World's population is now 8 billion, according to UN

There are eight billion people living on Earth today, according to the United Nations (UN).

It's hard to calculate the number of people in the world accurately, and the UN admits its sums could be out by a year or two - but it estimates that on 15 November the eight billion line will be crossed.

It is only 11 years since the population hit seven billion, and experts say this huge growth is because of many reasons including better health, nutrition and medicine.

Why has this happened?

The world reached one billion people in around 1800, then it took about another 100 years to get to the second billion - but since the 1950s how quickly the population is growing, has sped up.

Countries in Asia, including India, were responsible for a large amount of population growth over the last ten years.

The increase in population shows more children are being born, surviving adulthood and having children of their own.

People are also living longer because of better medicine and nutrition.

How quickly is the world growing?

If you saw a picture of every person on the planet every second, it would take 253 years.

Middle-income countries, mostly in Asia, accounted for most of the growth over the past decade, with 700 million more people since 2011.

India is expected to soon be the country with the biggest population

India has increased by roughly 180 million people, and is set to surpass China as the world's most populous nation next year for the first time in almost 2,000 years.

Birth rates in China have decreased since 1980 when the country's one-child policy was introduced, and more women have also been having children later in life to focus on their education and career opportunities.

When it comes comes to which countries are likely to grow more in the future, the UN says that most of the 2.4 billion people to be added before the global population peaks are likely to be born in sub-Saharan Africa.

This includes countries like Angola, Botswana, Cameroon and the Central African Republic.

But experts say that the rate of rapid growth is starting to slow down, meaning it will take about 15 years for the population to reach nine billion - which wouldn't be until the year 2037.

One of the main reasons for this is that people in many parts of the world are having less children. In the 1960s five births per woman was the global average, now it's nearly half at 2.4 per woman.

The UN is predicting that the global population will rise to around 10.4 billion people in the 2080s and remain at that level until 2100.

Why does it matter?

The population growing is seen as a success by the UN because it shows how much public health, nutrition, personal hygiene and medicine has improved - but it can also present challenges.

Having more people on Earth puts more pressure on nature, with people in competition with wildlife for water, food and space, as well as with with each other.

This could lead to mass migration and conflict in coming decades, experts say, particularly as extreme climate change could make parts of Africa and countries so hot they could be unsuitable for people to live in.

Countries in sub-Saharan African are expected to have the highest birth rate - but these are also countries hugely affect by climate change

More people means there are less resources to go around, and so governments will also need to think about how the way people and countries use what the world currently has and how this can this should be used.

This also includes how we are using energy and the impact on climate change if big countries with growing populations continue to use fossil fuels.

Although having more people on the planet will impact the environment, in fact it is the increase in producing and using materials which cause greenhouse gas emissions that causes more of an impact.

The UN Secretary General António Guterres said: "...it is a reminder of our shared responsibility to care for our planet and a moment to reflect on where we still fall short of our commitments to one another."