Nobody likes waking up in the morning to the sound of regular alarm clocks or smartphones, but the smell of just baked bread and freshly roasted coffee? Now you’re talking.

The Sensorwake takes a vastly different approach to getting your attention when it’s time to wake up. Instead of using sound to wake you up, the clock uses smell, thanks to the “timed release of an aroma of your choice”.

The invention of 19-year-old Guillaume Rolland, an engineering student from France, the Sensorwake was successfully supported last year to the amount of US$200,000, and Rolland is now taking pre-orders for retail units.

But do smells work as well as a regular audio alarm in terms of waking you up? While we might hate the sound of conventional alarms, they seem to be not effective for most regular sleepers. Rolland claims that the Sensorwake is just as good as audio alarms, with internal testing showing his scent-based alarm wakes 99 percent of people in 2 minutes.

Previous research on the rousing abilities of smells hasn’t been so positive. A 1997 study by fire and rescue workers in Irondale, Alabama was designed to test whether adults woke up in the presence of smoke, water and citrus smells. Of 10 sleeping participants, only two woke up when exposed to the aromas. A subsequent study at Brown University in 2004 also found that scents were not particularly effective at waking sleepers.

The Sensorwake comes with an insurance policy for any sleepers who aren’t awakened by its primary feature. For extra-heavy sleepers who don’t register the smell, there’s a backup audio alarm that’s caused to go off if the aroma hasn’t woken you up within 3 minutes.

We can’t wait to see the reviews when the finished product is released and find out if the Sensorwake smells as good as it sounds.

Do you have frightening dreams while sleeping? According to an email interview by clinical psychologist and sleep expert Dr. Michael Breus, roughly 5 percent of the general population has at least one bad dream per week. Nightmares typically happen during REM sleep, during the middle and later parts of the night.

There is no exact explanation for nightmares, but Breus says it’s possible that they help the brain practise, prepare for and even anticipate difficult or dangerous experiences in waking life. Of course, it’s possible that nightmares, like dreams in general, don’t have a primary function — that they’re a by-product of other activities in the body. But most sleep scientists think that dreams and nightmares exist for some purposes.

One study found the most common nightmare was falling, followed by dreams of being chased, feeling lost, and feeling trapped. Then why do nightmares happen?

“Certain circumstances and characteristics make some people more likely to have nightmares than others,” says sleep medicine specialist Dr. Barry Krakow. He thinks people who’ve been traumatized (使受精神创伤) are certainly at a higher risk of nightmares. Examples are offered of those who have suffered criminal attacks, or who have been in life-threatening accidents. People with some degree of sensitivity in their biological make-up are also more likely to have bad dreams, so they’re more common in people who suffer from anxiety or depression, or who use excess drugs or alcohol.

The traditional belief often has it that nightmares are the result of eating too much rich food before bedtime, but it is still uncertain whether this is true. One study from 2015 did find a link between eating dairy or hot foods before bedtime and having disturbing dreams, but the study authors noted that this couldn’t be proven definitely because the data was self-reported and there were a lot of other factors to consider.

However, research in recent decades has shown that people who suffer from sleep disorders are also more likely to have nightmares.

“Inspector Sands to the control room, please.” If you ever hear that at a British train station, don’t panic. But you might appreciate knowing that this is a codeword meant to inform staff that there is an emergency somewhere in the building. The idea is to avoid causing alarm among commuters (通勤者), but still get the message out to those trained to deal with the problem.

The subject of secret codewords like this was raised this week on Reddit, and the discussion has attracted thousands of examples. But what codewords and signs are really out there in the wild?

A good place to start is hospital emergency codes. These are often colour-coded, and one health centre in Canada has published its list online. “Code red” announces a fire, “code white” indicates a violent person while “code black” means a bomb threat is active. It’s been reported that hospital staff sometimes refer to the morgue as “Rose Cottage”, in order to avoid upsetting relatives of a patient who has recently died.

“I can see very good reasons for having these codes,” says Paul Baker, a linguist at the University of Lancaster. “It may be that people are unsure when they’re giving the code so there’s no point upsetting members of the public.”

Not all codes are alphanumeric (字母数字的). Some are visual, intended to be hidden in plain sight. As BBC Future discovered earlier this year, many banknotes feature a specific pattern of dots placed there to prevent people from photocopying money. Many copiers and scanners are programmed to spot it.

And finally, the spray-painted squiggles (波形曲线) you see on pavements in towns and cities all over the world are codes understood by construction workers and engineers. For example, in UK, different colours are related to different types of cable or pipe. Blue meant a water system while yellow indicated gas lines and green labelled CCTV or data wiring.

All of these codes have a purpose — to avoid causing panic, to transmit subtle signals in social groups, or to provide technical information quickly and easily. “People don’t like secrets, do they?” says Baker. “There is a drive to have as much information as possible — we do live in the information age,” he adds.