For most of history, an asteroid impact was something humans could only watch happen. Today, we have started building a real defense system. Apophis in 2029 is a perfect chance to test our knowledge.
You cannot deflect what you cannot see. Surveys such as Catalina, Pan-STARRS and ATLAS scan the sky every night. NASA has found the large majority of near-Earth asteroids over one kilometer wide, and none of them poses a threat for the next century. The harder task is finding smaller ones, a few hundred meters or less, which are far more numerous. New facilities, including the Vera C. Rubin Observatory and the planned NEO Surveyor space telescope, are built to find many more.
When an asteroid is found, astronomers measure its orbit repeatedly. Each measurement narrows the uncertainty. Risk is rated on tools such as the Torino Scale, from 0 (no hazard) to 10 (certain global catastrophe). Apophis was briefly rated 4 in 2004, the highest ever recorded, and was downgraded to 0 once more data arrived.
In September 2022, NASA's DART spacecraft deliberately crashed into Dimorphos, a small moonlet of the asteroid Didymos. The impact shortened its orbit around Didymos by about 32 minutes, much more than the 73-second minimum NASA had set as success. It was the first time humans changed the motion of a celestial body. The test showed that a "kinetic impactor" works, and ESA's Hera mission is following up to study the results in detail.
The key is time. If an asteroid is found decades ahead, a tiny change in speed adds up to a huge change in position by the time it reaches Earth. That is why early detection matters more than raw power.
Apophis will not hit us, but its 2029 flyby is a free natural experiment. Earth's gravity will tug on it, and scientists will see how a real asteroid responds. Spacecraft such as OSIRIS-APEX are planned to observe it, which will improve the models we would need if a dangerous asteroid were ever discovered. See the full story in our Apophis guide.
Asteroid impacts are one of the few natural disasters we can actually prevent. Humanity has the tools and is building more. Real space news in 2029 will be more exciting than any rumor.