To add further more: often also 810 or 820 numbers exist, where a phone call might have a toll up to 10 or 20 cents per minute respectively. With 900 numbers you usually dont know, how expensive they are, when only looking at the number.

It’s “ich_iel” on feddit.de

They get eliminated at first sight!

Are you sure about that? From m/s to km/h you multiply by 3600 (for the time) and divide by 1000 (for the distance) which leads to a factor of 3.6.

Personally i always remember 25 m/s = 90 km/h = 56 mph because of the somewhat round numbers.

Sooooo, wavelengths (λ) become longer when something moves away (redshift) and become shorter when something moves towards you (blueshift).

For a red flag (λ0=610nm) to become a green flag (λ1=549nm), it has to move towards you quite fast. But how fast is ‘quite fast’?

Using the formula

flag_velocity / speed of light © = difference in wavelengths / starting wavelength

we get

flag_velocity = (610-549) / 610 * c = 61 / 610 * c = 1/10 * c

This means: the flag has to move with about c/10 = 30 000 000 m/s = 108 000 000 km/h = 67 108 100 mph. Yeah, that’s quite fast.

(Disclaimer:

1. use info on own risk

2. values for λ were chosen in a way to make calculations easy. There is no info on what shade of red or green the flag is. The final result will be about the same.

3. With speeds at around 10% of c, I should use the formula considering the relativistic doppler effect… However, i wont. Thanks.)

Sooooo, wavelengths (λ) become longer when something moves away (redshift) and become shorter when something moves towards you (blueshift).

For a red flag (λ0=610nm) to become a green flag (λ1=549nm), it has to move towards you quite fast. But how fast is ‘quite fast’?

Using the formula

flag_velocity / speed of light © = difference in wavelengths / starting wavelength

we get

flag_velocity = (610-549) / 610 * c = 61 / 610 * c = 1/10 * c

This means: the flag has to move with about c/10 = 30 000 000 m/s = 108 000 000 km/h = 67 108 100 mph. Yeah, that’s quite fast.

(Disclaimer:

1. use info on own risk

2. values for λ were chosen in a way to make calculations easy. There is no info on what shade of red or green the flag is. The final result will be about the same.

3. With speeds at around 10% of c, I should use the formula considering the relativistic doppler effect… However, i wont. Thanks.)

Maybe she wasn’t able to start collage sooner… There are many reasons for why s1 is at collage at 29.

The actual unit is lower case, the multiplier is uppercase.

Wouldn’t agree with that… There are many different units and multipliers. the letter being uppercase or lowercase has nothing to do with it.

Examples:

letters for prefixes/multipliers being uppercase and lowercase: P, T, G, M, k, h, da, d, c, m, u, n (trillion, billion, million, thousand, hundred, ten, one tenth, one hundredth, one thousandth, one millionth, one billionth)

Letters for units being uppercase and lowercase: s, m, g, N, W, J, A, K, V, h, Hz (seconds, meter, gram, Newton, Watt, Joule, Ampere, Kelvin, Volt, hour, Hertz) (just recognised, that most units, which are named after scientists, are written with capital letters…)

km = thousand meters/kilometer

K = Kelvin (unit for temperature)

M = Mega (prefix for one million)

kJ = thousand joules

s = second

ms = millisecond (one thousandth)

S = siemens (electrical conductivity)

mS = milli siemens

mm = millimeter (one thousandth of a meter)

Mm = megameter (one million meters or thousand kilometers)

One friend of mine says the same all the time… In fact, he’s the worst driver I’ve ever driven with! In reality, I am much better and even exponentially better than the average driver.

Did the same some years back. Only black and white laser, but this thing just works!