TECHNOQUEST

Q. Is it true that brain cells start to die off after we're born?

A. Brain cell death does occur as soon as we're born, although these cells are replaced by new ones. But after the age of 20, dying cells are not replaced and the brain starts to lose about a gram of its weight per year. This must mean that some of the 100 billion nerve cells duplicate tasks, otherwise we wouldn't function very well by the time we reached 70.

Q. What is the fastest thing on earth?

A. It all depends on what you mean by thing. Here are some very fast things you can find on this planet, so take your pick.

1. Light. Nothing can move faster than light. It travels at 186,000mph.

2. A spacecraft. Both the Russian space station Mir and the US Space Shuttle orbit the earth at about 25,000mph. But, then, they're not actually on the earth.

3. Birds. It is very difficult to measure how fast a bird flies. Birds swoop all over the sky rather than fly in straight lines. But the spine- tailed swift has been measured by Russian scientists at 106mph. The fastest bird in Britain is the peregrine falcon, with a dive speed of 82mph.

4. The cheetah. It is thought to be the fastest animal on land. Its fastest recorded speed is 51mph, though many scientists think it can go as fast as 60mph.

Q. Why do we itch?

A. Itching is an early warning that the body has come into contact with a noxious substance. We itch because we release a substance called histamine from "mast" cells in the skin's connective tissue. Histamine binds to special receptors on local nerve endings, causing the sensation of itching. This reflex can be stimulated by various irritants. People with allergies overproduce histamine in response to a substance that may not affect other people. A good example is pollen and hay fever.

Q. Why doesn't the stomach dissolve itself?

A. Mucus produced by goblet cells in the stomach wall forms a protective layer. This stops the pepsin and hydrochloric acid from breaking through the stomach tissue. If this protection is not effective - for example, if there's an uncovered portion of lining, or the covering is thin - the gastric juices can attack the mucosa and an ulcer can form.

Q. Why do people get bags under their eyes?

A. Nobody seems to know - not even the Quaker Labs in the US, which do research into fluid balance within the body. One idea is that the loose tissue under the eye swells as a result of a drop in blood pressure.

Q. What is the lowest intensity of light that the human eye can detect?

A. A single photon of light is enough to cause a rod in the human eye to fire. Rods are one of the eye's two types of light-detecting cell. The other type, the cone, is used to detect colour and needs to be exposed to several photons before it is activated. This is why rods are more important than cones for vision in low light conditions. Cones don't work well enough to allow us to see colours at night.

Questions and answers are provided by Science Line. You can use its Dial-a-Scientist service on 0345 600444.

CHRISTOPHER RILEY

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksAn introduction to the ground rules of British democracy
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Area Sales Manager - Midlands

£20000 - £25000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: PHP Developer - 3-4 Month Fixed Contract - £30-£35k pro rata

£30000 - £35000 per annum: Recruitment Genius: This is a 3-4 month pro rata fi...

Recruitment Genius: Telesales Executive - OTE £26,000+

£16000 - £26000 per annum: Recruitment Genius: A Telesales Executive is requir...

Recruitment Genius: Area Sales Manager

£25000 per annum: Recruitment Genius: This is an exciting opportunity to join ...

Day In a Page

Seifeddine Rezgui: What motivated a shy student to kill 38 holidaymakers in Tunisia?

Making of a killer

What motivated a shy student to kill 38 holidaymakers in Tunisia?
UK Heatwave: Temperatures on the tube are going to exceed the legal limit for transporting cattle

Just when you thought your commute couldn't get any worse...

Heatwave will see temperatures on the Tube exceed legal limit for transporting cattle
Exclusive - The Real Stories of Migrant Britain: Swapping Bucharest for London

The Real Stories of Migrant Britain

Meet the man who swapped Romania for the UK in a bid to provide for his family, only to discover that the home he left behind wasn't quite what it seemed
Cheaper energy on the way, but it's not all sunshine and rainbows

Cheaper energy on the way, but it's not all sunshine and rainbows

Solar power will help bring down electricity prices over the next five years, according to a new report. But it’s cheap imports of ‘dirty power’ that will lower them the most
Katy Perry prevented from buying California convent for $14.5m after nuns sell to local businesswoman instead

No grace of God for Katy Perry as sisters act to stop her buying convent

Archdiocese sues nuns who turned down star’s $14.5m because they don’t approve of her
Ajmer: The ancient Indian metropolis chosen to be a 'smart city' where residents would just be happy to have power and running water

Residents just want water and power in a city chosen to be a ‘smart’ metropolis

The Indian Government has launched an ambitious plan to transform 100 of its crumbling cities
Michael Fassbender in 'Macbeth': The Scottish play on film, from Welles to Cheggers

Something wicked?

Films of Macbeth don’t always end well - just ask Orson Welles... and Keith Chegwin
10 best sun creams for body

10 best sun creams for body

Make sure you’re protected from head to toe in the heatwave
Wimbledon 2015: Nick Bollettieri - Milos Raonic has ability to get to the top but he must learn to handle pressure in big games

Nick Bollettieri's Wimbledon files

Milos Raonic has ability to get to the top but he must learn to handle pressure in big games
Women's World Cup 2015: How England's semi-final success could do wonders for both sexes

There is more than a shiny trophy to be won by England’s World Cup women

The success of the decidedly non-famous females wearing the Three Lions could do wonders for a ‘man’s game’ riddled with cynicism and greed
How to stop an asteroid hitting Earth: Would people co-operate to face down a global peril?

How to stop an asteroid hitting Earth

Would people cooperate to face a global peril?
Just one day to find €1.6bn: Greece edges nearer euro exit

One day to find €1.6bn

Greece is edging inexorably towards an exit from the euro
New 'Iron Man' augmented reality technology could help surgeons and firefighters, say scientists

'Iron Man' augmented reality technology could become reality

Holographic projections would provide extra information on objects in a person's visual field in real time
Sugary drinks 'are killing 184,000 adults around the world every year'

Sugary drinks are killing 184,000 adults around the world every year

The drinks that should be eliminated from people's diets
Pride of Place: Historians map out untold LGBT histories of locations throughout UK

Historians map out untold LGBT histories

Public are being asked to help improve the map