I Like To Imagine

[Mintaka]

as i walk along the beach I like to imagine.

 

It seems to me that light travels roughly a million miles in about, say, 5 seconds. I know, it's approximate.

 

 

1) How long would it take , say, the Voyager spacecraft to travel a million miles?

 

2) What is the average speed of a normal paced walk? And how long would it take me to walk 40, 000 km? ( if i didn't stop).

 

3) Am I right in thinking that a beam of light would travel 4 and a half times around the earth in one second?

 

4) Do all kinds of light travel at the same speed? Is the light from a candle the same as light from a torch, or the sun or a lighthouse?

 

( THere is a reason for question two, based on the scale which puts the earth at the size of a 1cm diameter grape, the sun 1.5 m tall and 150 metres distance from the grape, and the nearest star (on this scale) 40, 100 km away.

 

I want to know how long it would take me to walk to the nearest star , based on this scale).

 

Thank you,

 

ps- I am terrible at maths.

[Boerseun]

1) From memory, Voyager travels around 40,000km/h. A little more or a little less, but you can hit Wikipedia and get the correct answer. A million miles is roughly 1.6 million kms. Once again, you can hit Wiki and get the right figures. All you do now is to divide 1 600 000 by 40 000, which yields 40. Which means that Voyager will cover a million miles in about forty hours.

 

2) A normal paced walk is round about 5km/h. Once again, divide 40 000 by 5. That gives you 8,000 hours in which to walk around the earth, non-stop. Or 333.3 days, if you divide that by another 24.

 

3) 4.5 times 40 000(approx) is 180 000, which gives you the speed of light (roughly) in miles. That would indeed be 4.5 times around the Earth in a second. The problem is that you have used the circumference of the Earth in kilometers (40 000), and not miles. Don't worry - NASA themselves have crashed spacecraft into Mars because of an Imperial/Metric slip-up. The speed of light is exactly 299,792,458 meters per second, of, for ease of calculation, close to 300,000km/s. Divide that by 40 000, and you get a round-trip of 7.5 times around the Earth in a second.

 

4) Yup. All kinds of light travel at the exact same speed - in a vacuum. If it travels through a medium like glass or air, it might be slowed down a bit. But in space, light is light - be it from a candle or a torch. A photon doesn't care about its heritage.

 

5) The nearest star, Proxima Centauri, is approximately 4.2 light-years away. A light-year is exactly 9,460,730,472,580.8kms. Times that by 4.2 and you get 39,735,067,984,839.36kms. Divide that by 5km/h (average walking speed), and you get 7,947,013,596,967.872 hours. Divide that by 24, and you get 331,125,566,540.328 days. Divide that by 365 and you get 907,193,332.9872 years. Or, 907,193,332 years, 360 days, 7 hours, 52 minutes and 19 point 2 seconds. If you keep your average of 5km/h up, never sleep, never rest, never stop along the way to gawk at the scenery and never bending down to tie your shoelaces.

 

If you walk just a little slower, to make the answer easier to remember, it'll take you about a billion years to walk to the nearest star. But I wouldn't do that - when I walk, I wanna get there.

[Mintaka]

1) From memory, Voyager travels around 40,000km/h. A little more or a little less, but you can hit Wikipedia and get the correct answer. A million miles is roughly 1.6 million kms. Once again, you can hit Wiki and get the right figures. All you do now is to divide 1 600 000 by 40 000, which yields 40. Which means that Voyager will cover a million miles in about forty hours.

 

2) A normal paced walk is round about 5km/h. Once again, divide 40 000 by 5. That gives you 8,000 hours in which to walk around the earth, non-stop. Or 333.3 days, if you divide that by another 24.

 

3) 4.5 times 40 000(approx) is 180 000, which gives you the speed of light (roughly) in miles. That would indeed be 4.5 times around the Earth in a second. The problem is that you have used the circumference of the Earth in kilometers (40 000), and not miles. Don't worry - NASA themselves have crashed spacecraft into Mars because of an Imperial/Metric slip-up. The speed of light is exactly 299,792,458 meters per second, of, for ease of calculation, close to 300,000km/s. Divide that by 40 000, and you get a round-trip of 7.5 times around the Earth in a second.

 

4) Yup. All kinds of light travel at the exact same speed - in a vacuum. If it travels through a medium like glass or air, it might be slowed down a bit. But in space, light is light - be it from a candle or a torch. A photon doesn't care about its heritage.

 

5) The nearest star, Proxima Centauri, is approximately 4.2 light-years away. A light-year is exactly 9,460,730,472,580.8kms. Times that by 4.2 and you get 39,735,067,984,839.36kms. Divide that by 5km/h (average walking speed), and you get 7,947,013,596,967.872 hours. Divide that by 24, and you get 331,125,566,540.328 days. Divide that by 365 and you get 907,193,332.9872 years. Or, 907,193,332 years, 360 days, 7 hours, 52 minutes and 19 point 2 seconds. If you keep your average of 5km/h up, never sleep, never rest, never stop along the way to gawk at the scenery and never bending down to tie your shoelaces.

 

If you walk just a little slower, to make the answer easier to remember, it'll take you about a billion years to walk to the nearest star. But I wouldn't do that - when I walk, I wanna get there.

 

 

 

You guys are the best! That is just fantastic! :-) Thanks for your answer. Hmmmmmm.....now I am going to try and work out how long it would take me to walk to the nearest star based on my Earth=grape scale...hmmm think I work that out as about 335 days?

 

You have helped me lots with your answer, thank you. Imagination is a great thing, it helps us make sense of things which are impossible to understand.

[Mintaka]

You guys are the best! That is just fantastic! :-) Thanks for your answer. Hmmmmmm.....now I am going to try and work out how long it would take me to walk to the nearest star based on my Earth=grape scale...hmmm think I work that out as about 335 days?

 

You have helped me lots with your answer, thank you. Imagination is a great thing, it helps us make sense of things which are impossible to understand.

 

so, photons do actually travel?

 

how do they propel themselves , and so fast?