Åk 6–9

English/فارسی
 1.2 History Time Humans have throughout time had the need to be able to measure time.  They have seen the seasons pass.  Maybe our forefathers noticed that the moon regularly got larger and smaller.  In Arabic time calculations, a rotation of the moon was equivalent to one month.  The western way of calculating a month is a little different. Jesus’ birth was a large enough even that it is considered year 0, but the Arabs calculate time’s beginning when the prophet Mohammed fled to Mecca from Medina, in other words 622 years after the birth of Jesus.  This and the different calculations of the month, cause us to calculate from different points in time. One philosophical question is when time actually began.  Some researches thing that it all began with the “Big Bang”.  It was when the universe began to expand and move which it is still doing.  The question is then how were things before time and space? Speed When the mail was delivered in Sweden’s countryside during the 1600’s, farmhands walked with the letters.  They were required to keep a speed of 10 km in two hours.  If they walked slower than they could be jailed with only water and bread for a week. In the 1800’s, the mail was regularly sent between Stockholm and Ystad, a distance of 56 Swedish Miles (560 km).  There were many changes in horse on the way because the horses were only allow to be ridden for 3 Swedish miles (30 km) before they needed to be changed.  The trip started in Stockholm at 6 o’clock on Saturday evening and arrived in Ystad Thursday evening.  The speed has increased compared to walking. When the railroads were built in the middle of the 1800’s, mail delivery when much quicker.  A trip between Stockholm and Gothenburg took 12 hours. No one can travel faster than light, but trying to calculate how fast light moves has kept many a scientist busy.  It is said that Galileo Galilei tried to do a practical experiment to fine the speed of light.  He used two lamps and a watch.  A person would stand at the end of a measured distance and light a lamp and at the same time start his watch.  When the light got to the other end of that distance, the other person would light their lamp.  When the first person saw the light, he would stop his watch.  Then they had both a measured time and a distance for the light and could therefore calculate light’s speed, but the value they got was not exact.