[Music] hi and welcome back to free science lessons. co.uk by the end of this video you should be able to describe what's meant by order of magnitude you should then be able to carry out order of magnitude calculations we've already looked at the words that scientists use to describe the sizes of objects for example A millimeter is 1,000 of a meter however sometimes scientists want to to compare the approximate sizes of different objects and for this we use the idea of order of magnitude this shows an apple and an orange and you can see that they're about the same size scientists say that these are around the same order of magnitude this shows a pineapple and a small lemon the pineapple is around 10 times larger than the lemon so scientists would say that the pineapple is one order of magnitude larger than the lemon so one order of magnitude means 10 times okay here's a dog and down here is a woodlouse now a dog is around 100 times longer than a woodlouse so we would say that the dog is two orders of magnitude longer than a woodlouse the key idea is that every order of magnitude is 10 times greater than the one before an easy way of working that out is to count the number of zeros this tells you the order of magnitude so 10 * is one order of magnitude 100 times is two orders of magnitude and 1,000 times is three orders of magnitude here's a question for you to try a fox is around 40 cm long a tick living on a fox is around .4 cm long how many orders of magnitude is the fox longer than the tick pause the video and try this yourself okay so the first stage is to work out how many times longer the fox is than the tick if we divide 40 by 0.4 we can see that the fox is 100 times longer as I said before we can work out the order of magnitude by counting the zeros we've got two zeros and here they are so that means that the fox is two orders of magnitude longer than the tick remember that you'll find plenty of questions on orders of magnitude in my verion workbook and you can get that by clicking on the link above okay so hopefully now you should be able to describe what's meant by order of magnitude you should then be able to carry out order of magnitude calculations [Music]