The movie Ad Astra shows a space antenna, a spindly structure reaching up into the stars. We look at what it would take to build something that big.
Astronaut Roy McBride peers out over the Earth at the start of the new sci-fi flick Ad Astra. It’s not an unusual view for him. He does mechanical work atop an international space antenna. This spindly structure stretches up toward the stars. But this day, McBride’s sweet view is interrupted by an explosion that hurtles him off the antenna. He plummets from the blackness of space toward Earth until his parachute opens, slowing his descent.
In the movie, the space antenna looks like pipes stacked upon pipes that reach into space. But could anyone build something that tall? And can people actually climb up from Earth into space?
A tall order
There’s no set line between Earth and space. Where space begins depends on whom you ask. But most scientists agree that space starts somewhere between 80 and 100 kilometers (50 and 62 miles) above Earth’s surface.
Building a skinny tower that tall isn’t possible. Anyone who’s stacked up a tower of Legos knows that at some point the structure won’t be sturdy enough to hold its own weight. It eventually tilts to the side, before crashing and scattering its bricks. A better strategy is to build something like a pyramid that narrows as it grows in height.
The idea of using long ribbons in space has been around for a while. In 1992, this tethered satellite system was sent out from the space shuttle Atlantis. The shuttle successfully dragged the system around, but it didn’t reach its full potential. The cable was supposed to be 20 kilometers (12.5 miles), but it hit a snag when deploying and only 256 meters (840 feet) were released. CREDIT: TSS-1/STS-46 Crew/NASA
But even if we could build a tower that tall, there’d be problems, says Markus Landgraf. He’s a physicist at the European Space Agency. He’s based in Noordwijk, the Netherlands. A tower that could reach space would be too heavy for the Earth to support, he says. Earth’s crust isn’t very deep. It averages only around 30 kilometers (17 miles). And the mantle below is a bit squishy. The tower’s mass would push too hard on the Earth’s surface. “It would basically create a ditch,” Landgraf says. And, he adds, “It would keep doing so over thousands of years. It would go deeper and deeper. It would not be pretty.”
So physicists have concocted another solution — one that turns the tower approach on its head. Some scientists have proposed hanging a ribbon in Earth’s orbit and dangling its end down to the surface. Then people could climb up into space instead of blasting off in rockets.
