Radio signals keep coming from deep space. Here's what they really are.

When the New York Times first wrote about "mysterious radio waves" from the cosmos in 1933, they made sure to note one fundamental caveat: "No Evidence of Interstellar Signaling."
Indeed, the radio waves weren't signals from aliens. After all, it's never aliens.
Yet today, some 90 years later, you've undoubtedly seen headlines promoting more "strange radio signals coming from deep space." They're among the most clicked on internet space stories. In reality, our planet is constantly bombarded with radio waves, which are a type of energy or light naturally produced all over the cosmos (like visible light or X-rays). Radio waves are extremely valuable to detect using giant dished-shaped antennas because they reveal fascinating, extremely far-off events that we can't otherwise see, like stars exploding or black holes munching on cosmic dust. They are normal. And they aren't attempts at intergalactic communication.
"Since the dawn of radio astronomy, this is what astronomers do. They tell people, 'It's not aliens,'" Yvette Cendes, an astronomer and postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, told Mashable.
These detected radio waves often come from almost incomprehensibly distant galaxies, many light-years away. To us, they're like whispers drifting through the wind. That's why astronomers must use behemoth antennas to find them.

"Since the dawn of radio astronomy, this is what astronomers do. They tell people, 'It's not aliens.'"

"If you took your cell phone and put it on the moon, it would be one of the brightest radio sources in the sky," Cendes explained. "These are very faint signals. The amount of energy collected in radio astronomy's history is less than the energy needed to melt a snowflake."
Even so, they reveal momentous events in our galaxy, and beyond.
Radio signals keep coming from deep space. Here's what they really are.