Why Is It So Dark in Outer Space?

iStock/blackdovfx
iStock/blackdovfx

by Kenny Hemphill

Interstellar. Gravity. 2001: A Space Odyssey. Even Star Wars. They all have one thing in common: Beyond the lights of their spacecrafts, and aside from the faint needlepoint glow of distant stars, space is oil-slick dark.

Why that should be so is a question scientists have been asking for more than 400 years. Everyone from Johannes Kepler to Edmond Halley has had a go at trying to figure it out. But it was German astronomer Heinrich Wilhelm Olbers who gave his name to the paradox of the dark sky. Olbers wondered: If the universe is infinite, and there are an infinite number of infinitely old stars, why isn't the light from those stars visible from Earth? If it were, the night sky would be bright, not dark.

By the end of the 19th century, the idea of an infinite universe had been largely abandoned—something which was anticipated by Edgar Allan Poe in his 1848 essay, Eureka, where he wrote:

"Were the succession of stars endless, then the background of the sky would present us a uniform luminosity, like that displayed by the Galaxy—since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all."

In other words, Olbers' Paradox is resolved with the assumption that the universe has a finite age (something which is supported by the Big Bang Theory), that the speed of light is finite, and thus the observable universe has a horizon beyond which we can't see the stars. Fifty years later, Lord Kelvin used math to prove that in a finite universe, or one in which stars were born and died, the night sky should be dark.

There are other contributing factors to the darkness out there. Cosmic expansion over billions of years means that the energy from the radiation which was emitted following the Big Bang has been red-shifted, or reduced to the low temperature of microwaves. That puts it beyond the visible spectrum. And other radiation in space—infrared and ultra-violet light, radio waves, and X-rays—are all invisible to the human eye. If we could see them, space would seem a little less dark.

Universe Today has another explanation: "Space is black to our perception because there are few molecules of matter that can reflect or scatter light like our atmosphere on Earth. Since light goes in a straight line it seems to be absorbed by the void and vacuum of space. Otherwise space would look similar to the sky on Earth."

Think of a flashlight in a dark room. Look directly at the bulb and you see its light. Point it at furniture or a wall, and you see the light reflected. If there was nothing to reflect it, you wouldn't see any light at all. Which is exactly what happens in space.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

8 of Amazon's Bestselling Home Office Desks

JOISCOPE/Amazon
JOISCOPE/Amazon

If you've been working from home for the past six months (or longer), you're overdue for a high-quality office desk. And not just any old one, but a desk designed specifically for comfort and purpose, so you can organize everything you need for your 9-to-5 without having to worry about losing track of that important folder or planner.

The problem, though, is that there are so many options out there to choose from. That’s why we've stepped in to make the process a bit easier for you by compiling a list of the bestselling home office desks from Amazon. Check them out below.

1. Furinno Simplistic A-Frame Computer Desk; $237

Furinno/Amazon

This Furinno A-Frame desk is Amazon’s top home office desk at the moment. Though it may seem simple, sometimes that's all you need to make your space more efficient. The small desk hutch on top creates little cubbies for you to store papers, notebooks, or tools you may need throughout the day. There's even a bench on the bottom for you to put your feet up during the last few hours of the workday.

Buy it: Amazon

2. CubiCubi 40-inch Home Office Table; $95

CubiCubi/Amazon

For those looking for a sleek, modern desk that doesn't skimp on function, go for the CubiCubi. The metal frame, combined with the black wood surface, gives this table a sturdy, reliable feel. There's also a built-in side pocket to store all your papers out of eyesight but within arm’s reach. And according to the company, the whole thing should only take 10 minutes to assemble.

Buy it: Amazon

3. Coleshome 31-inch Computer Desk; $84

Coleshome/Amazon

This 31-inch desk from Coleshome is the perfect option for a small home office. Complete with adjustable leg pads for added stability, this desk can fit in any nook and is designed with simplicity in mind.

Buy it: Amazon

4. Mr. Ironstone Black L-Shaped Desk; $130

Mr. IRONSTONE/Amazon

This unique L-shaped desk is perfect for anyone looking to fit their workstation into the corner of a room. Measuring at 50.8 inches on both sides, you’ll get the most out of your surface by adding multiple monitors, a printer, and books all around.

Buy it: Amazon

5. Furinno Efficient Home Desk with Side Shelves; $53

Furinno/Amazon

If you want to make your office feel more like a study, then you’ll need somewhere to store all your tomes. This Furinno desk can help you make space to work and house all your favorite books nearby to grab whenever you need them. The multilevel shelves help make this desk feel more modern, while also creating plenty of storage space.

Buy it: Amazon

6. JOISCOPE 40-inch Computer Desk; $110

JOISCOPE/Amazon

This desk comes packed with plenty of storage space for your things while also providing a large, sleek worktop for you to spread out all day long. The oak finish on top also adds a bit of sophistication to your workday, even if you spend your lunch break perusing the latest cat memes.

Buy it: Amazon

7. Seville Classics Ergonomic Mobile Desk Cart; $44

Seville/Amazon

Standing desks have become more popular in recent years as people look for more ways to improve their posture and overall health. The Seville Ergonomic Mobile Desk can help you achieve your physical goals while assisting you with your work. The desk's height can be adjusted from 20.5 inches to 33 inches, and it has four swivel wheels, two of which lock in case you want to stay in one spot.

Buy it: Amazon

8. ComHoma Black Writing Computer Desk Office Folding Table; $100

ComHoma/Amazon

For a modern design, there's the ComHoma writing desk. The sleek metal bars on the sides and back of the desk add style, not clutter, and the 39-inch tabletop will give you ample space to work on whatever projects come your way.

Buy it: Amazon

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Why Can’t You Smell Your Own Breath? There Are a Few Theories

Hands are built-in tools for detecting bad breath.
Hands are built-in tools for detecting bad breath.
SIphotography/iStock via Getty Images

The fact that we rarely catch a whiff of our own breath seems fishy. For one, our noses are only a philtrum’s length away from our mouths. We also don’t have any trouble inhaling other people’s stale carbon dioxide, even with a solid few feet between us.

Though we don’t yet have a decisive scientific explanation for this olfactory phenomenon, there’s no shortage of promising theories. According to BreathMD, it could be that we became so accustomed to smelling our own breath that we simply don’t notice its odor anymore—similar to the way we can’t detect our own "house smell." This kind of habituation doesn’t just inure us to unpleasant aromas, it also leaves our noses free to focus on unfamiliar odors in our environment that could alert us to danger.

As HowStuffWorks reports, another hypothesis suggests that we’re more conscious of other people’s halitosis because breath released when speaking is different than breath released when exhaling regularly. All the tongue movement that happens when someone talks could push odors from the back of their mouth out into the air.

But if that’s true, it seems like you’d be able to smell your own breath—at least when you’re the one doing the talking. Which brings us to the next and final theory: That your bad breath dissipates before you get a chance to inhale it. When someone else exhales, you’re inhaling their air almost simultaneously. When you exhale, on the other hand, you have to wait until you’ve reached the very end of your expiration before breathing back in again. By that time, the malodorous particles may have already dispersed.

Even if you’re blissfully unaware of how your own breath smells, it could be a little nose-wrinkling for others—here are some tips for getting rid of halitosis.