At his Psychology Today blog, Michael Chorost delves into a question about exoplanets that I've not really thought much about before — how easy they would be to leave.
Many of the potentially habitable exoplanets that we've found — the ones we call "Earth-like" — are actually a lot bigger than Earth. That fact has an effect — both on how actually habitable those planets would be for us humans and how easily any native civilizations that developed could slip the surly bonds of gravity and make it to outer space.
The good news, says Chorost is that the change in surface gravity wouldn't be as large as you might guess, even for planets much bigger than Earth. The bad news: Even a relatively small increase in surface gravity can mean a big increase in how fast a rocket would have to be going in order to leave the planet. It starts with one equation — SG=M/R^2.
Let’s try it with [exoplanet] HD 40307g, using data from the Habitable Exoplanet Catalog. Mass, 8.2 Earths. Radius, 2.4 times that of Earth. That gets you a surface gravity of 1.42 times Earth.
... it’s amazingly easy to imagine a super-Earth with a comfortable gravity. If a planet had eight Earth masses and 2.83 times the radius, its surface gravity would be exactly 1g. This is the “Fictional Planet” at the bottom of the table. Fictional Planet would be huge by Earth standards, with a circumference of 70,400 miles and an area eight times larger.
Does that mean we could land and take off with exactly the same technology we use here, assuming the atmosphere is similar? Actually, no. Another blogger, who who goes by the moniker SpaceColonizer, pointed out that Fictional Planet has a higher escape velocity than Earth. Put simply, escape velocity is how fast you have to go away from a planet to ensure that gravity can never bring you back. For Earth, escape velocity is about 25,000 miles per hour. Fictional Planet has an escape velocity 68% higher. That’s 42,000 miles per hour.
Read the full story at Psychology Today blogs
Thanks to Apollo 18, who also helped with the math for Chorost's post.
Image: Vintage ad via Christian Montone
Despite Trump’s denial of climate change the the ghastly attacks on climate science and mitigation in the new proposed budget, the Carbon Bubble — which overprices hydrocarbons and the industries that rely on them, as though we’ll be burning all of them with impunity — is about to pop.
South American polka dot tree frogs are pretty cool, but Julián Faivovich and Carlos Taboada found out they are even cooler when an ultraviolet flashlight is trained on them. They fluoresce. Many animals can see beyond the spectrum visible to humans, and these frogs adapted with this trait. From the abstract: Fluorescence, the absorption of […]
A small (51 men aged 24 +/- 3 years) study published in Neuron tasked experimental subjects with practicing the ancient Greek mnemonic technique of “memory palaces” and then scanned their brains with functional magnetic resonance imaging, comparing the scans to scans from competitive “memory athletes” and also measuring their performance on memorization tasks.
The Lightning port has thus far resisted the cruel fate that befell the headphone jack, and despite rumors that it may be disappearing come iPhone 8, for the present and foreseeable future, Lightning cables are a hot commodity for iPhone users. As such, we must make do in this strange time in which long, glorified […]
All the filters in the world won’t save your smartphone pics from a shaky hand. To really step up your mobile photography game, you’ll need some kind of mount to hold it steady. You could buy a smartphone attachment for a conventional camera tripod, but who wants to carry that kind of gear everywhere they […]
The forced transition from analog to digital TV signals was probably met with relative indifference from people with Netflix subscriptions and the “I don’t even own a TV” snoots. But anyone living in the vast swaths of the country that don’t have guaranteed high-speed internet, broadcast TV is a perfectly valid (and 100% free) way […]