First, without any engines working, their plane was making almost no noise, and so people on the ground at the racetrack had no warning of their sudden landing.
The stars Slipher looked at showed unmistakable signs of a Doppler shift, the same mechanism behind that distinctive stretched-out yee-yummm sound cars make as they flash past on a racetrack.
The Belmont was supposed to take place on June 6. But horse racing in New York was halted in March after a racetrack worker was found to have the disease COVID-19.