You hear things all day. Some are facts and some are not. A fact is something you can check. An opinion is what a person thinks. Opinions can be backed up with good reasons, but a reason is not the same as a fact you can check.

In 1835 a New York newspaper printed that an astronomer had seen life on the Moon. The story was made up. It said that winged man-bats and other creatures lived on the Moon. It said a giant new telescope showed them.

How can you check a claim? Look at who wrote it, why, and when. Ask who says it and how they know. A good source should say where its facts came from. A diary or a letter from the time is a first-hand record. It is called a primary source.

Check a second place. A true fact can be found in more than one good place. It is also good to ask why something was made. Is it trying to teach you, or to sell you something? That tells you a lot about it.

Some myths are about the brain. You may have heard that people use only a tenth of it. In fact, people use almost every part. Brain scans show that when you talk, walk or listen to music, you use almost every region. No part is always switched off.

Fakes can fool experts. A skull and jaw found in England in 1912 were said to be an early human relative. It was a human skull put with an orangutan jaw. Tests in 1953 proved it fake, about 40 years later. Respected scientists were fooled too.

Experts who study the same thing can still have different opinions. So when you hear a big claim, do not stop at one place. Ask who says it, and ask how they know. Then look in a second place, and check it twice.

Words to know

• source: where facts start
• opinion: what someone thinks
• primary: first-hand
• astronomer: star scientist