had beaten the astronomers by a year with his story "Neutron Star," about a ship that gets too close to one.

So that physicist from 1914 would have had to relearn almost everything by 1970. Space, time, matter, the size of the universe, and where it came from had all changed.

1970 to Today

A 1970 physicist brought forward to 2026 would find the field fairly familiar, just more filled in.

Particle physics got its missing pieces, from new quarks in the 1970s to the Higgs boson in 2012. Gravitational waves were detected in 2015, about a century after Einstein predicted them. We have the first image of a black hole. The age of the universe is now known to within about 1%. The Big Bang is still the Big Bang.

The big reveal would be exoplanets. In 1970, not a single planet had been confirmed around another star, so Niven's Known Space stories were full of inhabited worlds at a time when nobody could point to one. Today there are more than 6,300 confirmed, and NASA's Nancy Grace Roman Space Telescope, launched in August, is expected to find about 100,000 more.

The Shocker

Our 1970 physicist would get one real surprise, and it still surprises people today.

In 1998, two teams measuring distant supernovas found that the expansion of the universe is speeding up, which hadn't been predicted by anyone. Some of their data came from the Hubble Space Telescope, launched in 1990. That's how dark energy was discovered, and dark matter had been found earlier. It started in the 1970s, when Vera Rubin and others discovered that the outer stars in galaxies were moving too fast. There wasn't enough visible matter to hold them in, so something unseen had to be adding gravity.

In 1970, it was reasonable to assume the universe was made mostly of atoms. Stars, planets, gas, dust. The Ringworld is built from some very strange material, but it's still ordinary matter. Today, estimates put ordinary matter at about 5% of the universe. Dark matter is about 27%, and dark energy is about 68%. We still don't know what either of them is.

The 1914 physicist had to learn a whole new set of rules. The 1970 physicist mostly got to keep the rules, and then found out they describe about 5% of what's out there.

I wonder what a ten-year-old reading Ringworld today will know by 2082.