Quandaries and Queries Hello I have a simple mathematical question: How long time would it take to accelerate up to the speed of light with an acceleration speed similar to 0-100 seconds in 5 seconds? I am not a skilled mathematician&. Thankful if you would take your time to answer Kindest greetings from Lars Hi Lars, I assume that you are thinking of acceleration in a car where where you might go from 0 to 100 km/hr in 5 seconds. If you actually do this then the acceleration is not constant throughout the 5 seconds, that is the velocity does not increase at a constant rate. However, since I don't know how the velocity changes I am going to assume that it changes at a constant rate. That is in every 5 second interval the velocity increases 100 km/hr. The speed of light is 299 792 458 m/sec but it is usually rounded off to 300 000 km/sec. To express this is kilometers per hour I need to multiply by 3600. That is 300 000 km/sec 60 sec/min 60 min/hr = 1 080 000 000 km/hr Your velocity is increasing 100 km/hr in every 5 second interval and hence it will take you 1 080 000 000/100 = 10 800 000 of these 5 second intervals to get to the speed of light. Hence the time to reach the speed of light is 10 800 000 5 = 54 000 000 seconds. I put this in more convenient time units. 54 000 000 sec  1/60 min/sec  1/60 hr/min  1/24 days/hr = 625 days. Penny Go to Math Central